HUMAN HERPESVIRUS-7 DIAGNOSTIC AND IMMUNOLOGIC REAGENTS AND METHODS THEREFOR

Abstract: The human herpesvirus-7 gene U14 is provided as encoding the major determinant of immunoresponse to HHV-7 infection, i.e., protein pp85. The invention provides specific reagents for serological detection, diagnosis, immunization, and for studies of pathogenesis of human herpesvirus-7.

Description: DESCRIPTION HUMAN HERPESVIRUS-7 DIAGNOSTIC AND IMMUNOLOGIC REAGENTS AND METHODS THEREFOR BACKGROUND OF THE INVENTION Human herpesvirus 7 (HHV-7) is a DNA-containing beta-herpesvirus isolated from peripheral blood mononuclear cells (PBMC's), from saliva of healthy individuals, or from individuals affected by chronic fatigue syndrome. The natural history of HHV- 7 infection in the human host is not well understood. An association of primary infection with exanthema subitum or febrile illness has been established, in some cases with central nervous system complications such as generalized convulsions and hemiplegia. The virus persists in the organism, is shed in the saliva from where it can be isolated, and can be reactivated by culturing PBMC's. Cells susceptible to HHV-7 infection include CD4+ T-lymphocytes in vivo and in vitro, and CD68+ cells of the monocyte/macrophage lineage in Kaposi's sarcoma lesions. CD4 is an essential component of the cellular receptor for virus entry. Preliminary seroepidemiological studies ' have shown that HHV-7 is widely diffused in the general population and that seroconversion for HHV-7 occurs in most individuals during the first four years of life. HHV-7 persists in the host in a latent state after primary infection and, therefore, is an opportunistic agent in immunocompromised hosts, such as transplant recipients. Once reactivated, HHV-7 may be pathogenic and would further worsen a state of immunodeficiency due to HHV-7 's selective tropism for CD4+ T-lymphocytes. Despite knowledge of the sequence of the entire genome of HHV-7 and, therefore, knowledge of the amino acid sequences of open reading frames of the genome, knowledge of the biochemical and immunological properties of the encoded proteins remains rudimentary mainly due to difficulties in efficiently growing the virus in cell cultures and the scarcity of specific antibodies. In particular, prior to the present disclosure, no function was ascribed to the HHV-7 U14 gene product. The gene encodes a protein of 648 amino acid residues, with a predicted molecular weight of about 74 kDa. HHV-7 genome organization overlaps with that of human herpesvirus-6 (HHV-6) and homologies at the encoded amino acid level vary from about 44% to about 85%. U.S. Patent 5,230,997 to Frenkel relates to HHV-7 as a newly characterized herpesvirus, and U.S. Patent 5,514,577 to Draper et al. relates to oligonucleotide therapies for modulating the effects of herpesviruses. PCT publication WO 94/03605 relates to compositions and methods for detecting human herpesvirus-6 strain Z29. None of these documents suggest reagents for serological detection of HHV-7 as provided by the present disclosure. Polyvalent mouse and rabbit sera, and monoclonal antibodies (MAbs) to HHV-7 have been developed. MAbs 5E1 and 3B1 recognize a family of five antigenically related proteins (87, 85, 70, 61 and 57 kDa, respectively). The 85 kDa species is phosphorylated, and the family of proteins is designated as the pp85 complex. In a sequential immunoprecipitation-immunoblot reaction, proteins immunoprecipitated with human sera are able to react by immunoblot with Mab 5E1. MAb 5E1 is specific for HHV-7-infected cells as measured by lack of reactivity to uninfected cells and lack of cross-reactivity to HHV-6-infected cells. Pp85 is the immunodominant target of the human response to HHV-7 infection. However, the gene that encodes pp85 and the source of pp85 (the host or the virus) were not known prior to the present disclosure. Convenient and standardized methods for specific HHV-7 serodiagnosis do not exist. Serological diagnoses of HHV-7 infections are currently carried out using HHV- 7 infected cells as antigen. An important issue related to interpretation of serologic assays is specificity, especially the need for distinguishing between HHV-6 and HHV-7. Because of genetic similarity between HHV-6 and HHV-7, cross-reaction can affect results obtained in most assays based on whole cell lysates. Therefore, absorption steps with infected cell antigens from the other virus are required to increase specificity of the assays. Because of the above-described problems with cross-reactivity of current serodiagnostic tests and the need for absorption steps, known procedures are not completely satisfactory for specific serological detection of HHV-7. Further, a safe and effective vaccine for protection to HHV-7 infection or reactivation does not exist. SUMMARY OF THE INVENTION The present invention seeks to overcome these and other drawbacks inherent in the prior art by providing reagents heretofore unavailable for use in specific serological detection of HHV-7. A serological assay uses antigen for the detection of specifically binding antibodies and, therefore, the success of the assay depends upon availability and purity of antigen. Accordingly, the present inventors have mapped the gene encoding pp85, the immunodominant protein of HHV-7 infection, and have demonstrated that pp85 is encoded by the U14 gene of HHV-7. The inventors have also defined a functional role for pp85 as a viral tegument protein. The invention thereby also provides reagents for recombinantly expressing protein pp85, and reagents for serological detection of HHV- 7. "Serological detection," as used herein, means detection of antibodies having binding specificity for pp85 protein, or for epitopic fragments thereof in a test sample. The invention provides a purified nucleic acid molecule having a nucleotide sequence encoding human herpesvirus-7 pp85 protein, or an epitopic fragment thereof, the protein having an amino acid sequence essentially as set forth in SEQ ID NO:3 or SEQ ID NO:4. The nucleic acid molecule may have a nucleotide sequence as set forth in SEQ ID NO: 1 or 2. The nucleic acid molecule may be a fragment of SEQ ID NO: 1 or 2 that encodes an HHV-7-specific epitope of HHV-7 pp85 protein. HHV-7 specific epitopes are provided as SEQ ID NOS.:6, 7, 8, 9, " 10, or 11. A further aspect of the invention is a purified nucleic acid molecule complementary to any of the above- described nucleic acid molecules. Table 1 lists the identity of sequences of the present disclosure having sequence identifiers. A purified nucleic acid molecule having a nucleotide sequence that encodes an amino acid sequence extending from about amino acid 471 to 586 of human herpesvirus-7 pp85 protein as set forth in SEQ ID NO:3, or as set forth in SEQ ID NO:4, or extending from about amino acid 484 to 509, or 484-502, or 504-516, or 489- 498 of human herpes virus-7 pp85 protein as set forth in SEQ ID NO.: 8, 9, 10, or 11, respectively, is a further aspect of the present invention. Another aspect of the invention is a purified human herpesvirus-7 pp85 protein having an amino acid sequence essentially as set forth in SEQ ID NO:3, or SEQ ID NO:4. An epitopic fragment of pp85 protein as defined by a peptide having an amino acid sequence extending from about amino acid 471 to 586 as set forth in SEQ ID NO:6, or as set forth in SEQ ID NO:7, or extending from about amino acid 484 to 509, or 484-502, or 504-516, or 489-498 of human herpes virus-7 pp85 protein as set forth in SEQ ID NO.: 8, 9, 10, or 11, respectively, the peptide having no cross-reactivity with human herpesvirus-6 is another embodiment of the present invention. "The peptide having no cross-reactivity," as used herein, means that antibodies having binding specificity for the peptide have no significant binding specificity for HHV-6 protein products. A method for serological detection of human herpesvirus-7 in a biological sample is an important embodiment of the present invention. The method provides substantially no cross reactivity with human herpesvirus-6 and comprises contacting the sample with a human herpesvirus-7-specific epitope of human herpesvirus-7 pρ85 protein; and determining binding of the epitope to the sample. Binding indicates presence of antibodies having binding specificity for human herpesvirus-7 in the biological sample. The human herpesvirus-7 specific epitope may be pp85 protein. Determining binding is by a method whereby binding of the pp85 protein or fragment thereof to the sample is detected, including immunofluorescence assay, enzyme-linked immunosorbent assay, radioimmunoassay, agglutination, hemagglutination, or immunoblotting, for example. A further embodiment of the invention is a method for diagnosis of human herpesvirus-7 infection in a subject. The method comprises contacting a biological sample from the subject with a human herpesvirus-7-specific epitope of human herpesvirus-7 pp85 protein; and determining binding of the epitope to the sample. Binding indicates diagnosis of human herpesvirus-7 infection in the subject. Another embodiment of the invention is a method for diagnosis of human herpesvirus-7 infection in a subject comprising contacting a first biological sample and a second biological sample obtained later in time than the first sample from the subject with a human herpesvirus-7-specific epitope of human herpesvirus-7 pp85 protein; and determining binding of the epitope to the first sample and the second sample. Greater binding of the epitope to the second sample compared to binding of the epitope in the first sample indicates diagnosis of human herpesvirus-7 infection in the subject. The level of binding in the first sample may be considered a background level of antibody present in the subject. In this way, the subject is his or her own control. A method of preparing recombinant human herpesvirus-7 pp85 protein encoded by the human herpesvirus-7 U14 gene is an aspect of the present invention. The method comprises preparing a recombinant host cell bearing the U14 gene, the host being capable of expressing the encoded protein, culturing the recombinant host cell to produce pp85 protein; and collecting the pp85 protein. The pp85 protein has an amino acid sequence essentially as set forth in SEQ ID NO:3, or SEQ ID NO:4. A method of preparing an epitopic fragment of pp85 using a recombinant system is a further aspect of the invention. In this case, the recombinant host cell may bear a fragment of the U14 gene encoding the epitopic fragment. Another embodiment of the present invention is a kit for serological detection of human herpesvirus-7 in a human biological sample. The kit comprises in packaged combination a carrier means adapted to receive a plurality of container means in close confinement therewith; a first container means including pp85 protein or an epitopic fragment of pp85 protein; and a second container means including a detectable antibody having specific binding affinity for human immunoglobulin. The kit may further comprise a detectable antibody having specific binding affinity for pp85 protein or for an epitopic fragment thereof for use as a control. A method for conferring protection to human herpesvirus-7 infection or to reactivation of HHV-7 in a subject comprising administering an epitope of pp85 protein to the subject, wherein the subject has an immune reaction to the epitope, thereby providing protection to human herpesvirus-7 infection or reactivation is a further embodiment of the present invention. Preferably, the pp85 protein, or epitopic fragment thereof, is produced by recombinant means and is , therefore, more pure than protein isolated from nonrecombinant sources. One of skill in the art could not have predicted prior to the present disclosure whether the i munodominant protein was virally encoded or cellularly encoded and induced by viral infection, or, if the protein was virally encoded, which open reading frame of the HHV-7 genome encoded the immunodominant protein. A homologue of the HHV-7 U14 gene was predicted to be encoded in the HHV-6 genome. However, the immunodominant protein for HHV-6 is not the U14 gene product, but protein pi 00, the product of the Ul l gene. The immunodominant protein in HCMV is ppl50 encoded by the UL32 gene, and pp65, encoded by the UL 38 gene. Therefore, one could not have predicted the open reading frame by homology to HHV-6 or to HCMV. In the human herpesviruses known to the present inventors, the U14 gene product has not previously been shown to be a major immunogenic protein. No immune response in humans to homologues of the U14 gene product has been reported prior to the present disclosure. The HHV-7 cDNA expression library constructed by the present inventors as described in Example 1 herein was the first to be successfully screened using monoclonal antibody 5E1. Other HHV-7 cDNA libraries failed to express material reactive with this antibody, including a library constructed in a DNA cosmid. Problems with growing infected cells in culture, and lack of optimal conditions for infection caused inadequate representation of cDNAs in previously screened libraries. Following long-standing patent law convention, the terms "a" and "an" mean "one or more" when used in this application, including the claims. BRIEF DESCRIPTION OF THE DRAWING The following drawing forms part of the present specification and is included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to the drawing in combination with the detailed description of specific embodiments presented herein. FIG. 1 shows the arrangement of clones pBLUESCRIPT™-2c and -8a identified by immunoscreening of a HHV-7-infected cell cDNA library with MAb 5E1. For both clones, the cDNA from U14 ORF is cloned and expressed in fusion with the prokaryotic β-galactosidase gene. Clone ρBLUESCRIPT™-8a lacks 153 bp at the N- terminus and the EcoRI cloning site is absent. The HHV-7 genomic coordinates of the inserted sequence are shown below each arrangment, and the locations of the start and stop codons are indicated. Non-coding region of the cDNA is shaded. MCS, multiple cloning site. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides compositions and methods for serological detection of human herpesvirus-7 where substantially no cross reactivity with human herpesvirus-6 occurs. Human herpesvirus-7 U14 recombinant nucleic acid molecules are provided for generation or synthesis of protein pp85 or epitopes thereof for serodiagnostic assays. Such protein or peptide epitopes are further provided for vaccines for conferring protection to herpesvirus-7 infection or reactivation. The present invention results from the identification of the gene that encodes the major determinant of immunoresponse to HHV-7 infection, i.e., protein pp85. The gene is viral as opposed to cellular and is the U14 gene of HHV-7. This information provides the basis for development of specific reagents for serological detection, diagnosis, immunization, and for studies of pathogenesis of HHV-7. By immunoscreening a cDNA library from HHV-7-infected cells with MAb 5E1 that is directed to the proteins of the pp85 complex, the present inventors mapped the gene encoding pp85 to the U14 open reading frame of the HHV-7 genome. A prokaryotically-expressed fusion protein containing the U14 open reading frame reacted with MAb 5E1 in immunoblot assay. Further, a functional role for pp85 was defined by immunoelectron microscopy studies. Immunogold labelling of cryosections of HHV-7-infected cord blood mononuclear cells at high resolution localized the reactivity of MAb 5E1 to the outer surface of the virion tegument. This finding demonstrates that pp85, the product of the U14 gene, is a component of the HHV-7 tegument, and suggests that the HHV-7 tegument is not a homogenous structure but rather is composed of substructures including an outermost layer containing pp85. The identified gene is U14 and the open reading frame (ORF) of U14 is provided for generating viral recombinant protein pρ85, or epitopic fragments thereof, and for serodiagnostic immunoassay tests such as Western blotting or ELISA assays, for example. Use of recombinantly expressed pp85 protein, or epitopic fragments thereof, provides standardization and increases the sensitivity of HHV-7 serodiagnostic methods. Nucleic acid embodiments of the present invention include deoxyribonucleic acid and ribonucleic acid molecules. In certain aspects, the invention concerns isolated DNA segments and recombinant vectors that include within their sequence a nucleic acid sequence essentially as set forth in SEQ ID NO:l, or SEQ ID NO:2. The term "essentially as set forth" means that the nucleic acid sequence substantially corresponds to a portion of SEQ ID NO:l, or SEQ ID NO:2, and has relatively few codons that are not identical, or functionally equivalent, to the codons of said sequences. The term "functionally equivalent codon" is used herein to refer to codons that encode the same amino acid, such as the six codons for arginine or serine, for example, and also refers to codons that encode biologically equivalent amino acids. - Included within the term "nucleic acid molecule" are nucleic acid segments and smaller fragments of such segments; and also recombinant vectors, including, for example, plasmids, cosmids, phage, viruses, and the like. The term "gene" is used for simplicity to refer to a functional protein-, polypeptide- or peptide-encoding unit. As will be understood by those in the art in light of this disclosure, this functional term includes genomic sequences, cDNA sequences or combinations thereof. "Purified" or "isolated substantially away from other coding sequences" means that the gene of interest forms the significant part of the coding region of the nucleic acid molecule, and that the nucleic acid molecule does not contain large portions of naturally-occurring coding nucleic acid, such as large genomic fragments or other functional genes or cDNA coding regions. This refers to the nucleic acid molecule as originally isolated, and does not exclude genes or coding regions later added to the segment by the hand of man. The amino acid sequence of the proteins and peptides of the present invention is also that encoded by messenger RNA. Phosphoprotein pp85 is phosphorylated in in vitro infection of mammalian cells, however, the present inventors have produced the protein recombinantly in E. coli where phosphorylation is not expected to occur as described in Example 2. The recombinantly-produced protein binds to Mab 5E1 and to human seropositive serum, therefore, phosphorylation is not required for use of pp85 or epitopes thereof in the immunoassays provided herein. Binding to human seropositive serum demonstrates the utility of the present reagents for diagnosis in human serum. "Pp85", as used herein, means either the phosphorylated or nonphosphorylated forms of the protein. The term "amino acid sequence essentially as set forth in SEQ ID NO:3, or SEQ ID NO:4," for example means that the sequence substantially corresponds to a portion of SEQ ID NO:3, or SEQ ID NO:4 and has relatively few amino acids which are not identical to, or a biologically functional equivalent of, the amino acids of SEQ ID NO:3 or SEQ ID NO:4. The term "biologically functional equivalent" is well understood in the art and is further defined as a protein having a sequence essentially as set forth in SEQ ID NO:3, or SEQ ID NO:4 capable of binding human seropositive serum. Modifications and changes may be made in the sequence of pp85, or an epitopic fragment thereof, and still obtain a peptide or protein having like or otherwise desirable characteristics. For example, certain amino acids may be substituted for other amino acids in a peptide without appreciable loss of function. Since it is the interactive capacity and nature of an amino acid sequence that defines the peptide's functional activity, certain amino acid sequences may be chosen (or its underlying DNA coding sequence) and nevertheless obtain a peptide with like properties. It is thus contemplated by the inventors that certain changes may be made in the sequence of pp85 protein, or epitopic fragments thereof, (or underlying DNA) without appreciable loss of its ability to function. Substitution of like amino acids can be made on the basis of hydrophilicity. U.S. Patent 4,554,101, incorporated herein by reference, states that the following hydrophilicity values have been assigned to amino acid residues: arginine (+3.0); lysine (+3.0); aspartate (+3.0 ± 1); glutamate (+3.0 ± 1); serine (+0.3); asparagine (+0.2) glutamine (+0.2); glycine (0); threonine (-0.4); proline (-0.5 ± 1); alanine (-0.5) histidine (-0.5); cysteine (-1.0); methionine (-1.3); valine (-1.5); leucine (-1.8) isoleucine (-1.8); tyrosine (-2.3); phenylalanine (-2.5); tryptophan (-3.4). It is understood that an amino acid may be substituted for another having a similar hydrophilicity value and still obtain a biologically equivalent peptide. In such changes, the substitution of amino acids whose hydrophilicity values are within ±2 is preferred, those which are within ±1 are more preferred, and those within ±0.5 are most preferred. As outlined above, amino acid substitutions are generally therefore based on the relative similarity of the amino acid side-chain substituents, for example, their hydrophobicity, hydrophilicity, charge, size, and the like. Exemplary substitutions which take various of the foregoing characteristics into consideration are well known to those of skill in the art and include: arginine and lysine; glutamate and aspartate; serine and threonine; glutamine and asparagine; and valine, leucine and isoleucine. Epitopic regions of protein pp85 are shown herein to be immunogenic or are predicted to be immunogenic, i.e., each region may be a substantial part of an epitope that induces an immune response in a host subject. An epitope is a relatively short sequence of amino acids that is "complementary" to and therefore will bind antigen binding sites on antibodies directed to that antigen. By "complementary," as related to protein embodiments, is meant the amino acids or peptides exhibit an attractive force towards each other. In particular, epitopes of pp85 of the present invention have specific binding affinity for human antibodies having binding specificity for HHV-7 and do not bind antibodies having specificity for HHV-6. Such epitopic sequences are useful for detection of antibodies that bind said epitopes, and for administering to a subject for conferring protection to HHV-7 infection or reactivation. As described in Example 6, a peptide region of pp85 from amino acids 471-586, 484 to 509, 484-502, 504-516, or 489-498 of human herpes virus-7 pp85 protein as set forth in SEQ ID NO.: 6, 7, 8, 9, 10, or 11, has been demonstrated to include an epitope of pp85. Further epitopes of pp85 may include amino acids 464-469, 489-498, 505-512, 545-550, 560- 563, 566-572, 581-585, 610-616, or 633-640 of SEQ ID NO:3 or SEQ ID NO:4. The size of the epitope is not believed to be particularly crucial, so long as it is at least large enough to carry the identified core amino acids. The smallest useful epitope sequence contemplated by the present inventors is about 4-8 amino acids in length. This size generally corresponds to the smallest peptide antigens prepared in accordance with the invention. However, the size of the antigen may be larger where desired, as long as it contains an epitopic core sequence. Further nucleic acid embodiments of the present invention include a recombinant vector comprising a purified nucleic acid molecule having a nucleotide sequence encoding a pp85 protein or epitopic peptide, the protein having an amino acid sequence essentially as set forth in SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO.: 6, SEQ ID NO.: 7, SEQ ID NO.: 8, SEQ ID NO.: 9, SEQ ID NO.: 10, or SEQ ID NO.: 11. As used herein, the term "recombinant vector", refers to a vector that has been modified to contain a nucleic acid segment that encodes a pp85 protein or epitopic peptide, or fragment of interest thereof. The recombinant vector may be further defined as an expression vector comprising a promoter operatively linked to said pp85 protein or peptide encoding nucleic acid molecule. The recombinant vector may also comprise other sequences such as expression control sequences, markers, amplifying genes, signal sequences, and the like. It will also be understood that amino acid and nucleic acid sequences may include additional residues, such as additional N- or C-terminal amino acids or 5' or 3' nucleotides, and yet still be essentially as set forth in one of the sequences disclosed herein, so long as the sequence meets the criteria set forth herein, including the maintenance of biological protein activity where protein expression is concerned. The addition of terminal sequences particularly applies to nucleic acid sequences which may, for example, include various non-coding sequences flanking either of the 5' or 3' portions of the coding region, or may include various coding or noncoding internal sequences, i.e., amino acids that form the junction between a protein fused to pp85 protein, for example. The nucleic acid segments of the present invention, regardless of the length of the coding sequence if self,, may be combined with other DNA sequences, such as promoters, polyadenylation signals, additional restriction enzyme sites, multiple cloning sites, other coding segments, and the like, such that their overall length may vary considerably. The pp85 protein has been successfully expressed in a prokaryotic expression system by the present inventors, in particular, using the pBLUESCRIPT™ vector in E. coli cells. Other expression systems contemplated by the present inventors include, yeast-based, insect-based, or mammalian cell-based systems. For expression, one would position the coding sequences adjacent to and under the control of the promoter. It is understood in the art that to bring a coding sequence under the control of such a promoter, one positions the 5' end of the transcription initiation site of the transcriptional reading frame of the protein between about 1 and about 50 nucleotides "downstream" of (i.e., 3' of) the chosen promoter. One will also typically desire to incorporate into the transcriptional unit which includes the U14 gene, an appropriate polyadenylation site if one was not contained within the original cloned segment. Typically, the poly A addition site is placed about 30 to 2000 nucleotides "downstream" of the termination site of the protein at a position prior to transcription termination. Examples of promoters include the polyhedrin promoter for baculovirus transfer vectors, β-galactosidase, lac, or trc, for bacterial vectors; or RSV LTR, CMV, SV40, MMTV-LTR (dexamethasone-inducible), HSV-TK (thymidine kinase) for mammaliam vectors, or the like. Preferred promoters are the polyhedrin or bacterial promoters. Of the mammalian promoters, SV40 and CMV are preferred. By way of example and not limitation, vectors may be further defined as eukaryotic plasmids such as SV40, baculovirus, or yeast vectors; prokaryotic vectors such as bacterial plasmids, e.g., pUC and derivatives thereof; or viral vectors such as a herpesvirus, pCMV, adenoviral, lambdaphage Ml 3 or derivatives thereof; or retroviral vectors such as HIV-, HHV-6- or HHV-7-based vectors. Preferred vectors are plasmid or baculovirus vectors, and most preferred vectors are plasmid vectors. In another embodiment of the invention, the recombinant vector may comprise a further DNA sequence encoding at least one polypeptide for co-expression with pp85, or an epitopic fragment thereof. This DNA sequence is operatively attached to the recombinant vector in reading frame so it is expressed in the host. The different structural DNA sequences carried by the vector may be separated by termination and start sequences so that the proteins will be expressed separately or they may be part of a single reading frame and therefore be produced as a fusion protein by methods known in the art. A fusion protein containing pp85 protein or epitopic peptide thereof where the fusion does not interfere with the immunogenic function of the protein or peptide is an aspect of the present invention. Example 2 provides a pp85 protein fused with β galactosidase sequences. A further aspect of the present invention is a host cell, made recombinant with a recombinant vector comprising a nucleic acid encoding pp85 protein or an epitopic peptide thereof. The recombinant host cell may be a prokaryotic or a eukaryotic cell. In a more preferred embodiment, the recombinant host cell is a eukaryotic cell. As used herein, the term "engineered" or "recombinant" cell is intended to refer to a cell into which a recombinant gene, such as a gene encoding pp85 protein or epitopic peptide thereof, has been introduced. Therefore, engineered cells are distinguishable from naturally occurring cells which do not contain a recombinantly introduced gene. Thus, engineered cells are cells having a gene or genes introduced through the hand of man. Recombinantly introduced genes will either be in the form of a cDNA gene (i.e., they will not contain introns), a copy of a genomic gene, or will include genes positioned adjacent to a promoter not naturally associated with the particular introduced gene, or combinations thereof. Exemplary host cells may be further defined as an insect cell line such as Spodoptera frugiperda (Sf9); mammalian cells such as human fibroblast cell lines, Vero cells, CHO cells, or COS cells; Saccharomyces cerevisiae, Escherichia coli cells, or the like. Preferred host cells are Sf9 or CHO cells, and most preferred host cells are CHO cells. For protein purification, various approaches are available to guide the protein of interest toward the cellular membrane or into growth medium to facilitate protein isolation and purification. Secretion of proteins from transfected eukaryotic cells permits the isolation and characterization free from complex intracellular milieu. Traditional methods for secretion include attachment of secretory signal sequences to intracellular proteins or deletion of the "retention signals", such as hydrophobic domains. Several expression vectors have been developed that allow simple purification of the recombinant proteins by designing .chimeric genes, encoding the protein of interest fused to a tag at the amino or carboxyl terminus. In fact, following this strategy, the present inventors have cloned and expressed related HHV-7 proteins in the form of fusion proteins with the Fc portion of human IgGl. This fusion system allows purification of the products by affinity chromatography using Protein A columns. Other commonly used tags for expression and affinity purification include glutathione -S-transferase (GST), maltose binding protein (MalBP), fusion with biotinylated purification tag, or polyhistidine. In these systems, the fusion between the protein of interest and the tag occurs through a sequence recognized by specific proteases, e.g. enterokinase, thrombin, or factor Xa that allow removal of the proteic tag sequence from the purified fusion protein. Alternatively, peptides including an antigenic epitope of pp85 may be synthesized synthetically. Synthesis of epitopic sequences, or peptides that include an antigenic epitope within their sequence is achieved using conventional synthetic techniques such as the solid phase method using an automatic peptide synthesizer (such as an Applied Biosystems Model430A Peptide Synthesizer) with standard t- butoxycarbonyl (t-Boc) chemistry that is well known to one skilled in this art in light of this disclosure. Peptide antigens synthesized in this manner may be aliquotted in predetermined amounts and stored in conventional manners, such as in aqueous solutions or, preferably, in a powder or lyophilized state pending use. The amino acid composition of the synthesized peptides may be determined by amino acid analysis with an automated amino acid analyzer to confirm that they correspond to the expected compositions. The purity of the peptides may be determined by sequence analysis or HPLC. While discussion has focused on functionally equivalent polypeptides arising from amino acid changes, it will be appreciated that these changes may be effected by alteration of the encoding DNA, taking into consideration also that the genetic code is degenerate and that two or more codons may code for the same amino acid. Pp85-derived epitopes exhibiting virtually no cross-reactivity with other known pathogens essentially allow elimination of serological cross-reactivity, further increasing the specificity of the assays. Such HHV-7-specific reagents are provided to substantially eliminate any potential cross-reactivity to the homolog gene product of genetically-related herpesvirus such as HHV-6 and HCMV. The specificity of the reagent, therefore, is significantly increased. A further embodiment of the invention is use of pp85 in assembly of a subunit vaccine for conferring protection to HHV-7 infection or reactivation of HHV-7 in a subject. "Subunit vaccine," as used herein, means an assembly of at least one epitope of the pp85 protein together with an HHV-7 immunogenic protein or peptide other than pp85 protein or peptide, or with an immunogenic protein from a closely related herpesvirus, such as a beta herpesvirus, as material for immunization of a human subject. Examples of an immunogenic protein from a closely related herpesvirus include, but are not limited to, the UI 1 gene product of HHV-6 or HHV-7, or the UL32 or UL38 gene products of HCMV. An advantage to a subunit vaccine is increased immunogenicity of the vaccine compared to immunogenicity of the pp85 protein alone. An amount of pp85, or an epitopic fragment thereof, effective to induce disease protection or reactivation in the subject is administered to the subject in order to confer protection to HHV-7 infection. The vaccine may be administered once to afford a certain degree of protection against HHV-7 or it may be repeated at preset intervals. The vaccine may suitably be readministered at anytime. A typical interval for revaccination is about 1 day to 6 months, and more preferably about 10 days to 4 months. However, the vaccine may be administered as a booster at other times as well. The protein pp85 or epitopic fragment thereof may be administered to a subject by administering an expression vector containing the U14 gene or fragment encoding an epitopic fragment of pp85. The expression vector is expressed in vivo thereby producing the pp85 protein or epitopic fragment thereof. In this way, a nucleic acid vaccine is provided that in vivo provides a protein vaccine. An immunoassay for serological detection of HHV-7 in a human biological sample is provided by the present invention. The immunoassay comprises the steps of contacting pp85 or an epitopic fragment thereof with the biological sample for a sufficient time to permit binding between antibody that may be present in the sample and pp85 protein, or epitopic fragment thereof, to form an incubate, and determining the presence of bound pp85 or epitopic fragment thereof in the incubate. Determining antibody-bound pp85 or epitopic fragment thereof may be by a number of detecting means. One detecting means uses a detectable label attached to pp85 or epitopic fragment thereof. Another detecting means is by contacting the incubate with a detectably labelled antibody specific for human immunoglobulin such as IgG, IgA, or IgM. A detectably labelled antibody may be an enzyme-linked antibody, a fluorescent- tagged antibody or a radiolabeled antibody, for example. Where the antigen is labeled, a secondary antibody having binding specificity for human immunoglobulin need not be labeled. The presence of antibodies that bind pp85 or an epitopic fragment thereof in the human biological sample is detectable as a measure of the detectable label and demonstrates detection of HHV-7. Antibodies fall into a number of different immunoglobulin classes and, generally, as used herein, antibodies mean immunoglobulins IgG, IgA, or IgM. IgG antibodies are the common circulating type of antibodies and a primary target of serological detection herein. Detection of IgM antibody is also important herein especially where HHV-7 reactivation is suspected or where a newly acquired infection is suspected such as may occur in a transplant recipient of an infected organ. A biological sample is a fluid sample from a human subject suspected of having HHV-7 infection or reactivation. If the human subject has HHV-7 infection or reactivation, then the sample would contain antibodies to HHV-7, in particular, antibodies of various immunoglobulin classes having binding specificity for pp85 or an epitopic fragment thereof. Such samples include blood, plasma, serum, cerebrospinal fluid, semen, pleural fluid, B-cell secretions, saliva, urine, sputum, mucus, or the like. One of skill in the art in light of the present disclosure could design further immunoassays capable of using reagents of the present invention to serologically detect HHV-7. Such immunoassays are intended or fall within the scope of the present invention and include competition assays where MAb 5E1, for example, would compete with antibody present in a test sample for binding pp85 or an epitope thereof; or indirect assays (sandwiched); for example. A detectable antigen may be added to a test sample, and a second antibody having binding specificity for human immunoglobulin may be used to detect the antigen-primary antibody complex. In certain embodiments, it will be advantageous to employ appropriate means, such as a label, for determining binding of pp85 or epitope thereof to the sample. A wide variety of appropriate indicator means are known in the art, including fluorescent, radioactive, enzymatic, colorimetric, bioluminescent, or other ligands, such as avidin/biotin, fluorescein, or rhodamine, which are capable of giving a detectable signal. In preferred embodiments, one will likely desire to employ a fluorescent label or an enzyme tag, such as urease, alkaline phosphatase or peroxidase, instead of radioactive or other environmental undesirable reagents. In the case of enzyme tags, colorimetric indicator substrates are known which can be employed to provide a means visible to the human eye or spectrophotometrically, to identify specific binding. A kit for vaccination of a human is an aspect of the present invention. The kit comprises in packaged combination a carrier means adapted to receive a container means in close confinement therewith and a first container means including pp85 protein or epitopic peptide thereof, or a recombinant molecule capable of expressing pp85 protein or an epitopic peptide thereof. Preferably, the first container means includes recombinantly produced pp85, or epitopic fragments thereof. In a further embodiment, the kit further comprises an HHV-7 immunogenic protein or peptide other than pp85 protein or peptide, or an immunogenic protein from a closely related herpesvirus, such as a beta herpesvirus. A further aspect of the present invention is an HHV-7 vaccine comprising a human subject-protecting amount of pp85 protein or epitopic peptide thereof. The vaccine may comprise a recombinant vector, including viral vectors other than HHV-7 itself, capable of expressing pp85 protein or an epitopic peptide thereof in a host. The vaccine may comprise a physiologically acceptable carrier. The vaccine according to the invention is administered in amounts sufficient to stimulate the immune system and confer protection to HHV-7 infection or reactivation. The vaccine may be provided in powder form as a unit form, or in about 1-1000 doses of vaccine per sealed container, and more preferably about 10 to 100 doses. Physiologically acceptable carriers for vaccination must not interfere with the immunological response elicited by the vaccine and/or with the expression of its protein or peptide product. Exemplary carriers are water, saline, dextrose, glycerol, ethanol, or the like. The carrier or diluent may be compatible with administration methods such as injection, eye drops, nose drops, and the like. Other additives, such as adjuvants and stabilizers, among others, may also be contained in the vaccine. Preferably, adjuvants such as aluminum hydroxide, aluminum phosphate, plant and animal oils, and the like, are administered with the vaccine in amounts sufficient to enhance the immune response to pp85 immunogenic protein or peptide. The amount of adjuvant added to the vaccine will vary depending on the nature of the adjuvant, generally ranging from about 0.1 . o about 100 times the weight of the active ingredient, preferably from about 1 to about 10 times the weight of the active ingredient. The vaccine of the present invention may also contain various stabilizers. Any suitable stabilizer can be used including carbohydrates such as sorbitol, mannitol, starch, sucrose, dextrin, or glucose; proteins such as albumin or casein; and buffers such as alkaline metal phosphate and the like. A stabilizer is particularly advantageous when a dry vaccine preparation is prepared by lyophilization. The vaccine may be administered by any suitable known method of inoculating including nasally, ophthalmically, by injection, in drinking water, in food, by exposure, and the like. A vaccine according to the present invention can be administered by injection. When administered by injection, the vaccines are preferably administered parenterally. Parenteral administration as used herein means administration by intravenous, subcutaneous, intramuscular, or intraperitoneal injection. The vaccine may be provided in a sterile container in unit form or in other amounts. It is preferably stored frozen, below -20° C, and more preferably below -70° C. It is thawed prior to use, and may be refrozen immediately thereafter. Even though the invention has been described with a certain degree of particularity, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing disclosure. Accordingly, it is intended that all such alternatives, modifications, and variations which fall within the spirit and the scope of the invention be embraced by the defined claims. The following examples are included to demonstrate preferred embodiments of the invention. It should be appreciated by those of skill in the art that the techniques disclosed in the examples which follow represent techniques discovered by the inventor to function well in the practice of the invention, and thus can be considered to constitute preferred modes for its practice. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention. EXAMPLE 1 Mapping of the Gene Encoding pp85 The present example provides data demonstrating that the HHV-7 gene encoding pp85 is U14. Cells and viruses. Primary cord blood mononuclear cells (CBMCs) were purified from heparinized blood by Ficoll-Hypaque (Pharmacia) gradient centrifugation. SupTl T lymphoblastoid CD4+ T cells were cultured in RPMI 1640, 90%; and fetal bovine serum, 10%. After Ficoll-purification, CBMCs were grown for two days with phytohemagglutinin (PHA-P) (Sigma Biochimici, Milano, Italy), 5U/ml, and two further days with PHA-P and recombinant interleukin 2 (5U/ml) (Boehringer, Mannheim, Germany) prior to infection. The HHV-7 strains were RK and AL. Strain RK was obtained from Dr. N. Frenkel, National Institutes of Health) and strain AL was isolated by the present inventors. CBMCs and SupTl were infected with HHV-7 (RK or AL). Progress of infection was monitored by indirect immunofluorescence assay (IF A) microscopy with MAb 5E1 (Dr. Gabriella Campadelli-Fiume, Univ. of Bologna, Italy). Construction of a cDNA library from HHV-7 -infected cells. SupTl cells infected with HHV-7 (AL) were harvested 6 days after infection, when approximately 70% of the cells were infected (as evaluated by the appearance of cytopathic effect (CPE) and by IF A). RNA was extracted and polyadenylated RNA was selected by oligo(dT)-cellulose column chromatography using standard techniques. cDNA was retrotranscribed with an oligo(dT)-XhoI primer and using 5μg of purified polyadenylated RNA as template. A directional cDNA library was constructed based on the ZAPII kit (EcoRI-Xhol) (Stratagene, La Jolla, CA). Screening of the HHV-7 cDNA library with MAb 5E1. The amplified library was screened for reactivity of the lytic plaques with MAb 5E1 by plating a total of 7.5 x 10 5 PFU in 15 x 150-mm agar plates. After incubation at 42°C for 4-5 h, the phage plaques were transferred to nitrocellulose discs treated with 10 mM isopropyl-β- D-thiogalactopyranoside (IPTG). The membranes were blocked with 5% skimmed milk in phosphate-buffered saline (PBS) solution and allowed to react with MAb 5E1 (1:300 dilution). Reactivity was detected by the biotin-avidin-amplified anti-mouse IgG-peroxidase ABC kit (Vectastain, Vector Laboratories, Burlingame, CA). The plaques testing positive were harvested, diluted, replated, and tested again for reactivity to MAb 5E1 four times, until they were clonally pure. BLUESCRIPT™ phagemids were rescued by excision from lambda ZAPII™ by superinfection with the EXASSIST™ helper phage (Stratagene). Rescued phagemids were then used to infect E. coli SOLR™ cells (Stratagene), and ampicillin-resistant colonies were selected. Plasmid DNA was prepared by using the QIAPREP™ Plasmid kit (Qiagen, Chatsworth, CA) and the presence of inserts was verified by restriction enzyme digestion and agarose gel electrophoresis. Nucleotide sequence of the insert was then determined with a Taq DYEDEOXY™ cycle sequencing kit (Applied Biosystems Inc. [ABI], Foster City, CA), according to the manufacturer's instructions, using an ABI automated DNA sequencer. DNA sequence analysis was performed with PC/GENE™ (IntelliGenetics, Mountain View, CA). Protein alignments were performed with BESTFIT™ program. Mapping of the Gene encoding pp85. In order to map the gene encoding pp85, the cDNA library derived from HHV-7(AL)-infected SupTl cells was immunoscreened. The lytic areas produced by the phages and transferred to nitrocellulose discs were assayed for reactivity to MAb 5E1 using a biotin-avidin amplified detection system. Ten clones were serially purified through four cycles of plating. Phagemids were rescued from lambda ZAPII vectors, and their DNA was preliminary characterized by restriction nuclease digestion. Nine of the ten clones showed the same restriction pattern with several restriction enzymes, and their inserts were the same size. Two clones, pBLUESCRIPT™-2c and pBLUESCRIPT™-8a representative of the two groups, were sequenced. Their inserts were 2.355 and 2.195 bp, respectively. Comparison of the inserts' sequence with that of the HHV-7 genome showed that the sequence of both clones were virtually identical to that of the U14 open reading frame (ORF) of the HHV-7 JI genome. The arrangement of the HHV-7 sequence in pBLUESCRIPT™-2c and -8a is schematically depicted in FIG. 1. For clone pBLUESCRIPT™-2c, the insert contains the entire U14 ORF and additional 402 bp at the 3' terminus. The initiating methionine is inserted in frame with Escherichia coli β-galactosidase sequences, giving a fusion protein of β-gal:U14 that stops at the U14 stop codon at the 21.831 map unit in the genome (FIG. 1). No other significant open reading frame is apparent in this insert. For clone pBLUESCRIPT™-8a, the insert also contained the HHV-7 U14 ORF in frame with the β-galactosidase sequence, although it lacked 153 bp at the 5' end of the ORF. Comparison of the sequence derived from the HHV-7(AL) U14 cDNA with the genomic sequence of HHV-7 (JI) showed very limited variability at the nucleic acid level (identity 99.89%). The predicted amino acid sequences obtained from the two different strains were the same with the exception of a histidine substitution at position 476, which was an arginine residue in strain AL. The mapping experiments taken together with the specificity of Mab 5E1 for pp85 demonstrate that the HHV-7 gene encoding pp85 is U14. The mapping studies were unequivocally confirmed by the ability of MAb 5E1 to react with the prokaryotically-expressed fusion protein β-gal:U14 as provided in Example 2. Alignment of HHV-7 and HHV-6 U14 protein sequences as deduced from the nucleic acid sequences shows an overall degree of identity of 48.9%. This figure is lower than that obtained with the proteins that display the highest degree of conservation, such as the major capsid protein (68.8% identity and 82.6% similarity) and helicase (74.9% identity and 85.7% similarity). A closer insight into the alignment of HHV-7 and HHV-6 U14 homologues shows that the similarity is not uniformly distributed throughout the entire sequence. EXAMPLE 2 Reactivity of Prokaryotically-Expressed U14 Gene Product with MAb 5E1 In this example, clone pBLUESCRIPT™-2c that contained the entire U14 ORF in frame with β-galactosidase sequences was used to verify if the prokaryotically- expressed U14 maintains reactivity with MAb 5E1. The DNA of pBLUESCRIPT™ clone 2c from Example 1 was transfected into BL21 (protease deficient) and XL-1BLUE bacterial cells (Stratagene). Bacteria transfected with pBLUESCRIPT™ alone without any insert served as a control. Expression from the transfected cells was either uninduced or induced with 1 mM IPTG and incubated at 30°C for 2 h. Cells were pelletted, lysed with 1% NP40, 1% DOC in PBS in the presence of protease inhibitors and centrifuged. The proteins were separated by denaturing electrophoresis, transferred to nitrocellulose sheet, and reacted with MAb 5E1, after blocking non-specific binding sites with 5% skimmed milk in PBS. The antibody reacted with a major band of apparent molecular weight of about 88 kDa expressed specifically from pBLUESCRIPT™ 2c and absent from pBLUESCRIPT™ alone. The antibody also reacted with a number of minor species of lower apparent molecular weight, some of which were present also in the immunoblot with pBLUESCRIPT™ alone. The apparent molecular weight of the prokaryotically-expressed protein is higher than the predicted molecular weight of U14 gene product (73,893 Da), and is consistent with the apparent molecular weight of the major protein species (85 kDa) detected by MAb 5E1 in lysates of HHV-7-infected CBMCs. EXAMPLE 3 pp85 is a Viral Structural Protein Positioned at the Outer Periphery of the Tegument Immunoelectronmicroscopy studies of the present example clearly demonstrate that pp85 is a viral structural protein and define a functional role for pp85. Electronmicroscopy. HHV-7(RK)-infected and uninfected CBMCs were fixed five days after infection, or mock infection, with a freshly-made solution of 3% paraformaldehyde in PBS for 30 min at room temperature, washed and further processed for cryomicrotomy and immunolabeling. An aliquot of cells was post-fixed with 3% glutaraldehyde and 2% osmium tetroxide for standard embedding and thin- sectioning. Cultures employed for cryomicrotomy contained more than 10% of cells displaying virus particles. Frozen-thawed sections were indirectly labelled with MAb 5E1 followed by a 6 nm colloidal gold coated with goat anti-mouse IgG (Aurion, Netherlands). Control studies were performed on uninfected cells or infected cells incubated with an unrelated MAb. The ultra thin sections were examined with a Phillips EM400 electron microscope. Immunoelectronmicroscopy of HHV-7 -infected CBMCs. In order to identify a functional role for pp85 in the viral replicative cycle, its localization in the infected cells was determined at the electron microscopy level. HHV-7(RK)-infected or uninfected CBMCs were harvested at day 6 after infection, fixed with 3% paraformaldehyde in PBS and processed for cryomicrotomy and immunolabelling. In preliminary studies, the concentrations of MAb 5E1 and of gold-conjugated anti-mouse antibodies were adjusted to produce no detectable background in control uninfected cell samples. Cultures of CBMCs infected with HHV-7 include a mixture of cells exhibiting various degrees of structural preservation, depending on the cytopathic effect of the infection and the age of the cells. As expected, virus particles were most frequently associated with cells displaying advanced cytopathic effect, and included all forms of morphogenetic maturation typical of members of the Herpesviridae family. Cryosectioned HHV-7 particles typically included a core surrounded by the electron- opaque substance of the tegument and, in the more mature forms, of the outer envelope membrane. The immunogold reactivity of MAb 5E1 with virus-infected cells was specifically directed to the virus particles and to electron-dense amorphous cytoplasmic areas. Cytoplasmic membranes or other compartments of the host cell were not labeled. Most immunogold granules were precisely positioned at the outer periphery of the virion tegument. In particular, this reaction took place irrespective of the presence of the viral envelope membrane. The reactivity of MAb 5E1 with the surface of immature virus particles consisting solely of core and tegument indicated that pp85 forms an important structural element of the outskirts of the tegument. In addition to virions, large pools of electron-dense material, often detectable in the cytoplasm of infected cells, were also strongly reactive with MAb 5E1. The structural similarity of this material with the virion tegument suggests that it represents a biosynthetic site or depot of tegument protein(s). Neither the cytoplasmic or nuclear membranes nor the nucleoplasm were tagged with immunogold. The peripheral position of the gold particles suggests that the antibody recognized a substructure of the tegument, which can not be readily detected at the ultrastructural level, unless immunocytochemical techniques are applied. EXAMPLE 4 Reactivity of Human Sera to Recombinant pp85 In this example, clone pBLUESCRIPT-2c that contained the entire U14 ORF in frame with β-galactosidase sequences was used to verify if human sera known to carry antibodies to HHV-7, including antibodies to pp85 made in HHV-7-infected cord blood mononuclear cells (CBMCs), react to prokaryotically expressed pp85. BL21 or XL- 1 BLUE cells carrying pBLUESCRIPT-2c were induced to express U14 gene product by induction with lmM IPTG and incubated at 30°C for 2 h, as in Example 2. Cells were pelleted, lysed in 1% NP40, l%DOC in PBS in the presence of protease inhibitors and pelleted. The proteins present in the supernatant were separated by SDS-PAGE, transferred to nitrocellulose and reacted with a number of human sera. The human sera employed had previously been tested for reactivity to pp85 made in HHV-7-infected CBMCs. The HHV-7-positive human sera reacted with the prokaryotically-expressed pp85. To ascertain that the reactivity observed with prokaryotically-expressed pp85 was specific, human sera known not to carry antibodies to HHV-7 were tested. The HHV-7-negative sera did not show reactivity to prokaryotically-expressed pp85. EXAMPLE 5 Cloning of HHV-7 U14 Gene into a Eukaryotic Vector In this example, HHV-7 U14 cDNA was excised from the pBLUESCRIPT-2c construct by digestion with Knpl and Notl restriction enzymes. The purified insert was ligated into pcDNA3.1 vector (Invitrogen), via sites Kpnl and Notl, under the control of CMV promoter. Expression of U14 was analyzed in transient transfection experiments, by using the human 293 cell line. Positive reactivity to Mab 4E1 was specifically observed in the cells transfected with the expression vector containing the U14 cDNA, and not in the control cells transfected with the expression vector without insert. EXAMPLE 6 Construction of Deletion Mutants for Determining Epitopes In order to identify a pp85 epitope reacting with Mab 5E1, a series of C- terminus deletion mutants were constructed. Clone pBLUESCRIPT-2c was digested with Xhol (the 3' terminus restriction site employed for cloning of the U14 c-DNA) and with Ncol (21.642 genome coordinate), or EcoRI (21.294 genome coordinate), or Hindi (21.130 genome coordinate); the plasmids were religated, transfected into DH5 cells to confirm the correct deletion, and then transferred to BL21 cells for expression of the recombinant deletion proteins, as detailed in Example 4. The recombinant deletion proteins were then separated by SDS-PAGE, transferred to nitrocellulose, and reacted with Mab 5E1. Reactivity was detected with the clone collapsed between Xhol and Ncol sites, and was no longer detectable in clones collapsed between Xhol and EcoRI, or between Xhol and Hindi. These results indicate that an epitope recognized by Mab 5E1 is located between aa residue 471 and 586 (SEQ ID NOS: 6 or 7) of the pp85 protein. Epitopes were further determined by overlapping peptides. Twelve overlapping peptides were synthesized covering the region between amino acid positions 471 to 586 of SEQ ID NO: 4. Reactivity between each peptide and monoclonal antibody 5E1 was measured in ELISA tests. HHV-7 specific epitopes were thus mapped to peptide 484- 509 (SEQ ID NO: 8), to peptide 484-502 (SEQ ID NO:9), and to peptide 504-516 (SEQ ID NO: 10). In particular, amino acids in the region of residues 489-498 (SEQ ID NO: 11) are absent from the HHV-6 herpesvirus. While the region from amino acids 471-586 of pp85 provides a binding region for MAB 5E1, the present inventors expect that human seropositive serum having binding specificity for pp85 would also have binding affinity for the specified region. Human seropositive serum is expected to have antibodies having binding specificity for a number of epitopic regions of protein pp85 in addition to the epitopic region from 471-586. In preliminary studies, reactivity of human sera to peptides carrying the HHV-7 specific epitope as set forth herein was demonstrated, albeit, at a level lower than that of reactivity with pp85. Particularly preferred are epitopic peptides 484-509 (SEQ ID NO:8) and 484-502 (SEQ ID NO:9). All of the compositions and methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the compositions and methods of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the composition, methods and in the steps or in the sequence of steps of the method described herein without departing from the concept, spirit and scope of the invention. More specifically, it will be apparent that certain agents which are both chemically and physiologically related may be substituted for the agents described herein while the same or similar results would be achieved. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined by the appended claims.

Claims: CLAIMS: 1. A purified nucleic acid molecule having a nucleotide sequence encoding human heφesvirus-7 pp85 protein, the protein having an amino acid sequence essentially as set forth in SEQ ID NO:3 or SEQ ID NO:4. 2. A purified nucleic acid molecule complementary to the nucleic acid molecule of Claim 1. 3. The purified nucleic acid molecule of Claim 1 further defined as having a nucleotide sequence as set forth in SEQ ID NO:l or SEQ ID NO:2. 4. A purified nucleic acid molecule having a nucleotide sequence encoding a human heφesvirus-7-specific epitope of a human heφesvirus-7 pp85 protein. 5. A recombinant vector comprising the purified nucleic acid molecule of Claim 1. 6. The recombinant vector of Claim 5, further defined as an expression vector comprising a promoter operatively linked to said nucleic acid molecule. 7. The recombinant vector of Claim 6, further defined as a bacterial plasmid, or Baculovirus vector. 8. A recombinant host cell comprising the recombinant vector of Claim 6. 9. The recombinant host cell of Claim 8, further defined as a Spodoptera frugiperda or Escherichia coli cell. 10. A purified nucleic acid molecule having a nucleotide sequence that encodes an amino acid sequence extending from amino acid 471 to 586 of human heφesvirus-7 pp85 protein as set forth in SEQ ID NO:3 , or as set forth in SEQ ID NO:4. 11. A purified human heφesvirus-7 pp85 protein having an amino acid sequence essentially as set forth in SEQ ID NO: 3 or SEQ ID NO: 4. 12. A purified human heφesvirus-7 pp85 peptide having an amino acid sequence extending from amino acid 471 to 586 as set forth in SEQ ID NO:6, or as set forth in SEQ ID NO:7; or extending from amino acid 484 to 509, or 484 to 502, or 504 to 516, or 489 to 498 as set forth in SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, or SEQ ID NO: 11, respectively, the peptide having no cross-reactivity with human heφesvirus-6. 13. The purified human heφesvirus-7 pp85 peptide of Claim 12 wherein the amino acid sequence extends from amino acid 484 to 509 as set forth in SEQ ID NO: 8, the peptide having no cross-reactivity with human heφesvirus-6. 14. A method for serological detection of human heφesvirus-7 in a biological sample, the method providing substantially no cross reactivity with human heφesvirus-6, comprising: contacting the sample with a human heφesvirus-7-specific epitope of human heφesvirus-7 pp85 protein; and determining binding of the epitope to the sample; wherein binding indicates presence of antibodies having binding specificity for human heφesvirus-7, the presence of antibodies demonstrating detection of human heφesvirus-7 in the biological sample. 15. The method of Claim 14 wherein the human heφesvirus-7 specific epitope is pp85 protein or an epitopic fragment thereof. 16. The method of Claim 14 wherein determining binding is by immuno fluorescence assay, enzyme-linked immunosorbent assay, radioimmunoassay, agglutination, hemagglutination, RIST, or immunoblotting. 17. A method for diagnosis of human heφesvirus-7 infection in a subject, comprising: contacting a biological sample from the subject with a human heφesvirus-7-specific epitope of human heφesvirus-7 pp85 protein; and determining binding of the epitope to the sample; wherein binding indicates diagnosis of human heφesvirus-7 infection in the subject. 18. A method for diagnosis of human heφesvirus-7 infection in a subject, comprising: contacting a first biological sample and a second biological sample obtained later than the first sample from the subject with a human heφesvirus-7-specific epitope of human heφesvirus-7 pp85 protein; and determining binding of the epitope to the first sample and the second sample; wherein greater binding of the epitope to the second sample compared to binding of the epitope in the first sample indicates diagnosis of human heφesvirus-7 infection in the subject. 19. A method of preparing human heφesvirus-7 pp85 protein encoded by the purified nucleic acid molecule of Claim 1, comprising: preparing a recombinant host cell bearing the nucleic acid molecule of Claim 1 , the host being capable of expressing encoded protein; culturing the recombinant host cell to produce pp85 protein; and collecting the pp85 protein having an amino acid sequence essentially as set forth in SEQ ID NO: 3, or SEQ ID NO: 4. 20. The method of Claim 19 wherein the recombinant host is a Spodoptera frugiperda cell or an Escherichia coli cell. 21. A kit for serological detection of human heφesvirus-7 in a human biological sample, the kit comprising in packaged combination: a carrier means adapted to receive a plurality of container means in close confinement therewith; a first container means including pp85 protein or an epitopic fragment of pp85 protein; and a second container means including a detectable antibody having specific binding affinity for human immunoglobulin. 22. The kit of Claim 21 wherein the detectable antibody is enzyme-linked, fluorescent, or radiolabeled. 23. The kit of Claim 21 wherein the detectable antibody is enzyme-linked, and the kit further includes a third container means including a quantity of a substrate for the enzyme sufficient to produce a visually detectable product. 24. The kit of Claim 21 wherein the detectable antibody has specific binding affinity for human immunoglobulin IgG. 25. The kit of Claim 21 wherein the detectable antibody has specific binding affinity for human immunoglobulin IgM. 26. A method for conferring protection to human heφesvirus-7 infection or to reactivation of human heφesvirus-7 in a subject comprising: administering the pp85 protein of claim 11, or epitopic fragment thereof, to the subject, wherein the subject has an immune reaction to pp85 protein, or epitopic fragment thereof, that provides protection to human heφesvirus-7 infection or to reactivation of human heφesvirus-7. 27. The method of Claim 26 wherein the pp85 protein, or epitopic fragment thereof, is recombinant protein. 28. The method of Claim 26 wherein administering the pp85 protein, or epitopic fragment thereof, is by administering a recombinant expression vector capable of expressing pp85 protein. 29. The method of claim 28 where the recombinant expression vector is a viral vector. 30. A subunit vaccine comprising an epitope of pp85 protein and a human heφesvirus-7 immunogenic protein or peptide other than pp85 protein or peptide, or an immunogenic protein from a related beta heφesvirus. 31. Use of the nucleic acid molecule of Claim 1 in the preparation of a pharmaceutical composition for serological detection of HHV-7, for diagnosis of a human subject suspected of having HHV-7 infection, or for treatment of a human subject having HHV-7 infection. 32. Use of the protein of Claim 11 in the preparation of a pharmaceutical composition for serological detection of HHV-7, for diagnosis of a human subject suspected of having HHV-7 infection, or for treatment of a human subject having HHV-7 infection. 33. Use of the peptide of Claim 12 in the preparation of a pharmaceutical composition for serological detection of HHV-7, for diagnosis of a human subject suspected of having HHV-7 infection, or for treatment of a human subject having HHV-7 infection.

Inventors: CAMPADELLI-FIUME GABRIELLA, SECCHIERO PAOLA, CAMPADELLI-FIUME, GABRIELLA, SECCHIERO, PAOLA
Applicants: CAMPADELLI FIUME GABRIELLA, SECCHIERO PAOLA, UNIV BOLOGNA, UNIV MARYLAND BIOTECH INST, CAMPADELLI-FIUME, GABRIELLA, SECCHIERO, PAOLA, UNIVERSITY OF BOLOGNA, UNIVERSITY OF MARYLAND BIOTECHNOLOGY INSTITUTE
Application year: 1998
Main classification: C07K14
IPC codes: A61K38, A61K39, C07K14