Patent Publication Number: US-2016235833-A1

Title: Chimeric Factor H Binding Proteins (fHBP) and Methods of Use

Description:
CROSS REFERENCED TO RELATED APPLICATION 
     This application claims priority to U.S. Provisional Application No. 61/174,424 filed Apr. 30, 2009, which is incorporated herein by reference in its entirety and for all purposes. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     This invention was made with government support under Public Health Service grant nos. R01 AI46464 and C06 RR16226. The government has certain rights in this invention. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to vaccines for diseases caused by  Neisseria meningitidis.    
     INTRODUCTION 
       Neisseria meningitidis  is a Gram-negative bacterium which colonizes the human upper respiratory tract and is responsible for worldwide sporadic and cyclical epidemic outbreaks of, most notably, meningitis and sepsis. The attack and morbidity rates are highest in children under 2 years of age. Like other Gram-negative bacteria,  Neisseria meningitidis  typically possess a cytoplasmic membrane, a peptidoglycan layer, an outer membrane which together with the capsular polysaccharide constitute the bacterial wall, and pili, which project into the outside environment. Encapsulated strains of  Neisseria meningitidis  are a major cause of bacterial meningitis and septicemia in children and young adults. The prevalence and economic importance of invasive  Neisseria meningitidis  infections have driven the search for effective vaccines that can confer immunity across different strains, and particularly across genetically diverse group B strains with different serotypes or serosubtypes. 
     Factor H Binding Protein (fHbp, also referred to in the art as lipoprotein 2086 (Fletcher et al, Infect Immun 2004; 72:2088-2100), Genome-derived Neisserial antigen (GNA) 1870 (Masignani et al. J Exp Med 2003; 197:789-99) or “741”) is an  N. meningitidis  protein which is expressed in the bacterium as a surface-exposed lipoprotein. An important function of fHbp is to bind human complement fH, which down-regulates complement activation. Binding of fH to the bacterial surface is an important mechanism by which the pathogen survives in non-immune human serum or blood and evades innate host defenses. 
     From analysis of 71  N. meningitidis  strains in the first study, and more than 200 strains in the second study, representative of its genetic and geographic diversity,  N. meningitidis  strains have been sub-divided into three fHbp variant groups (referred to as variant 1 (v.1), variant 2 (v.2), and variant 3 (v.3)) based on amino acid sequence variability and immunologic cross-reactivity (Masignani et al. J Exp Med 2003; 197:789-99). Other workers (Fletcher et al, 2004) have subdivided the protein into two sub-families designated A (which includes v.2 and v.3 of Masignani) and B (v.1). Variant 1 strains account for about 60% of disease-producing group B isolates (Masignani et al. 2003, supra). Within each variant group, there is on the order of about 92% or greater conservation of amino acid sequence. Specifically, conservation within each variant group ranges between 89 and 100%, while between the variant groups (e.g., between v.1 and v.2) the conservation can be as low as 59%. The protein is expressed by all known strains of  N. meningitidis.    
     There remains a need for a single fHbp polypeptide that can elicit bactericidal antibody responses that are effective against a broad spectrum of strains expressing different fHbp variants. 
     SUMMARY 
     Chimeric fHbps that can elicit antibodies that are bactericidal for different fHbp variant strains of  N. meningitidis , and methods of use, are provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A-1G  is Table 7 that lists the source strains and characteristics of about 69 unique factor H binding proteins. 
         FIG. 2A-2E  is Table 8 that lists unique sequences in fHbp variable segment A through E and number of unique peptides from each variant group containing the segment ID. Segment ID is an identifier for each variable segment. Distinct sequence variants were assigned a unique identifier beginning with a letter, A through E, to represent the segment; followed by an α or β to indicate homology of the segment with either the corresponding fHbp segment from peptide ID 1 (fHbp v.1) or peptide ID 28 (fHbp v.3), respectively, followed by a number for each distinct sequence. Numbers in variant groups 1, 2, and 3 are provided for some segment IDs of each segment (A through E) in subtables. 
         FIG. 3  is a phylogram of fHbp based on 69 unique amino acid sequences. 
         FIG. 4 , panel A is a schematic representation of fHbp showing positions of linkers, which are also referred herein as invariant segment (I), shown as vertical rectangles, together with variable segments (V). Panel B is a table listing the amino acid sequence for each invariant segment. 
         FIG. 5  is a phylogram of unique fHbp amino acid sequences in variable segments A (residues 8-73) (panel A) and B (residues 79-93) (panel B). 
         FIG. 6  is a phylogram of unique fHbp amino acid sequences in variable segments C (residues 98-159) (panel A) and D (residues 162-180) (panel B). 
         FIG. 7  is a phylogram of unique fHbp amino acid sequences in variable segment E (residues 186-253). 
         FIG. 8 , panel A is a schematic representation of 9 fHbp modular architectures deduced from phylogenic analysis, including the more common 6 modular group types. Gray segments represent α progenitor sequences homologous to peptide ID 1 while white segments represent β progenitor sequences homologous to peptide 28. About 94% of the unique fHbp amino acid sequences analyzed herein belong to one of the first six modular group types (I, II, III, IV, V, and VI). Panel B, Four of the analyzed fHbps are classified as one of three modular architectures shown. The architectures contain junction points within a variable segment, designated by arrows. Panel C is a table listing the amino acid residues at which an α progenitor sequence switches to a β or vice versa (J 1 , J 2 , and J 3 ) within a variable segment. 
         FIG. 9  presents structural models of factor H binding protein based on the coordinates of fHbp in a complex with a fragment of human factor H (Schneider et al. (2009)  Nature  458:890-3). Left models in each of the following panels show fHbps facing membrane side; center models are facing exposed side; and the right models depict membrane side of the fHbp down. Panel A, Cartoon representation depicting the two structural domains. B, Space-filling model with factor H-binding residues depicted in black and the amino acid residues of the invariant segments in white. C, Space-filling model with the amino acid residues of the invariant segments depicted in white as in panel B, and the residues affecting the epitopes of anti-fHbp mAbs shown in black. 
         FIG. 10A-10I  is Table 9 that lists certain characteristics of unique factor H binding protein variants use in an analysis that include 275 peptide IDs. Sequence identifiers for N-terminal variable sequences are as follows: GGGS (SEQ ID NO: 7), SGSGG (SEQ ID NO: 8), GGGSGG (SEQ ID NO:9), GGGSGS (SEQ ID NO:10), GSGG (SEQ ID NO:11), GGGSGGGG (SEQ ID NO:12), GGGSGGGSGG (SEQ ID NO:13), and GGSGG (SEQ ID NO:14). 
         FIG. 11  shows fHbp expression measured by immunoblotting with infrared detection. Panels A and C, Recombinant proteins in modular groups I (ID 1) or VI (ID 77), or heat-killed bacterial cells from strains expressing fHbp in the corresponding modular groups. The modular group I proteins were detected with murine anti-fHbp mAb JAR 5, which recognizes nearly all fHbps in modular groups I and IV. The modular group VI proteins were detected with anti-fHbp mAb JAR 31, which recognizes nearly all proteins in modular groups II, III, V and VI (See Table 6 in example section). Panels B and D, Standard curves from the corresponding binding of the recombinant proteins shown in Panels A and C. 
         FIG. 12  shows the frequencies of fHbp modular groups among systematically collected  N. meningitidis  group B case isolates. Data are from sequences of isolates collected in the United States (N=432), United Kingdom (N=536) and France (N=244) reported by Murphy et al [16], and newly obtained sequences of 143 additional U.S. isolates from California (2003-2004), Maryland (1995 and 2005), and pediatric hospitals in 9 states (2001-2005). 
         FIG. 13  shows serum bactericidal activities of serum pools from mice immunized with fHbps from modular groups I to VI. The black bars represent the median titers of 3 to 4 serum pools for each modular group tested against homologous test strains. The white bars represent the median titer of the respective heterologous serum pools against the test strain. +, refers to relative expression of fHbp by each of the strains; strains with +/− representing low fHbp-expressing strains (see values in Table 5 in example section) 
     
    
    
     Before the present invention and specific exemplary embodiments of the invention are described, it is to be understood that this invention is not limited to particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims. 
     Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges is also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either both of those included limits are also included in the invention. 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention, the preferred methods and materials are now described. All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited. 
     It must be noted that as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “an antigen” includes a plurality of such antigens and reference to “the protein” includes reference to one or more proteins, and so forth. 
     The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION 
     The present disclosure provides chimeric fHbps that can elicit antibodies that are bactericidal for different fHBP variant strains of  N. meningitidis , and methods of use. 
     DEFINITIONS 
     “Factor H Binding Protein” (fHbp), which is also known in the literature as GNA1870, GNA 1870, ORF2086, LP2086 (lipoprotein 2086), and “741” refers to a polypeptide of  N. meningitidis  that is a lipoprotein presented on the surface of the bacterium.  N. meningitidis  strains have been sub-divided into three fHbp variant groups (referred to as variant 1 (v.1), variant 2 (v.2), and variant 3 (v.3) in some reports (Masignani et al. 2003, supra) and Family A and B in other reports (see, e.g., Fletcher et al. 2004 Infect Immun 2088-2100)) based on amino acid sequence variability and immunologic cross-reactivity (Masignani et al. J Exp Med 2003; 197:789-99). Each unique fHbp found in  N. meningitidis  is also assigned a peptide ID according to neisseria.org, as shown in  FIGS. 1A-1G  (Table 7) and  FIGS. 10A-10I  (Table 9). For clarity, the present disclosure uses the v.1, v.2 and v.3 terminology. Because the length of variant 2 (v.2) fHbp protein (from strain 8047, peptide ID 77) and variant 3 (v.3) fHBP (from strain M1239, peptide ID 28) differ by −1 and +7 amino acid residues, respectively, from that of MC58 (peptide ID 1), the numbering used to refer to residues for v.2 and v.3 fHbp proteins differs from numbering based on the actual amino acid sequences of these proteins. Thus, for example, reference to a leucine residue (L) at position 166 of the v.2 or v.3 fHBP sequence refers to the residue at position 165 of the v.2 protein and at position 173 in the v.3 protein. 
     The term “heterologous” or “chimeric” refers to two components that are defined by structures derived from different sources. For example, where “heterologous” is used in the context of a chimeric polypeptide, the chimeric polypeptide includes operably linked amino acid sequences that can be derived from different polypeptides of different phylogenic groupings (e.g., a first component from an α and a second component from a β progenitor amino acid sequences). Similarly, “heterologous” in the context of a polynucleotide encoding a chimeric polypeptide includes operably linked nucleic acid sequence that can be derived from different genes (e.g., a first component from a nucleic acid encoding a fHbp v.1 polypeptide and a second component from a nucleic acid encoding a fHbp v.2 polypeptide). Such chimeric polypeptides as described herein provide for presentation of epitopes in a single polypeptide that are normally found in different polypeptides. Other exemplary “heterologous” nucleic acids include expression constructs in which a nucleic acid comprising a coding sequence is operably linked to a regulatory element (e.g., a promoter) that is from a genetic origin different from that of the coding sequence (e.g., to provide for expression in a host cell of interest, which may be of different genetic origin relative to the promoter, the coding sequence or both). For example, a T7 promoter operably linked to a polynucleotide encoding an fHbp polypeptide or domain thereof is said to be a heterologous nucleic acid. “Heterologous” in the context of recombinant cells can refer to the presence of a nucleic acid (or gene product, such as a polypeptide) that is of a different genetic origin than the host cell in which it is present. For example, a Neisserial amino acid or nucleic acid sequence of one strain is heterologous to a Neisserial host of another strain. 
     “Derived from” in the context of an amino acid sequence or polynucleotide sequence (e.g., an amino acid sequence “derived from” a v.1 fHbp) is meant to indicate that the polypeptide or nucleic acid has a sequence that is based on that of a reference polypeptide or nucleic acid (e.g., a naturally occurring fHbp protein or encoding nucleic acid), and is not meant to be limiting as to the source or method in which the protein or nucleic acid is made. “Derived from” in the context of bacterial strains is meant to indicate that a strain was obtained through passage in vivo, or in in vitro culture, of a parental strain and/or is a recombinant cell obtained by modification of a parental strain. 
     “Conservative amino acid substitution” refers to a substitution of one amino acid residue for another sharing chemical and physical properties of the amino acid side chain (e.g., charge, size, hydrophobicity/hydrophilicity). “Conservative substitutions” are intended to include substitution within the following groups of amino acid residues: gly, ala; val, ile, leu; asp, glu; asn, gln; ser, thr; lys, arg; and phe, tyr. Conservative amino acid substitutions in the context of a chimeric fHBP disclosed herein are selected so as to preserve presentation of an epitope of interest. Guidance for such substitutions can be drawn from alignments of amino acid sequences of polypeptides presenting the epitope of interest. 
     The term “protective immunity” means that a vaccine or immunization schedule that is administered to a mammal induces an immune response that prevents, retards the development of, or reduces the severity of a disease that is caused by  Neisseria meningitidis , or diminishes or altogether eliminates the symptoms of the disease. Protective immunity can be accompanied by production of bactericidal antibodies. It should be noted that production of bactericidal antibodies against  Neisseria meningitidis  is accepted in the field as predictive of a vaccine&#39;s protective effect in humans. (Goldschneider et al., 1969, J. Exp. Med. 129:1307; Borrow et al. 2001 Infect Immun. 69:1568). 
     The phrase “a disease caused by a strain of capsular group B of  Neisseria meningitidis ” encompasses any clinical symptom or combination of clinical symptoms that are present in an infection of a human with a member of capsular group B of  Neisseria meningitidis . These symptoms include but are not limited to: colonization of the upper respiratory tract (e.g. mucosa of the nasopharynx and tonsils) by a pathogenic strain of capsular group B of  Neisseria meningitidis , penetration of the bacteria into the mucosa and the submucosal vascular bed, septicemia, septic shock, inflammation, haemmorrhagic skin lesions, activation of fibrinolysis and of blood coagulation, organ dysfunction such as kidney, lung, and cardiac failure, adrenal hemorrhaging and muscular infarction, capillary leakage, edema, peripheral limb ischaemia, respiratory distress syndrome, pericarditis and meningitis. 
     The phrase “broad spectrum protective immunity” means that a vaccine or immunization schedule elicits “protective immunity” against at least more than one strain (and can be against at least two, at least three, at least four, at least five, against at least eight, or more strains) of  Neisseria meningitidis , wherein each of the strains expresses a different fHbp subvariant or fHbp variant. The present disclosure specifically contemplates and encompasses a vaccine or vaccination regimen that confers protection against a disease caused by a member of any capsular group (e.g., A, B, or C), with protection against disease caused by a capsular group B strain of  Neisseria meningitidis  being of interest due to the epidemiological prevalence of strains causing disease with this capsular group and lack of broadly effective group B vaccines. 
     The phrase “specifically binds to an antibody” or “specifically immunoreactive with”, in the context of an antigen (e.g., a polypeptide antigen) refers to a binding reaction which is based on and/or is probative of the presence of the antigen in a sample which may also include a heterogeneous population of other molecules. Thus, under designated conditions, the specified antibody or antibodies bind(s) to a particular antigen or antigens in a sample and do not bind in a significant amount to other molecules present in the sample. “Specifically binds to an antibody” or “specifically immunoreactive with” in the context of an epitope of an antigen (e.g., an epitope of a polypeptide) refers to a binding reaction which is based on and/or is probative of the presence of the epitope in an antigen (e.g., polypeptide) which may also include a heterogeneous population of other epitopes, as well as a heterogeneous population of antigens. Thus, under designated conditions, the specified antibody or antibodies bind(s) to a particular epitope of an antigen and do not bind in a significant amount to other epitopes present in the antigen and/or in the sample. 
     The phrase “in a sufficient amount to elicit an immune response” means that there is a detectable difference between an immune response indicator measured before and after administration of a particular antigen preparation. Immune response indicators include but are not limited to: antibody titer or specificity, as detected by an assay such as enzyme-linked immunoassay (ELISA), bactericidal assay, flow cytometry, immunoprecipitation, Ouchter-Lowny immunodiffusion; binding detection assays of, for example, spot, Western blot or antigen arrays; cytotoxicity assays, etc. 
     A “surface antigen” is an antigen that is present in a surface structure of  Neisseria meningitidis  (e.g. the outer membrane, capsule, pili, etc.). 
     “Isolated” refers to an entity of interest that is in an environment different from that in which the compound may naturally occur. “Isolated” is meant to include compounds that are within samples that are substantially enriched for the compound of interest and/or in which the compound of interest is partially or substantially purified.” 
     “Enriched” means that a sample is non-naturally manipulated (e.g., by an experimentalist or a clinician) so that a compound of interest is present in a greater concentration (e.g., at least a three-fold greater, at least 4-fold greater, at least 8-fold greater, at least 64-fold greater, or more) than the concentration of the compound in the starting sample, such as a biological sample (e.g., a sample in which the compound naturally occurs or in which it is present after administration), or in which the compound was made (e.g., as in a bacterial polypeptide, antibody, chimeric polypeptide, and the like) 
     A “knock-out” or “knockout” of a target gene refers to an alteration in the sequence of the gene that results in a decrease of function of the target gene, e.g., such that target gene expression is undetectable or insignificant, and/or the gene product is not functional or not significantly functional. For example, a “knockout” of a gene involved in LPS synthesis indicates means that function of the gene has been substantially decreased so that the expression of the gene is not detectable or only present at insignificant levels and/or a biological activity of the gene product (e.g., an enzymatic activity) is significantly reduced relative to prior to the modification or is not detectable. “Knock-outs” encompass conditional knock-outs, where alteration of the target gene can occur upon, for example, exposure to a predefined set of conditions (e.g., temperature, osmolarity, exposure to substance that promotes target gene alteration, and the like. A “knock-in” or “knockin” of a target gene refers to a genetic alteration in a host cell genome that that results in an increase in a function provided by the target gene. 
     “Non-naturally occurring”, as used herein, refers to a protein (e.g. fHbp) that is not normally found in nature and is instead artificially produced and/or modified by a human. A non-naturally occurring subject fHbp can be made via chemical synthesis or recombinant methods. For example, “non-naturally occurring chimeras” refers to “man-made chimeras” and encompass fHbp with heterologous components that are not found in nature. 
     fHBP and fHBP-Encoding Nucleic Acids 
     Before describing further exemplary chimeric fHbps contemplated by the present disclosure, it is helpful to describe naturally-occurring fHbps. 
     For convenience and clarity, the native amino acid sequence of the v.1 fHBP of the  N. meningitidis  strain MC58 (peptide ID 1) was arbitrarily selected as a reference sequence for all native v.1, v.2, and v.3 fHbp amino acid sequences, as well as for the chimeric fHbps described herein. Unless otherwise noted, amino acid residue positions are also referred herein with reference to peptide ID 1. The sequence of peptide ID 1 is presented below: 
     
       
         
           
               
            
               
                 (SEQ ID NO: 1) 
               
               
                 CSSGGGGVAADIGAGLADALTAPLDHKDKGLQSLTLDQSVRKNEKLKLAA 
               
               
                   
               
               
                 QGAEKTYGNGDSLNTGKLKNDKVSRFDFIRQIEVDGQLITLESGEFQVYK 
               
               
                   
               
               
                 QSHSALTAFQTEQIQDSEHSGKMVAKRQFRIGDIAGEHTSFDKLPEGGRA 
               
               
                   
               
               
                 TYRGTAFGSDDAGGKLTYTIDFAAKQGNGKIEHLKSPELNVDLAAADIKP 
               
               
                   
               
               
                 DGKRHAVISGSVLYNQAEKGSYSLGIFGGKAQEVAGSAEVKTVNGIRHIG 
               
               
                   
               
               
                 LAAKQ 
               
            
           
         
       
     
     Despite the diversity of variant groups and other classification schemes for the sequences listed in  FIGS. 1A-1G  (Table 7) and  FIGS. 10A-10I  (Table 9), a first analysis of 69 unique fHbp sequences and a second analysis of all 275 peptide IDs, as described in the Examples below revealed that several different stretches of amino acid sequences within the fHbps are conserved among all the fHbps analyzed. As shown by the phylogenic studies presented in the Examples section below, these conserved amino acid sequences separate fHbp into modular segments of amino acid sequences that cluster in the phylogram to define two progenitor sequences from which each variable segment may be derived. As illustrated in  FIGS. 5-7 , each of the variable segments in fHbps can be classified as being of one of the two progenitor amino acid sequences: designated for convenience, a or 3. 
     The nomenclature architecture used to characterize fHbp based on modular segments is illustrated in  FIG. 4 , panel A. The rectangles in  FIG. 4 , panel A represent the conserved sequences (I) and the variable segments are designated as the N-terminal element, V A , V B , V C , V D , or V E  segments. The amino acid sequence of the conserved sequences are listed in  FIG. 4 , panel B. 
     As such, naturally occurring fHbps can be defined by the formula: I 1 -Nte-I 2 -V A -I 3 -V B -I 4 -V C -I 5 -V D -I 6 -V E -I 7 , wherein “Nte” refers to the N-terminal element, “I” refers to an “invariant” segment, and “V” refers to a variable segment of either an α or a β progenitor type. 
     As disclosed below in more detail, the non-naturally occurring chimeric fHbps of the present disclosure can be constructed by various combinations of the V segments which are flanked by I segments. The invariant and variable segments which can be used in construction of such chimeric fHbps are described from N-terminus to C-terminus in more detail below. This modular classification can also be found on the Neisseria.org website (neisseria.org/perl/agdbnet/agdbnet.pl?file=nm_fhbp.xml). On the website the progenitor groups α and β as described below are referred to 1 and 2, respectively. For example, V A α2-V B α1-V C β5-V D α5-V E α8 becomes A1.2-B1.1-C2.5-D1.5-E1.8. 
     Invariant Segments 
     fHbps contain amino acid sequences that are conserved among all fHbp amino acid sequences analyzed herein. The conserved sequences flank variable segments that are derived from either the α or β progenitor amino acid sequences. These conserved sequences are referred to herein as “invariant sequences” or “invariant segments”, and may serve as sites of recombination in naturally-occurring fHbps. Where these invariant segments are flanked by variable segments, the invariant segments may be referred to as “linker” sequences. While these sequences exhibit amino acid sequence identity between the fHbps disclosed herein, such amino acid sequences may still tolerate certain conservative amino acid substitutions. As such, the term “invariant segment” as used herein should not be construed to be limited to the specific amino acid sequences described herein, and may at least contain one or more conservative amino acid substitutions. 
     As illustrated in  FIG. 4 , the most N-terminal invariant segment found in naturally-occurring fHbps starts at residue 1 and is of the amino acid sequence CSSG (SEQ ID NO:2). Immediately C-terminal to the first invariant segment CSSG (I 1 ) is a variable N-terminal element of about 1 to about 6 glycine or serine residues. The various N-terminal elements are listed in  FIG. 1A-1G  (Table 7) and  FIGS. 10A-10I  (Table 9). The second invariant segment (I 2 ) is of the amino acid sequence GG, which is positioned C-terminal to the N-terminal element and starts at residue 6, 7, or 11, depending on the length of the N-terminal element (e.g., in peptide ID 28 of variant 3, I 2  starts at residue 11). The next invariant segment, I 3 , is defined by the amino acid sequence of SRFDF (SEQ ID NO:3) and is positioned at residue 74, C-terminal to I 2  and a variable segment. I 4 , which is C-terminal to I 3 , is defined by the amino acid sequence GEFQ (SEQ ID NO:4) and is positioned at residue 94. I 5  is defined by the amino acid sequence DD and is C-terminal to I 4  at residue 159. I 6 , positioned C-terminal to Is, is defined by IEHLK (SEQ ID NO:5) or IEHLE (SEQ ID NO: 6) and starts at residue 180. Lastly, I 7 , the most C-terminal invariant segment in naturally-occurring fHbps, starts at residue 252 and is defined by the amino acid sequence of KQ. 
     The residue position listed above at which each invariant segment starts may be shifted from 1 to 8 residues depending on the length of the N-terminal element and the amino acid sequence of the variable segments. As noted above, for convenience and clarity residue numbering used in reference to non-naturally occurring chimeric fHbps throughout the present disclosure is based on the amino acid sequence numbering of the fHbp of MC58 (peptide ID 1), which is a variant 1 strain. 
     Based on the sequences analyzed herein, the length of the invariant segments ranges from about 2 amino acid residues to about 5 amino acid residues. 
     Variable Segments 
     As noted above, variable segments (V) are flanked by linkers, also referred herein as invariant segments (I). In addition to a variable N-terminal element, there are five variable segments in an fHbp and they are designated from N-terminus to C-terminus as V A , V B , V C , V D , and V E , each flanked by the invariant segments discussed above. As mentioned previously, each of the variable segments may be classified as being of one of the two progenitor amino acid sequences: α or β. For example, V A α indicates that variable segment A is derived from an α progenitor amino acid sequence while V A β refers to a variable segment A derived from a β progenitor amino acid sequence. In a more specific example, V A α1 denotes that the variable segment A is of the amino acid sequence set forth as Segment ID A.α.1 in  FIG. 2A  (Table 8, segment A), which is one allele of the α progenitor sequences of variable segment A. As described below, the chimeric fHbp of the present disclosure contain a non-naturally occurring combination of variable segments in which each segment may be independently selected from either an α and a β progenitor type and/or a non-naturally occurring combination of any alleles of the corresponding segment shown in  FIGS. 2A-2E , Table 8. 
     The α and β progenitor variable segments are each defined by certain signature amino acid residues. In addition, the α progenitor variable segments exhibit sequence similarity to fHbp of variant 1 group (e.g. peptide ID 1), while the β progenitor variable segments exhibit sequence similarity to fHbp of variant 3 group (e.g. peptide ID 28). Signature amino acid residues of α or β progenitors for each variable segment are be discussed below. 
     In addition to being defined by their corresponding amino acid signature sequence, variable segments of the same progenitor type share amino acid sequence identity of at least 80%, at least 85%, at least 90%, at least 95%, and can be 100%. When amino acid sequences of the same variable segments of different progenitor types are compared, the amino acid sequence identity drops by at least 10% to 40%. 
     See Table 4 in Example section below for amino acid identities within and between sequence groups by segment. 
     Various alleles for each variable segment and their sequences are presented in  FIG. 2A-2E  (Table 8) and are described in detail below. 
     The most N-terminal variable segment is referred to herein as the N-terminal element (Nte) ( FIG. 4 ). The various N-terminal elements found in the fHbps analyzed are listed in  FIGS. 1A-1G  (Table 7) and also in  FIGS. 10A-10I  (Table 9). They range in length from 1 to 6 residues of glycine or a combination of glycine and serine. 
     The variable segment V A  starts at residue 7, C-terminal to 12, and ends at residue 73, N-terminal to I 3 . V A  of an α progenitor (V A ) comprises an amino acid sequence that is about 89 to 100% identical to Segment ID A.α.1 as presented in  FIG. 2A  (Table 8): V A ADIG AG LA DAL T A P LDHK DK S LQS LT LD QSVR KN E KL K L A AQGAEK T Y GNGD S L N  TGKLKNDK V  (SEQ ID NO: 15). V A α is further characterized by signature amino acid residues QSV, bolded in sequence. Certain residues that may have alternative amino acid residues among V A α of different fHbps are underlined. 
     V A  of a β progenitor (V A β) comprises an amino acid sequence that is about 89 to 100% identical to Segment ID A.β.1 as set forth in  FIG. 2A  (Table 8): VAADIG T GLA DALTAPLDHK DKGLKSLTLE DSI P QNGTLT LSAQGAE K T F   KA GD KDN SLN TGKLKNDK I  (SEQ ID NO:67). V A β is further characterized by signature amino acid residues DSI and/or KDN, bolded in sequence. Certain residues that have alternative or deleted amino acid residues among V A β of different fHbps are underlined. 
     The variable segment V B  starts at residue 79, and ends N-terminal to where I 4  is located, at residue 93. V B  of an α progenitor (V B α) comprises an amino acid sequence that is about 80% to 100% identical to Segment ID B.α.1 as set forth in  FIG. 2B  (Table 8): I R QIEV DGQL  ITL ES  (SEQ ID NO:85). V B α is further characterized by signature amino acid residues IRQ, bolded in the sequence. Certain residues that have alternative or deleted amino acid residues among V B α of different fHbps are underlined. 
     V B  of a β progenitor (V B β) comprises an amino acid sequence that is about 100% identical to Segment ID B.β.1 as set forth in  FIG. 2B  (Table 8): VQKIEVDGQT ITLAS (SEQ ID NO:95). V B β is further characterized by signature amino acid residues VQK, bolded in the sequence. 
     The variable segment V C  starts around residue 98, C-terminal to I 4  and ends at residue 158, N-terminal to I 5 . V C  of an α progenitor (V C α) comprises an amino acid sequence that is about 85 to 100% identical to Segment ID C.α.1 as presented in  FIG. 2C  (Table 8): VYKQS H SALT A L QTE QV QD S  E H S GK MVAKR  Q F R IGDI A GE HT S FDKL PEG   GRAT YRGTAF  G S (SEQ ID NO:96). V C α is further characterized by signature amino acid residues QDS, bolded in the sequence. Certain residues that have alternative or deleted amino acid residues among V C α of different fHbps are underlined. 
     V C  of a β progenitor (V C β) comprises an amino acid sequence that is about 93 to 100% identical to Segment ID C.β.1 as presented in  FIG. 2C  (Table 8): IYK QD HSAVV ALQIEKINNP DK I DSLINQR SFLVSGLGGE HTAFNQL PG   G KAEYHGKAF S S  (SEQ ID NO:152). V C β is further characterized by signature amino acid residues NNP, bolded in sequence. This signature is found in all of V C β amino acid sequences. Certain residues that have alternative or deleted amino acid residues among V C β of different fHbps are underlined. 
     The variable segment V D  starts at residue 161, C-terminal to I 5  and ends at residue 179, N-terminal to I 6 . V D  of an α progenitor (V D α) comprises an amino acid sequence that is about 89 to 100% identical to Segment ID D.α.1 as presented in  FIG. 2D  (Table 8): A G GKL T YTID FA A KQG H GK (SEQ ID NO: 174). V D α is further characterized by signature amino acid residues AG or AS, of which AG is bolded in sequence. Certain residues that have alternative or deleted amino acid residues among V D α of different fHbps are underlined. 
     V D  of a β progenitor (V D β) comprises an amino acid sequence that is about 84 to 100% identical to Segment ID D.β.1 as presented in  FIG. 2D  (Table 8): PNGRLHY S ID FTKKQGYG R  (SEQ ID NO: 192). V D β is further characterized by signature amino acid residues PN, bolded in sequence. Certain residues that have alternative or deleted amino acid residues among V D β of different fHbps are underlined. 
     The variable segment V E  starts around residue 185, C-terminal to I 6  and ends at residue 253, N-terminal to I 7 . V E  of an α progenitor (V E α) comprises an amino acid sequence that is about 86 to 100% identical to Segment ID E.α.1 as presented in  FIG. 2E  (Table 8): SPELNV D LA A   AY IKPD E K HH  AVISGSVLYN Q A EKGSYSLG IFG GKA QEVA  GSAE V K T V NG I R HIGLAA (SEQ ID NO:195). V E α is further characterized by signature amino acid residues SLGI, bolded in sequence. Certain residues that have alternative or deleted amino acid residues among V E α of different fHbps are underlined. 
     V E  of a β progenitor (V E β) comprises an amino acid sequence that is about 94 to 100% identical to Segment ID E.β.1 as set forth in  FIG. 2E  (Table 8):  T PE Q NV E LA S  AELKADEKSH AVILGDTRY G   G EEKGTYHLA LFGDRAQEIA GSATVKI R E K  VHEI G IAG (SEQ ID NO:262). V E β is further characterized by signature amino acid residues HLAL, bolded in sequence. Certain residues that have alternative or deleted amino acid residues among V E β of different fHbps are underlined. 
     As noted above, for convenience and clarity residue numbering used in reference to non-naturally occurring chimeric fHbps throughout the present disclosure is based on the amino acid sequence numbering of the fHbp of MC58 (peptide ID 1). In addition, the residue position listed above at which each variable segment starts and ends may be shifted from 1 to 8 residues depending on the length of the N-terminal element and the amino acid sequence of the variable segments. 
     fHbp Modular Groups 
     Naturally occurring fHbp amino acid sequences can be described according to a modular architecture based on a combination of α or β progenitor segments flanked by invariable segments, as shown in  FIG. 1A-1G  (Table 7) and  FIGS. 10A-10I  (Table 9). As described in the Examples below, naturally occurring fHbps exhibit particular combinations of modular segments, and can be classified accordingly into nine modular group types as shown in  FIG. 8 , where gray variable segments correspond to the α progenitor sequences and white segments correspond to the β progenitor sequences. 
     The Type I modular group is characterized by variable segments, all of which are derived from the α progenitor amino acid sequences. FHbps classified as belonging to the Type I modular group may be represented by the following formula: I 1 -Nte-I 2 -V A α-I 3 -V B α-I 4 -V C α-I 5 -V D α-I 6 -V E α-I 7 . An example of a fHbp that is of the Type I modular group is peptide ID 1 from strain MC58. As noted above, peptide ID is from the factor H-binding protein database at Neisseria.org. 
     The Type II modular group is characterized by variable segments, all of which are derived from the β progenitor. FHbps classified as belonging to the Type II modular group may be represented by the following formula: I 1 -Nte-I 2 -V A β-I 3 -V B β-I 4 -V C β-I 5 -V D β-I 6 -V E β-I 7 . An example of a fHbp that is of the Type II modular group is peptide ID 28 from strain M1239. Nearly 60% of the fHbps in  FIG. 1A-1G  (Table 7) belong in either Type I or II modular group. 
     Some fHbp, however, have variable segments from both α and β progenitors. One modular group defined by variable segments derived from both progenitors is Type III, in which variable segments V A  and V B  are derived from the α progenitor and the rest of the variable segments from the β progenitor. FHbps classified as belonging to the Type III modular group may be represented by the following formula: I 1 -Nte-I 2 -V A α-I 3 -V B -I 4 -V C β-I 3 -V D β-I 6 -V E β-I 7 . One example of a fHbp that belongs to the Type III modular group is peptide ID 22 from strain RM1090. 
     Another modular group defined by variable segments derived from both progenitors is Type IV. Type IV is a modular group that has a variable segment V A  derived from the β progenitor and the rest of the variable segments from the α progenitor. FHbps classified as belonging to the Type IV modular group may be represented by the following formula: I 1 -Nte-I 2 -V A β-I 3 -V B α-I 4 -V C α-I 5 -V D α-I 6 -V E α-I 7 . One example of a fHbp that belongs to the Type IV modular group is peptide ID 15 from strain NM452. 
     An additional modular group is Type V, in which the variable segment V D  is derived from the α progenitor and the rest of the variable segments from the β progenitor. FHbps classified as belonging to the Type V modular group may be represented by the following formula: I 1 -Nte-I 2 -V A β-I 3 -V B β-I 4 -V C β-I 5 -V D -I 6 -V E β-I 7 . One example of a fHbp that belongs to the Type V modular group is peptide ID 79 from strain S3032. 
     Another modular group set forth in  FIG. 8  is Type VI, in which variable segments V C  and V E  are derived from the β progenitor and the rest of the variable segments from the α progenitor. FHbps classified as belonging to the Type VI modular group may be represented by the following formula: I 1 -Nte-I 2 -V A α-I 3 -V B α-I 4 -V C β-I 5 -V D α-I 6 -V E β-I 7 . One example of a fHbp that belongs to the Type VI modular group is peptide ID 16 from strain 961-5945. 
     Another modular group set forth in  FIG. 8  is Type VII, in which variable segment V E  are derived from the β progenitor and the rest of the variable segments from the α progenitor. FHbps classified as belonging to the Type VI modular group may be represented by the following formula: I 1 -Nte-I 2 -V A α-I 3 -V B α-I 4 -V C β-I 5 -V D α-I 6 -V E β-I 7 . One fHbp found to have the Type VI modular group is peptide ID 207 from strain 0167/03. 
     Another modular group set forth in  FIG. 8  is Type VIII, in which variable segments V B  is derived from the α progenitor and the rest of the variable segments from the β progenitor. FHbps classified as belonging to the Type VI modular group may be represented by the following formula: I 1 -Nte-I 2 -V A β-I 3 -V B α-I 4 -V C β-I 5 -V D β-I 6 -V E β-I 7 . One fHbp found to have the Type VIII modular group is peptide ID 67 from strain MA-5756. 
     The last modular group set forth in  FIG. 8  is Type IX, in which variable segments V B  and V D  are derived from the α progenitor and the rest of the variable segments from the β progenitor. FHbps classified as belonging to the Type VI modular group may be represented by the following formula: I 1 -Nte-I 2 -V A β-I 3 -V B α-I 4 -V C β-I 5 -V D α-I 6 -V E β-I 7 . One Example of a fHbp that belongs to the Type IX modular group is peptide ID 175 from strain 19498. 
     More than 98% of the unique fHbp amino acid sequences analyzed herein belong to one of the first six types of modular groups (I, II, III, IV, V, and VI) described above and schematically presented in  FIG. 8 . The numbers of unique fHbp that belong to each of the modular groups are also listed on the right of the schematic in  FIG. 8 . 
     Four naturally occurring fHbps vary at least slightly from this nomenclature, and do not precisely fit into the first six modular group types set forth in  FIG. 8 , panel A. These four fHbps “switch” from one progenitor amino acid sequence to another at a residue position that is within a canonical variable segment as described above. As a result, they each contain a heterologous variable segments and their junction points deviate from junction points of the rest of the fHbps found to be at I 3 , I 4 , I 5 , or I 6  defined above. See  FIG. 8 , panel B for the modular architecture of these four fHbps along with the arrow pointing at the junction point for each. However, the junction points of these four naturally occurring fHbps still reside at conserved residue(s) found within the variable segment. See table in  FIG. 8 , panel C. 
     One such fHbp is a naturally occurring fHbp derived from strain CDC-1573 (peptide ID 55), in which the junction point where V A β switches to V A α resides in the middle of V A . The heterologous V A  of peptide ID 55 may be represented as V A (β→α), signifying that the variable segment A comprises a β progenitor amino acid sequence starting at the N-terminus and switches to an α progenitor amino acid sequence toward the C-terminus. The junction point (J 1 ) of peptide ID 55 resides at a sequence of AQGAE (SEQ ID NO:278) conserved among all the V A  sequences, which starts at residue position 50. Two other fHbps, which contain junction points that are not in the residue position of I 3 , I 4 , I 5 , or I 6 , are peptide ID 24 and peptide ID 25, derived from strain M08 240117 and strain 6275, respectively. Their junction points (J 2 ) at which V B α switches to V B β reside in the middle of V B  (residue 82), at which there is an amino acid sequence of IEV) conserved among all V B s. The V B  of peptide ID 24 and 25 may be represented as V B (α→β). Lastly, peptide ID 82 from strain MD1475 switches from V E α to V E β at residue A196 (J 3 ), which is conserved among all V E . The variable segment E of peptide ID 82 may be represented as V E (α→β). 
     As will be discussed in detail below, chimeric fHbps can be constructed using the invariant and variable segments of this modular architecture to produce amino acid sequences not found in nature. 
     Nucleic Acids Encoding fHbp Segments 
     fHbp polypeptides, and encoding nucleic acids, from which segments of the chimeric fHbps of the present disclosure can be derived may be from any suitable  N. meningitidis  strain. As is known in the art,  N. meningitidis  strains are divided into serologic groups (capsular groups), serotypes (PorB phenotypes) and subtypes (PorA phenotypes) on the basis of reactions with polyclonal (Frasch, C. E. and Chapman, 1973 , J. Infect. Dis.  127: 149-154) or monoclonal antibodies that interact with different surface antigens. Capsular grouping traditionally has been based on immunologically detectable variations in the capsular polysaccharide but is being replaced by PCR of genes encoding specific enzymes responsible for the biosynthesis of the structurally different capsular polysaccharides. About 12 capsular groups (including A, B, C, X, Y, Z, 29-E, and W-135) are known. Strains of the capsular groups A, B, C, Y and W-135 account for nearly all meningococcal disease. Serotyping traditionally has been based on monoclonal antibody defined antigenic differences in an outer membrane protein called Porin B (PorB). Antibodies defining about 21 serotypes are currently known (Sacchi et al., 1998 , Clin. Diag. Lab. Immunol.  5:348). Serosubtyping has been based on antibody defined antigenic variations on an outer membrane protein called Porin A (PorA). Both serotyping and serosubtyping are being replaced by PCR and/or DNA sequencing for identification of genes encoding the variable regions of PorB and PorA, respectively that are associated with mAb reactivity (e.g. Sacchi, Lemos et al., supra; Urwin et al., 1998 , Epidem. and Infect.  120:257). 
     While  N. meningitidis  strains of any capsular group may be used,  N. meningitidis  strains of capsular group B are of particular interest as sources from which nucleic acid encoding fHbp and domains thereof are derived. 
     While the specification provides the amino acid sequence of examples of fHbps from which the chimeric fHbp can be derived, this is not intended to be limiting. For example, the chimeric fHbp can contain amino acid sequences that are at least 80%, at least 85%, at least 90%, or at least 95% identical to an amino acid sequence of a naturally occurring fHbp. 
     Nucleic acids encoding fHbp polypeptides for use in construction of chimeric fHbps contemplated herein are known in the art. Examples of fHbp polypeptides are described in, for example, WO 2004/048404; Masignani et al. 2003 J Exp Med 197:789-799; Fletcher et al. Infect Immun 2004 2088-2100; Welsch et al. J Immunol 2004 172:5606-5615; and WO 99/57280. Nucleic acid (and amino acid sequences) for fHbp variants and subvariants are also provided in GenBank as accession nos.: NC_003112, GeneID: 904318 (NCBI Ref. NP_274866), peptide ID 1 from  N. meningitidis  strain MC58; AY548371 (AAT01290.1) (from  N. meningitidis  strain CU385); AY548370 (AAT01289.1) (from  N. meningitidis  strain H44/76); AY548377 (AAS56920.1) peptide ID 4 from  N. meningitidis  strain M4105; AY548376 (AAS56919.1) (from  N. meningitidis  strain M1390); AY548375 (AAS56918.1) (from  N. meningitidis  strain NZ98/254); AY548374 (AAS56917.1) (from  N. meningitidis  strain M6190); AY548373 (AAS56916.1) (from  N. meningitidis  strain 4243); and AY548372 (AAS56915.1) (from  N. meningitidis  strain BZ83). 
     For purposes of identifying relevant amino acid sequences contemplated for use in the chimeric fHbps disclosed herein, it should be noted that the immature fHbp protein includes a leader sequence of about 19 residues. Furthermore, when provided an amino acid sequence the ordinarily skilled person can readily envision the sequences of nucleic acid that can encode for, and provide for expression of, a polypeptide having such an amino acid sequence. 
     In addition to the specific amino acid sequences and nucleic acid sequences provided herein, the disclosure also contemplates polypeptides and nucleic acids having sequences that are at least 80%, at least 85%, at least 90%, or at least 95% identical in sequence to the amino acid and nucleic acids. The terms “identical” or percent “identity,” in the context of two or more polynucleotide sequences, or two or more amino acid sequences, refers to two or more sequences or subsequences that are the same or have a specified percentage of amino acid residues or nucleotides that are the same (e.g., at least 80%, at least 85%, at least 90%, or at least 95% identical over a specified region), when compared and aligned for maximum correspondence over a designated region, e.g., a V E  or a region at least about 40, 45, 50, 55, 60, 65 or more amino acids or nucleotides in length, and can be up to the full-length of the reference amino acid or nucleotide sequence (e.g., a full-length fHbp). The disclosure specifically contemplates both naturally-occurring polymorphisms and synthetically produced amino acid sequences and their encoding nucleic acids. 
     For sequence comparison, typically one sequence acts as a reference sequence (e.g., a naturally-occurring fHbp polypeptide sequence), to which test sequences are compared. When using a sequence comparison algorithm, test and reference sequences are input into a computer program, sequence coordinates are designated, if necessary, and sequence algorithm program parameters are designated. The sequence comparison algorithm then calculates the percent sequence identity for the test sequence(s) relative to the reference sequence, based on the designated program parameters. 
     Examples of algorithms that are suitable for determining percent sequence identity are the BLAST and BLAST 2.0 algorithms, which are described in Altschul et al. (1990) J. Mol. Biol. 215: 403-410 and Altschul et al. (1977) Nucleic Acids Res. 25: 3389-3402, respectively. Software for performing BLAST analyses is publicly available through the National Center for Biotechnology Information (www.ncbi.nlm.nih.gov). Further exemplary algorithms include ClustalW (Higgins D., et al. (1994) Nucleic Acids Res 22: 4673-4680), available at www.ebi.ac.uk/Tools/clustalw/index.html. 
     In one embodiment, residue positions which are not identical differ by conservative amino acid substitutions. Conservative amino acid substitutions refer to the interchangeability of residues having similar side chains. For example, a group of amino acids having aliphatic side chains is glycine, alanine, valine, leucine, and isoleucine; a group of amino acids having aliphatic-hydroxyl side chains is serine and threonine; a group of amino acids having amide-containing side chains is asparagine and glutamine; a group of amino acids having aromatic side chains is phenylalanine, tyrosine, and tryptophan; a group of amino acids having basic side chains is lysine, arginine, and histidine; and a group of amino acids having sulfur-containing side chains is cysteine and methionine. 
     Sequence identity between two nucleic acids can also be described in terms of hybridization of two molecules to each other under stringent conditions. The hybridization conditions are selected following standard methods in the art (see, for example, Sambrook, et al., Molecular Cloning: A Laboratory Manual, Second Edition, (1989) Cold Spring Harbor, N.Y.). An example of stringent hybridization conditions is hybridization at 50° C. or higher and 0.1×SSC (15 mM sodium chloride/1.5 mM sodium citrate). Another example of stringent hybridization conditions is overnight incubation at 42° C. in a solution: 50% formamide, 5×SSC (150 mM NaCl, 15 mM trisodium citrate), 50 mM sodium phosphate (pH7.6), 5×Denhardt&#39;s solution, 10% dextran sulfate, and 20 mg/ml denatured, sheared salmon sperm DNA, followed by washing the filters in 0.1×SSC at about 65° C. Stringent hybridization conditions are hybridization conditions that are at least as stringent as the above representative conditions, where conditions are considered to be at least as stringent if they are at least about 80% as stringent, typically at least 90% as stringent as the above specific stringent conditions. 
     The chimeric fHbps of the present disclosure are described in more detail below in the context of modular architecture described above. 
     Chimeric Factor H Binding Proteins 
     The chimeric fHbp of the present disclosure refers to non-naturally occurring chimeric fHbp, including fHbps that may be described by a modular architecture as those set forth in  FIG. 8 , panels A and B and a modular architecture not shown in  FIG. 8 , panels A and B. The term “chimeric factor H binding protein” or “chimeric fHbp” refers to a polypeptide comprising, from N-terminus to C-terminus, a group of five variable segments represented by V A , V B , V C , V D , and V E , in which the combination of α/β progenitor segments and/or combination of alleles of which is not found in nature. One example of the chimeric fHbps of the present disclosure can contain at least one or more of the variable segments derived from a different progenitor than at least one other variable segment in the chimeric fHbp. In other words, the chimeric fHbp contains at least one variable segment of an α progenitor amino acid sequences and at least one variable segment of a β progenitor, such that the combination is not found in nature. In another example, the fHbp may also be of a modular architecture shown in  FIG. 8 , panel A (e.g. modular I or II in which all variable segments are α or β, respectively), in which each segment is of an allele such that the combination of the alleles is not found in nature. 
     The variable segments may be flanked by invariant segments (I 2 , I 3 , I 4 , I 5 , I 6 , I 7 ), which can act as linkers for the variable segments. Accordingly, the chimeric fHbps of the present disclosure can be described by the formula: 
         V   A - I   3 - V   B - I   4 - V   C - I   5 - V   D - I   6 - V   E    
     wherein each of the variable segments (V A , V B , V C , V D , and V E ) can be derived from either an α or a β progenitor amino acid sequence. 
     Chimeric fHbp can optionally include a leader sequence, e.g., to provide for expression of the chimeric fHbp on a cell surface of a bacterial host cell. Chimeric fHbp may also include about 1, 5, 10, or more residues as an N-terminal element (Nte) and/or C-terminal element (Cte). For example, the Nte may comprise 1, 2, or 6 glycine residues, or about 6 residues of a mixture of glycines and serines following the N-terminal most invariant segment (I 1 ). 
     In addition, chimeric fHbps of the present disclosure can optionally include an N-terminal element, one or both of invariant segments that flank the N-terminal element, and/or most C-terminal invariant segment (1 7 ). A chimeric fHbp comprising one or more of these optional features can be described by the following formula: 
         I   2 - V   A - I   3 - V   B - I   4 - V   C - I   5 - V   D - I   6 - V   E ; 
         Nte - I   2 - V   A - I   3 - V   B - I   4 - V   C - I   5 - V   D - I   6 - V   E ; 
         I   1 - Nte - I   2 - V   A - I   3 - V   B - I   4 - V   C - I   5 - V   D - I   6 - V   E ; 
         V   A - I   3 - V   B - I   4 - V   C - I   5 - V   D - I   6 - V   E - I   7 ; 
         I   2 - V   A - I   3 - V   B - I   4 - V   C - I   5 - V   D - I   6 - V   E - I   7 ; 
         Nte - I   2 - V   A - I   3 - V   B - I   4 - V   C - I   5 - V   D - I   6 - V   E - I   7 ; and 
         I   1 - Nte - I   2 - V   A - I   3 - V   B - I   4 - V   C - I   5 - V   D - I   6 - V   E - I   7 . 
     in which the variable segments (V A , V B , V C , V D , and V E ) can be derived from either an α or β progenitor amino acid sequence. 
     In addition to having various combinations of variable segments, each derived from either an α or β progenitor amino acid sequence, chimeric fHbp of the present disclosure may also contain one or more variable segments that are heterologous with respect to α and β progenitor amino acid sequences. A heterologous variable segment refers to a variable segment that comprises both a contiguous α and a contiguous β progenitor amino acid sequences, with the point at which the amino acid sequence “switches” to the other progenitor sequence referred to herein as a “junction point”. E.g. See V A  of peptide ID 55, V B  of peptide ID 24 and ID 25, and V E  of peptide ID 82. Particularly, one or more of the junction points (J 1 , J 2 , or J 3 ) within a variable segment described above for peptide ID 55, 24, 25, and 82 may be used to construct a chimeric fHbp having a heterologous variable segment. See table in  FIG. 8 , panel C for the conserved residues in each variable segment that serve as junction points. 
     Variable segments of the non-naturally occurring chimeric fHbps of the present disclosure may have an amino acid sequence of at least 80%, at least 85%, at least 90%, at least 95% identical to a corresponding segment in a naturally occurring fHbp, and can be 100% identical in amino acid sequence. 
     Examples of chimeric fHbps include those containing one or more of the following variable segments. Each segment can be independently selected from any alleles in the corresponding segment shown in  FIGS. 2A-2E , Table 8. The variable segments are described in more detail below using certain alleles as examples. 
     VA contains a contiguous amino acid sequence that is at least 85%, at least 90%, or at least 95% identical to Segment ID A.α.1 or A.β.1 (SEQ ID NO:15 or NO:67) shown in  FIG. 2A  (Table 8), e.g., at least 85%, at least 90%, or at least 95% identical to one of the amino acid sequences shown in  FIG. 2A  (Table 8) for Segment A. 
     V B  contains a contiguous amino acid sequence that is at least 75%, at least 80%, at least 90%, or at least 95% identical to Segment ID B.α.1 or B.β.1 (SEQ ID NO:85 or NO:95) shown in  FIG. 2B  (Table 8), e.g., at least 75%, at least 80%, at least 90%, or at least 95% identical to one of the amino acid sequences shown in  FIG. 2B  (Table 8) for Segment B. 
     V C  contains s a contiguous amino acid sequence that is at least 80%, at least 85%, at least 90%, or at least 95% identical to Segment ID C.α.1 or C.β.1 (SEQ ID NO:96 or NO:152) shown in  FIG. 2C  (Table 8), e.g., at least 80%, at least 85%, at least 90%, or at least 95% identical to one of the amino acid sequences shown in  FIG. 2C  (Table 8) for Segment C. 
     V D  contains a contiguous amino acid sequence that is at least 80%, at least 85%, at least 90%, or at least 95% identical to Segment ID D.α.1 or D.β.1 (SEQ ID NO:174 or NO:192) shown in  FIG. 2D  (Table 8), e.g., at least 80%, at least 85%, at least 90%, or at least 95% identical to one of the amino acid sequences shown in  FIG. 2D  (Table 8) for Segment D. 
     V E  contains a contiguous amino acid sequence that is at least 80%, at least 85%, at least 90%, or at least 95% identical to Segment ID E.α.1 or E.β.1 (SEQ ID NO: 195 or NO:262) shown in  FIG. 2E  (Table 8), e.g., at least 80%, at least 85%, at least 90%, or at least 95% identical to one of the amino acid sequences shown in  FIG. 2E  (Table 8) for Segment E. 
     The variable segments in the chimeric fHbp of the present disclosure may also be of the similar length as the corresponding segments listed in  FIG. 2A-2E  (Table 8). For example, a variable segment may be no more than about 50, 30, 20, 10, 5, or 1 amino acid residues less or more than one of the corresponding amino acid sequences shown in  FIG. 2A-2E  (Table 8). 
     The chimeric fHbps of the present disclosure have a full length amino acid sequence that is not found in a naturally occurring fHbp. Most of the naturally occurring fHbps which contain only α or only β progenitor sequences or combinations thereof fall into one of the following modular groups: I, II, III, IV, V, VI, VII, VIII, or IX (see  FIG. 8 ). Non-naturally occurring fHbps of the present disclosure can also be of a modular group other than I, II, III, IV, V, VI, VII, VIII, or IX. The non-naturally occurring fHbps of the present disclosure can be described by new modular groups encompassing non-naturally occurring amino acid sequences that are built based on the modular architecture described herein. Some examples of chimeric fHbps of the present disclosure are presented below. 
     Examples of Chimeric fHbps 
     The chimeric fHbps of the present disclosure encompass those that can be described in terms of one or more of, for example, the invariant and variable segments and their progenitor type, the presence or absence of an epitope(s) specifically bound by a mAb, or any combination of such features that may be present in the chimeric fHbps. 
     Many combinations may be generated by switching α or β segments in and out of various segments for a different type of modular group. Any alleles of α or β segments can also be independently chosen from those shown  FIG. 2A-2E  (Table 8). Modular group may also be designed to maintain or include certain antibody epitopes. Certain antibodies are found to be bactericidal against a specific variant of  N. meningitidis  but not a different variant. If a chimeric fHbp of a modular group contains variable segments that present multiple epitopes, each specific for an antibody bactericidal against a different variant, the chimeric fHbp may be useful to elicit antibodies or immune response effective against a broad spectrum of  N. meningitidis . For example, in a case where epitopes for JAR4, JAR3, and JAR32 antibodies are known and are desirable to be incorporated into an fHbp, a chimeric fHbp may be made to comprise V A α, V C α, and V D β, where epitopes of JAR4, JAR3, and JAR32 reside, respectively. 
     For example, a chimeric fHbp may have V D  that is derived from 3 progenitor sequences while the rest of the variable segments remain as derivations from α progenitor sequences. Such chimeric fHbp comprises variable segments represented as V A α, V B α, V C α, V D β, and V E α; and its first and second junction points are at I 5  and I 6 , respectively. In a different example, an fHbp belonging to another modular group encompassing non-naturally occurring chimeric fHbp may contain V A α, V B α, V C α, V D β, and V E β; and its junction point resides at Is. An additional example of a modular group encompasses non-naturally occurring fHbp that comprises V A α, V B α, V C α, V D α, and V E β as the invariable segments. 
     Accordingly, examples of non-naturally occurring chimeric fHbps including those described above may be of modular groups represented by the following formula but not limited to: 
         V   A α- I   3 - V   B α- I   4 - V   C α- I   5 - VD β- I   6 - V   E α;
 
         V   A α- I   3 - V   B α- I   4 - V   C α- I   5 - V   D β- I   6 - V   E β;
 
         V   A α- I   3 - V   B α- I   4 - V   C α- I   5 - V   D α- I   6 - V   E β;
 
         V   A α- I   3 - V   B α- I   4 - V   C α- I   5 - V   D - I   6 - V   E α;
 
         V   A α- I   3 - V   B β- I   4 - V   C - I   5 - V   D - I   6 - V   E ;
 
         V   A β- I   3 - V   B α- I   4 - V   C α- I   5 - V   D α- I   6 - V   E β;
 
         V   A β- I   3 - V   B α- I   4 - V   C α- I   5 - V   D β- I   6 - V   E α;
 
         V   A β- I   3 - V   B α- I   4 - V   C - I   5 - V   D - I   6 - V   E ;
 
         V   A β- I   3 - V   B - I   4 - V   C - I   5 - V   D α- I   6 - V   E α; or
 
         V   A β- I   3 - V   B β- I   4 - V   C - I   5 - V   D β- I   6 - V   E α;
 
     In any group shown above in which a variable segment (V A , V B , V C , V D , or V E ) is not followed by an α or a β (e.g. V C , V D , and V E  in the fifth modular group from the top) represents a variable segment that can be derived from either an α or a β progenitor amino acid sequence. The formula may also include a variable N-terminal element, its flanking invariable sequences (I 1  and I 2 ), or the most C-terminal invariable segment (I 7 ), omitted in the formula above. As noted above for fHbp of the present disclosure, each variable segment of the fHbps described by the formulas above can be of any allele. 
     In another example, the chimeric fHbp of the present disclosure also encompass those that contain all a or all 0 segments, in which each of the segments is of an allele such that the combination of all a or all 0 allelic segments is not found in nature. 
     Chimeric fHbp Comprising Heterologous Variable Segment 
     In certain cases, non-naturally occurring fHbp of the present disclosure may comprise one or more heterologous variable segments. These heterologous variable segment-containing fHbps may also be described by modular architectures other than those set forth in  FIG. 8 , panel A. Thus, for example, non-naturally occurring fHbp of the present disclosure include those having: a heterologous V A (β→α), but do not have α progenitor sequence for all of V B , V C , V D , and V E ; a heterologous V B (α→β), but do not have a V A  of α progenitor sequence together with V C , V D , and V E  of β progenitor sequence; and a heterologous V E (α→β), but do not have β progenitor sequence for all of V A , V B , and V C  together with a progenitor sequence for V D . Exemplary non-naturally occurring fHbps are presented by several examples below, each containing one heterologous variable segment. However, non-naturally occurring fHbps are not limited to the examples, e.g. an fHbp may comprise more than one heterologous variable segment. 
     For example, a heterologous variable segment-containing fHbp may be one comprising a heterologous V A , such as V A (β→α) as exemplified by peptide ID 55, in which not all of V B , V C , V D , and V E  are of the α progenitor amino acid sequences. A non-naturally occurring fHbp may also comprise V A (α→β), and in which V B , V C , V D , and V E  are independently selected from α and β. Another exemplary non-naturally occurring fHbp may comprise V B (α→β) as exemplified by peptide ID 24, in which V A  is of a α progenitor and not all of V C , V D , and V E  are of the β progenitor amino acid sequences. A non-naturally occurring fHbp may comprise V B (αβ), in which V A  is of a β progenitor. A non-naturally occurring fHbp may comprise V B (β→α) in which V A , V C , V D , and V E  are independently selected from α and β. Additionally, a non-naturally occurring fHbp may comprise a heterologous V E , such as V E (αβ) seen in peptide ID 82, together with V D α, in which not all of V A , V B , V C  are of the β progenitor origin. A non-naturally occurring fHbp may comprise V E (αβ) together with V D β, in which V A , V B , and V C  are independently selected from a and β. Another example of a non-naturally occurring fHbp that contains a heterologous variable segment is one that comprises V E (β→α), in which V A , V B , V C , and V D  are independently selected from a and 3. 
     Chimeric fHbp Having Modified Epitope(s) 
     The chimeric fHbp of the present disclosure may comprise one or more variable segments in which one or more residues may be mutated relative to the amino acid sequence found in the naturally occurring fHbp so as to introduce an epitope of interest. These epitopes are referred to herein “heterologous epitopes” since they are heterologous to the variable segment in which they reside. Site-directed mutagenesis may be used to introduce one or more heterologous epitopes for a specific antibody of interest into a variable segment that naturally does not contain such epitope. As such, mutations to insert, delete, or substitute one or more amino acid residues may be used to create chimeric fHbp of the present disclosure. Various mutations may be also screened for an fHbp that is effective as vaccines or may be immunogenic to elicit bactericidal antibodies. 
     For example, an fHbp may comprise an epitope that binds to an antibody JAR13, normally found in V E  of a β progenitor sequence and not in an α progenitor sequence. To generate a fHbp that includes V E α while at the same time contains the JAR13 epitope, the epitope may be introduced into a V E α sequence. Selective mutation allows the amino acid sequence of V E  to be derived from the α progenitor type except for a specific site for the JAR13 epitope. As such, regardless of the amino acid sequence used to derive the sequences of the variable segments of the chimeric fHbp, epitopes may be introduced into the corresponding variable segment to include or maintain regions of desired antigenicity. 
     Chimeric fHbps also encompass chimeric fHbp that contain two or more epitopes that elicit antibodies that, when both are bound to their respective epitopes, exhibit enhanced bactericidal activity against  N. meningitidis  than when either one is bound alone. For example, the combination of JAR 4 and JAR 5 mAbs exhibit higher level of bactericidal activity against  N. meningitidis  than when each is used alone in a human-complement-mediated assay. Chimeric fHbp can be designed so as to ensure that such epitopes are maintained or to introduce such combination of epitopes. Chimeric fHbps can also be designed to include an epitope(s) that elicits antibodies that, when bound to fHbp, inhibit fH binding. For example, when the epitopes bound by the monoclonal antibodies JAR3, JAR 5, JAR11, or JAR32/35 are bound by antibody, binding of fHbp to fH is inhibited. Thus, the presence of such fH-binding epitopes in the chimeric fHbp polypeptides can provide for production of antibodies that can facilitate protection through this pathway. 
     The antibodies that bind epitopes that may be of interest to introduce or maintain in the segments of a chimeric fHbp are disclosed in WO 09/114485, the disclosure of which is incorporated in its entirety by reference. Certain epitopes of interest with a corresponding JAR mAbs are presented in the table 1 below and pointed out in  FIG. 9 , panel C. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Antibodies and their corresponding epitopes. 
               
            
           
           
               
               
               
               
            
               
                   
                 (Immunogen) 
                   
                   
               
               
                   
                 Antibody 
                 Reactive Residue(s) 
                 fHbp variant bound 
               
               
                   
               
               
                   
                 mAb 502 
                 R204 
                 1 
               
               
                   
                 JAR 3 
                 G121 and K122 
                 1 
               
               
                   
                 JAR 4 
                 DHK (starting at 25); 
                 v.1, v.2 (high reactivity) 
               
               
                   
                   
                 YGN (starting at 57) 
                 and v.3 (lower reactivity) 
               
               
                   
                 JAR 5 
                 G121 and K122 
                 v.1 
               
               
                   
                 JAR 10 
                 K180 and E192 
                 v.1 (subset), v.2 (subset) 
               
               
                   
                   
                   
                 and v.3 (subset) 
               
               
                   
                 JAR 11 
                 A174 
                 v.2 (subset) and v.3 
               
               
                   
                   
                   
                 (subset) 
               
               
                   
                 JAR 13 
                 S216 
                 v.2 (subset) and v.3 
               
               
                   
                   
                   
                 (all) 
               
               
                   
                 JAR 32 
                 K174 
                 v.3 and v.2 (subset) 
               
               
                   
                 JAR 33 
                 E180 and R192 
                 v.3 and v.2 (subset) 
               
               
                   
                 JAR 35 
                 K174 
                 v.3 and v.2 (subset) 
               
               
                   
               
            
           
         
       
     
     Other Features of Interest 
     Chimeric polypeptides described herein can include additional heterologous amino acid sequences, e.g., to provide an N-terminal methionine or derivative thereof (e.g., pyroglutamate) as a result of expression in a bacterial host cell (e.g.,  E. coli ) and/or to provide a chimeric polypeptide having a fusion partner at its N-terminus or C-terminus. Fusion partners of interest include, for example, glutathione-S-transferase (GST), maltose binding protein (MBP), His 6 -tag, and the like, as well as leader peptides from other proteins, particularly lipoproteins. Fusion partners can provide for additional features, such as in facilitating isolation and purification of the chimeric polypeptide. 
     Native fHbp usually contains an N-terminal cysteine to which a lipid moiety can be covalently attached. This cysteine residue is usually lipidated in the naturally-occurring protein, and can be lipidated in the chimeric fHbps disclosed herein. Thus, in the amino acid sequences described herein (including those presented in any Sequence Listing), reference to “cysteine” or “C” at this position specifically includes reference to both an unmodified cysteine as well as to a cysteine that is lipidated (e.g., due to post-translational modification). Thus, the chimeric fHbp can be lipidated or non-lipidated. Methods for production of lipidated proteins in vitro, (see, e.g., Andersson et al., 2001 J. Immunological Methods 255(1-2):135-48) or in vivo are known in the art. For example, lipidated fHbp previously has been purified from the membrane fraction of  E. coli  protein by detergent extraction (Fletcher et al., 2004 Infection and Immunity 72(4):2088-100), which method may be adapted for the production of lipidated chimeric fHbp. Lipidated proteins may be of interest as such can be more immunogenic than soluble protein (see, e.g., Fletcher et al., 2004 Infection and Immunity 72(4):2088-100). 
     Nucleic Acid Encoding Chimeric fHBP 
     The chimeric fHbp can be generated using recombinant techniques to manipulate nucleic acids of different fHbps known in the art to provide constructs encoding a chimeric fHbp of interest. As noted above, nucleic acids encoding a variety of different v.1, v.2, and v.3 fHbps of  N. meningitidis  are available in the art, and their nucleotide sequences are known. 
     Amino acid and nucleic acid sequences of the naturally occurring fHbps are provided in  FIG. 2A-2E  (Table 5) and available in the art. It will be appreciated that the nucleotide sequences encoding the chimeric fHbps can be modified so as to optimize the codon usage to facilitate expression in a host cell of interest (e.g.,  E. coli, N. meningitidis , human (as in the case of a DNA-based vaccine), and the like). Methods for production of codon optimized sequences are known in the art. 
     Methods of Screening 
     The present disclosure also features methods of screening for an immunogenic composition comprising a chimeric fHbp, vaccine against bacterial pathogens, antibodies and nucleic acid encoding the same. The methods may involve evaluating the ability of a specific chimeric fHbp to elicit bactericidal antibodies and/or to provide a broad spectrum immunity against bacterial pathogens. The methods can involve assessing the ability of antibodies elicited by immunization with a chimeric fHbp of the present disclosure to inhibit fH binding to fHbp of  N. meningitidis  of diverse variant groups and/or to elicit bactericidal activity. The antibody may be elicited in a host animal immunized with an immunogenic composition comprising a chimeric fHbp of the present disclosure or screened in a phage display library for its specific affinity to a candidate chimeric fHbp. Among other aspects, the methods find particular use in identifying and/or evaluating antibody having bactericidal and/or anti-neoplastic activity. 
     In one embodiment, a method of evaluating binding of an antibody to a bacterial cell is provided. The method comprises: (a) immunizing a host animal with a composition comprising a chimeric fHbp of the present disclosure, (b) isolating antibodies from the host animal that have binding affinity to the chimeric fHbp, (c) contacting a bacterial cell with the isolated antibodies; and (d) assessing binding of the antibody to the bacterial cell. Additional steps may include assessing the competitive binding of the antibody to fHbp with human factor H; assessing the bactericidal activity against a bacterial pathogen when incubated in vitro with complement; or assessing the ability of the antibody administered to an animal to confer passive protection against infection. In some embodiments, the antibody is in an antibody population, and the method further comprises: (c) isolating one or more antibodies of the antibody population that bind the bacterial cell. A featured aspect is isolated antibody that is bactericidal against the bacterial cell, which may include, for example, complement-mediated bactericidal activity and/or opsonophagocytic activity capable of decreasing the viability of the bacteria in human blood. The subject method may also include assessing the susceptibility of a host animal administered with a vaccine comprising a chimeric fHbp to a bacterial pathogen. 
     Bacterial pathogen of particular interest are  N. meningitidis  of any or all fHbp variant groups, of diverse capsular groups, such as  N. meningitidis  Serogroup B,  N. meningitidis  Serogroup C,  N. meningitidis  Serogroup X,  N. meningitidis  Serogroup Y,  N. meningitidis  Serogroup W-135, and the like. 
     Methods of Production 
     Chimeric fHbps can be produced by any suitable method, including recombinant and non-recombinant methods (e.g., chemical synthesis). Where the chimeric fHbp is produced using recombinant techniques, the methods can involve any suitable construct and any suitable host cell, which can be a prokaryotic or eukaryotic cell, usually a bacterial or yeast host cell, more usually a bacterial cell. Methods for introduction of genetic material into host cells include, for example, transformation, electroporation, conjugation, calcium phosphate methods and the like. The method for transfer can be selected so as to provide for stable expression of the introduced chimeric fHbp-encoding nucleic acid. The chimeric fHbp-encoding nucleic acid can be provided as an inheritable episomal element (e.g., plasmid) or can be genomically integrated. 
     Suitable vectors for transferring chimeric fHbp-encoding nucleic acid can vary in composition. Integrative vectors can be conditionally replicative or suicide plasmids, bacteriophages, and the like. The constructs can include various elements, including for example, promoters, selectable genetic markers (e.g., genes conferring resistance to antibiotics (for instance kanamycin, erythromycin, chloramphenicol, or gentamycin)), origin of replication (to promote replication in a host cell, e.g., a bacterial host cell), and the like. The choice of vector will depend upon a variety of factors such as the type of cell in which propagation is desired and the purpose of propagation. Certain vectors are useful for amplifying and making large amounts of the desired DNA sequence. Other vectors are suitable for expression in cells in culture. Still other vectors are suitable for transfer and expression in cells in a whole animal. The choice of appropriate vector is well within the skill of the art. Many such vectors are available commercially. 
     The vector can be an expression vector based on episomal plasmids containing selectable drug resistance markers and elements that provide for autonomous replication in different host cells (e.g., in both  E. coli  and  N. meningitidis ). One example of such a “shuttle vector” is the plasmid pFP10 (Pagotto et al. Gene 2000 244:13-19). 
     Constructs can be prepared by, for example, inserting a polynucleotide of interest into a construct backbone, typically by means of DNA ligase attachment to a cleaved restriction enzyme site in the vector. Alternatively, the desired nucleotide sequence can be inserted by homologous recombination or site-specific recombination. Typically homologous recombination is accomplished by attaching regions of homology to the vector on the flanks of the desired nucleotide sequence, while site-specific recombination can be accomplished through use of sequences that facilitate site-specific recombination (e.g., cre-lox, att sites, etc.). Nucleic acid containing such sequences can be added by, for example, ligation of oligonucleotides, or by polymerase chain reaction using primers comprising both the region of homology and a portion of the desired nucleotide sequence. 
     Vectors can provide for extrachromosomal maintenance in a host cell or can provide for integration into the host cell genome. Vectors are amply described in numerous publications well known to those in the art, including, e.g., Short Protocols in Molecular Biology, (1999) F. Ausubel, et al., eds., Wiley &amp; Sons. Vectors may provide for expression of the nucleic acids encoding a chimeric fHBP, may provide for propagating the subject nucleic acids, or both. 
     Examples of vectors that may be used include but are not limited to those derived from recombinant bacteriophage DNA, plasmid DNA or cosmid DNA. For example, plasmid vectors such as pBR322, pUC 19/18, pUC 118, 119 and the M13 mp series of vectors may be used. pET21 is also an expression vector that may be used. Bacteriophage vectors may include λgt10, λgt11, λgt18-23, λZAP/R and the EMBL series of bacteriophage vectors. Further vectors that may be utilized include, but are not limited to, pJB8, pCV 103, pCV 107, pCV 108, pTM, pMCS, pNNL, pHSG274, COS202, COS203, pWE15, pWE16 and the charomid 9 series of vectors. 
     For expression of a chimeric fHbp of interest, an expression cassette may be employed. Thus, the present disclosure provides a recombinant expression vector comprising a subject nucleic acid. The expression vector provides transcriptional and translational regulatory sequences, and may provide for inducible or constitutive expression, where the coding region is operably linked under the transcriptional control of the transcriptional initiation region, and a transcriptional and translational termination region. These control regions may be native to an fHbp from which the chimeric fHbp is derived, or may be derived from exogenous sources. In general, the transcriptional and translational regulatory sequences may include, but are not limited to, promoter sequences, ribosomal binding sites, transcriptional start and stop sequences, translational start and stop sequences, and enhancer or activator sequences. Promoters can be either constitutive or inducible, and can be a strong constitutive promoter (e.g., T7, and the like). 
     Expression vectors generally have convenient restriction sites located near the promoter sequence to provide for the insertion of nucleic acid sequences encoding proteins of interest. A selectable marker operative in the expression host may be present to facilitate selection of cells containing the vector. In addition, the expression construct may include additional elements. For example, the expression vector may have one or two replication systems, thus allowing it to be maintained in organisms, for example in mammalian or insect cells for expression and in a prokaryotic host for cloning and amplification. In addition the expression construct may contain a selectable marker gene to allow the selection of transformed host cells. Selection genes are well known in the art and will vary with the host cell used. 
     It should be noted that chimeric fHbp of the present disclosure may comprise additional elements, such as a detectable label, e.g., a radioactive label, a fluorescent label, a biotin label, an immunologically detectable label (e.g., an HA tag, a poly-Histidine tag) and the like. Additional elements of chimeric fHbp can be provided to facilitate isolation (e.g., biotin tag, immunologically detectable tag) through various methods (e.g., affinity capture, etc.). Chimeric fHbp can optionally be immobilized on a support through covalent or non-covalent attachment. 
     Isolation and purification of chimeric fHbp can be accomplished according to methods known in the art. For example, chimeric fHbp can be isolated from a lysate of cells genetically modified to express a chimeric fHbp, or from a synthetic reaction mix, by immunoaffinity purification, which generally involves contacting the sample with an anti-chimeric fHbp antibody (e.g., an anti-chimeric fHBP mAb, such as a JAR 5 mAb or other appropriate JAR mAb described herein), washing to remove non-specifically bound material, and eluting specifically bound chimeric fHbp. Isolated chimeric fHbp can be further purified by dialysis and other methods normally employed in protein purification methods. In one embodiment, the chimeric fHbp can be isolated using metal chelate chromatography methods. 
     Host Cells 
     Any of a number of suitable host cells can be used in the production of chimeric fHbp. In general, the chimeric fHbp described herein may be expressed in prokaryotes or eukaryotes, usually bacteria, more usually  E. coli  or  Neisseria  (e.g.,  N. meningitidis ) in accordance with conventional techniques. Thus, the present disclosure further provides a genetically modified host cell, which contains a nucleic acid encoding a chimeric fHBP. Host cells for production (including large scale production) of a chimeric fHBP can be selected from any of a variety of available host cells. Exemplary host cells for expression include those of a prokaryotic or eukaryotic unicellular organism, such as bacteria (e.g.,  Escherichia coli  strains), yeast (e.g.,  S. cerevisiae, Pichia  spp., and the like), and may include host cells originally derived from a higher organism such as insects, vertebrates, particularly mammals, (e.g. CHO, HEK, and the like). Generally bacterial host cells and yeast are of particular interest for chimeric fHBP production. 
     Chimeric fHbps can be prepared in substantially pure or substantially isolated form (i.e., substantially free from other Neisserial or host cell polypeptides) or substantially isolated form. In certain embodiments, the chimeric fHbp is present in a composition that is enriched for the polypeptide relative to other components that may be present (e.g., other polypeptides or other host cell components). Purified chimeric fHbp can be provided such that the polypeptide is present in a composition that is substantially free of other expressed polypeptides, e.g., less than 90%, usually less than 60% and more usually less than 50% of the composition is made up of other expressed polypeptides. 
     Host Cells for Vesicle Production 
     Where a chimeric fHbp is to be provided in a membrane vesicle (as discussed in more detail below), a Neisserial host cell is genetically modified to express a chimeric fHbp. Any of a variety of  Neisseria  spp. strains can be modified to produce a chimeric fHbp, and, optionally, which produce or can be modified to produce other antigens of interest, such as PorA, can be used in the methods disclosed herein. 
     Methods and vectors to provide for genetic modification of Neisserial strains and expression of a desired polypeptide are known in the art. Examples of vectors and methods are provided in WO 02/09746 and O&#39;Dwyer et al. Infect Immun 2004; 72:6511-80. 
     Strong promoters, particularly constitutive strong promoters are of particular interest. 
     Exemplary promoters include the promoters of porA, porB, lbpB, tbpB, p110, hpuAB, lgtF, opa, p110, 1st, hpuAB. and rmp. 
     Pathogenic  Neisseria  spp. or strains derived from pathogenic  Neisseria  spp., particularly strains pathogenic for humans or derived from strains pathogenic or commensal for humans, are of particular interest for use in membrane vesicle production. Examples of Neisserial spp. include  N. meningitidis, N. flavescens, N. gonorrhoeae, N. lactamica, N. polysaccharea, N. cinerea, N. mucosa, N. subflava, N. sicca, N. elongata , and the like. 
       N. meningitidis  strains are of particular interest for genetic modification to express a chimeric fHbp and for use in vesicle production. The strain used for vesicle production can be selected according to a number of different characteristics that may be desired. For example, the strain may be selected according to: a desired PorA type (a “serosubtype”, as described above), capsular group, serotype, and the like; decreased capsular polysaccharide production; and the like. For example, the production strain can produce any desired PorA polypeptide, and may express one or more PorA polypeptides (either naturally or due to genetic engineering). Examples of strains include those that produce a PorA polypeptide which confers a serosubtype of P1.7,16; P1.19,15; P1.7,1; P1.5,2; P1.22a,14; P1.14; P1.5,10; P1.7,4; P1.12,13; as well as variants of such PorA polypeptides which may or may not retain reactivity with conventional serologic reagents used in serosubtyping. Also of interest are PorA polypeptides characterized according to PorA variable region (VR) typing (see, e.g., Russell et al. Emerging Infect Dis 2004 10:674-678; Sacchi C T, et al, Clin Diagn Lab Immunol 1998; 5:845-55; Sacchi et al, J. Infect Dis 2000; 182:1169-1176). A substantial number of distinct VR types have been identified, which can be classified into VR1 and VR2 family “prototypes”. A web-accessible database describing this nomenclature and its relationship to previous typing schemes is found at neisseria.org/nm/typing/pora. Alignments of exemplary PorA VR1 and VR2 types are provided in Russell et al. Emerging Infect Dis 2004 10:674-678. 
     Alternatively or in addition, the production strain can be a capsule deficient strain. Capsule deficient strains can provide vesicle-based vaccines that provide for a reduced risk of eliciting a significant autoantibody response in a subject to whom the vaccine is administered (e.g., due to production of antibodies that cross-react with sialic acid on host cell surfaces). “Capsule deficient” or “deficient in capsular polysaccharide” as used herein refers to a level of capsular polysaccharide on the bacterial surface that is lower than that of a naturally-occurring strain or, where the strain is genetically modified, is lower than that of a parental strain from which the capsule deficient strain is derived. A capsule deficient strain includes strains that are decreased in surface capsular polysaccharide production by at least 10%, 20%, 25%, 30%, 40%, 50%, 60%, 75%, 80%, 85%, 90% or more, and includes strains in which capsular polysaccharide is not detectable on the bacterial surface (e.g., by whole cell ELISA using an anti-capsular polysaccharide antibody). 
     Capsule deficient strains include those that are capsule deficient due to a naturally-occurring or recombinantly-generated genetic modification. Naturally-occurring capsule deficient strains (see, e.g., Dolan-Livengood et al. J. Infect. Dis. (2003) 187(10):1616-28), as well as methods of identifying and/or generating capsule-deficient strains (see, e.g., Fisseha et al. (2005) Infect. Immun. 73(7):4070-4080; Stephens et al. (1991) Infect Immun 59(11):4097-102; Frosch et al. (1990) Mol Microbiol. 1990 4(7):1215-1218) are known in the art. 
     Modification of a Neisserial host cell to provide for decreased production of capsular polysaccharide may include modification of one or more genes involved in capsule synthesis, where the modification provides for, for example, decreased levels of capsular polysaccharide relative to a parent cell prior to modification. Such genetic modifications can include changes in nucleotide and/or amino acid sequences in one or more capsule biosynthesis genes rendering the strain capsule deficient (e.g., due to one or more insertions, deletions, substitutions, and the like in one or more capsule biosynthesis genes). Capsule deficient strains can lack or be non-functional for one or more capsule genes. 
     Of particular interest are strains that are deficient in sialic acid biosynthesis. 
     Such strains can provide for production of vesicles that have reduced risk of eliciting anti-sialic acid antibodies that cross-react with human sialic acid antigens, and can further provide for improved manufacturing safety. Strains having a defect in sialic acid biosynthesis (due to either a naturally occurring modification or an engineered modification) can be defective in any of a number of different genes in the sialic acid biosynthetic pathway. Of particular interest are strains that are defective in a gene product encoded by the N-acetylglucosamine-6-phosphate 2-epimerase gene (known as synX AAF40537.1 or siaA AAA20475), with strains having this gene inactivated being of especial interest. For example, in one embodiment, a capsule deficient strain is generated by disrupting production of a functional synX gene product (see, e.g., Swartley et al. (1994) J Bacteriol. 176(5):1530-4). 
     Capsule-deficient strains can also be generated from naturally-occurring strains using non-recombinant techniques, e.g., by use of bactericidal anti-capsular antibodies to select for strains that reduced in capsular polysaccharide. 
     Where the disclosure involves use of two or more strains (e.g., to produce antigenic compositions containing a chimeric fHbp-presenting vesicles from different strains), the strains can be selected so as to differ in one or more strain characteristics, e.g., to provide for vesicles that differ in the chimeric fHbp used, PorA, and the like. 
     Preparation of Vesicles 
     The antigenic compositions contemplated by the present disclosure generally include vesicles prepared from Neisserial cells that express a chimeric fHbp. As referred to herein “vesicles” is meant to encompass outer membrane vesicles as well as microvesicles (which are also referred to as blebs). 
     The antigenic composition can contain outer membrane vesicles (OMV) prepared from the outer membrane of a cultured strain of  Neisseria meningitidis  spp. genetically modified to express a chimeric fHbp. OMVs may be obtained from  Neisseria meningitidis  grown in broth or solid medium culture, preferably by separating the bacterial cells from the culture medium (e.g. by filtration or by a low-speed centrifugation that pellets the cells, or the like), lysing the cells (e.g. by addition of detergent, osmotic shock, sonication, cavitation, homogenization, or the like) and separating an outer membrane fraction from cytoplasmic molecules (e.g. by filtration; or by differential precipitation or aggregation of outer membranes and/or outer membrane vesicles, or by affinity separation methods using ligands that specifically recognize outer membrane molecules; or by a high-speed centrifugation that pellets outer membranes and/or outer membrane vesicles, or the like); outer membrane fractions may be used to produce OMVs. 
     The antigenic composition can contain microvesicles (MV) (or “blebs”) containing chimeric fHbp, where the MV or blebs are released during culture of a  Neisseria meningitidis  strain genetically modified to express a chimeric fHbp. For example, MVs may be obtained by culturing a strain of  Neisseria meningitidis  in broth culture medium, separating whole cells from the broth culture medium (e.g. by filtration, or by a low-speed centrifugation that pellets only the cells and not the smaller blebs, or the like), and then collecting the MVs that are present in the cell-free culture medium (e.g. by filtration, differential precipitation or aggregation of MVs, or by a high-speed centrifugation that pellets the blebs, or the like). Strains for use in production of MVs can generally be selected on the basis of the amount of blebs produced in culture (e.g., bacteria can be cultured in a reasonable number to provide for production of blebs suitable for isolation and administration in the methods described herein). An example of a strain that produces high levels of blebs is described in PCT Publication No. WO 01/34642. In addition to bleb production, strains for use in MV production may also be selected on the basis of NspA production, where strains that produce higher levels of NspA may be of particular interest (for examples of  N. meningitidis  strains having different NspA production levels, see, e.g., Moe et al. (1999 Infect. Immun. 67: 5664). Other strains of interest for use in production of blebs include strains having an inactivated GN33 gene, which encodes a lipoprotein required for cell separation, membrane architecture and virulence (see, e.g., Adu-Bobie et al. Infect Immun. 2004; 72:1914-1919). 
     The antigenic compositions of the present disclosure can contain vesicles from one strain, or from 2, 3, 4, 5 or more strains, which strains may be homologous or heterologous, usually heterologous, to one another. For example, the strains may be homologous or heterologous with respect to PorA. The vesicles can also be prepared from strains that express more than one chimeric fHbp (e.g., 1, 2, 3, or more chimeric fHbp) which may be composed of fHbp amino acid sequences from different variants (v.1, v.2, or v.3) or subvariants (e.g., a subvariant of v.1, v.2, or v.3). 
     The antigenic compositions can contain a mixture of OMVs and MVs presenting the same or different chimeric fHbps, where the chimeric fHbps may optionally present epitopes from different combinations of fHbp variants and/or subvariants and where the OMVs and/or MVs may be from the same or different strains. Vesicles from different strains can be administered as a mixture, or can be administered serially. The antigentic composition may contain vesicles containing one or more different chimeric fHbp, in which the vesicles and the fHbp are both derived from the same host cells. The composition can also be made from vesicles and fHbp that are derived from different host cells so that the vesicles and fHbp are admixed after their separate purification. 
     Where desired (e.g., where the strains used to produce vesicles are associated with endotoxin or particular high levels of endotoxin), the vesicles are optionally treated to reduce endotoxin, e.g., to reduce toxicity following administration. Although less desirable as discussed below, reduction of endotoxin can be accomplished by extraction with a suitable detergent (for example, BRIJ-96, sodium deoxycholate, sodium lauroylsarcosinate, Empigen BB, Triton X-100, TWEEN 20 (sorbitan monolaurate polyoxyethylene), TWEEN 80, at a concentration of 0.1-10%, preferably 0.5-2%, and SDS). Where detergent extraction is used, it is preferable to use a detergent other than deoxycholate. 
     The vesicles of the antigenic compositions can be prepared without detergent, e.g., without use of deoxycholate. Although detergent treatment is useful to remove endotoxin activity, it may deplete the native fHbp lipoprotein and/or chimeric fHbp (including lipidated chimeric fHbp) by extraction during vesicle production. Thus it may be particularly desirable to decrease endotoxin activity using technology that does not require a detergent. In one approach, strains that are relatively low producers of endotoxin (lipopolysaccharide, LPS) are used so as to avoid the need to remove endotoxin from the final preparation prior to use in humans. For example, the vesicles can be prepared from  Neisseria  mutants in which lipooligosaccharide or other antigens that may be undesirable in a vaccine (e.g. Rmp) is reduced or eliminated. 
     Vesicles can be prepared from  N. meningitidis  strains that contain genetic modifications that result in decreased or no detectable toxic activity of lipid A. For example, such strain can be genetically modified in lipid A biosynthesis (Steeghs et al. Infect Immun 1999; 67:4988-93; van der Ley et al. Infect Immun 2001; 69:5981-90; Steeghs et al. J Endotoxin Res 2004; 10:113-9; Fissha et al, Infect Immun 73:4070, 2005). The immunogenic compositions may be detoxified by modification of LPS, such as downregulation and/or inactivation of the enzymes encoded by 1p×L1 or 1p×L2, respectively. Production of a penta-acylated lipid A made in 1p×L1 mutants indicates that the enzyme encoded by 1p×L1 adds the C12 to the N-linked 3-OH C14 at the 2′ position of GlcN II. The major lipid A species found in 1p×L2 mutants is tetra-acylated, indicating the enzyme encoded by 1p×L2 adds the other C12, i.e., to the N-linked 3-OH C14 at the 2 position of GlcN I. Mutations resulting in a decreased (or no) expression of these genes (or decreased or no activity of the products of these genes) result in altered toxic activity of lipid A (van der Ley et al. 2001; 69:5981-90). Tetra-acylated (1p×L2 mutant) and penta acylated (1p×L1 mutant) lipid A are less toxic than the wild-type lipid A. Mutations in the lipid A 4′-kinase encoding gene (1p×K) also decrease the toxic activity of lipid A. Of particular interest for use in production of vesicles (e.g., MV or OMV) are  N. meningitidis  strains genetically modified so as to provide for decreased or no detectable functional LpxLl-encoded protein. Such vesicles provide for reduced toxicity as compared to  N. meningitidis  strains that are wild-type for LPS production, while retaining immunogenicity of chimeric fHbp. 
     LPS toxic activity can also be altered by introducing mutations in genes/loci involved in polymyxin B resistance (such resistance has been correlated with addition of aminoarabinose on the 4′ phosphate of lipid A). These genes/loci could be pmrE that encodes a UDP-glucose dehydrogenase, or a region of antimicrobial peptide-resistance genes common to many enterobacteriaciae which could be involved in aminoarabinose synthesis and transfer. The gene pmrF that is present in this region encodes a dolicol-phosphate manosyl transferase (Gunn J. S., Kheng, B. L., Krueger J., Kim K., Guo L., Hackett M., Miller S. I. 1998. Mol. Microbiol. 27: 1171-1182). 
     Mutations in the PhoP-PhoQ regulatory system, which is a phospho-relay two component regulatory system (e.g., PhoP constitutive phenotype, PhoPc), or low Mg++ environmental or culture conditions (that activate the PhoP-PhoQ regulatory system) lead to the addition of aminoarabinose on the 4′-phosphate and 2-hydroxymyristate replacing myristate (hydroxylation of myristate). This modified lipid A displays reduced ability to stimulate E-selectin expression by human endothelial cells and TNF secretion from human monocytes. 
     Polymyxin B resistant strains are also suitable for use, as such strains have been shown to have reduced LPS toxicity (see, e.g., van der Ley et al. 1994. In: Proceedings of the ninth international pathogenic  Neisseria  conference. The Guildhall, Winchester, England). Alternatively, synthetic peptides that mimic the binding activity of polymyxin B may be added to the antigenic compositions to reduce LPS toxic activity (see, e.g., Rustici et al. 1993, Science 259:361-365; Porro et al. Prog Clin Biol Res. 1998; 397:315-25). 
     Endotoxin can also be reduced through selection of culture conditions. For example, culturing the strain in a growth medium containing 0.1 mg-100 mg of aminoarabinose per liter medium provides for reduced lipid toxicity (see, e.g., WO 02/097646). 
     Formulations 
     “Antigen composition”, “antigenic composition” or “immunogenic composition” is used herein as a matter of convenience to refer generically to compositions comprising a chimeric fHbp as disclosed herein, which chimeric fHbp may be optionally conjugated to further enhance immunogenicity. Compositions useful for eliciting antibodies, particularly antibodies against  Neisseria meningitidis  group B (NmB), in a human are specifically contemplated by the present disclosure. Antigenic compositions can contain 2 or more different chimeric fHbps, where the chimeric fHbps may present epitopes from different combinations of fHbp variants and/or subvariants. 
     Antigenic compositions generally comprise an immunologically effective amount of chimeric fHbp, and may further include other compatible components, as needed. By “immunologically effective amount” is meant that the administration of that amount to an individual, either in a single dose, as part of a series of the same or different antigenic compositions, is effective to elicit an antibody response effective for treatment or prevention of a symptom of, or disease caused by, for example, infection by  Neisseria , particularly  N. meningitidis , more particularly Group B  N. meningitidis . This amount varies depending upon the health and physical condition of the individual to be treated, age, the capacity of the individual&#39;s immune system to produce antibodies, the degree of protection desired, the formulation of the vaccine, the treating clinician&#39;s assessment of the medical situation, and other relevant factors. It is expected that the amount will fall in a relatively broad range that can be determined through routine trials. 
     Dosage regimen may be a single dose schedule or a multiple dose schedule (e.g., including booster doses) with a unit dosage form of the antigenic composition administered at different times. The term “unit dosage form,” as used herein, refers to physically discrete units suitable as unitary dosages for human and animal subjects, each unit containing a predetermined quantity of the antigenic compositions of the present disclosure in an amount sufficient to produce the desired effect, which compositions are provided in association with a pharmaceutically acceptable excipient (e.g., pharmaceutically acceptable diluent, carrier or vehicle). The antigenic composition may be administered in conjunction with other immunoregulatory agents. 
     Antigenic compositions can be provided in a pharmaceutically acceptable excipient, which can be a solution such as a sterile aqueous solution, often a saline solution, or they can be provided in powder form. Such excipients can be substantially inert, if desired. 
     The antigenic compositions can further comprise an adjuvant. Examples of known suitable adjuvants that can be used in humans include, but are not necessarily limited to, alum, aluminum phosphate, aluminum hydroxide, MF59 (4.3% w/v squalene, 0.5% w/v Tween 80™, 0.5% w/v Span 85), CpG-containing nucleic acid (where the cytosine is unmethylated), QS21, MPL, 3DMPL, extracts from Aquilla, ISCOMS, LT/CT mutants, poly(D,L-lactide-co-glycolide) (PLG) microparticles, Quil A, interleukins, and the like. For experimental animals, one can use Freund&#39;s, N-acetyl-muramyl-L-threonyl-D-isoglutamine (thr-MDP), N-acetyl-nor-muramyl-L-alanyl-D-isoglutamine (CGP 11637, referred to as nor-MDP), N-acetylmuramyl-L-alanyl-D-isoglutaminyl-L-alanine-2-(1′-2′-dip-almitoyl-sn-glycero-3-hydroxyphosphoryloxy)-ethylamine (CGP 19835A, referred to as MTP-PE), and RIBI, which contains three components extracted from bacteria, monophosphoryl lipid A, trehalose dimycolate and cell wall skeleton (MPL+TDM+CWS) in a 2% squalene/Tween 80 emulsion. The effectiveness of an adjuvant may be determined by measuring the amount of antibodies directed against the immunogenic antigen or antigenic epitope thereof. 
     Further exemplary adjuvants to enhance effectiveness of the composition include, but are not limited to: (1) oil-in-water emulsion formulations (with or without other specific immunostimulating agents such as muramyl peptides (see below) or bacterial cell wall components), such as for example (a) MF59™ (WO 90/14837; Chapter 10 in Vaccine design: the subunit and adjuvant approach, eds. Powell &amp; Newman, Plenum Press 1995), containing 5% Squalene, 0.5% Tween 80, and 0.5% Span 85 (optionally containing MTP-PE) formulated into submicron particles using a microfluidizer, (b) SAF, containing 10% Squalane, 0.4% Tween 80, 5% pluronic-blocked polymer L121, and thr-MDP either microfluidized into a submicron emulsion or vortexed to generate a larger particle size emulsion, and (c) RIBI™ adjuvant system (RAS), (Ribi Immunochem, Hamilton, Mont.) containing 2% Squalene, 0.2% Tween 80, and one or more bacterial cell wall components such as monophosphorylipid A (MPL), trehalose dimycolate (TDM), and cell wall skeleton (CWS), preferably MPL+CWS (Detox™); (2) saponin adjuvants, such as QS21 or Stimulon™ (Cambridge Bioscience, Worcester, Mass.) may be used or particles generated therefrom such as ISCOMs (immunostimulating complexes), which ISCOMS may be devoid of additional detergent e.g. WO 00/07621; (3) Complete Freund&#39;s Adjuvant (CFA) and Incomplete Freund&#39;s Adjuvant (IFA); (4) cytokines, such as interleukins (e.g. IL-1, IL-2, IL-4, IL-5, IL-6, IL-7, IL-12 (WO99/44636), etc.), interferons (e.g. gamma interferon), macrophage colony stimulating factor (M-CSF), tumor necrosis factor (TNF), etc.; (5) monophosphoryl lipid A (MPL) or 3-O-deacylated MPL (3dMPL) e.g. GB-2220221, EP-A-0689454, optionally in the substantial absence of alum when used with pneumococcal saccharides e.g. WO 00/56358; (6) combinations of 3dMPL with, for example, QS21 and/or oil-in-water emulsions e.g. EP-A-0835318, EP-A-0735898, EP-A-0761231; (7) oligonucleotides comprising CpG motifs (Krieg Vaccine 2000, 19, 618-622; Krieg Curr opin Mol Ther2001 3:15-24; Roman et al., Nat. Med, 1997, 3, 849-854; Weiner et al., PNAS USA, 1997, 94, 10833-10837; Davis et al, J. Immunol, 1998, 160, 810-876; Chu et al., J. Exp. Med, 1997, 186, 1623-1631; Lipford et al, Ear. J. Immunol., 1997, 27, 2340-2344; Moldoveami e/al., Vaccine, 1988, 16, 1216-1224, Krieg et al., Nature, 1995, 374, 546-549; Klinman et al., PNAS USA, 1996, 93, 2879-2883; Ballas et al, J. Immunol, 1996, 157, 1840-1845; Cowdery et al, J. Immunol, 1996, 156, 4570-4575; Halpern et al, Cell Immunol, 1996, 167, 72-78; Yamamoto et al, Jpn. J. Cancer Res., 1988, 79, 866-873; Stacey et al, J. Immunol., 1996, 157,2116-2122; Messina et al, J. Immunol, 1991, 147, 1759-1764; Yi et al, J. Immunol, 1996, 157,4918-4925; Yi et al, J. Immunol, 1996, 157, 5394-5402; Yi et al, J. Immunol, 1998, 160, 4755-4761; and Yi et al, J. Immunol, 1998, 160, 5898-5906; International patent applications WO 96/02555, WO 98/16247, WO 98/18810, WO 98/40100, WO 98/55495, WO 98/37919 and WO 98/52581, i.e. containing at least one CG dinucleotide, where the cytosine is unmethylated; (8) a polyoxyethylene ether or a polyoxyethylene ester e.g. WO 99/52549; (9) a polyoxyethylene sorbitan ester surfactant in combination with an octoxynol (WO 01/21207) or a polyoxyethylene alkyl ether or ester surfactant in combination with at least one additional non-ionic surfactant such as an octoxynol (WO 01/21152); (10) a saponin and an immunostimulatory oligonucleotide (e.g. a CpG oligonucleotide) (WO 00/62800); (11) an immunostimulant and a particle of metal salt e.g. WO 00/23105; (12) a saponin and an oil-in-water emulsion e.g. WO 99/11241; (13) a saponin (e.g. QS21)+3dMPL+IM2 (optionally+a sterol) e.g. WO 98/57659; (14) other substances that act as immunostimulating agents to enhance the efficacy of the composition. Muramyl peptides include N-acetyl-muramyl-L-threonyl-D-isoglutamine (thr-MDP), N-25 acetyl-normuramyl-L-alanyl-D-isoglutamine (nor-MDP), N-acetylmuramyl-L-alanyl-D-isoglutarninyl-L-alanine-2-(1′-2′-dipalmitoyl-sn-glycero-3-hydroxyphosphoryloxy)-ethylamine MTP-PE), etc. Adjuvants suitable for administration to a human are of particular interest. 
     The antigen compositions may comprise other components, such as pharmaceutical grades of mannitol, lactose, starch, magnesium stearate, sodium saccharin, talcum, cellulose, glucose, sucrose, magnesium, carbonate, and the like. The compositions may contain pharmaceutically acceptable auxiliary substances as required to approximate physiological conditions such as pH adjusting and buffering agents, toxicity adjusting agents and the like, for example, sodium acetate, sodium chloride, potassium chloride, calcium chloride, sodium lactate and the like. 
     The concentration of chimeric fHbp in a formulation can vary widely (e.g., from less than about 0.1%, usually at or at least about 2% to as much as 20% to 50% or more by weight) and will usually be selected primarily based on fluid volumes, viscosities, and patient-based factors in accordance with the particular mode of administration selected and the patient&#39;s needs. 
     Chimeric fHBP-containing formulations can be provided in the form of a solution, suspension, tablet, pill, capsule, powder, gel, cream, lotion, ointment, aerosol or the like. It is recognized that oral administration can require protection of the compositions from digestion. This is typically accomplished either by association of the composition with an agent that renders it resistant to acidic and enzymatic hydrolysis or by packaging the composition in an appropriately resistant carrier. Means of protecting from digestion are well known in the art. 
     Chimeric fHbp-containing formulations can also be provided so as to enhance serum half-life of chimeric fHBP following administration. For example, where isolated chimeric fHbp are formulated for injection, the chimeric fHbp may be provided in a liposome formulation, prepared as a colloid, or other conventional techniques for extending serum half-life. A variety of methods are available for preparing liposomes, as described in, e.g., Szoka et al., Ann. Rev. Biophys. Bioeng. 9:467 (1980), U.S. Pat. Nos. 4,235,871, 4,501,728 and 4,837,028. The preparations may also be provided in controlled release or slow-release forms. 
     Immunization 
     The chimeric fHbp-containing antigenic compositions are generally administered to a human subject that is at risk of acquiring a Neisserial disease so as to prevent or at least partially arrest the development of disease and its complications. An amount adequate to accomplish this is defined as a “therapeutically effective dose.” Amounts effective for therapeutic use will depend on, e.g., the antigenic composition, the manner of administration, the weight and general state of health of the patient, and the judgment of the prescribing physician. Single or multiple doses of the antigenic compositions may be administered depending on the dosage and frequency required and tolerated by the patient, and route of administration. 
     The chimeric fHbp-containing antigenic compositions are generally administered in an amount effective to elicit an immune response, particularly a humoral immune response, in the host. As noted above, amounts for immunization will vary, and can generally range from about 1 Vag to 100 μg per 70 kg patient, usually 5 μg to 50 ag/70 kg. Substantially higher dosages (e.g. 10 mg to 100 mg or more) may be suitable in oral, nasal, or topical administration routes. The initial administration can be followed by booster immunization of the same of different chimeric fHbp-containing antigenic composition. Usually vaccination involves at least one booster, more usually two boosters. 
     In general immunization can be accomplished by administration by any suitable route, including administration of the composition orally, nasally, nasopharyngeally, parenterally, enterically, gastrically, topically, transdermally, subcutaneously, intramuscularly, in tablet, solid, powdered, liquid, aerosol form, locally or systemically, with or without added excipients. Actual methods for preparing parenterally administrable compositions will be known or apparent to those skilled in the art and are described in more detail in such publications as Remington&#39;s Pharmaceutical Science, 15th ed., Mack Publishing Company, Easton, Pa. (1980). 
     An anti-chimeric fHbp immune response can be assessed by known methods (e.g. by obtaining serum from the individual before and after the initial immunization, and demonstrating a change in the individual&#39;s immune status, for example an immunoprecipitation assay, or an ELISA, or a bactericidal assay, or a Western blot, or flow cytometric assay, or the like). 
     The antigenic compositions can be administered to a human subject that is immunologically naive with respect to  Neisseria meningitidis . In a particular embodiment, the subject is a human child about five years or younger, and preferably about two years old or younger, and the antigenic compositions are administered at any one or more of the following times: two weeks, one month, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11 months, or one year or 15, 18, or 21 months after birth, or at 2, 3, 4, or 5 years of age. 
     It may be generally desirable to initiate immunization prior to the first sign of disease symptoms, or at the first sign of possible or actual exposure to infection or disease (e.g., due to exposure or infection by  Neisseria ). 
     ATCC Deposit 
     Hybridomas producing the JAR 4, JAR 5, JAR 11, and JAR 32 monoclonal antibodies were deposited under the terms of the Budapest Treaty with the American Type Culture Collection, 10801 University Blvd., Manassas, Va. 20110-2209, USA (ATCC) on the date indicated in the table below, and were assigned the designations set out in the table below. 
     
       
         
           
               
               
               
             
               
                   
               
               
                   
                 ATCC Deposit No. 
                   
               
               
                   
                 (Deposit Date) 
                 Material Deposited 
               
               
                   
               
             
            
               
                   
                 PTA-8943 (Feb. 7, 2008) 
                 Hybridoma producing JAR 4  
               
               
                   
                   
                 Monoclonal Antibody 
               
               
                   
                 PTA-8941 (Feb. 7, 2008) 
                 Hybridoma producing JAR 5  
               
               
                   
                   
                 Monoclonal Antibody 
               
               
                   
                 PTA-8940 (Feb. 7, 2008) 
                 Hybridoma producing JAR 10  
               
               
                   
                   
                 Monoclonal Antibody 
               
               
                   
                 PTA-8938 (Feb. 7, 2008) 
                 Hybridoma producing JAR 11  
               
               
                   
                   
                 Monoclonal Antibody 
               
               
                   
                 PTA-8942 (Feb. 7, 2008) 
                 Hybridoma producing JAR 32  
               
               
                   
                   
                 Monoclonal Antibody 
               
               
                   
                 PTA-8939 (Feb. 7, 2008) 
                 Hybridoma producing JAR 33  
               
               
                   
                   
                 Monoclonal Antibody 
               
               
                   
               
            
           
         
       
     
     It should be noted that JAR 5 mAb specifically binds to an epitope that at least overlaps with the epitope specifically bound by JAR 3 mAb, and that JAR 32 mAb specifically binds to an epitope that at least overlaps with the epitope specifically bounds by JAR 35 mAb. 
     These deposits were made under the provisions of the Budapest Treaty on the International Recognition of the Deposit of Microorganisms for the Purpose of Patent Procedure and the Regulations there under (Budapest Treaty). This assures maintenance of a viable culture of the deposit for 30 years from the date of deposit and for at least five (5) years after the most recent request for the furnishing of a sample of the deposit received by the depository. The deposits will be made available by ATCC under the terms of the Budapest Treaty, and subject to an agreement between Children&#39;s Hospital &amp; Research Center at Oakland and the ATCC (the assignee of the present application) which assures that all restrictions imposed by the depositor on the availability to the public of the deposited material will be irrevocably removed upon the granting of the pertinent U.S. patent, assures permanent and unrestricted availability of the progeny of the culture of the deposit to the public upon issuance of the pertinent U.S. patent or upon laying open to the public of any U.S. or foreign patent application, whichever comes first, and assures availability of the progeny to one determined by the U.S. Commissioner of Patents and Trademarks to be entitled thereto according to 35 U.S.C. §122 and the Commissioner&#39;s rules pursuant thereto (including 37 C.F.R. §1.14 with particular reference to 886 OG 638). 
     The assignee(s) of the present application has agreed that if a culture of the materials on deposit should die or be lost or destroyed when cultivated under suitable conditions, the materials will be promptly replaced on notification with another of the same. Availability of the deposited material is not to be construed as a license to practice the invention in contravention of the rights granted under the authority of any government in accordance with its patent laws. 
     EXAMPLES 
     It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims. All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety for all purposes. 
     Materials and Methods 
     The following methods and materials were used in the Examples below. 
     fHbp Sequencing. 
     The fHbp gene was amplified from genomic DNA prepared with the DNeasy Tissue kit (Qiagen, Valencia, Calif.) by polymerase chain reaction using primers A1 and B2 and cycling parameters described previously (Masignani et al.  J Exp Med  2003, 197:789-99). The PCR products were purified using QiaQuick PCR purification kit (Qiagen) and were eluted in 30 μl of sterile deionized H 2 O. The fHbp DNA sequences were determined by a commercial sequencing facility using the primers A1 and 22 described previously (Masignani et al., 2003). 
     Source of Data. 
     Protein sequences analyzed in the first study were encoded by 69 fHbp genes from  Neisseria meningitidis  case isolates from the United States (Beernink et al.  J Infect Dis  2007, 195:1472-9), Europe (Beernink and Granoff  Infect Immun  2008, 76:2568-2575; Beernink et al. Infect Immun 2008, 76:4232-4240) and Africa (Beernink et al.,  J Infect Dis  2009, doi: 10.1086/597806). This data set included 48 sequences determined as part of our previous studies and 21 new sequences performed for the present study. 95 additional fHbp gene sequences were obtained from Genbank (www.ncbi.nlm.nih.gov) by performing translated BLAST (tblastn) searches with fHbp amino acid sequences from strains MC58 (variant 1/sub-family B) and M1239 (variant 3/sub-family A). Among these 164 nucleotide sequences from our collection and Genbank, which included three genome sequences (Parkhill et al.  Nature  2000, 404:502-506; Peng et al.  Genomics  2008, 91:78-87; Tettelin et al.  Science  2000, 287:1809-1815), fHbp genes that encoded 63 unique protein sequences were identified. These 63, plus 6 additional unique fHbp amino acid sequences obtained from the Neisseria.org fHbp peptide database (neisseria.org), were used for the analysis of 69 unique fHbp peptides. The respective Genbank accession numbers and/or peptide identification numbers and the characteristics of the source strains are listed in  FIG. 1A-1G  (Table 7). 
     Thirty-eight (55%) of the 69 peptides were classified in the variant 1 group of Masignani et al. 2003, 15 (22%) in the variant 2 group, and 16 (23%) in the variant 3 group. Of the 69 source strains, one was capsular group A, 57 were group B, seven were group C, two were group W-135, and two were group X. Multi-locus sequence type (MLST) information was available for 58 of the strains of which 15 were from the ST-269 clonal complex, 12 each were from the ST-11, 10 were from the ST-41/44 complexes, four were from the ST-162, five were from the ST-213 complexes, three each were from the ST-8 and ST-32 complexes. Six strains were from other clonal complexes and had sequence types ST-4, ST-35, ST-751, ST-4821, ST-5403 and ST-6874. The 11 strains without MLST information were not available for testing. 
     In a second study, the dataset further included 172 additional distinctive sequences that were subsequently added to the Neisseria.org database (http://neisseria.org/perl/agdbnet/agdbnet.pl?file=nm_fhbp.xml) as of November 2009. In describing the 242 unique proteins ( FIGS. 10A-10I , Table 9), the protein identification (ID) numbers from the peptide database at the Neisseria.org website were employed. 
     A combination of approaches for analysis of complete or partial protein sequences was used. Sequences were aligned with MUSCLE (EBI, v3.7, ebi.ac.uk/Tools/muscle/index.html) (Edgar R C. (2004)  Nucleic Acids Res.  32:1792-7; Edgar R C (2004)  BMC Bioinform.  5:113) configured for highest accuracy. The accuracy of the alignments was confirmed by visual inspection and using the program JALVIEW (Water house A M et al. (2009)  Bioinformatics  25:1189-91). Alignments also were performed on the individual modular variable segments between the blocks of invariant residues. Networks were generated using SplitsTree, version 4.0 (Huson D H et al., (2006)  Mol Biol Evol  23:254-67), with default parameters. Statistical tests for branch support were performed using the bootstrapping method (1000 replicates). 
     Phylogenic Analysis. 
     The analysis of complete or partial protein sequences was performed on the platform at www.phylogeny.fr (Dereeper et al.  Nucleic Acids Res  2008, 36:W465-469) and comprised the following steps. Sequences were aligned with MUSCLE (v3.7) (Edgar  Nucleic Acids Res  2004, 32:1792-1797) configured for highest accuracy. The respective alignments, which contained up to three sites of insertions or deletions, were inspected and verified by adjacent invariant sequences. The phylogenic tree was reconstructed using the maximum likelihood method implemented in the PhyML program (v3.0 aLRT). Reliability for internal branch was assessed using the bootstrapping method (100 bootstrap replicates). Phylograms were displayed with MEGA 4.0 (Tamura et al.  Mol Biol Evol  2007, 24:1596-1599). The phylograms were rooted on peptide 1 for consistency. The percent sequence identities within and between variable segment types of sequences were determined using ClustalW (Larkin et al. Bioinformatics 2007, 23:2947-2948). 
     Cloning, Expression and Purification of Recombinant Proteins. 
     Expression plasmids were constructed by PCR amplification of fHbp genes from genomic DNA as described previously (Masignani et al. (2003)  J Exp Med  197:789-99). The genes encoded fHbp ID 1 (Modular group I), 28 (group II), 22 (group III), 15 (group IV), 79 (group V) and 77 (group VI). C-terminal hexahistidine-tagged recombinant fHbps were expressed in  Escherichia coli  BL21(DE3) (Novagen, Madison, Wis., US), and purified as described elsewhere (Beernink P T et al. (2008)  Infect Immun  76:2568-75). 
     Mouse Antisera. 
     Groups of five-week-old CD-1 female mice (10 mice per group) were obtained from Charles River (Wilmington, Md., US). The mice were immunized via the intraperitoneal route (IP) with three doses of vaccine given at 3-week intervals. Each 100-01 dose contained 20 D g of recombinant protein mixed with Freund&#39;s adjuvant (FA) (Sigma-Aldrich, St. Louis, Mo., US). (Complete FA for the first dose and incomplete for subsequent doses). Terminal blood samples were obtained three weeks after the last dose. The animal procedures were performed under a protocol approved by the Institutional Animal Care and Use Committee of the Children&#39;s Hospital Oakland Research Institute. 
     Bacterial Strains. 
     Characteristics of the  N. meningitidis  strains used to measure serum bactericidal activity are summarized in Tables 7 and 9. Two isolates each was selected from modular groups I to VI. For five of the modular groups, one strain from each pair was a low expresser of fHbp and the other a higher expresser as measured as described below. For modular group V, only strains that expressed intermediate quantities of fHbp were identified and, therefore, used for the assays. 
     Complement-Dependent Serum Bactericidal Antibody Activity. 
     The bactericidal assay was performed as described elsewhere, using early log phase bacteria grown for approximately 2 h in Mueller-Hinton broth (BD Biosciences, Franklin Lakes, N.J., US) supplemented with 0.25% glucose (w/v) and 0.02 mM cytidine 5′-monophospho-N-acetylneuraminic acid (Sigma-Aldrich, St, Louis, Mo., US) [11]. The complement source was serum from a non-immune healthy adult with normal hemolytic complement activity. The serum was passed over a protein G Sepharose column (HiTrap Protein G HP, GE Healthcare, Piscataway, N.J., US) to remove IgG antibodies (Beernink P T et al. (2009)  J Infect Dis  199:1360-8). 
     Quantitative Western Blotting of fHbp. 
       N. meningitidis  cells were grown in broth cultures to early log phase, heat-killed (56° C. for 1 h), collected by centrifugation, and resuspended in PBS to an optical density of 0.6. Proteins in the heat-killed cells (1-4×10 7  CFU) were separated by SDS-PAGE using 4-12% NuPAGE gels (Invitrogen, Carlsbad, Calif., US) as specified by the manufacturer, and were transferred to PVDF membranes (Immobilon-FL; Millipore, Billerica, Mass., US) using a Western blot module (Invitrogen, Carlsbad Calif., US). After blocking overnight at 4° C. in blocking buffer (Li-Cor Biosciences, Lincoln, Nebr., US), fHbp modular groups I and IV (variant 1 group) were detected with anti-fHbp JAR 5 or, JAR 31, for modular groups II, III, V or VI (variant groups 2 or 3) (Beernink P T et la. (2008)  Infect Immun  76:4243-40). The secondary antibody was goat anti-mouse IgG-IRDye800CW (1:10,000, Rockland Immunochemicals, Gilbertsville, Pa., US). 
     To determine the quantity of bound protein, the membranes were scanned at 800 nm wavelength using an infrared scanner (Li-Cor Odyssey, Lincoln, Nebr., US), and the integrated intensities of the bands were calculated with software provided by the manufacturer (version 3.0.21). The results of testing purified, recombinant fHbp from each of the six modular groups indicated that the IR signal intensities were proportional to the log 10  of the quantities loaded in the range of 0.03 to 2 μg (representative data for control proteins in modular groups I and VI are shown in  FIG. 11 ). Representative expression data are shown for two strains with fHbp in modular group I, and two strains in modular group VI ( FIG. 11 ). 
     Statistical Analysis. 
     Statistical calculations were performed using Prism 5 for Mac OSX, version 5.0α (GraphPad Software, La Jolla, Calif., US). The proportion of isolates with fHbp in different modular groups in each country was computed along with the respective 95 percent confidence intervals calculated from the binomial distribution. Differences found in the proportion of isolates in the respective modular groups were compared by Fisher Exact Test (two-tailed) or chi-square analyses. 
     OVERVIEW OF EXAMPLES 
     Based on previous analyses of the sequences of the mature peptide, fHbp was classified into two sub-families (Fletcher et al.  Infect Immun  2004, 72:2088-2100) or three variant groups (Masignani et al., 2003) ( FIG. 3 ). Analysis presented herein indicated that the overall architecture of meningococcal fHbp contains a limited number of specific modular combinations of five variable segments, with each segment corresponding to one of two types, designated as a or f, based on sequence similarity to the respective segments of fHbp peptides 1 (variant 1 group) or 28 (variant 3 group). As described in the Examples section below and shown in  FIG. 4 , the amino acid sequences of two  N. gonorrhoeae  orthologs had architectures corresponding to natural chimeras in modular group V ( FIG. 8 ). The propensity for  Neisseria  to transfer genes horizontally (Hotopp et al.  Microbiology  2006, 152:3733-3749), coupled with the similar modular architectures of meningococcal and gonococcal fHbp peptides described here, suggests that during evolution, the respective progenitor genes recombined at conserved sequences encoding the invariant blocks of residues hypothesized to be points of junction. 
     Among the 69 distinct meningococcal fHbp peptides, 65 (94%) could be assigned to one of six modular groups ( FIG. 8 ). Nearly 60% of the peptides were in modular groups I or II, which comprised only α or β type segments, respectively. The remaining peptides were natural chimeras of α and β segments. Modular fHbp groups, III, IV, and V ( FIG. 8 ), could each have been generated from the two progenitor types by a single recombination event. The modular fHbp group VI could have been generated by two recombination events. Similarly the four exceptional sequences described in the Examples section could each have been generated through recombination at loci encoding alternative blocks of other conserved residues. For a protein comprising five segments, each of which can be of one of two types, there are 2 5 =32 theoretical independent modular combinations. That we identified only six modular groups suggests that there are functional or structural constraints on the molecule that select for certain combinations of the modules found in the prevalent fHbp modular groups. 
     fHbp structural data are available from two recent NMR studies (Cantini et al.,  J Biol Chem  2009, doi:10.1074/jbc.C800214200; Mascioni et al.  J Biol Chem  2009, doi:10.1074/jbc.M808831200) and a crystallographic study of fHbp in a complex with a complement regulatory protein (Cantini et al., 2009; Mascioni et al., 2009; Schneider et al.  Nature  2009, doi: 10.1038/nature07769). In the crystal structure, Schneider et al reported that binding to residues located on the short consensus repeat region 6 (SCR 6) of fH was mediated by charged amino acid residues in the fHbp structure that mimicked portions of sugar molecules known to bind to fH (Schneider et al. 2009). Analysis as presented in  FIG. 9  indicated that these fH contact residues were located on three of the five variable segments identified in the present study. Of the 21 fH contact residues, five were invariant among the 69 unique fHbp peptides analyzed in our study and ten other contact residues were conserved. 
     All three fHbp variable segments with fH contact residues also contained amino acids that affected epitopes recognized by bactericidal murine anti-fHbp mAbs ( FIG. 9 ). The central locations of the fH contact residues in the amino- or carboxyl-terminal domains appeared to be distinct from the peripheral locations of the residues affecting epitope expression. This reciprocal relationship suggests that the fHbp structures in contact with fH infrequently elicited bactericidal antibodies. 
     One limitation of fHbp as a vaccine candidate is antigenic variability (Beernink &amp; Granoff, 2009; Masignani et al., 2003). Thus, serum antibodies to recombinant fHbp in the variant 1 group were bactericidal primarily only against strains with variant 1 proteins (Beernink et al. 2007; Fletcher et al.  Infect Immun  2004, 72; 2088-2100; Masignani et al. 2003), while antibodies to fHbp in the variant 2 or 3 groups had activity primarily against strains with homologous variant 2 or 3 proteins but had no activity against strains with fHbp in the variant 1 group. These observations suggest that epitopes in the C and E segments of fHbp, for which variant 1 proteins were phylogenetically separated from those of variant 2 and 3 proteins ( FIGS. 6 and 7 ), are more important for eliciting bactericidal antibodies than those in the A, B or D segments, where variant 1 proteins clustered together with variant 2 and/or 3 proteins ( FIGS. 5 and 6 ). However, all of the variable segments with the exception of segment B contained residues previously identified as affecting epitopes recognized by murine bactericidal anti-fHbp mAbs (Beernink et al. 2008; Beernink et al.  Mol Immunol  2009b, doi: 10.1016/j.molimm.2009.02.021; Guiliani et al  Infect Immun  2005, 73:1151-1160). Further, some of the mAbs inhibited binding of fH to the bacterial surface (Madico et al.  J Immunol  2006, 177:501-510), and some combinations of mAbs that individually were not bactericidal elicited cooperative bactericidal activity (Beernink et al. 2008; Beernink et al. 2009b; Welsch et al.  J Infect Dis  2008, 197:1053-1061). The latter included mAb JAR 4, which was specific for an epitope on variable segment A (Beernink et al. 2009b), and elicited cooperative bactericidal activity with second mAbs with epitopes on variable segment C (for example JAR 3 or 5) or variable segment E (for example, JAR 13 or mAb502). 
     To minimize the possibility of fHbp escape mutants, an ideal meningococcal vaccine should include antigenic targets other than fHbp (Giuliani et al., 2006). However, there may be limits to the number of recombinant proteins that can be combined in a multicomponent vaccine because of the large dose of total protein required, poor tolerability, or loss of immunogenicity of the individual components. To decrease the number of individual fHbp components, we engineered chimeric fHbp molecules containing the amino-terminal domain of a variant 1 fHbp with the carboxyl-terminal domain of a variant 2 protein using G136 as the junctional point (Beernink &amp; Granoff, 2008). The resulting chimeric protein expressed epitopes from all three variant groups, and the chimeric fHbp vaccines elicited serum antibodies with bactericidal activity against a panel of genetically diverse strains expressing fHbp variant 1, 2 or 3. The junctional point selected for creation of the recombinant chimeric vaccines was located in an invariant portion of the middle of the variable C segment, which, in the present study, was not identified as a junctional point for any of the natural fHbp chimeric proteins described here. The use of natural junctional points that flank the C segment may result in improved recombinant chimeric fHbp vaccines that elicit broad bactericidal antibodies than other vaccines. It may also be possible to introduce amino acid mutations in one or more of the variable segments to introduce epitopes from heterologous fHbp variants (Beernink &amp; Granoff 2008; Beernink et al. 2009b). Thus, the presence of such fH-binding epitopes in the chimeric fHbp polypeptides can provide for production of antibodies that can facilitate protection against  N. meningitidis.    
     In conclusion, the analysis herein shows that the overall architecture of fHbp can be defined by a limited number of specific modular combinations of variable segments flanked by invariant sequences. Collectively, the data suggest that recombination occurred between  N. meningitidis  and  N. gonorrhoeae  progenitor sequences to generate an antigenically diverse family of meningococcal factor H-binding proteins. The data presented in the Examples thus provide insights into the evolution of fHbp variants, and provide a rational basis for classification of groups of peptide variants. Population-based surveillance studies will be required to define the prevalence of fHbp from different modular groups among strains causing carriage and/or disease, and the relationship between the fHbp modular group and other strain characteristics such as capsular group, clonal complex and PorA variable regions. 
     Details of the studies that led to this discovery are set out below. 
     Example 1 
     Phylogenic Analysis 
     69 unique fHbp amino acid sequences were aligned to generate a phylogram shown in  FIG. 3 . For each sequence, the peptide identification number assigned in fHbp peptide database at neisseria.org is shown and, if known, the multi-locus sequence type (MLST) clonal complex is shown in parentheses. The lower left branch shows variant group 1 as defined by Masignani et al 2003 (sub-family B of Fletcher et al 2004); sub-family A contained two branches, variant groups 2 and 3. Prototype peptides for each of the variant groups 1, 2 and 3 are indicated with arrows and labeled with the name of the source strain of the respective genes. The phylogram was constructed by multiple sequence alignment as described in Methods. The scale bar shown at the bottom indicates 5 amino acid changes per 100 residues. 
     The analysis showed the two major branches previously designated as sub-families A and B (Fletcher et al. 2004). Sub-family A contained fHbp sequences in antigenic variant groups 2 and 3, and sub-family B corresponded to fHbps in the antigenic variant group 1 (Masignani et al. 2003). For some clonal complexes, there were examples of strains with fHbp in each of the variant groups (for example, for ST-11, peptides 2, 3, 6, 9, 10, 11 and 78 in the variant 1 group, peptides 17, 22, 23 and 27 in the variant 2 group and peptide 59 in the variant 3 group). The strains from the ST-32 clonal complex had fHbp in two of the variant groups (peptides 1 and 89 in the variant 1 group and peptide 76 in the variant 3 group) and the ST-8 clonal complex had fHbp only in one variant group (peptides 16, 50, and 77 in the variant 2 group). The distribution of fHbp variants in all of the observed clonal complexes is given in Table 2 below. Peptide IDs listed are assigned by the fHbp peptide database at neisseria.org. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Distribution of factor H binding protein  
               
               
                 variants in each clonal complex. 
               
            
           
           
               
               
               
            
               
                 Clonal  
                 Number in Variant group (peptide ID) 
                   
               
            
           
           
               
               
               
               
               
            
               
                 Complex 
                 Variant 1 
                 Variant 2 
                 Variant 3 
                 Total 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 ST-4 
                 1 (5) 
                 0 
                 0 
                 1 
               
               
                 ST-8 
                 0 
                 3 (16, 50, 77) 
                 0 
                 3 
               
               
                 ST-11 
                 7 (2, 3, 6, 9, 10,  
                 4 (17, 22, 23, 27) 
                 1 (59) 
                 12 
               
               
                   
                 11, 78) 
                   
                   
                   
               
               
                 ST-32 
                 2 (1, 89) 
                 0 
                 1 (76) 
                 3 
               
               
                 ST-35 
                 1 (7) 
                 0 
                 0 
                 1 
               
               
                 ST-41/44 
                 6 (4, 8, 12, 14,  
                 2 (19, 20) 
                 2 (28, 84) 
                 10 
               
               
                   
                 86, 87) 
                   
                   
                   
               
               
                 ST-162 
                 1 (88) 
                 1 (21) 
                 2 (29, 82) 
                 4 
               
               
                 ST-213 
                 1 (90) 
                 1 (24) 
                 3 (30, 31, 85) 
                 5 
               
               
                 ST-269 
                 10 (13, 15, 60-63, 
                 2 (68, 83) 
                 3 (64, 70, 72) 
                 15 
               
               
                   
                 65, 66, 69, 71) 
                   
                   
                   
               
               
                 ST-4821 
                 1 (80) 
                 0 
                 0 
                 1 
               
               
                 Unassigned 
                 2 (73, 74) 
                 0 
                 1 (79) 
                 3 
               
               
                 Not done 
                 6 (40, 54-58) 
                 2 (25, 49) 
                 3 (45-47) 
                 11 
               
               
                   
               
            
           
         
       
     
     Example 2 
     The Architecture of fHbp is Modular 
     Blocks of two to five invariant residues were identified that separate the proteins into segments of variable residues. See  FIG. 4  for detail. The invariant residues are shown as vertical rectangles. The top three panels show representative architectures of three  N. meningitidis  fHbp variants in groups 1, 2 and 3 (peptide ids, 1, 16 and 28, respectively). Each of the three variants had repetitive amino-terminal elements (N-term), and variable segments A through E, which in some cases differed in length among the variants. The amino acid positions of the last residue in each variable segment are shown. 
     With the exception of the amino-terminal element, there were identical respective invariant amino acid sequences and homologous variable segments in two  N. gonorrhoeae  orthologs (Genbank accession numbers AE004969 and CP001050), which overall had 96% amino acid sequence identity with meningococcal fHbp peptide 79 (variant 3 meningococcal proteins). In the first study, all 69 fHbp sequence variants had blocks of 2 to 5 invariant residues that flanked five modular variable segments ( FIG. 4 ). These invariant residues were also conserved in 170 of the 172 additional fHbp variants analyzed in study 2. One exception, protein ID 33, had SHFDF instead of SRFDF between the A and B segments, and the other exception, protein, ID 150, had IEHLE instead of IEHLK between the D and A segments ( FIG. 4 ). 
     The blocks of invariant residues appeared to represent natural junctional points for recombination of the respective genes encoding the meningococcal and gonococcal proteins. The phylogeny of each the variable segments defined by these junctional points was analyzed. In the analysis of the 69 distinctive meningococcal fHbp peptide variants described below, the numbering of the amino acid residues is based on the mature fHbp peptide 1 encoded by a gene from MC58 in the variant 1 group (Masignani et al. 2003). The numbering for the respective variant 2 and 3 proteins differ from that of the variant 1 protein by −1 and +7, respectively ( FIG. 4 ). 
     Example 3 
     The Amino-Terminal Repetitive Element 
     For all 69 sequences, the mature fHbp began with a cysteine residue that is lipidated by signal peptidase II, which was followed by three invariant amino acid residues, SSG. This invariant sequence was followed by a repetitive variable sequence consisting of 1 to 6 glycine and/or serine residues and then by two invariant glycine residues ( FIG. 4 ). The variable portion of the amino-terminal element consisted of a single glycine residue for 34 of the 69 peptides (nearly all in the variant 1 group, Table 3 shown below), or GG residues for 12 of the peptides (all in the variant 2 group). The other common variable sequence was GGGSGG (8 in the variant 1 group and 7 in the variant 3 group). 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Sequence and distribution of amino-terminal repetitive element 
               
            
           
           
               
               
            
               
                 Variable 
                 Number of Peptides in Variant Group 
               
            
           
           
               
               
               
               
            
               
                 Sequence 1   
                 Variant 1 
                 Variant 2 
                 Variant 3 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 G 
                 29 
                 3 
                 2 
               
               
                 GG 
                 0 
                 12 
                 0 
               
               
                 SGG 
                 0 
                 0 
                 1 
               
               
                 GGGS  
                 0 
                 0 
                 2 
               
               
                 (SEQ ID NO: 7) 
                   
                   
                   
               
               
                 SGSGG  
                 0 
                 0 
                 1 
               
               
                 (SEQ ID NO: 8) 
                   
                   
                   
               
               
                 GGGSGG  
                 8 
                 0 
                 6 
               
               
                 (SEQ ID NO: 9) 
                   
                   
                   
               
               
                 GGGSGS  
                 1 
                 0 
                 4 
               
               
                 (SEQ ID NO: 10) 
               
               
                   
               
               
                   1 The mature fHbp begins with an invariant tetrapeptide, CSSG, which is followed by a repetitive variable sequence consisting of 1 to 6 glycine and/or serine residues, which is then followed by two invariant glycine residues. 
               
            
           
         
       
     
     Example 4 
     Downstream Variable Segments 
     There were five variable segments, which we designated A, B, C, D or E ( FIG. 4 ). Based on the presence of certain signature amino acid residues and sequence similarity (Table 4), each of the five segments could be segregated into one of two types. One of the types had signature amino acid residues and sequence similarity to peptides in the antigenic variant 1 group. The other type had signature amino acid residues and sequence similarity to peptides in the antigenic variant 3 group, which also were similar to those of the gonococcal ortholog (see  FIG. 4 ). Also see Table 4 presented below. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Amino acid identity within and between sequence groups by 
               
               
                 segment. 
               
            
           
           
               
               
               
               
            
               
                   
                 α Sequence Types 
                 β Sequence Types 
                 Identity 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                   
                 Identity 
                   
                   
                 Identity 
                 between α 
               
               
                 Variable 
                   
                 Invariant 
                 Signature 
                   
                 Range 
                 Signature 
                   
                 Range 
                 and β Types 
               
               
                 Segment 
                 Residue Range 1   
                 Block 2   
                 residues 3   
                 No. 4   
                 (%) 
                 residues 3   
                 No. 4   
                 (%) 4   
                 (%) 4   
               
               
                   
               
               
                 A 
                  8-73 
                 SRFDF 
                 QSV 
                 48 
                 89-100 
                 DSI and 
                 21 
                     89-100 5   
                 69-78 5   
               
               
                   
                   
                   
                   
                   
                   
                 KDN 
               
               
                 B 
                 79-93 
                 GEFQ 
                 IRQ 
                 53 
                     80-100 5   
                 VQK 
                 16 
                 100 
                 60-66 5   
               
               
                 C 
                  98-159 
                 DD 
                 QDS 
                 38 
                 85-100 
                 NNP 
                 31 
                 93-100 
                 32-45     
               
               
                 D 
                 162-180 
                 IEHLK 
                 AG or 
                 58 
                 89-100 
                 PN 
                 11 
                 84-100 
                 52-63     
               
               
                   
                   
                   
                 AS 
               
               
                 E 
                 186-253 
                 KQ 6   
                 SLGI 
                 38 
                 86-100 
                 HLAL 
                 31 
                     94-100 5   
                 48-57 5   
               
               
                   
               
               
                   1 Amino acid numbering based on the mature fHbp from strain MC58. 
               
               
                   2 Invariant block of residues immediately following each variable segment. The invariant sequence immediately before segment A was GG (See FIG. 4). 
               
               
                   3 See FIG. 2A-2E: (Table 8) for complete sequences of each variable segment. 
               
               
                   4 Number of sequences in each sequence type for each variable segment (N = 61 peptides). 
               
               
                   5 Four fHbp sequences with exceptional junctional positions at other conserved blocks of residues were excluded from the percent identity analyses (see text). 
               
               
                   6 Corresponds to carboxyl-terminal end of fHbp sequence 
               
            
           
         
       
     
     For purposes of classification, the first group of segments is designated as a types and the second group as 0 types. The amino acid identity of the respective segments within an α or β type ranges from 80 to 100% (Table 4). In contrast, the identity of segments between types ranged from 69-78% for segment A, which was located in a conserved region of the N-terminal portion of the molecule, to 32-45% in the C segment, which encompassed resides 98-159 in a much less conserved region of the protein (Table 4). For each segment, distinct sequence variants were assigned a unique identifier beginning with a letter, A through E, to represent the variable segment; followed by an α or β to indicate the presence of residues with the respective types described above, followed by a number for each distinct sequence (listed in  FIG. 2A-2E  (Table 8)). 
     Segment A began at amino acid residue 8 immediately after the invariant GG sequence and extended to position 73 (Table 4). Among the 69 fHbp variants, segment A contained 16 distinctive α sequence variants, and 9 distinctive β sequence variants ( FIG. 5 ). Where multiple peptides possessed an identical sequence in a segment, the number of peptides is given in parentheses. The scale bar indicates 5 amino acid changes per 100 residues. Based on the phylogram, the A segments of most of the fHbps in the variant 1 group (shown in  FIG. 5 ) clustered with those in the variant 2 group, whereas the A segments of fHbps in the variant 3 group were in a separate cluster. The most common α variant (N=14) was designated A.α.1, which was present in 4 fHbp peptides in the variant 1 group and 10 in the variant 2 group. The most common β variant was designated A.β.1, which was present in 6 peptides, all in the variant 3 group. 
     Segment B began at position 79 immediately after an invariant SRFDF sequence and extended to position 93 (Table 4). Among the 69 fHbp peptides, segment B contained 7 different α variant sequences and a single β sequence ( FIG. 5 ). The phylogenic analysis showed that the B segments of fHbp peptides in the variant 1 and 2 groups clustered together ( FIG. 5 ), which were distinct from those in the variant β group. The most common B segment, B.α.1, was present in 40 fHbp peptides (28 in the variant 1 group and 12 in the variant 2 group). 
     In contrast to the A and B segments, the respective C (residues 98-159) and E (residues 186-253) segments of fHbp in the variant 2 and 3 groups clustered together and were separated from those of fHbps in the variant 1 group 1 ( FIG. 6 ). All of the D segments (residues 162-180) of strains with fHbp in the variant group 1 were α types while those of fHbp peptides in the variant 2 or 3 groups were α or β ( FIG. 7 ). The most common D segment, D.α.1 (N=39), was present in 21 fHbp v.1 peptides, 9 v.2 peptides and 9 v.3 peptides. 
     Example 5 
     Classification of fHbp Variants by Modular Groups 
     Based on the phylogenic analysis of the variable segments of fHbp described above, the majority of these different fHbp variants studied were categorized into six distinct fHbp modular groups (I to VI) ( FIG. 8 ). Forty of the 69 fHbp peptides (58%) comprised only α (N=33) or β (N=7) type segments, which were designated fHbp modular groups I and II, respectively ( FIG. 8 ). The α segments are shown in gray and the β segments are shown in white. The remaining 29 peptides (42%) could be classified into one of four chimeras derived from recombination of different α or β segments (designated fHbp modular groups III, IV, V or VI; N=25) or, as described below, were other chimeras (N=4) in which one of the five segments used an exceptional junctional position at other conserved blocks of sequences. As seen in  FIG. 6 , a representative peptide in each modular group is indicated by the peptide identification number from the fHbp database at neisseria.org. The number of unique sequences observed within each fHbp modular group is indicated at the right. This analysis excluded four peptides sequences with exceptional junctional points at one of their segments. 
     Although the amino-terminal repetitive segment described above was not used to define the modular fHbp groups, the majority (88 to 100%) of modular group I, III and VI peptides sequences had amino-terminal repetitive elements of 1 or 2 glycine residues (Table 3). In contrast, the majority (75 to 100%) of the peptides in modular groups II, IV and V had amino-terminal elements of 3 to 6 glycine and serine residues. The length of this amino-terminal element may affect the distance of the protein from the bacterial membrane and surface-accessibility of certain epitopes. 
     In the second study, all but three of the 172 new fHbp variants could be classified into one of the six modular groups (I to VI,  FIG. 4 , Panel A). The three exceptions (protein ID 207, 67 and 175) had distinctive combinations of modular segments derived from α or β type lineages and were assigned to one of three new modular groups (VII, VIII and IX, respectively). 
     Of 242 distinct fHbp variants in the expanded database, 125 proteins were in modular group I ( FIG. 4 ), which contained only α segments, and 20 proteins were in modular group II (entirely β □ segments). The remaining 97 fHbp sequence variants were natural chimeras of α and β segments and were assigned to modular groups III through IX (together, 40 percent of all variants).  FIG. 4  shows the fHbp variant groups as described by Masignani et al. (2003)  J Exp Med  1997:789-99 for each of the modular groups. The variant groups were assigned based on the relatedness of the overall amino acid sequences of the respective proteins. 
     Example 6 
     Chimeric fHbp Peptides Containing Junction Points within a Variable Segment 
     Four fHbp sequences had modular structures similar to those described above except that one of the junctional points between two of the segments utilized alternative invariant sequences. For example, fHbp peptide 55 was similar to peptides in modular group IV ( FIG. 8 ) except that the A segment switched from a β type sequence to an α type sequence at an invariant AQGAE starting at residue 50 rather than at SRFDF starting at residue 74. This A segment was designated A.β.9 (β because of its higher sequence identity to other β type A segments than to the α type A segments;  FIG. 5 ). Two other fHbp peptides, 24 and 25 ( FIG. 2A-2E  (Table 8)), had modular structures similar to peptides in modular group III ( FIG. 8 ) but had B segments that switched from an α type to a β type sequence at an invariant IEV beginning at residue 82 instead of GEFQ at position 94. This exceptional B segment, designated B.α.3, was categorized as an α type because of its higher sequence identity to other α type B segments than to the 0 type B segments ( FIG. 5 ). The fourth exceptional fHbp modular structure, peptide 82 ( FIG. 2A-2E  (Table 8)), was similar to type V, except that its E segment, designated E.β.10, switched from an α type sequence to a p type at residue A196 instead of at IEHLK starting at position 181 ( FIG. 6 ). 
     Example 7 
     Structural Features of the Variable and Invariant fHbp Segments 
     The respective variable and invariant segments of fHbp were mapped onto a molecular model based on the published coordinates from the fHbp crystal structure ( FIG. 9 ) (Schneider et al. 2009). The amino- and carboxyl-termini, labeled N and C, respectively, in panel A are in identical positions in panels B and C. The figure was constructed with PyMol (pymol.org). The models in the center of panels A, B and C have been rotated 180 degrees on the Y-axis from the corresponding models on the far left, while the models on the far right have been rotated 90 degrees on the X-axis as compared with the models in the middle. 
     The ribbon models in panel A show the two previously described major domains of fHbp (Cantini et al. 2009; Mascioni et al. 2009; Schneider et al. 2009), each containing independently folded beta-structures, which are connected together by a structured, four amino acid residue linker located in variable segment C. The amino-terminal domain, which begins at residue 8 and extends to residue 136, includes variable segments A and B and part of C (note that the first 14 residues of the mature protein are not present in the crystal structure). The carboxyl-terminal domain, which extends from residue 141 to 255, includes the carboxyl-terminal portion of the C and the entire D and E variable segments. 
     Panel B shows the corresponding space-filled models. The amino acid residues previously reported to be in contact with fH based on the structure of the fHbp-fH complex are depicted in black. These residues form clusters on variable segments A, C and E and are visible in the models shown in the middle and far right of panel B. Since fH is known to bind to fHbp on live bacteria (Madico et al. 2006; Schneider et la. 2006), this binding site must be surface-exposed. The invariant blocks of residues that flank each of the five variable segments, are localized on the opposite face of the protein and shown in white in panels B and C (far left model). Since the amino-terminus, which contains the signal anchor, extends from this face of the protein (bottom surface of model at far right, panel B), the invariant residues are predicted to be located entirely on the surface of the molecule anchored to the cell wall. The presence of these invariant sequences on the membrane-associated surface suggests that there are structural constraints, perhaps a requirement for a partner protein, for anchoring and/or orienting fHbp on the bacterial cell membrane. 
     Previous studies mapped the epitopes of eleven bactericidal anti-fHbp mAbs (Beernink et al. 2008; Beernink et al. 2009b; Giuliani et al. 2005; Scarselli et al J Mol Biol 2009, 386:97-108). In panel C ( FIG. 9 ), the amino acids affecting expression of each of these epitopes are depicted in black and the previously defined fH contact residues (shown in black as in panel B). With the exception of segment B, all of the variable segments contained epitopes recognized by bactericidal mAbs. The amino acids affecting the epitopes generally were located on the periphery of the amino- and carboxyl-terminal domains of fHbp whereas the residues in contact with fH were located in clusters in the central portions of each of the two domains. The epitopes of certain mAbs such as JAR 3, 5 or 13, which were previously reported to inhibit binding of fH to fHbp (Beernink et al. 2008; Beernink et al. 2009b), involved amino acids located in proximity to some of the fH contact residues. However, there was no example of overlap between the two sets of residues. 
     Example 8 
     Frequency of fHbp Modular Groups Among Isolates Causing Disease in Different Countries 
     The analysis described above provided information on the extent of fHbp modular group diversity. For this following analysis, the fHbp sequence data from systematically collected group B isolates in the U.S. and Europe reported by Murphy et al. (2009)  J Infect Dis  200:379-89 were used. The isolates were from cases in the United States between 2001 and 2005 (N=432), and from the United Kingdom (N=536), France (N=244), Norway (N=23) and the Czech Republic (N=27) for the years 2001 to 2006. The U.S. data were supplemented with fHbp sequences of 143 additional isolates that had been systematically collected at multiple sites in the U.S. as part of another study (Beernink P T et al. (2007)  J Infect Dis  195:1472-9). 
     Among the total of 1405 systematically collected group B isolates, modular group I was found in 59.7%, group II in 1.7%, group III in 8.1%, group IV in 10.6%, group V in 6.1%, and group VI in 13.6%. The new modular groups, VII, VIII and IX, were each found in ≦0.1%. The respective distributions of the fHbp modular groups in the different countries as stratified by the variant group classification of Masignani et al. (2003)  J Exp Med  197:789-99 are shown in  FIG. 12 . For this analysis, the data from Norway and Czech Republic were excluded, since the number of isolates in each of these collections was too small for precise estimates of the respective frequencies of the modular groups. The respective percentages of the modular groups in the two U.S. collections are shown separately. 
     Isolates in variant 1 group of Masignani consisted of modular groups I, IV and VII. Modular group I strains, which have entirely α-type segments, predominated in all three countries (54 to 64 percent of all isolates). In the UK, however, 23% of all isolates were modular group IV, which are natural chimeras of α- and β-type segments ( FIG. 8 ), as compared with &lt;1% in the two U.S. collections, and 3 percent of isolates from France (P&lt;0.001 by chi square). Since there was only one isolate in modular group VII (France), the frequency of this modular group is not shown in  FIG. 12 . 
     Isolates in variant 2 group included modular groups III and VI, which are all natural chimeras of α- and β-type segments. Modular groups III or VI were present in approximately equal proportions of isolates in the two U.S. collections, while modular group VI predominated among variant 2 isolates from the UK and France. 
     Isolates with variant 3 group included modular group II (entirely 3-type segments) and modular groups V, VIII and IX, which are chimeras. In France and the UK, modular group V accounted for the majority of the isolates with variant 3 fHbp, while in the two U.S. collections there were approximately equal numbers of modular group II or V proteins. Modular groups VIII and IX accounted for &lt;0.1% of the isolates. Because of the low percentages, these groups are not shown on  FIG. 12 . 
     Example 9 
     Strain Susceptibility to Anti-fHbp Serum Bactericidal Activity in Relation to Modular Group and fHbp Expression 
       FIG. 13  depicts human complement bactericidal titers of serum pools from mice immunized with recombinant fHbp vaccines representative of modular groups I-VI. The heights of the bars represent the respective median titers of each of the six antisera (3 to 4 pools per modular group) when tested against the specific test strain. For example, the upper left panel shows the data for strain H44/76, which is a high expresser of fHbp in modular group I (relative expression is designated by +++; actual values are shown in Table 5 below). The median bactericidal titer of the homologous anti-fHbp modular group I antiserum (black bar) was ˜1:6000. The respective titers of the five heterologous anti-fHbp modular group antisera (white bars) against strain H44/76 were 1 to 2 log 10  lower, ranging from &lt;1:10 (antisera to modular group II) to ˜1:200 (antisera to modular group IV). The corresponding median titers of the anti-modular group II and IV antisera when tested against control strains with homologous fHbp modular groups II (strain SK104 in the Variant 3 panel) or IV (NM452 in the Variant 1 panel) were &gt;1:2000. Thus, these and the other heterologous antisera had high antibody activity when measured against control strains with the respective homologous fHbp modular groups. 
     There were lower bactericidal titers against low fHbp expressing strains than against high expressing strains (compare respective graphs on the right side of  FIG. 13  showing data for low expressing strains [designated+/−], with those on the left showing higher expressers). For example the anti-modular group I antiserum had a titer of 1:6000 against H44/76, a high fHbp modular group I expressing strain, but a titer of ˜1:100 against strain 03S-0408, a low fHbp modular group I expresser. (For modular group V, both test strains were intermediate expressers, since a pair of high and low fHbp expressing strains were not available). 
     There was a trend for lower cross-reactivity of anti-fHbp bactericidal activity against strains with low expression of fHbp from heterologous modular groups than for high expressing strains (see for example, data for low expressing strains 03S-0408 (modular group I), M01573 (modular group IV), and RM1090 (modular group III), which were killed only by their respective homologous modular group antisera as compared with the broader bactericidal activity against the respective higher fHbp expressing strains (H44/76, NM452, and 03S-0673;  FIG. 13 ). Strain NMB (fHbp modular group VI) was completely resistant to anti-fHbp bactericidal activity (titer &lt;1:10), which apparently was a result of low fHbp expression (Table 5). The amino acid sequence of the vaccine used to prepare the anti-modular group VI antisera differed by a single amino acid from fHbp expressed by NMB, and the resulting antisera were bactericidal against a higher expressing strain (961-5945) with fHbp modular group VI. Further, the resistant strain, NMB, was killed by a control anti-PorA mAb at a concentration of 0.15 ag/ml, which was identical to that of an anti-PorA mAb required for killing of the anti-fHbp susceptible 961-5945 strain. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Characteristics of  N. meningitidis  strains used for measuring serum 
               
               
                 bactericidal activity. 
               
            
           
           
               
               
            
               
                   
                 Factor H-binding protein 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                   
                   
                 Expression 
                 Genbank 
               
               
                 Strain 
                 sequence 
                 clonal 
                 Variant 
                 Protein 
                 Modular 
                 (ng/10 6   
                 accession 
               
               
                 name 
                 types 
                 complex 
                 group 
                 ID 
                 group 
                 cells) 
                 number 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 H44/76 
                 32 
                 32 
                 1 
                 1 
                 I 
                 31 
                 AY548370 
               
               
                 03S-0408 
                 11 
                 11 
                 1 
                 78 
                 I 
                 3 
                 ACF35432 
               
               
                 SK104 
                 5748 
                 162 
                 3 
                 99 
                 II 
                 11 
                 GQ219769 
               
               
                 M1239 
                 437 
                 41/44 
                 3 
                 28 
                 II 
                 2 
                 ABF82029 
               
               
                 03S-0673 
                 1364 
                 32 
                 2 
                 23 
                 III 
                 14 
                 GU056306 
               
               
                 RM1090 
                 11 
                 11 
                 2 
                 22 
                 III 
                 2 
                 ABY26518 
               
               
                 NM452 
                 283 
                 269 
                 1 
                 15 
                 IV 
                 20 
                 ABL14232 
               
               
                 M01573 
                 44 
                 41/44 
                 1 
                 55 
                 IV 
                 1 
                 AAR84481 
               
               
                 S3032 
                 6874 
                 n/a 
                 3 
                 79 
                 V 
                 8 
                 ACH48234 
               
               
                 MD1475 
                 162 
                 162 
                 3 
                 82 
                 V 
                 7 
                 GQ219772 
               
               
                 961-5945 
                 153 
                 8 
                 2 
                 16 
                 VI 
                 5 
                 AAR84453 
               
               
                 NMB 
                 8 
                 8 
                 2 
                 50 
                 VI 
                 1 
                 AY330379 
               
               
                   
               
            
           
         
       
     
     The antibodies used for the quantitative measurement of fHbp and the reactivity of various modular group proteins for each antibody is shown in the Table below. 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 Anti-fHbp monoclonal antibody reactivity of recombinant proteins 
               
               
                 used to prepare antisera in relationship to locations of epitopes. 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                 JAR 3 or 
                   
                   
                   
                   
                 JAR 32 
                   
               
               
                 Anti-fHbp mAb 
                 JAR1 
                 JAR 4 
                 JAR 5 
                 JAR 10 
                 JAR 11 
                 JAR 13 
                 JAR 31 
                 JAR 35 
                 JAR 33 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Epitope 
                 Amino 
                 R204 
                 (25-27) 
                 G121, 
                 K180 
                 A174 
                 S216 
                 Unk 6   
                 K174 
                 R180 
               
               
                 location 
                 acid 
                   
                 YGN 
                 K122 
                 and 
                   
                   
                   
                   
                 and 
               
               
                   
                 residue(s) 
                   
                 (57-59) 
                   
                 E192 4   
                   
                   
                   
                   
                 E192 4   
               
               
                   
                   
                   
                 KDN 
               
               
                   
                 Modular 
                 Eα 
                 Aα 
                 Cα 
                 Dα and 
                 Dα 
                 Eβ 
                 UD 6   
                 Dβ 
                 Dβ and 
               
               
                   
                 segment 
                   
                   
                   
                 Eβ 
                   
                   
                   
                   
                 E β 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 Modular 
                 Variant 
                 Protein 
                   
               
               
                 Group 
                 Group 
                 ID No. 
                 Reactivity of Recombinant Protein by ELISA 5   
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 I 
                 1 
                 1 
                 1 
                 1 
                 1 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                 II 
                 3 
                 28 
                 0 
                 0 
                 0 
                 0 
                 0 
                 1 
                 1 
                 1 
                 1 
               
               
                 III 
                 2 
                 22 
                 0 
                 1 
                 0 
                 0 
                 0 
                 0 
                 1 
                 1 
                 1 
               
               
                 IV 
                 1 
                 15 
                 0 
                 0 
                 1 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                 V 
                 3 
                 79 
                 0 
                 0 
                 0 
                 1 
                 1 
                 1 
                 1 
                 0 
                 0 
               
               
                 VI 
                 2 
                 77 
                 0 
                 1 
                 0 
                 1 
                 1 
                 1 
                 1 
                 0 
                 0 
               
               
                   
               
               
                   1 All of the MAbs were bactericidal when tested in certain combinations with human complement  3 Discontinuous epitope; presence of KDN suppresses epitope [1] 
               
               
                   4 Discontinuous epitope requiring specific combinations of charged residues 
               
               
                   5 Assigned “1” if Optical density &gt;3 SD above background binding when tested at 1 μg/ml, “0”, negative. 
               
               
                   6 UD, location of epitope undetermined