Patent Publication Number: US-7906296-B2

Title: Detection of anaplasma platys

Description:
PRIORITY 
     This application is a divisional application of U.S. Ser. No. 11/697,769, filed Apr. 9, 2007, U.S. Pat. No. 7,507,789, which is incorporated herein by reference in its entirety. 
    
    
     INCORPORATION BY REFERENCE 
     This application incorporates by reference the sequence listing material submitted along with this application in an electronic text file. The name of the text file is “06786ST25.txt” and it was created on Feb. 10, 2009. The text file is 20.5 KB and is incorporated by reference herein in its entirety. 
     BACKGROUND OF THE INVENTION 
       Anaplasma platys  (Apl) is an obligate intracellular bacteria that infects platelets and causes a cyclic thrombocytopenia in the dog. The dog appears, at this time, to be the only species affected by this rickettsial agent, and the disease is most likely transmitted by the  Rhipicephalus  spp of ticks. Apl was first reported in the United States in 1978 and has since been reported in Europe, Asia, South America, the Middle East, Australia, and Africa. Because of the common vector, Apl infection is often found as a co-infection with  Ehrlichia canis . The ability of the organism to produce clinical disease in the dog appears to vary with geography, suggesting that strain differences may contribute to virulence. Apl is related to another  Anaplasma  species known to cause clinical disease in the dog,  Anaplasma phagocytophilum  (Aph). Aph is capable of infecting a wide range of mammals, including humans, and can produce significant morbidity. Clinical signs are usually non-specific and include anorexia, lethargy, lameness, fever, and thrombocytopenia. Aph is transmitted by the  Ixodes  spp of ticks and infections have been reported throughout the United States, the UK, and Europe. 
     Current diagnostic tests that attempt to distinguish Aph and Apl have limited specificity. PCR for Aph and Apl using 16SrRNA has also had problems with specificity. Therefore, PCR assays for specific detection of Apl are needed in the art. Additionally, serological tests for Apl that use Aph polypeptides or antibodies specific for Apl tend not to detect all instances of Apl infection or exposure. Therefore, serological tests that more accurately detect Apl are needed in the art. 
     SUMMARY OF THE INVENTION 
     One embodiment of the invention provides a purified polypeptide comprising SEQ ID NO: 12 or at least about 10 contiguous amino acids of SEQ ID NO: 12, wherein the at least about 10 contiguous amino acids are chosen from amino acids 16-150 or 209-240 of SEQ ID NO:12. A polypeptide can comprise SEQ ID NO:10; SEQ ID NO:11; SEQ ID NO:13, SEQ ID NO:14 or SEQ ID NO: 15. The invention also provides isolated polynucleotides that encode these polypeptides. A purified polypeptide can further comprising a carrier. A purified polypeptide can be in a multimeric form. A purified polypeptide can be linked to an indicator reagent, an amino acid spacer, an amino acid linker, a signal sequence, a stop transfer sequence, a transmembrane domain, a protein purification ligand, a heterologous polypeptide or a combination thereof. 
     Another embodiment of the invention provides a method of detecting antibodies that specifically bind an  Anaplasma platys  or an  Anaplasma phagocytophilum  polypeptide or both. The method comprises contacting a purified polypeptide of the invention with a test sample, under conditions that allow polypeptide/antibody complexes to form and detecting polypeptide/antibody complexes. The detection of polypeptide/antibody complexes is an indication that antibodies specific for  Anaplasma platys  and/or  Anaplasma phagocytophilum  are present in the test sample, and the absence of polypeptide/antibody complexes is an indication that antibodies specific for  Anaplasma platys  and/or  Anaplasma phagocytophilum  are not present in the test sample. The complexes can be contacted with an indicator reagent prior to the detection step. The amount of antibody in the test sample can be determined. The purified polypeptide can be attached to a substrate. The purified polypeptide can be a fusion protein wherein the purified polypeptide is fused to an indicator reagent, an amino acid spacer, an amino acid linker, a signal sequence, a stop transfer sequence, a transmembrane domain, a protein purification ligand, a heterologous protein, or a combination thereof. The purified polypeptide can be in multimeric form. The method can comprise a microtiter plate assay, reversible flow chromatographic binding assay, an enzyme linked immunosorbent assay, a radioimmunoassay, a hemagglutination assay a western blot assay, a fluorescence polarization immunoassay, or an indirect immunofluorescence assay. 
     Yet another embodiment of the invention provides a method of detecting an  Anaplasma platys  and/or  Anaplasma phagocytophilum  infection and/or exposure to  Anaplasma platys  and/or  Anaplasma phagocytophilum  in a subject. The method comprises obtaining a biological sample from the subject; contacting a purified polypeptide of the invention with the biological sample under conditions that allow polypeptide/antibody complexes to form; and detecting polypeptide/antibody complexes. The detection of polypeptide/antibody complexes is an indication that the subject has an  Anaplasma platys  and/or  Anaplasma phagocytophilum  infection and/or exposure to  Anaplasma platys  and/or  Anaplasma phagocytophilum . The absence of polypeptide/antibody complexes is an indication that the mammal has not had an  Anaplasma platys  and/or  Anaplasma phagocytophilum  infection and/or exposure to  Anaplasma platys  and/or  Anaplasma phagocytophilum . The polypeptide/antibody complexes can be contacted with an indicator reagent that generates a measurable signal prior to the performance of the detection step. The purified polypeptide can be a fusion protein wherein the purified polypeptide is fused to an indicator reagent, an amino acid spacer, an amino acid linker, a signal sequence, a stop transfer sequence, a transmembrane domain, a protein purification ligand, a heterologous protein or a combination thereof. The polypeptide/antibody complexes can detected at about 10 days after exposure or infection of subject by  Anaplasma platys  and/or  Anaplasma phagocytophilum.    
     Still another embodiment of the invention provides an antibody that specifically binds to an  Anaplasma platys  p44 polypeptide, wherein the polypeptide comprises at least about 10 contiguous amino acids of SEQ ID NO: 12, wherein the at least about 10 contiguous amino acids are chosen from amino acids 16-150 or 209-240 of SEQ ID NO:12. The antibody can be a monoclonal antibody, polyclonal antibody, a Fab fragment, a Fab′ fragment, Fab′-SH fragment, F(ab′) 2  fragment, Fv fragment, or a single chain antibody. 
     Even another embodiment of the invention provides a method of detecting an  Anaplasma platys  or  Anaplasma phagocytophilum  polypeptide in a sample. The method comprises contacting one or more antibodies that specifically bind to a  Anaplasma platys  polypeptide with the sample under conditions that allow polypeptide/antibody complexes to form; wherein the  Anaplasma platys  polypeptide comprises at least about 10 contiguous amino acids of SEQ ID NO:12, wherein the at least about 10 contiguous amino acids are chosen from amino acids 16-150 or 209-240 of SEQ ID NO: 12 and detecting polypeptide/antibody complexes. The detection of polypeptide/antibody complexes is an indication that an  Anaplasma platys  polypeptide is present in the sample and the absence of polypeptide/antibody complexes is an indication that a  Anaplasma platys  polypeptide is not present in the sample. 
     Another embodiment of the invention provides a method of detecting  Anaplasma platys  p44 polynucleotides. The method comprises contacting a test sample with probe polynucleotides comprising SEQ ID NOs: 6, 7, 8, 9, or combinations thereof, under conditions that allow hybridization complexes between  Anaplasma platys  p44 polynucleotides and the probe polynucleotides; and detecting  Anaplasma platys  p44 polynucleotide/probe polynucleotide complexes; wherein the absence of  Anaplasma platys  p44 polynucleotide/probe polynucleotide complexes is an indication that  Anaplasma platys  polynucleotides are not present in the test sample and wherein the presence of  Anaplasma platys  p44 polynucleotide/probe polynucleotide complexes is an indication that  Anaplasma platys  polynucleotides are present in the test sample. 
     Yet another embodiment of the invention provides methods of detecting  Anaplasma platys  polynucleotides. The methods comprise contacting a test sample with nucleic acid primers comprising SEQ ID NO:6 and SEQ ID NO:7; and performing a nucleic acid amplification reaction. Amplification products comprising  Anaplasma platys  polynucleotides are produced if  Anaplasma platys  polynucleotides are present in the test sample. Nucleic acid probes comprising SEQ ID NO:8 or SEQ ID NO:9 or both can be used to detect the amplification products. Any  Anaplasma phagocytophilum  polynucleotides present in the test sample may not be amplified. The nucleic acid probes can comprise a detectable label. The nucleic acid amplification reaction can be a polymerase chain reaction (PCR), an end-point PCR, a real-time PCR, a nested PCR assay. The quantity of  Anaplasma platys  polynucleotides in the sample can be determined. 
     Still another embodiment of the invention provides a method for diagnosing  Anaplasma platys  infection in a subject comprising detecting the presence of polynucleotides that encode all or part of an  Anaplasma platys  p44 polypeptide and/or detecting the presence of an  Anaplasma platys  p44 polypeptide in a test sample. 
     Even another embodiment of the invention provides a method for detecting and/or quantifying  Anaplasma platys  polynucleotides in a test sample. The method comprises adding sense primers and antisense primers to the test sample under conditions suitable for a polymerase chain reaction, wherein the primers hybridize with  Anaplasma platys  p44 polynucleotides such that an amplification product is formed if  Anaplasma platys  p44 polynucleotides are present in the test sample; and detecting the amplification product, whereby the presence and/or quantity of  Anaplasma platys  p44 polynucleotides are detected. Any  Anaplasma phagocytophilum  polynucleotides present in the test sample may not be amplified. 
     Therefore, the invention provides methods and compositions for serological detection of  Anaplasma platys  or  Anaplasma phagocytophilum  and nucleic acid-based specific detection of  Anaplasma platys.    
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  shows an alignment of Apl p44 polynucleotide sequences.  FIG. 1B  shows an alignment of Apl p44 polypeptide sequences. 
         FIG. 2A  shows the analytical sensitivity of a real time PCR assay for Apl p44 polynucleotides.  FIG. 2B  shows the specificity of a real time PCR assay for Apl p44 polynucleotides. 
         FIG. 3  shows a comparison of ELISA results using Aph p44 peptide and Apl p44 peptide on a population of serum samples derived from dogs living in areas endemic for  A. platys  and free of  A. phagocytophilum.    
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The current invention describes polynucleotide sequences for a major outer surface protein of Apl, p44, and peptides from the translated protein that can be used for robust detection of Apl and Aph infection and/or exposure. Additionally, this Apl p44 sequence provides a PCR target to distinguish Apl and Aph infections using, e.g., a real-time PCR with hybridization probes. 
     Apl Polypeptides 
     A polypeptide is a polymer of three or more amino acids covalently linked by amide bonds. A polypeptide can be post-translationally modified. A purified polypeptide is a polypeptide preparation that is substantially free of cellular material, other types of polypeptides, chemical precursors, chemicals used in synthesis of the polypeptide, or combinations thereof. A polypeptide preparation that is substantially free of cellular material, culture medium, chemical precursors, chemicals used in synthesis of the polypeptide has less than about 30%, 20%, 10%, 5%, 1% or more of other polypeptides, culture medium, chemical precursors, and/or other chemicals used in synthesis. Therefore, a purified polypeptide is about 70%, 80%, 90%, 95%, 99% or more pure. 
     One embodiment of the invention provides an Apl p44 polypeptide as shown in SEQ ID NO: 12. 
     
       
         
           
               
            
               
                 YFYVGLDYXP AFSKI N   GFEI RESTGETAAV YPYMKDGTRV   
               
               
                   
               
               
                 
                   EWKAEKFDWN TPDPRIKFKN NPIVALEGSV GYSIGVARVE 
                 
               
               
                   
               
               
                 
                   LEIGYEQFKT KGIRDTGSKE EEADAVYLLA KKLPHTLVSD 
                 
               
               
                   
               
               
                   QSDKFLEELK NTKAAEIVKF AEAVGTSAKD  IDXKVCKKXX 
               
               
                   
               
               
                 XNAAXSWXCX QXGSXXXXXX KXXSXXFTKA GVXXXXXGKA 
               
               
                   
               
               
                 WPNGXXXX AA KAEDLSTALN RELTSAEKNK VAGLLTRTIS   
               
               
                   
               
               
                 GGEVVEIRAV STTSVMXNAC YDLLS 
               
            
           
         
       
     
     In one embodiment of the invention the amino acid at position 9 is S or C, the amino acid at position 153 is G or K, the amino acid at position 159 is N or H, the amino acid at position 160 is T or N, the amino acid at position 161 is N or G, the amino acid at position 165 is D, N, or G, the amino acid at position 168 is K or Q, the amino acid at position 170 is E or T, the amino acid at position 172 is T or P, the amino acid at position 175 is G or E, the amino acid at position 176 is S or T, the amino acid at position 177 is D, E, or S, the amino acid at position 178 is T or absent, the amino acid at position 179 is S or absent, the amino acid at position 180 is G or A, the amino acid at position 182 is E, A, or T, the amino acid at position 183 is F or L, the amino acid at position 185 is K or E, the amino acid at position 186 is L or I, the amino acid at position 193 is D or N, the amino acid at position 194 is A or T, the amino acid at position 195 is N or D, the amino acid at position 196 is E, G, or absent, the amino acid at position 197 is K or absent, the amino acid at position 205 is H or S, the amino acid at position 206 is T or absent, the amino acid at position 207 is D or absent, the amino acid at position 208 is S or D, the amino acid at position 257 is L or I. Polypeptides according to SEQ ID NO: 12 incorporating any combination of the before mentioned alternative amino acid residues are included in the invention. 
     One embodiment of the invention is a polypeptide shown in SEQ ID NO: 10: KDGTRV EWKAEKFDWNTPDPRI 
     One embodiment of the invention is a polypeptide shown in SEQ ID NO: 11: KDGTRV EWKAEKFDWNTPDPRIKFKN 
     One embodiment of the invention is a polypeptide shown in SEQ ID NO: 13 RVELEIGYEQFKT KGIRDTGSKEEEADA. 
     One embodiment of the invention provides a purified polypeptide comprising at least about 20, 25, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, or more contiguous amino acids, wherein the contiguous amino acids are chosen from amino acids 16-150 or 209-240 of SEQ ID NO: 12. The amino acid sequence of Aph p44 has less than 70% identity with Apl p44. Two amino acid sequence regions that are least variable among the different Apl p44 isolates ( FIG. 1B ), and that are at the same time divergent between p44 from Apl and p44 from Aph, extend from amino acids 16-150 and 209-240 (see, underlining of SEQ ID NO: 12, above). 
     Purified polypeptides of the invention can either be full-length polypeptides or fragments of polypeptides. For example, fragments of polypeptides of the invention can comprise about 10, 15, 20, 50, 75, 100, 150, 200, 250 or more amino acids of polypeptides of the invention. Variant polypeptides are at least about 80, or about 90, 96, 98, or 99% identical to the polypeptide sequences shown in SEQ ID NOs: 10, 11, 12, 13, 14, or 15 and are also polypeptides of the invention. Variant polypeptides have one or more conservative amino acid variations or other minor modifications and retain biological activity, i.e., are biologically functional equivalents. A biologically active equivalent has substantially equivalent function when compared to the corresponding wild-type polypeptide. 
     Percent sequence identity has an art recognized meaning and there are a number of methods to measure identity between two polypeptide or polynucleotide sequences. See, e.g., Lesk, Ed.,  Computational Molecular Biology , Oxford University Press, New York, (1988); Smith, Ed.,  Biocomputing: Informatics And Genome Projects , Academic Press, New York, (1993); Griffin &amp; Griffin, Eds.,  Computer Analysis Of Sequence Data, Part I , Humana Press, New Jersey, (1994); von Heinje,  Sequence Analysis In Molecular Biology , Academic Press, (1987); and Gribskov &amp; Devereux, Eds.,  Sequence Analysis Primer , M Stockton Press, New York, (1991). Methods for aligning polynucleotides or polypeptides are codified in computer programs, including the GCG program package (Devereux et al.,  Nuc. Acids Res.  12:387 (1984)), BLASTP, BLASTN, FASTA (Atschul et al.,  J. Molec. Biol.  215:403 (1990)), and Bestfit program (Wisconsin Sequence Analysis Package, Version 8 for Unix, Genetics Computer Group, University Research Park, 575 Science Drive, Madison, Wis. 53711) which uses the local homology algorithm of Smith and Waterman ( Adv. App. Math.,  2:482-489 (1981)). For example, the computer program ALIGN which employs the FASTA algorithm can be used, with an affine gap search with a gap open penalty of −12 and a gap extension penalty of −2. 
     When using any of the sequence alignment programs to determine whether a particular sequence is, for instance, about 95% identical to a reference sequence, the parameters are set such that the percentage of identity is calculated over the full length of the reference polynucleotide and that gaps in identity of up to 5% of the total number of nucleotides in the reference polynucleotide are allowed. 
     Variants can generally be identified by modifying one of the polypeptide sequences of the invention, and evaluating the properties of the modified polypeptide to determine if it is a biological equivalent. A variant is a biological equivalent if it reacts substantially the same as a polypeptide of the invention in an assay such as an immunohistochemical assay, an enzyme-linked immunosorbent Assay (ELISA), a radioimmunoassay (RIA), immunoenzyme assay or a western blot assay, e.g. has 90-110% of the activity of the original polypeptide. In one embodiment, the assay is a competition assay wherein the biologically equivalent polypeptide is capable of reducing binding of the polypeptide of the invention to a corresponding reactive antigen or antibody by about 80, 95, 99, or 100%. An antibody that specifically binds a corresponding wild-type polypeptide also specifically binds the variant polypeptide. Variant polypeptides of the invention can comprise about 1, 2, 3, 4, 5, 10, or 20 conservative amino acid substitutions. 
     A conservative substitution is one in which an amino acid is substituted for another amino acid that has similar properties, such that one skilled in the art of peptide chemistry would expect the secondary structure and hydropathic nature of the polypeptide to be substantially unchanged. In general, the following groups of amino acids represent conservative changes: (1) ala, pro, gly, glu, asp, gln, asn, ser, thr; (2) cys, ser, tyr, thr; (3) val, ile, leu, met, ala, phe; (4) lys, arg, his; and (5) phe, tyr, trp, his. 
     A polypeptide of the invention can further comprise a signal (or leader) sequence that co-translationally or post-translationally directs transfer of the protein. The polypeptide can also comprise a linker or other sequence for ease of synthesis, purification or identification of the polypeptide (e.g., poly-His), or to enhance binding of the polypeptide to a solid support. For example, a polypeptide can be conjugated to an immunoglobulin Fc region or bovine serum albumin. 
     A polypeptide can be covalently or non-covalently linked to an amino acid sequence to which the polypeptide is not normally associated with in nature, i.e., a heterologous amino acid sequence. A heterologous amino acid sequence can be from a non-Apl organism (e.g., an Aph organism), a synthetic sequence, or an Apl sequence not usually located at the carboxy or amino terminus of a polypeptide of the invention. Additionally, a polypeptide can be covalently or non-covalently linked to compounds or molecules other than amino acids. For example, a polypeptide can be linked to an indicator reagent, an amino acid spacer, an amino acid linker, a signal sequence, a stop transfer sequence, a transmembrane domain, a protein purification ligand, or a combination thereof. In one embodiment of the invention a protein purification ligand can be one or more C amino acid residues at, for example, the amino terminus or carboxy terminus of a polypeptide of the invention. An amino acid spacer is a sequence of amino acids that are not usually associated with a polypeptide of the invention in nature. An amino acid spacer can comprise about 1, 5, 10, 20, 100, or 1,000 amino acids. 
     If desired, a polypeptide can be a fusion protein, which can also contain other amino acid sequences, such as amino acid linkers, amino acid spacers, signal sequences, TMR stop transfer sequences, transmembrane domains, as well as ligands useful in protein purification, such as glutathione-S-transferase, histidine tag, and  Staphylococcal  protein A, or combinations thereof. More than one polypeptide of the invention can be present in a fusion protein. Fragments of polypeptides of the invention can be present in a fusion protein of the invention. A fusion protein of the invention can comprise one or more of Apl polypeptides of the invention, fragments thereof, or combinations thereof. 
     Polypeptides of the invention can be in a multimeric form. That is, a polypeptide can comprise one or more copies of an Apl polypeptide of the invention or a combination thereof. A multimeric polypeptide can be a multiple antigen peptide (MAP). See e.g., Tam, J. Immunol. Methods, 196:17-32 (1996). 
     Polypeptides of the invention can comprise an antigen that is recognized by an antibody specific for Apl p44. The antigen can comprise one or more epitopes (i.e., antigenic determinants). An epitope can be a linear epitope, sequential epitope or a conformational epitope. Epitopes within a polypeptide of the invention can be identified by several methods. See, e.g., U.S. Pat. No. 4,554,101; Jameson &amp; Wolf,  CABIOS  4:181-186 (1988). For example, a polypeptide of the invention can be isolated and screened. A series of short peptides, which together span an entire polypeptide sequence, can be prepared by proteolytic cleavage. By starting with, for example, 100-mer polypeptide fragments, each fragment can be tested for the presence of epitopes recognized in an ELISA. For example, in an ELISA assay an Apl polypeptide, such as a 100-mer polypeptide fragment, is attached to a solid support, such as the wells of a plastic multi-well plate. A population of antibodies are labeled, added to the solid support and allowed to bind to the unlabeled antigen, under conditions where non-specific absorption is blocked, and any unbound antibody and other proteins are washed away. Antibody binding is detected by, for example, a reaction that converts a colorless substrate into a colored reaction product. Progressively smaller and overlapping fragments can then be tested from an identified 100-mer to map the epitope of interest. 
     A polypeptide of the invention can be produced recombinantly. A polynucleotide encoding a polypeptide of the invention can be introduced into a recombinant expression vector, which can be expressed in a suitable expression host cell system using techniques well known in the art. A variety of bacterial, yeast, plant, mammalian, and insect expression systems are available in the art and any such expression system can be used. Optionally, a polynucleotide encoding a polypeptide can be translated in a cell-free translation system. A polypeptide can also be chemically synthesized or obtained from Apl cells. 
     An immunogenic polypeptide of the invention can comprise an amino acid sequence shown in SEQ ID NOs: 10, 11, 12, 13, 14, 15 or fragments thereof. An immunogenic polypeptide can elicit antibodies or other immune responses (e.g., T-cell responses of the immune system) that recognize epitopes of a polypeptide having SEQ ID NO: 12. An immunogenic polypeptide of the invention can also be a fragment of a polypeptide that has an amino acid sequence shown in SEQ ID NO: 12. An immunogenic polypeptide fragment of the invention can be about 10, 15, 20, 25, 30, 40, 50 or more amino acids in length. 
     Apl Polynucleotides 
     Polynucleotides of the invention contain less than an entire microbial genome and can be single- or double-stranded nucleic acids. A polynucleotide can be RNA, DNA, cDNA, genomic DNA, chemically synthesized RNA or DNA or combinations thereof. The polynucleotides can be purified free of other components, such as proteins, lipids and other polynucleotides. For example, the polynucleotide can be 50%, 75%, 90%, 95%, 96%, 97%, 98%, 99%, or 100% purified. The polynucleotides of the invention encode the polypeptides described above. In one embodiment of the invention the polynucleotides encode a polypeptide shown in SEQ ID NO: 12 or fragments thereof. Polynucleotides of the invention can comprise other nucleotide sequences, such as sequences coding for linkers, signal sequences, TMR stop transfer sequences, transmembrane domains, or ligands useful in protein purification such as glutathione-S-transferase, histidine tag, and Staphylococcal protein A. 
     Polynucleotides of the invention can be isolated. An isolated polynucleotide is a naturally-occurring polynucleotide that is not immediately contiguous with one or both of the 5′ and 3′ flanking genomic sequences that it is naturally associated with. An isolated polynucleotide can be, for example, a recombinant DNA molecule of any length, provided that the nucleic acid sequences naturally found immediately flanking the recombinant DNA molecule in a naturally-occurring genome is removed or absent. Isolated polynucleotides also include non-naturally occurring nucleic acid molecules. A nucleic acid molecule existing among hundreds to millions of other nucleic acid molecules within, for example, cDNA or genomic libraries, or gel slices containing a genomic DNA restriction digest are not to be considered an isolated polynucleotide. 
     Polynucleotides of the invention can also comprise fragments that encode immunogenic polypeptides. Polynucleotides of the invention can encode full-length polypeptides, polypeptide fragments, and variant or fusion polypeptides. 
     Degenerate nucleotide sequences encoding polypeptides of the invention, as well as homologous nucleotide sequences that are at least about 80, or about 90, 96, 98, or 99% identical to the polynucleotide sequences of the invention and the complements thereof are also polynucleotides of the invention. Percent sequence identity can be calculated as described in the “Polypeptides” section. Degenerate nucleotide sequences are polynucleotides that encode a polypeptide of the invention or fragments thereof, but differ in nucleic acid sequence from the wild-type polynucleotide sequence, due to the degeneracy of the genetic code. Complementary DNA (cDNA) molecules, species homologs, and variants of Apl polynucleotides that encode biologically functional Apl polypeptides also are Apl polynucleotides. 
     Polynucleotides of the invention can be isolated from nucleic acid sequences present in, for example, a biological sample, such as blood, serum, saliva, or tissue from an infected individual. Polynucleotides can also be synthesized in the laboratory, for example, using an automatic synthesizer. An amplification method such as PCR can be used to amplify polynucleotides from either genomic DNA or cDNA encoding the polypeptides. 
     Polynucleotides of the invention can comprise coding sequences for naturally occurring polypeptides or can encode altered sequences that do not occur in nature. If desired, polynucleotides can be cloned into an expression vector comprising expression control elements, including for example, origins of replication, promoters, enhancers, or other regulatory elements that drive expression of the polynucleotides of the invention in host cells. An expression vector can be, for example, a plasmid, such as pBR322, pUC, or ColE1, or an adenovirus vector, such as an adenovirus Type 2 vector or Type 5 vector. Optionally, other vectors can be used, including but not limited to Sindbis virus, simian virus 40, alphavirus vectors, poxvirus vectors, and cytomegalovirus and retroviral vectors, such as murine sarcoma virus, mouse mammary tumor virus, Moloney murine leukemia virus, and Rous sarcoma virus. Minichromosomes such as MC and MC1, bacteriophages, phagemids, yeast artificial chromosomes, bacterial artificial chromosomes, virus particles, virus-like particles, cosmids (plasmids into which phage lambda cos sites have been inserted) and replicons (genetic elements that are capable of replication under their own control in a cell) can also be used. 
     Methods for preparing polynucleotides operably linked to an expression control sequence and expressing them in a host cell are well-known in the art. See, e.g., U.S. Pat. No. 4,366,246. A polynucleotide of the invention is operably linked when it is positioned adjacent to or close to one or more expression control elements, which direct transcription and/or translation of the polynucleotide. 
     Polynucleotides of the invention can be used, for example, as probes or primers, for example, PCR primers, to detect the presence of Apl polynucleotides in a test sample, such as a biological sample. Probes are molecules capable of interacting with a target nucleic acid, typically in a sequence specific manner, for example, through hybridization. Primers are a subset of probes that can support an enzymatic manipulation and that can hybridize with a target nucleic acid such that the enzymatic manipulation occurs. A primer can be made from any combination of nucleotides or nucleotide derivatives or analogs available in the art that do not interfere with the enzymatic manipulation. 
     The hybridization of nucleic acids is well understood in the art and discussed herein. Typically a probe can be made from any combination of nucleotides or nucleotide derivatives or analogs available in the art. The ability of such probes and primers to specifically hybridize to Apl polynucleotide sequences will enable them to be of use in detecting the presence of complementary sequences in a given test sample. Polynucleotide probes and primers of the invention can hybridize to complementary sequences in a test sample such as a biological sample, including saliva, sputum, blood, plasma, serum, urine, feces, cerebrospinal fluid, amniotic fluid, wound exudate, or tissue. Polynucleotides from the sample can be, for example, subjected to gel electrophoresis or other size separation techniques or can be immobilized without size separation. The polynucleotide probes or primers can be labeled. Suitable labels and methods for labeling probes and primers are known in the art, and include, for example, radioactive labels incorporated by nick translation or by kinase, biotin labels, fluorescent labels, chemiluminescent labels, bioluminescent labels, metal chelator labels and enzyme labels. The polynucleotides from the sample are contacted with the probes or primers under hybridization conditions of suitable stringencies. 
     Depending on the application, varying conditions of hybridization can be used to achieve varying degrees of selectivity of the probe or primer towards the target sequence. For applications requiring high selectivity, relatively stringent conditions can be used, such as low salt and/or high temperature conditions, such as provided by a salt concentration of from about 0.02 M to about 0.15 M salt at temperatures of from about 50° C. to about 70° C. For applications requiring less selectivity, less stringent hybridization conditions can be used. For example, salt conditions from about 0.14 M to about 0.9M salt, at temperatures ranging from about 20° C. to about 55° C. The presence of a hybridized complex comprising the probe or primer and a complementary polynucleotide from the test sample indicates the presence of Apl or an Apl polynucleotide sequence in the sample. 
     Antibodies 
     Antibodies of the invention are antibody molecules that specifically and stably bind to an Apl p44 polypeptide of the invention or fragment thereof. Antibodies of the invention may also specifically and stably bind to an Aph p44 polypeptide or fragment thereof. One of skill in the art can easily determine if an antibody is specific for an Aph or Apl polypeptide using assays described herein. An antibody of the invention can be a polyclonal antibody, a monoclonal antibody, a single chain antibody (scFv), or an antigen binding fragment of an antibody. Antigen-binding fragments of antibodies are a portion of an intact antibody comprising the antigen binding site or variable region of an intact antibody, wherein the portion is free of the constant heavy chain domains of the Fc region of the intact antibody. Examples of antibody fragments include Fab, Fab′, Fab′-SH, F(ab′) 2  and F v  fragments. 
     An antibody of the invention can be any antibody class, including for example, IgG, IgM, IgA, IgD and IgE. An antibody or fragment thereof binds to an epitope of a polypeptide of the invention. An antibody can be made in vivo in suitable laboratory animals or in vitro using recombinant DNA techniques. Means for preparing and characterizing antibodies are well know in the art. See, e.g., Dean,  Methods Mol. Biol.  80:23-37 (1998); Dean,  Methods Mol. Biol.  32:361-79 (1994); Baileg,  Methods Mol. Biol.  32:381-88 (1994); Gullick,  Methods Mol. Biol.  32:389-99 (1994); Drenckhahn et al.  Methods Cell. Biol.  37:7-56 (1993); Morrison,  Ann. Rev. Immunol.  10:239-65 (1992); Wright et al.  Crit. Rev. Immunol.  12:125-68 (1992). For example, polyclonal antibodies can be produced by administering a polypeptide of the invention to an animal, such as a human or other primate, mouse, rat, rabbit, guinea pig, goat, pig, dog, cow, sheep, donkey, or horse. Serum from the immunized animal is collected and the antibodies are purified from the plasma by, for example, precipitation with ammonium sulfate, followed by chromatography, such as affinity chromatography. Techniques for producing and processing polyclonal antibodies are known in the art. 
     “Specifically binds” or “specific for” means that a first antigen, e.g., an Apl or Aph polypeptide, recognizes and binds to an antibody of the invention with greater affinity than other, non-specific molecules. A non-specific molecule is an antigen that shares no common epitope with the first antigen. In this case, Apl or Aph p44 polypeptides would not generally be desirable choices for non-specific control molecules. For example, an antibody raised against a first antigen (e.g., a polypeptide) to which it binds more efficiently than to a non-specific antigen can be described as specifically binding to the first antigen. In a preferred embodiment, an antibody or antigen-binding portion thereof specifically binds to a polypeptide of SEQ ID NO: 12 or fragments thereof when it binds with a binding affinity K a  of 10 7  l/mol or more. Specific binding can be tested using, for example, an enzyme-linked immunosorbant assay (ELISA), a radioimmunoassay (RIA), or a western blot assay using methodology well known in the art. 
     Additionally, monoclonal antibodies directed against epitopes present on a polypeptide of the invention can also be readily produced. For example, normal B cells from a mammal, such as a mouse, which was immunized with a polypeptide of the invention can be fused with, for example, HAT-sensitive mouse myeloma cells to produce hybridomas. Hybridomas producing Apl- or Aph-specific antibodies can be identified using RIA or ELISA and isolated by cloning in semi-solid agar or by limiting dilution. Clones producing Apl- or Aph-specific antibodies are isolated by another round of screening. Monoclonal antibodies can be screened for specificity using standard techniques, for example, by binding a polypeptide of the invention to a microtiter plate and measuring binding of the monoclonal antibody by an ELISA assay. Techniques for producing and processing monoclonal antibodies are known in the art. See e.g., Kohler &amp; Milstein, Nature, 256:495 (1975). Particular isotypes of a monoclonal antibody can be prepared directly, by selecting from the initial fusion, or prepared secondarily, from a parental hybridoma secreting a monoclonal antibody of a different isotype by using a sib selection technique to isolate class-switch variants. See Steplewski et al.,  P.N.A.S. U.S.A.  82:8653 1985; Spria et al.,  J. Immunolog. Meth.  74:307, 1984. Monoclonal antibodies of the invention can also be recombinant monoclonal antibodies. See, e.g., U.S. Pat. No. 4,474,893; U.S. Pat. No. 4,816,567. Antibodies of the invention can also be chemically constructed. See, e.g., U.S. Pat. No. 4,676,980. 
     Antibodies of the invention can be chimeric (see, e.g., U.S. Pat. No. 5,482,856), humanized (see, e.g., Jones et al.,  Nature  321:522 (1986); Reichmann et al.,  Nature  332:323 (1988); Presta,  Curr. Op. Struct. Biol.  2:593 (1992)), caninized, canine, or human antibodies. Human antibodies can be made by, for example, direct immortilization, phage display, transgenic mice, or a Trimera methodology, see e.g., Reisener et al.,  Trends Biotechnol.  16:242-246 (1998). 
     Antibodies that specifically bind Apl or Aph antigens (e.g., Apl or Aph polypeptides), are particularly useful for detecting the presence of Apl or Apl antigens in a sample, such as a serum, blood, plasma, urine, fecal, or saliva sample from an Apl- or Aph-infected animal. An immunoassay for Aph or an Apl antigen can utilize one antibody or several antibodies. An immunoassay for Aph or an Apl antigen can use, for example, a monoclonal antibody specific for an Apl epitope, a combination of monoclonal antibodies specific for epitopes of one Apl polypeptide, monoclonal antibodies specific for epitopes of different Apl polypeptides, polyclonal antibodies specific for the same Apl antigen, polyclonal antibodies specific for different Apl antigens, or a combination of monoclonal and polyclonal antibodies. Immunoassay protocols can be based upon, for example, competition, direct reaction, or sandwich type assays using, for example, labeled antibody. Antibodies of the invention can be labeled with any type of label known in the art, including, for example, fluorescent, chemiluminescent, radioactive, enzyme, colloidal metal, radioisotope and bioluminescent labels. 
     Antibodies of the invention or fragments thereof can be bound to a support and used to detect the presence of Aph or an Apl antigen. Supports include, for example, glass, polystyrene, polypropylene, polyethylene, dextran, nylon, amylases, natural and modified celluloses, polyacrylamides, agaroses and magletite. 
     Antibodies of the invention can further be used to isolate Apl organisms, Apl antigens, Aph organisms or Aph antigens by immunoaffinity columns. The antibodies can be affixed to a solid support by, for example, adsorbtion or by covalent linkage so that the antibodies retain their immunoselective activity. Optionally, spacer groups can be included so that the antigen binding site of the antibody remains accessible. The immobilized antibodies can then be used to bind Apl organisms, Apl antigens, Apl organisms, or Apl antigens from a sample, such as a biological sample including saliva, serum, sputum, blood, urine, feces, cerebrospinal fluid, amniotic fluid, wound exudate, or tissue. The bound Apl organisms, Apl antigens, Apl organisms, or Apl antigens are recovered from the column matrix by, for example, a change in pH. 
     Antibodies of the invention can also be used in immunolocalization studies to analyze the presence and distribution of a polypeptide of the invention during various cellular events or physiological conditions. Antibodies can also be used to identify molecules involved in passive immunization and to identify molecules involved in the biosynthesis of non-protein antigens. Identification of such molecules can be useful in vaccine development. Antibodies of the invention, including, for example, monoclonal antibodies and single chain antibodies, can be used to monitor the course of amelioration of a disease caused by Apl or Aph. By measuring the increase or decrease of Apl antibodies and/or Aph antibodies to Apl antigens and/or Aph antigens in a test sample from an animal, it can be determined whether a particular therapeutic regiment aimed at ameliorating the disorder is effective. Antibodies can be detected and/or quantified using for example, direct binding assays such as RIA, ELISA, or western blot assays. 
     Methods of Detection 
     The methods of the invention can be used to detect antibodies or antibody fragments specific for Apl; Apl polypeptides; Aph; Aph polypeptides; Apl polynucleotides, or a combination thereof in a test sample, such as a biological sample, an environmental sample, or a laboratory sample. A test sample can potentially comprise Apl polynucleotides, Apl polypeptides, Aph polypeptides, antibodies specific for Apl, and/or antibodies specific for Aph. A biological sample can include, for example, sera, blood, cells, plasma, or tissue from a mammal such as a horse, cat, dog or human. The test sample can be untreated, precipitated, fractionated, separated, diluted, concentrated, or purified. 
     In one embodiment methods of the invention comprise contacting an Apl polypeptide with a test sample under conditions that allow a polypeptide/antibody complex, i.e., an immunocomplex, to form. That is, a polypeptide of the invention specifically binds to an antibody specific for Apl and/or Aph antigens located in the sample. One of skill in the art is familiar with assays and conditions that are used to detect antibody/polypeptide complex binding. The formation of a complex between polypeptides and anti-Apl and/or anti-Aph antibodies in the sample is detected. In one embodiment of the invention antibody-polypeptide complexes can be detected at about 10, 15, 20, 25, 30 or less days after exposure or infection of the subject by  Anaplasma platys  and/or  Anaplasma phagocytophilum.    
     Antibodies of the invention can be used in a method of the diagnosis of Apl and/or Aph infection by obtaining a test sample from, e.g., a human or animal suspected of having an Apl and/or Aph infection. Exposure to Apl or Aph can also be detected. Exposure would include the presence of Aph or Apl organisms without clinical symptoms and prior infection with Aph or Apl. The test sample is contacted with antibodies of the invention under conditions enabling the formation of antibody-antigen complexes (i.e., immunocomplexes). The amount of antibody-antigen complexes can be determined by methodology known in the art. A level that is higher than that formed in a control sample indicates an Apl and/or Aph infection. A control sample is a sample that does not comprise any Apl and/or Aph polypeptides or antibodies specific for Apl or Aph. In one embodiment of the invention an antibody is specific for Apl antigens only. Alternatively, a polypeptide of the invention can be contacted with a test sample. Apl and/or Aph antibodies in a positive body sample will form an antigen-antibody complex under suitable conditions. The amount of antibody-antigen complexes can be determined by methods known in the art. 
     In one embodiment of the invention, the polypeptide/antibody complex is detected when an indicator reagent, such as an enzyme conjugate, which is bound to the antibody, catalyzes a detectable reaction. Optionally, an indicator reagent comprising a signal generating compound can be applied to the polypeptide/antibody complex under conditions that allow formation of a polypeptide/antibody/indicator complex. The polypeptide/antibody/indicator complex is detected. Optionally, the polypeptide or antibody can be labeled with an indicator reagent prior to the formation of a polypeptide/antibody complex. The method can optionally comprise a positive or negative control. 
     In one embodiment of the invention, antibodies of the invention are attached to a solid phase or substrate. A test sample potentially comprising a protein comprising a polypeptide of the invention is added to the substrate. Antibodies that specifically bind polypeptides of the invention are added. The antibodies can be the same antibodies used on the solid phase or can be from a different source or species and can be linked to an indicator reagent, such as an enzyme conjugate. Wash steps can be performed prior to each addition. A chromophore or enzyme substrate is added and color is allowed to develop. The color reaction is stopped and the color can be quantified using, for example, a spectrophotometer. 
     In another embodiment of the invention, antibodies of the invention are attached to a solid phase or substrate. A test sample potentially comprising a protein comprising a polypeptide of the invention is added to the substrate. Second anti-species antibodies that specifically bind polypeptides of the invention are added. These second antibodies are from a different species than the solid phase antibodies. Third anti-species antibodies are added that specifically bind the second antibodies and that do not specifically bind the solid phase antibodies are added. The third antibodies can comprise an indicator reagent such as an enzyme conjugate. Wash steps can be performed prior to each addition. A chromophore or enzyme substrate is added and color is allowed to develop. The color reaction is stopped and the color can be quantified using, for example, a spectrophotometer. 
     Assays of the invention include, but are not limited to those based on competition, direct reaction or sandwich-type assays, including, but not limited to enzyme linked immunosorbent assay (ELISA), western blot, IFA, radioimmunoassay (RIA), hemagglutination (HA), fluorescence polarization immunoassay (FPIA), and microtiter plate assays (any assay done in one or more wells of a microtiter plate). One assay of the invention comprises a reversible flow chromatographic binding assay, for example a SNAP® assay. See U.S. Pat. No. 5,726,010. 
     Assays can use solid phases or substrates or can be performed by immunoprecipitation or any other methods that do not utilize solid phases. Where a solid phase or substrate is used, a polypeptide of the invention is directly or indirectly attached to a solid support or a substrate such as a microtiter well, magnetic bead, non-magnetic bead, column, matrix, membrane, fibrous mat composed of synthetic or natural fibers (e.g., glass or cellulose-based materials or thermoplastic polymers, such as, polyethylene, polypropylene, or polyester), sintered structure composed of particulate materials (e.g., glass or various thermoplastic polymers), or cast membrane film composed of nitrocellulose, nylon, polysulfone or the like (generally synthetic in nature). A preferred substrate is sintered, fine particles of polyethylene, commonly known as porous polyethylene, for example, 10-15 micron porous polyethylene from Chromex Corporation (Albuquerque, N. Mex.). All of these substrate materials can be used in suitable shapes, such as films, sheets, or plates, or they may be coated onto or bonded or laminated to appropriate inert carriers, such as paper, glass, plastic films, or fabrics. Suitable methods for immobilizing peptides on solid phases include ionic, hydrophobic, covalent interactions and the like. 
     In one type of assay format, one or more polypeptides can be coated on a solid phase or substrate. A test sample suspected of containing an anti-Apl and/or anti-Aph antibody or fragment thereof is incubated with an indicator reagent comprising a signal generating compound conjugated to an antibody or antibody fragment specific for Apl and/or Aph for a time and under conditions sufficient to form antigen/antibody complexes of either antibodies of the test sample to the polypeptides of the solid phase or the indicator reagent compound conjugated to an antibody specific for Apl and/or Aph to the polypeptides of the solid phase. The reduction in binding of the indicator reagent conjugated to an anti-Apl and/or anti-Aph antibody to the solid phase can be quantitatively measured. A measurable reduction in the signal compared to the signal generated from a confirmed negative Apl and/or Aph test sample indicates the presence of anti-Apl and/or anti-Aph antibody in the test sample. This type of assay can quantitate the amount of anti-Apl and/or anti-Aph antibodies in a test sample. 
     In another type of assay format, one or more polypeptides of the invention are coated onto a support or substrate. A polypeptide of the invention is conjugated to an indicator reagent and added to a test sample. This mixture is applied to the support or substrate. If Apl and/or Aph antibodies are present in the test sample they will bind the polypeptide conjugated to an indicator reagent and to the polypeptide immobilized on the support. The polypeptide/antibody/indicator complex can then be detected. This type of assay can quantitate the amount of anti-Apl and/or anti-Aph antibodies in a test sample. 
     In another type of assay format, one or more polypeptides of the invention are coated onto a support or substrate. The test sample is applied to the support or substrate and incubated. Unbound components from the sample are washed away by washing the solid support with a wash solution. If Apl specific and/or Aph specific antibodies are present in the test sample, they will bind to the polypeptide coated on the solid phase. This polypeptide/antibody complex can be detected using a second species-specific antibody that is conjugated to an indicator reagent. The polypeptide/antibody/anti-species antibody indicator complex can then be detected. This type of assay can quantitate the amount of anti-Apl and/or anti-Aph antibodies in a test sample. 
     The formation of a polypeptide/antibody complex or a polypeptide/antibody/indicator complex can be detected by radiometric, colormetric, fluorometric, size-separation, or precipitation methods. Optionally, detection of a polypeptide/antibody complex is by the addition of a secondary antibody that is coupled to an indicator reagent comprising a signal generating compound. Indicator reagents comprising signal generating compounds (labels) associated with a polypeptide/antibody complex can be detected using the methods described above and include chromogenic agents, catalysts such as enzyme conjugates fluorescent compounds such as fluorescein and rhodamine, chemiluminescent compounds such as dioxetanes, acridiniums, phenanthridiniums, ruthenium, and luminol, radioactive elements, direct visual labels, as well as cofactors, inhibitors, magnetic particles, and the like. Examples of enzyme conjugates include alkaline phosphatase, horseradish peroxidase, beta-galactosidase, and the like. The selection of a particular label is not critical, but it will be capable of producing a signal either by itself or in conjunction with one or more additional substances. 
     Formation of the complex is indicative of the presence of anti-Apl and/or anti-Aph antibodies in a test sample. Therefore, the methods of the invention can be used to diagnose Apl and/or Aph infection in a patient. 
     The methods of the invention can also indicate the amount or quantity of anti-Apl and/or Aph antibodies in a test sample. With many indicator reagents, such as enzyme conjugates, the amount of antibody present is proportional to the signal generated. Depending upon the type of test sample, it can be diluted with a suitable buffer reagent, concentrated, or contacted with a solid phase without any manipulation. For example, it usually is preferred to test serum or plasma samples that previously have been diluted, or concentrate specimens such as urine, in order to determine the presence and/or amount of antibody present. 
     The invention further comprises assay kits (e.g., articles of manufacture) for detecting anti-Apl and/or anti-Aph antibodies or antibody fragments, Apl, Apl polypeptides, Aph, and/or Aph polypeptides in a sample. A kit comprises one or more polypeptides of the invention and means for determining binding of the polypeptide to anti-Apl antibodies and/or or anti-Aph antibodies or antibody fragments in the sample. A kit or article of manufacture can also comprise one or more antibodies or antibody fragments of the invention and means for determining binding of the antibodies or antibody fragments to Apl, Apl polypeptides, Aph, and/or Aph polypeptides in the sample. A kit can comprise a device containing one or more polypeptides or antibodies of the invention and instructions for use of the one or more polypeptides or antibodies for, e.g., the identification of an Apl and/or Aph infection in a mammal. The kit can also comprise packaging material comprising a label that indicates that the one or more polypeptides or antibodies of the kit can be used for the identification of Apl and/or Aph infection. Other components such as buffers, controls, and the like, known to those of ordinary skill in art, can be included in such test kits. The polypeptides, antibodies, assays, and kits of the invention are useful, for example, in the diagnosis of individual cases of Apl and/or Aph infection in a patient, as well as epidemiological studies of Apl and/or Aph outbreaks. Exposure to Apl or Aph can also be detected. Exposure would include the presence of Aph or Apl organisms without clinical symptoms and prior infection with Aph or Apl. 
     Polypeptides and assays of the invention can be combined with other polypeptides or assays to detect the presence of Apl along with other organisms. For example, polypeptides and assays of the invention can be combined with reagents that detect heartworm and/or  Borrelia burgdorferi  and/or  Anaplasma phagocytophilium  and/or  Ehrlichia canis.    
     Polynucleotides of the invention can be used to detect the presence of Apl polynucleotides in a sample. The polynucleotides can be used to detect Apl polynucleotides in a sample by a simple hybridization reaction and can also be used in, e.g., polymerase chain reactions (PCR) such as a real-time PCR reaction. Methods and compositions of the invention can also be used to differentially detect the presence Apl from Aph. 
     PCR assays are well described in the art, including, for example, U.S. Pat. Nos. 4,683,195; U.S. Pat. No. 4,683,202;U.S. Pat. No. 4,965,188. Generally, polynucleotide primers are annealed to denatured strands of a target nucleic acid. Primer extension products are formed by polymerization of deoxynucleoside triphosphates by a polymerase. PCR then involves repetitive cycles of template nucleic acid denaturation, primer annealing and extension of the annealed primers by the action of a thermostable polymerase. The process results in exponential amplification of the target Apl nucleic acids in the test sample, which allows for the detection of target polynucleotides existing in very low concentrations in a sample. 
     Real-time PCR assays are based on the detection of a signal, e.g., a fluorescent reporter signal. This signal increases in direct proportion to the amount of PCR product in a reaction. Real-time PCR is any amplification technique that makes it possible to monitor the evolution of an ongoing amplification reaction. See, Quantitation of DNA/RNA Using Real-Time PCR Detection, Perkin Elmer Applied Biosystems (1999); PCR Protocols (Academic Press New York, 1989). By recording the amount of fluorescence emission at each cycle, it is possible to monitor the PCR reaction during exponential phase where the first significant increase in the amount of PCR product correlates to the initial amount of target template. The higher the starting copy number of the nucleic acid target, the sooner a significant increase in fluorescence is observed. 
     One embodiment of the invention provides a method for detecting and/or quantifying  Anaplasma platys  polynucleotides in a test sample. Sense primers and antisense primers can be added to a test sample under conditions suitable for a polymerase chain reaction. The primers hybridize with  Anaplasma platys  p44 polynucleotides such that an amplification product is formed if  Anaplasma platys  p44 polynucleotides are present in the test sample. In one embodiment, the primers are SEQ ID NOs:6 and 7. Amplification products are detected and the presence and/or quantity of  Anaplasma platys  p44 polynucleotides is determined. Amplification products can be detected with a polynucleotide probe that hybridizes, under conditions suitable for a polymerase chain reaction, with an Apl p44 polynucleotide sequence. Examples of probes include SEQ ID NOs:8 and 9. The amplification product can be quantified by measuring a detection signal from the probe and comparing said detection signal to a second probe detection signal from a quantification standard. The quantification standard can be extracted in parallel with the test sample. 
     In another embodiment of the invention PCR primers can be selected from the variable regions of an Apl p44 polynucleotide. For example, primers of 10, 15, 20, 25, 30, or 40 contiguous nucleotides can be selected from the region between position 20 and 450 of SEQ ID NOs: 16, 17 and/or 18. 
     All patents, patent applications, and other scientific or technical writings referred to anywhere herein are incorporated by reference in their entirety. The invention illustratively described herein suitably can be practiced in the absence of any element or elements, limitation or limitations that are not specifically disclosed herein. Thus, for example, in each instance herein any of the terms “comprising”, “consisting essentially of”, and “consisting of” may be replaced with either of the other two terms, while retaining their ordinary meanings. The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention that in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by embodiments, optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the description and the appended claims. 
     In addition, where features or aspects of the invention are described in terms of Markush groups or other grouping of alternatives, those skilled in the art will recognize that the invention is also thereby described in terms of any individual member or subgroup of members of the Markush group or other group. 
     EXAMPLES 
     Example 1 
     Cloning of a p44 homolog from Apl 
     A homolog of an Aph p44 gene from Apl was cloned from the blood of an infected dog. The blood sample was obtained from a dog residing on the Hopi Reservation in Arizona. Genomic DNA was isolated from 200 ul of whole blood using standard techniques (QiaAmp DNA Blood Miniprep Kit—Part #51104). Degenerate primers were designed to target the conserved regions of Aph p44 , Anaplasma marginale  msp2 , Anaplasma ovis  msp2, and  Anaplasma centrale  msp2 genes (Forward primer: 5′ TAT TTT TAT GTT GGT YTR GAY TAT WSH CC 3′ (SEQ ID NO: 1) Reverse primer: 5′ GCT CAG CAG ATC GTA RCA NGC RTT YAW CAT 3′ (SEQ ID NO:2)). 
     Degenerate primer-based PCR on a conventional thermocycler was used to amplify a polynucleotide with a length of approximately 800 nucleotides from an Apl p44 gene according to standard protocols (Platinum® Taq, Invitrogen). PCR products were cloned, sequenced, and analyzed relative to those reported for other species of  Anaplasma .  FIG. 1A  shows an alignment of the partial sequences obtained from different isolates of Apl p44. The cloned Apl p44 gene contained a hypervariable region flanked by conserved sequences at the 5′ and 3′ ends. This is similar to Aph p44, but the length of the hypervariable region was shorter for Apl p44.  FIG. 1B  shows an amino acid alignment for Apl p44 with the corresponding region from a published Aph sequence (Aph p44-1; Accession No. ABA26590). While Apl p44 nucleotide sequences of present the invention (e.g.  FIG. 1A ) show greater than 90% identity to each other, they share less than 70% identity with that of Aph p44, and the same is true for the amino acid sequences. 
     Example 2 
     Detection of Apl by Real Time PCR Assay 
     A real-time PCR assay was developed to detect an Apl p44 polynucleotide from genomic DNA. Sample types for analysis included canine whole blood, as well as nymph and adult ticks. Primers and hybridization probes were selected to be specific for an Apl p44 gene and did not amplify the p44 gene of Aph. Sequences of the primers and probes are shown below: 
     
       
         
           
               
               
               
               
            
               
                 Apl p44 forward primer: 
                 5′ CCGGCGTTTAGTAAGATAAATG 3′ 
                 (SEQ ID NO: 6) 
                   
               
               
                   
               
               
                 Apl p44 reverse primer: 
                 5′ GCAAATTTAACGATCTCCGCC 3′ 
                 (SEQ ID NO: 7) 
               
               
                   
               
               
                 Apl p44 probe 1129-FITC: 
                 5′ ACAGTATCGGGGTAGCGAGAGTAGAA 3′ 
                 (SEQ ID NO: 8) 
               
               
                   
               
               
                 Apl p44 probe 1183-LC670: 
                 5′ GGAGATCGGCTATGAACAGTTCAAGAC 3′ 
                 (SEQ ID NO: 9) 
               
               
                   
               
            
           
         
       
     
     These were synthesized by a commercial vendor. The real-time PCR was optimized for the Roche LightCycler® 480 using Roche reagents (Genotyping Master Mix #04707524001). Primers were used at a concentration of 0.3 μM for the forward primer and 0.6 μM for the reverse primer. Both probes were used at a concentration of 0.3 μM. PCR was performed under the following conditions: a single hot-start cycle at 95° C. for 10 minutes followed by 50 cycles of denaturation at 95° C. for 30 seconds, annealing at 58° C. for 25 seconds, and extension at 72° C. for 20 seconds. A melting curve was performed by heating the PCR product to 95° C. for 1 minute, cooling to 40° C. for one minute, and then gradually heating to 80° C. Positive samples were identified from the software as having both positive crossing points and a melting curve temperature of 66.5° C.+/−1° C. Analytical sensitivity was determined to be at least 0.1 fg in negative canine genomic DNA ( FIG. 2A ). The Apl p44 PCR detected strains of Apl from across the US, the Caribbean and Brazil. The Apl p44 PCR did not detect Aph p44 DNA from a control plasmid containing the Aph p44 template or PCR-positive field samples ( FIG. 2B ). 
     Example 3 
     Detection of Apl by an Anti-Species, Indirect ELISA 
     A synthetic peptide derived from the p44 gene of Apl was tested in an ELISA format to determine serological reactivity in dogs from an area with a high burden of  Rhipicephalus  ticks and high seroprevalence for  E. canis . These geographic areas have been shown to have relatively high levels of  A. platys  infections and an absence of  A. phagocytophilum  infections in dogs by PCR. The peptide sequence is shown below: 
     
       
         
           
               
            
               
                 (SEQ ID NO: 15) 
               
               
                 Cys-Lys-Asp-Gly-Thr-Arg-Val-Glu-Trp-Lys-Ala-Glu- 
               
               
                   
               
               
                 Lys-Phe-Asp-Trp-Asn-Thr-Pro-Asp-Pro-Arg-Ile. 
               
               
                   
               
            
           
         
       
     
     An alternate peptide sequence comprises: 
     
       
         
           
               
            
               
                 (SEQ ID NO: 14) 
               
               
                 Cys-Lys-Asp-Gly-Thr-Arg-Val-Glu-Trp-Lys-Ala-Glu- 
               
               
                   
               
               
                 Lys-Phe-Asp-Trp-Asn-Thr-Pro-Asp-Pro-Arg-Ile-Lys- 
               
               
                   
               
               
                 Phe-Lys-Asn 
               
            
           
         
       
     
     The synthetic peptide of SEQ ID NO: 15 was solubilized in DMSO and coated on Immulon 2Hb plates (Thermo Electron Corporation #3455) at a concentration of 0.25 μg/ml in 50 mM Tris, pH 7.5 overnight at room temperature. The plates were blocked with a Tris/TWEEN® buffer (0.1M Tris, pH 7.6 with 2% TWEEN® 20) for 4 hours. The plates were washed three times with plate wash (PBS, pH 7.2 with 0.05% TWEEN® 20). Serum was added at a 1:100 dilution in sample diluent (PBS, pH 7.2 with 0.05% TWEEN® 20 and 1% BSA) and allowed to incubate at room temperature for 1 hour. Plates were washed 5 times and a anti-dog conjugate (Jackson ImmunoResearch # 304-035-003) was added at a 1:2000 dilution in sample diluent and allowed to incubate for 1 hour at room temperature. The plates were washed 3 times and a one component TMB substrate was added and allowed to incubate for 5 minutes before the reaction was stopped with 1% SDS. Absorbance measurements were read on a standard plate reader at a wavelength of 650 nm. A cut-off of 0.4 was determined. Samples were compared to a similar in-clinic ELISA for Aph p44 (Snap®4Dx™, IDEXX Laboratories, Inc.) and the results are shown in  FIG. 3 . The column labeled “SNAP® AP result” shows results obtained by visual inspection. The column labeled “SNAP® NET AP” shows quantitative results obtained by densitometric measurement. 
     A total of 67 samples were tested. Twenty-seven samples tested negative and 16 samples tested positive on both assays. Twenty-four samples tested negative on the in-clinic ELISA for Aph p44, but tested positive by the Apl p44 anti-species, indirect ELISA. Thus, the Apl assay detects Apl exposure in dogs that would be missed by testing with Aph assays. 
     Apl p44 provides a means of detecting Apl infection beyond what is identified by cross-reactivity to the p44 from Aph. Apl p44 polynucleotides allow for differentiation between Apl and Aph. 
     Example 4 
     Sensitivity of direct Apl ELISA 
     Dogs were experimentally infected with Apl and serum samples were collected following a time course. Serum antibodies to Apl were assayed using a direct Apl ELISA and the SNAP® 4Dx. Specifically, the synthetic peptide derived from the p44 gene of Apl (SEQ ID NO: 14, and designated as Apl p44L in Tables 1 and 2) was solubilized in DMSO and coated on Immulon™ 2Hb plates (Thermo Electron Corporation #3455) at a concentration of 0.25 μg/ml in 50 mM Sodium Carbonate, pH 9.6, overnight at room temperature. The plates were blocked (2% TWEEN® 20 in 0.1M Tris, pH 7.6) for 2 hours. Serum (25 ul) was mixed with 50 ul of a specific conjugate (the conjugate, Apl_p44L:HRPO, was made at 1:1 ratio and diluted to 0.5 μg/ml in 50 mM Tris pH 7.6, 0.05% TWEEN®20, 5% BSA, and 10% FBS), and added immediately to coated well for incubation at room temperature for 1 hour. Plates were then washed 6 times before a one component TMB substrate was added for color development. Absorbance measurements were read on a standard plate reader at a wavelength of 650 nm. A cut-off of 0.07 was determined. The same samples were also tested using an in-clinic ELISA developed for Aph (Snap®4Dx™, IDEXX Laboratories, Inc.) and the results are shown in Table 1 (the column labeled “SNAP® NET AP” shows quantitative results obtained by densitometric measurement. “Days PI” refers to the number of days post-infection.) 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Time course study by Apl p44 peptide ELISA 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Canine 
                 IDEXX 
                 Apl_P44L 
                 SNAP ® 
                   
               
               
                   
                 ID 
                 ID 
                 cutoff 0.07 
                 NET AP 
                 Days PI 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 105376 
                 A1_0 
                 0.03 
                 0 
                 3 
               
               
                   
                   
                 A1_1 
                 0.04 
                 0 
                 7 
               
               
                   
                   
                 A1_2 
                 0.45 
                 0 
                 10 
               
               
                   
                   
                 A1_3 
                 0.68 
                 0 
                 14 
               
               
                   
                   
                 A1_4 
                 0.37 
                 0.01 
                 17 
               
               
                   
                   
                 A1_5 
                 0.17 
                 0.03 
                 21 
               
               
                   
                   
                 A1_6 
                 0.07 
                 0.05 
                 24 
               
               
                   
                   
                 A1_7 
                 0.11 
                 0.2 
                 28 
               
               
                   
                   
                 A1_8 
                 0.26 
                 0.34 
                 35 
               
               
                   
                   
                 A1_9 
                 0.20 
                 0.31 
                 42 
               
               
                   
                   
                 A1_10 
                 0.25 
                 0.29 
                 49 
               
               
                   
                   
                 A1_11 
                 0.20 
                 0.13 
                 56 
               
               
                   
                   
                 A1_12 
                 0.46 
                 0.18 
                 63 
               
               
                   
                   
                 A1_13 
                 1.11 
                 0.43 
                 71 
               
               
                   
                   
                 A1_15 
                 0.32 
                 0.17 
                 84 
               
               
                   
                 125011 
                 A2_0 
                 0.03 
                 0 
                 3 
               
               
                   
                   
                 A2_1 
                 0.03 
                 0 
                 7 
               
               
                   
                   
                 A2_2 
                 0.24 
                 0.05 
                 10 
               
               
                   
                   
                 A2_3 
                 0.20 
                 0.15 
                 13 
               
               
                   
                   
                 A2_4 
                 0.17 
                 0.02 
                 17 
               
               
                   
                   
                 A2_5 
                 0.10 
                 0.11 
                 21 
               
               
                   
                   
                 A2_6 
                 0.07 
                 0.15 
                 24 
               
               
                   
                   
                 A2_7 
                 0.07 
                 0.29 
                 28 
               
               
                   
                   
                 A2_8 
                 0.15 
                 0.38 
                 35 
               
               
                   
                   
                 A2_9 
                 0.21 
                 0.41 
                 42 
               
               
                   
                   
                 A2_10 
                 0.19 
                 0.29 
                 49 
               
               
                   
                   
                 A2_11 
                 0.18 
                 0.24 
                 56 
               
               
                   
                   
                 A2_12 
                 0.14 
                 0.2 
                 64 
               
               
                   
                   
                 A2_13 
                 0.17 
                 0.11 
                 71 
               
               
                   
                   
                 A2_14 
                 0.20 
                 0.09 
                 78 
               
               
                   
                   
                 A2_15 
                 0.19 
                 0.11 
                 86 
               
               
                   
                 257818 
                 A3_0 
                 0.03 
                 0 
                 3 
               
               
                   
                   
                 A3_1 
                 0.03 
                 0 
                 7 
               
               
                   
                   
                 A3_2 
                 0.21 
                 0 
                 10 
               
               
                   
                   
                 A3_3 
                 0.23 
                 0 
                 13 
               
               
                   
                   
                 A3_4 
                 0.23 
                 0.02 
                 17 
               
               
                   
                   
                 A3_5 
                 0.13 
                 0.06 
                 21 
               
               
                   
                   
                 A3_6 
                 0.11 
                 0.01 
                 24 
               
               
                   
                   
                 A3_7 
                 0.15 
                 0.15 
                 28 
               
               
                   
                   
                 A3_8 
                 0.37 
                 0.27 
                 35 
               
               
                   
                   
                 A3_9 
                 0.49 
                 0.24 
                 42 
               
               
                   
                   
                 A3_10 
                 0.58 
                 0.22 
                 49 
               
               
                   
                   
                 A3_11 
                 0.55 
                 0.23 
                 56 
               
               
                   
                   
                 A3_12 
                 0.54 
                 0.16 
                 64 
               
               
                   
                   
                 A3_13 
                 0.49 
                 0.1 
                 71 
               
               
                   
                   
                 A3_14 
                 1.28 
                 0.28 
                 78 
               
               
                   
                   
                 A3_15 
                 1.39 
                 0.25 
                 86 
               
               
                   
                 264347 
                 A4_0 
                 0.03 
                 0 
                 3 
               
               
                   
                   
                 A4_1 
                 0.03 
                 0 
                 7 
               
               
                   
                   
                 A4_2 
                 0.04 
                 0 
                 10 
               
               
                   
                   
                 A4_3 
                 0.06 
                 0 
                 14 
               
               
                   
                   
                 A4_4 
                 0.08 
                 0 
                 17 
               
               
                   
                   
                 A4_5 
                 0.05 
                 0.05 
                 21 
               
               
                   
                   
                 A4_6 
                 0.04 
                 0.09 
                 24 
               
               
                   
                   
                 A4_7 
                 0.06 
                 0.05 
                 28 
               
               
                   
                   
                 A4_8 
                 0.07 
                 0.09 
                 35 
               
               
                   
                   
                 A4_9 
                 0.07 
                 0.08 
                 42 
               
               
                   
                   
                 A4_10 
                 0.09 
                 0.07 
                 49 
               
               
                   
                   
                 A4_11 
                 0.11 
                 0.06 
                 56 
               
               
                   
                   
                 A4_12 
                 0.20 
                 0.04 
                 63 
               
               
                   
                   
                 A4_13 
                 0.37 
                 0.06 
                 71 
               
               
                   
                   
                 A4_14 
                 1.41 
                 0.27 
                 79 
               
               
                   
                   
                 A4_15 
                 0.24 
                 0.06 
                 84 
               
               
                   
                 280610 
                 A5_0 
                 0.03 
                 0 
                 3 
               
               
                   
                   
                 A5_1 
                 0.03 
                 0 
                 7 
               
               
                   
                   
                 A5_2 
                 0.06 
                 0 
                 10 
               
               
                   
                   
                 A5_3 
                 0.58 
                 0 
                 14 
               
               
                   
                   
                 A5_4 
                 0.42 
                 0 
                 17 
               
               
                   
                   
                 A5_5 
                 0.12 
                 0 
                 21 
               
               
                   
                   
                 A5_6 
                 0.07 
                 0.08 
                 24 
               
               
                   
                   
                 A5_7 
                 0.14 
                 0.16 
                 28 
               
               
                   
                   
                 A5_8 
                 0.08 
                 0.07 
                 35 
               
               
                   
                   
                 A5_9 
                 0.40 
                 0.06 
                 42 
               
               
                   
                   
                 A5_10 
                 0.53 
                 0.04 
                 49 
               
               
                   
                   
                 A5_11 
                 0.70 
                 0.06 
                 56 
               
               
                   
                   
                 A5_12 
                 0.88 
                 0.27 
                 63 
               
               
                   
                   
                 A5_13 
                 0.78 
                 0.06 
                 71 
               
               
                   
                   
                 A5_14 
                 1.45 
                 0.14 
                 79 
               
               
                   
                   
                 A5_15 
                 0.73 
                 0.08 
                 84 
               
               
                   
                 287099 
                 A6_0 
                 0.03 
                 0 
                 3 
               
               
                   
                   
                 A6_1 
                 0.03 
                 0 
                 7 
               
               
                   
                   
                 A6_2 
                 0.71 
                 0 
                 10 
               
               
                   
                   
                 A6_3 
                 0.95 
                 0.03 
                 13 
               
               
                   
                   
                 A6_4 
                 0.40 
                 0.03 
                 17 
               
               
                   
                   
                 A6_5 
                 0.13 
                 0 
                 21 
               
               
                   
                   
                 A6_6 
                 0.07 
                 0 
                 24 
               
               
                   
                   
                 A6_7 
                 0.10 
                 0.09 
                 28 
               
               
                   
                   
                 A6_8 
                 0.10 
                 0.18 
                 34 
               
               
                   
                   
                 A6_9 
                 0.15 
                 0.16 
                 42 
               
               
                   
                   
                 A6_10 
                 0.22 
                 0.2 
                 49 
               
               
                   
                   
                 A6_11 
                 0.36 
                 0.28 
                 56 
               
               
                   
                   
                 A6_12 
                 0.26 
                 0.11 
                 62 
               
               
                   
                   
                 A6_13 
                 0.41 
                 0.17 
                 70 
               
               
                   
                   
                 A6_14 
                 1.08 
                 0.46 
                 78 
               
               
                   
                   
                 A6_15 
                 0.90 
                 0.36 
                 83 
               
               
                   
                   
               
            
           
         
       
     
     The results show that a direct ELISA assay using peptide Apl-p44L (SEQ ID NO: 14) detected an immune response to Apl in serum of experimentally infected dogs. The results further show that the Apl assay detected an immune response to Apl earlier than the in-clinic Aph ELISA. In four of the six dogs, a response was detected at day 10 post-infection. 
     Example 5 
     Detection of Aph infection by Apl ELISA 
     The same direct ELISA procedure described in Example 4, based on Apl_p44L peptide (SEQ ID NO: 14), was used to test serum samples that were previously tested positive for Aph infection. These include samples from dogs experimentally infected with Aph (i.e. Pinky and Brain), as well as field dogs from an area with a high Aph seroprevalence (with ME as prefix in ID). Five samples from an area with a high Apl seroprevalence (i.e. P or HP as prefix in ID) were used as positive controls, and five from normal dogs (RAR as prefix in ID) served as negative controls. The same set of samples were also tested using an in-clinic ELISA developed for Aph (Snap®4Dx™, IDEXX Laboratories, Inc.) and the results are shown in Table 2 (the column labeled “SNAP® NET AP” shows quantitative results obtained by densitometric measurement.) 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Detection of Aph infection by Apl p44 peptide ELISA 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 Apl p44L 
                 SNAP ® 
               
               
                   
                 ID 
                 cut off 0.07 
                 (net AP) 
               
               
                   
                   
               
               
                   
                 ME307 
                 0.11 
                 0.55 
               
               
                   
                 ME308 
                 0.27 
                 0.30 
               
               
                   
                 ME314 
                 0.05 
                 0.09 
               
               
                   
                 ME478 
                 0.05 
                 0.12 
               
               
                   
                 ME485 
                 0.10 
                 0.52 
               
               
                   
                 ME487 
                 0.04 
                 − 
               
               
                   
                 ME492 
                 0.55 
                 0.47 
               
               
                   
                 ME513 
                 0.09 
                 0.04 
               
               
                   
                 ME562 
                 0.05 
                 0.42 
               
               
                   
                 ME593 
                 0.04 
                 0.34 
               
               
                   
                 ME631 
                 0.10 
                 0.27 
               
               
                   
                 ME635 
                 0.26 
                 0.44 
               
               
                   
                 ME668 
                 0.06 
                 0.66 
               
               
                   
                 ME703 
                 0.04 
                 0.58 
               
               
                   
                 ME724 
                 0.14 
                 0.10 
               
               
                   
                 ME741 
                 0.08 
                 0.05 
               
               
                   
                 ME758 
                 0.08 
                 0.13 
               
               
                   
                 pinky 62 
                 0.62 
                 + 
               
               
                   
                 Brain 69 
                 0.21 
                 + 
               
               
                   
                 p9 
                 0.62 
                 − 
               
               
                   
                 p34 
                 1.75 
                 − 
               
               
                   
                 p43 
                 0.22 
                 − 
               
               
                   
                 HP127 
                 0.12 
                 − 
               
               
                   
                 HP145 
                 0.20 
                 − 
               
               
                   
                 RAR 1758 
                 0.03 
                 − 
               
               
                   
                 RAR 1769 
                 0.04 
                 − 
               
               
                   
                 RAR 1755 
                 0.03 
                 − 
               
               
                   
                 RAR 1756 
                 0.03 
                 − 
               
               
                   
                 RAR 1760 
                 0.03 
                 − 
               
               
                   
                 BLK 
                 0.03 
               
               
                   
                   
               
            
           
         
       
     
     The results show that the Apl_p44 peptide was able to detect 12 out of 18 Aph positive samples, demonstrating the utility of the peptide for detection of Aph as well as Apl.