Production of herpes B virus recombinant glycoproteins and evaluation of their diagnostic potential

Towards a comprehensive view of the herpes B virus

Herpes B virus is a biosafety level 4 pathogen and widespread in its natural host species, macaques. Although most infected monkeys show asymptomatic or mild symptoms, human infections with this virus can cause serious neurological symptoms or fatal encephalomyelitis with a high mortality rate. Herpes B virus can be latent in the sensory ganglia of monkeys and humans, often leading to missed diagnoses. Furthermore, the herpes B virus has extensive antigen crossover with HSV, SA8, and HVP-2, causing false-positive results frequently. Timely diagnosis, along with methods with sensitivity and specificity, are urgent for research on the herpes B virus. The lack of a clear understanding of the host invasion and life cycle of the herpes B virus has led to slow progress in the development of effective vaccines and drugs. This review discusses the research progress and problems of the epidemiology of herpes B virus, detection methods and therapy, hoping to inspire further investigation into important factors associated with transmission of herpes B virus in macaques and humans, and arouse the development of effective vaccines or drugs, to promote the establishment of specific pathogen-free (SPF) monkeys and protect humans to effectively avoid herpes B virus infection.

Serological Analysis of Herpes B Virus at Individual Epitope Resolution: From Two-Dimensional Peptide Arrays to Multiplex Bead Flow Assays

Macacine herpesvirus or B Virus (BV) is a zoonotic agent that leads to high mortality rates in humans if transmitted and untreated. Here, BV is used as a test case to establish a two-step procedure for developing high throughput serological assays based on synthetic peptides. In step 1, peptide microarray analysis of 42 monkey sera (30 of them tested BV positive by ELISA) revealed 1148 responses against 369 different peptides. The latter could be grouped into 142 different antibody target regions (ATRs) in six different glycoproteins (gB, gC, gD, gG, gH, and gL) of BV. The high number of newly detected ATRs was made possible inter alia by a new preanalytical protocol that reduced unspecific binding of serum components to the cellulose-based matrix of the microarray. In step 2, soluble peptides corresponding to eight ATRs of particularly high antigenicity were synthesized and coupled to fluorescently labeled beads, which were subsequently employed in immunochemical bead flow assays. Their outcome mirrored the ELISA results used as reference. Hence, convenient, fast, and economical screening of arbitrarily large macaque colonies for BV infection is now possible. The study demonstrates that a technology platform switch from two-dimensional high-resolution peptide arrays used for epitope discovery to a readily available bead array platform for serology applications is feasible.

Genistein Has Antiviral Activity against Herpes B Virus and Acts Synergistically with Antiviral Treatments to Reduce Effective Dose

Herpes B virus is a deadly zoonotic agent that can be transmitted to humans from the macaque monkey, an animal widely used in biomedical research. Currently, there is no cure for human B virus infection and treatments require a life-long daily regimen of antivirals, namely acyclovir and ganciclovir. Long-term antiviral treatments have been associated with significant debilitating side effects, thus, there is an ongoing search for alternative efficacious antiviral treatment. In this study, the antiviral activity of genistein was quantified against B virus in a primary cell culture model system. Genistein prevented plaque formation of B virus and reduced virus production with an IC₅₀ value of 33 and 46 μM for human and macaque fibroblasts, respectively. Genistein did not interfere directly with viral entry, but instead targeted an event post-viral replication. Finally, we showed that genistein could be used at its IC₅₀ concentration in conjunction with both acyclovir and ganciclovir to reduce their effective dose against B virus with a 93% and 99% reduction in IC₅₀ values, respectively. The results presented here illuminate the therapeutic potential of genistein as an effective antiviral agent against B virus when used alone or in combination with current antiviral therapies.

Questioning the Extreme Neurovirulence of Monkey B Virus (Macacine alphaherpesvirus 1)

Monkey B virus (Macacine alphaherpesvirus 1; BV) occurs naturally in macaques of the genus Macaca, which includes rhesus and long-tailed (cynomolgus) monkeys that are widely used in biomedical research. BV is closely related to the human herpes simplex viruses (HSV), and BV infections in its natural macaque host are quite similar to HSV infections in humans. Zoonotic BV is extremely rare, having been diagnosed in only a handful of North American facilities with the last documented case occurring in 1998. However, BV is notorious for its neurovirulence since zoonotic infections are serious, usually involving the central nervous system, and are frequently fatal. Little is known about factors underlying the extreme neurovirulence of BV in humans. Here we review what is actually known about the molecular biology of BV and viral factors affecting its neurovirulence. Based on what is known about related herpesviruses, areas for future research that may elucidate mechanisms underlying the neurovirulence of this intriguing virus are also reviewed.

Preventive, Diagnostic and Therapeutic Applications of Baculovirus Expression Vector System

Different strategies are being worked out for engineering the original baculovirus expression vector (BEV) system to produce cost-effective clinical biologics at commercial scale. To date, thousands of highly variable molecules in the form of heterologous proteins, virus-like particles, surface display proteins/antigen carriers, heterologous viral vectors and gene delivery vehicles have been produced using this system. These products are being used in vaccine production, tissue engineering, stem cell transduction, viral vector production, gene therapy, cancer treatment and development of biosensors. Recombinant proteins that are expressed and post-translationally modified using this system are also suitable for functional, crystallographic studies, microarray and drug discovery-based applications. Till now, four BEV-based commercial products (Cervarix^®, Provenge^®, Glybera^® and Flublok^®) have been approved for humans, and myriad of others are in different stages of preclinical or clinical trials. Five products (Porcilis^® Pesti, BAYOVAC CSF E2^®, Circumvent^® PCV, Ingelvac CircoFLEX^® and Porcilis^® PCV) got approval for veterinary use, and many more are in the pipeline. In the present chapter, we have emphasized on both approved and other baculovirus-based products produced in insect cells or larvae that are important from clinical perspective and are being developed as preventive, diagnostic or therapeutic agents. Further, the potential of recombinant adeno-associated virus (rAAV) as gene delivery vector has been described. This system, due to its relatively extended gene expression, lack of pathogenicity and the ability to transduce a wide variety of cells, gained extensive popularity just after the approval of first AAV-based gene therapy drug alipogene tiparvovec (Glybera^®). Numerous products based on AAV which are presently in different clinical trials have also been highlighted.

Identification of unique B virus (Macacine Herpesvirus 1) epitopes of zoonotic and macaque isolates using monoclonal antibodies

Our overall aim is to develop epitope-based assays for accurate differential diagnosis of B virus zoonotic infections in humans. Antibodies to cross-reacting epitopes on human-simplexviruses continue to confound the interpretation of current assays where abundant antibodies exist from previous infections with HSV types 1 and 2. To find B virus-specific epitopes we cloned ten monoclonal antibodies (mAbs) from the hybridomas we produced. Our unique collection of rare human sera from symptomatic and asymptomatic patients infected with B virus was key to the evaluation and identification of the mAbs as reagents in competition ELISAs (mAb-CE). The analysis of the ten mAbs revealed that the target proteins for six mAbs was glycoprotein B of which two are reactive to simian simplexviruses and not to human simplexviruses. Two mAbs reacted specifically with B virus glycoprotein D, and two other mAbs were specific to VP13/14 and gE-gI complex respectively. The mAbs specific to VP13/14 and gE-gI are strain specific reacting with B virus isolates from rhesus and Japanese macaques and not with isolates from cynomolgus and pigtail macaques. The mAb-CE revealed that a high proportion of naturally B virus infected rhesus macaques and two symptomatic humans possess antibodies to epitopes of VP13/14 protein and on the gE-gI complex. The majority of sera from B virus infected macaques and simplexvirus-infected humans competed with the less specific mAbs. These experiments produced a novel panel of mAbs that enabled B virus strain identification and confirmation of B virus infected macaques by the mAb-CE. For human sera the mAb-CE could be used only for selected cases due to the selective B virus strain-specificity of the mAbs against VP13/14 and gE/gI.

To fully accomplish our aim to provide reagents for unequivocal differential diagnosis of zoonotic B virus infections, additional mAbs with a broader range of specificities is critical.

Detection systems for antibody responses against herpes B virus

Herpes B virus (BV) infection is highly prevalent among adult Asian macaques and rarely causes severe disease in infected animals. In contrast, BV infection of humans can induce fatal encephalitis in the absence of treatment. Therefore, the development of diagnostic tests for specific and sensitive detection of antibodies against BV is an important task. The cross-reactivity of antibodies against BV with related simplex viruses of other primates may afford an opportunity to obtain sensitive detection systems without the need to work with the highly pathogenic BV. Moreover, it has been proposed that use of recombinant viral glycoproteins may allow for a detection of antibody responses against BV with high specificity. However, limited data are available for both approaches to BV diagnostic. Here, we report that simian agent 8 (SA8; infects African green monkeys)- and herpesvirus papio 2 (HVP-2; infects baboons)-infected cells allow for a more sensitive detection of antibody responses against BV in macaques than lysates of herpes simplex virus type 1 and 2 (HSV-1/2; infect humans)-infected cells and a commercial HSV ELISA (Enzygnost^® Anti-HSV/IgG). In addition, we show that sera from BV-infected macaques frequently contain antibodies against the recombinant BV glycoprotein gD (BV gD) that has been previously proposed as a diagnostic target for discriminating BV- and HSV-induced antibodies. However, we found that antibodies of some HSV-infected human patients also reacted with BV gD. In contrast, only sera of HSV-1- and HSV-2-infected humans, but not sera from BV-infected macaques, reacted with HSV-1/2 gG. Collectively, these results suggest that both SA8 and HVP-2 allow for sensitive and comparable detection of BV-directed antibody responses in macaques and that the combination of BV gD and HSV-1/2 gG needs to be complemented by a least one additional viral glycoprotein for reliable discrimination between antibody responses against BV and HSV-1/2 in humans.

Understanding Primate Herpesviruses

Viruses related to the herpes simplex viruses of humans are present in all nonhuman primate (NHP) species tested and cross species transmission has been documented. The herpesvirus present in macaques, Herpes B virus (BV) rarely causes disease in its natural macaque host. However, when transmitted to a nonnative host, BV has occasionally caused severe and even fatal disease if not treated immediately. Here we present a comprehensive review of the taxonomy, molecular biology, physiology, epidemiology, diagnosis and treatment of BV. We also summarizes what is known about related herpesviruses of other NHP species and the zoonotic potential of these viruses.

Optimized Expression, Purification of Herpes B Virus gD Protein in Escherichia coli, and Production of Its Monoclonal Antibodies

BACKGROUND

Herpes B virus (BV) is a zoonotic disease caused by double-stranded enveloped DNA virus with cercopithecidae as its natural host. The mortality rate of infected people could be up to 70% with fatal encephalitis and encephalomyelitis. Up to now, there are no effective treatments for BV infection. Among the various proteins encoded by monkey B virus, gD, a conserved structural protein, harbors important application value for serological diagnosis of frequent variations of the monkey B virus.

OBJECTIVES

This study aimed to expressed the gD protein of BV in Escherichia coli by a recombinant vector, and prepare specific monoclonal antibodies against gD of BV to pave the way for effective and quick diagnosis reagent research.

MATERIALS AND METHODS

The gD gene of BV was optimized by OptimWiz to improve codon usage bias and synthesis, and the recombinant plasmid, pET32a/gD, was constructed and expressed in E. coli Rosetta (DE3). The expressed fusion protein, His-gD, was purified and the BALB/c mice were immunized by this protein. Spleen cells from the immunized mice and SP2/0 myeloma cells were fused together, and the monoclonal cell strains were obtained by indirect enzyme-linked immunosorbent assay (ELISA) screening, followed by preparation of monoclonal antibody ascetic fluid.

RESULTS

The optimized gD protein was highly expressed in E. coli and successfully purified. Five monoclonal antibodies (mAbs) against BV were obtained and named as 4E3, 3F8, 3E7, 1H3 and 4B6, and with ascetic fluid titers of 2 × 10(6), 2 × 10(5), 2 × 10(5), 2 × 10(3) and 2 × 10(2), respectively. The 1H3 and 4E3 belonged to the IgG2b subclass, while 3E7, 3F8 and 4B6 belonged to the IgG1 subclass.

CONCLUSIONS

The cell lines obtained in this work secreted potent, stable and specific anti-BV mAbs, which were suitable for the development of herpes B virus diagnosis reagents.

Specific pathogen free macaque colonies: a review of principles and recent advances for viral testing and colony management

Specific pathogen free (SPF) macaques provide valuable animal models for biomedical research. In 1989, the National Center for Research Resources [now Office of Research Infrastructure Programs (ORIP)] of the National Institutes of Health initiated experimental research contracts to establish and maintain SPF colonies. The derivation and maintenance of SPF macaque colonies is a complex undertaking requiring knowledge of the biology of the agents for exclusion and normal physiology and behavior of macaques, application of the latest diagnostic technology, facilitiy management, and animal husbandry. This review provides information on the biology of the four viral agents targeted for exclusion in ORIP SPF macaque colonies, describes current state-of-the-art viral diagnostic algorithms, presents data from proficiency testing of diagnostic assays between laboratories at institutions participating in the ORIP SPF program, and outlines management strategies for maintaining the integrity of SPF colonies using results of diagnostic testing as a guide to decision making.

B Virus (Macacine herpesvirus 1) Glycoprotein D Is Functional but Dispensable for Virus Entry into Macaque and Human Skin Cells

Glycoprotein D (gD) plays an essential role in cell entry of many simplexviruses. B virus (Macacine herpesvirus 1) is closely related to herpes simplex virus 1 (HSV-1) and encodes gD, which shares more than 70% amino acid similarity with HSV-1 gD. Previously, we have demonstrated that B virus gD polyclonal antibodies were unable to neutralize B virus infectivity on epithelial cell lines, suggesting gD is not required for B virus entry into these cells. In the present study, we confirmed this finding by producing a B virus mutant, BV-ΔgDZ, in which the gD gene was replaced with a lacZ expression cassette. Recombinant plaques were selected on complementing VD60 cells expressing HSV-1 gD. Virions lacking gD were produced in Vero cells infected with BV-ΔgDZ. In contrast to HSV-1, B virus lacking gD was able to infect and form plaques on noncomplementing cell lines, including Vero, HEp-2, LLC-MK2, primary human and macaque dermal fibroblasts, and U373 human glioblastoma cells. The gD-negative BV-ΔgDZ also failed to enter entry-resistant murine B78H1 cells bearing a single gD receptor, human nectin-1, but gained the ability to enter when phenotypically supplemented with HSV-1 gD. Cell attachment and penetration rates, as well as the replication characteristics of BV-ΔgDZ in Vero cells, were almost identical to those of wild-type (wt) B virus. These observations indicate that B virus can utilize gD-independent cell entry and transmission mechanisms, in addition to generally used gD-dependent mechanisms.

IMPORTANCE

B virus is the only known simplexvirus that causes zoonotic infection, resulting in approximately 80% mortality in untreated humans or in lifelong persistence with the constant threat of reactivation in survivors. Here, we report that B virus lacking the gD envelope glycoprotein infects both human and monkey cells as efficiently as wild-type B virus. These data provide evidence for a novel mechanism(s) utilized by B virus to gain access to target cells. This mechanism is different from those used by its close relatives, HSV-1 and -2, where gD is a pivotal protein in the virus entry process. The possibility remains that unidentified receptors, specific for B virus, permit virus entry into target cells through gD-independent pathways. Understanding the molecular mechanisms of B virus entry may help in developing rational therapeutic strategies for the prevention and treatment of B virus infection in both macaques and humans.

Herpes B virus gD interaction with its human receptor--an in silico analysis approach

Background

The glycoprotein D (gD) is essential for Herpes B virus (BV) entry into mammalian cells. Nectin-1, an HSV-1 gD receptor, is found to be the receptor which mediated BV induced cell-cell fusion, while HVEM does not mediate fusion by BV glycoprotein. However, the specific sequence and structural requirements of the BV gD for the recognition of and binding to Nectin-1 are unknown. Moreover, the 3D structures of BV gD and the BV gD-receptor complex have not been determined. In this study, we propose a reliable model of the interaction of the BV gD with receptor using bioinformatics tools.

Results

The three-dimensional structures of two BV gD-receptor complexes were constructed using homology modelling and docking strategy. Based on the models of these complexes, the BV gD receptor interaction patterns were calculated. The results showed that the interface between the BV gD and nectin-1 molecule is not geometrically complementary. The computed molecular interactions indicated that two terminal extensions were the main region of BV gD that binds to nectin-1 and that hydrophobic contacts between the two molecules play key roles in their recognition and binding. The constructed BV gD-HVEM complex model showed that this complex had a lower shape complementarity value and a smaller interface area compared with the HSV-1 gD-HVEM complex, and the number of intermolecular interactions between BV gD-HVEM were fewer than that of HSV-1 gD-HVEM complex. These results could explain why HVEM does not function as a receptor for BV gD.

Conclusion

In this study, we present structural model for the BV gD in a complex with its receptor. Some features predicted by this model can explain previously reported experimental data. This complex model may lead to a better understanding of the function of BV gD and its interaction with receptor and will improve our understanding of the activation of the BV fusion and entry process.

Multiple antibody targets on herpes B glycoproteins B and D identified by screening sera of infected rhesus macaques with peptide microarrays

Herpes B virus (or Herpesvirus simiae or Macacine herpesvirus 1) is endemic in many populations of macaques, both in the wild and in captivity. The virus elicits only mild clinical symptoms (if any) in monkeys, but can be transmitted by various routes, most commonly via bites, to humans where it causes viral encephalitis with a high mortality rate. Hence, herpes B constitutes a considerable occupational hazard for animal caretakers, veterinarians and laboratory personnel. Efforts are therefore being made to reduce the risk of zoonotic infection and to improve prognosis after accidental exposure. Among the measures envisaged are serological surveillance of monkey colonies and specific diagnosis of herpes B zoonosis against a background of antibodies recognizing the closely related human herpes simplex virus (HSV). 422 pentadecapeptides covering, in an overlapping fashion, the entire amino acid sequences of herpes B proteins gB and gD were synthesized and immobilized on glass slides. Antibodies present in monkey sera that bind to subsets of the peptide collection were detected by microserological techniques. With 42 different rhesus macaque sera, 114 individual responses to 18 different antibody target regions (ATRs) were recorded, 17 of which had not been described earlier. This finding may pave the way for a peptide-based, herpes B specific serological diagnostic test.

An automated ELISA using recombinant antigens for serologic diagnosis of B virus infections in macaques

B virus (Macacine herpesvirus 1) occurs naturally in macaques and can cause lethal zoonotic infections in humans. Detection of B virus (BV) antibodies in macaques is essential for the development of SPF breeding colonies and for diagnosing infection in macaques that are involved in human exposures. Traditionally, BV infections are monitored for presence of antibodies by ELISA (a screening assay) and western blot analysis (WBA; a confirmatory test). Both tests use lysates of infected cells as antigens. Because WBA often fails to confirm the presence of low-titer serum antibodies detected by ELISA, we examined a recombinant-based ELISA as a potential alternative confirmatory test. We compared a high-throughput ELISA using 384-well plates for simultaneous antibody screening against 4 BV-related, recombinant proteins with the standard ELISA and WBA. The recombinant ELISA results confirmed more ELISA-positive sera than did WBA. The superiority of the recombinant ELISA over WBA was particularly prominent for sera with low (<500 ELISA units) antibody titers. Among low-titer sera, the relative sensitivity of the recombinant ELISA ranged from 36.7% to 45.0% as compared with 3.3% to 10.0% for WBA. In addition, the screening and confirmatory assays can be run simultaneously, providing results more rapidly. We conclude that the recombinant ELISA is an effective replacement for WBA as a confirmatory assay for the evaluation of macaque serum antibodies to BV.

Reassessing the detection of B-virus-specific serum antibodies

B virus, a natural pathogen of macaques, can cause a fatal zoonotic disease in humans. Serologic screening of macaques by titration ELISA (tELISA, screening test) and by Western blot analysis (WBA, confirmatory test) is one of the principle measures to prevent human infection. Here we slightly modified these 2 tests and reevaluated their correlation. We developed a high-throughput tELISA and used it to screen 278 sera simultaneously against the homologous BV antigen and the heterologous antigens of Papiine herpesvirus 2 and Human herpesvirus 1. More sera (35.6%) were positive by the BV-ELISA than by the HVP2-ELISA (21.6%) or HSV1-ELISA (19.8%). The superiority of the homologous tELISA over the heterologous tELISA was prominent in low-titer sera. WBA confirmed only 21% of the tELISA-positive sera with low or intermediate antibody titers. These sera might have contained antibodies to conformational epitopes that could not be detected by WBA, in which denatured antigens are used, but that could be detected by tELISA, which detects both linear and conformational epitopes. WBA confirmed 82% of the tELISA high-titer sera. However, WBA defined the remaining 18% of sera, which were negative by tELISA, as nonnegative. This finding can be attributed to the difficulties encountered with the subjective interpretation of results by WBA. Together, the current results indicate the inadequacy of WBA as a confirmatory assay for sera with low antibody titers.

Simultaneous detection of antibodies to five simian viruses in nonhuman primates using recombinant viral protein based multiplex microbead immunoassays

Routine screening for infectious agents is critical in establishing and maintaining specific pathogen free (SPF) nonhuman primate (NHP) colonies. More efficient, higher throughput, less costly reagent, and reduced sample consumption multiplex microbead immunoassays (MMIAs) using purified viral lysates have been developed previously to address some disadvantages of the traditional individual enzyme-linked immunosorbent assay (ELISA) methods. To overcome some of the technical and biosafety difficulties in preparing antigens from live viruses for viral lysate protein based MMIAs, novel MMIAs using recombinant glycoprotein D precursor (gD) protein of herpesvirus B and four viral gag proteins of simian immunodeficiency virus (SIV), simian T Cell lymphotropic virus (STLV), simian foamy virus (SFV), and simian betaretrovirus (SRV) as antigens have been developed in the current study. The data showed that the recombinant viral protein based MMIAs detected simultaneously antibodies to each of these five viruses with high sensitivity and specificity, and correlated well with viral lysate based MMIAs. Therefore, recombinant viral protein based MMIA is an effective and efficient routine screening method to determine the infection status of nonhuman primates.

Recombinant protein-based viral disease diagnostics in veterinary medicine

Identification of pathogens or antibody response to pathogens in human and animals modulates the treatment strategies for naive population and subsequent infections. Diseases can be controlled and even eradicated based on the epidemiology and effective prophylaxis, which often depends on development of efficient diagnostics. In addition, combating newly emerging diseases in human as well as animal healthcare is challenging and is dependent on developing safe and efficient diagnostics. Detection of antibodies directed against specific antigens has been the method of choice for documenting prior infection. Other than zoonosis, development of inexpensive vaccines and diagnostics is a unique problem in animal healthcare. The advent of recombinant DNA technology and its application in the biotechnology industry has revolutionized animal healthcare. The use of recombinant DNA technology in animal disease diagnosis has improved the rapidity, specificity and sensitivity of various diagnostic assays. This is because of the absence of host cellular proteins in the recombinant derived antigen preparations that dramatically decrease the rate of false-positive reactions. Various recombinant products are used for disease diagnosis in veterinary medicine and this article discusses recombinant-based viral disease diagnostics currently used for detection of pathogens in livestock and poultry.

Monkey B virus (Cercopithecine herpesvirus 1)

Macaques are a particularly valuable nonhuman primate model for a wide variety of biomedical research endeavors. B virus (Cercopithecine herpesvirus 1; BV) is an alpha-herpesvirus that naturally infects conventional populations of macaques. Serious disease due to BV is rare in macaques, but when transmitted to humans, BV has a propensity to invade the central nervous system and has a fatality rate greater than 70% if not treated promptly. The severe consequences of human BV infections led to the inclusion of BV in the original NIH list of target viruses for elimination by development of specific pathogen-free rhesus colonies. In macaques and especially in humans, diagnosis of BV infection is not straightforward. Furthermore, development and maintenance of true BV specific pathogen-free macaque colonies has proven dif cult. In this overview we review the natural history of BV in macaques, summarize what is known about the virus at the molecular level, and relate this information to problems associated with diagnosis of BV infections and development of BV-free macaque colonies.

Anti-CeHV1 antibodies of two cynomolgus macaques cross-react with HSV2 but not HSV1 antigens in ELISA

BACKGROUND

The aim of the study was to compare the cross-reactivity of macaque anti-CeHV1 antibodies with type 1 and type 2 human herpes simplex viruses (HSV1 and HSV2).

METHODS

We studied the serum of 344 animals which had been tested either positive (n = 39) or negative (n = 305) for the presence of CeHV1 antibodies by expert laboratories. Macaque serums were studied by means of two ELISA: one based on HSV1 antigen-coated wells, the other on polystyrene beads coated with HSV1 and HSV2 antigens in approximately equal proportions.

RESULTS

In the serum of two animals originating from Vietnam, we found anti-CeHV1 antibodies cross-reacting with HSV2 but not with HSV1 antigens. For the serum with the highest titer, inhibition by soluble antigens confirmed the high affinity of the antibodies for HSV2 antigens.

CONCLUSIONS

Tests using HSV1 and HSV2 in a combined way are better suited to macaque screening than tests using only HSV1 antigens.

Discrimination of antibody to herpes B virus from antibody to herpes simplex virus types 1 and 2 in human and macaque sera

The antigenic cross-reactive characteristics of herpes B virus and herpes simplex virus (HSV) type 1 (HSV-1) and HSV-2 are responsible for false-positive diagnoses by serological assays in humans and macaques. In the present study, we developed a fluorometric indirect enzyme-linked immunosorbent assay (ELISA) with recombinant herpes B virus glycoprotein D (gD) and HSV-1 and HSV-2 gG (gG-1 and gG-2, respectively) to discriminate between the three primate herpesvirus infections. The secreted form of gD, gDdTM, was used to detect antibody to herpes B virus gD. Sera positive for herpes B virus, HSV-1, and HSV-2 showed specific reactions to gD, gG-1, and gG-2, respectively. Sera collected from humans and rhesus macaques were investigated for the presence of antibodies to the recombinant proteins of the three herpesviruses. The results suggested that the approach is able to discriminate between herpes B virus and HSV infections. The ELISA was also found to be able to detect infections with multiple primate herpesviruses and may have the potential to identify a subsequent infection in individuals that have already been infected with another herpesvirus. In addition, we found evidence of a greater cross-reactivity of herpes B virus with HSV-1 than with HSV-2. It is suggested that the ELISA with the recombinant antigens is useful not only for the serodiagnosis of primate herpesvirus infections but also for elucidation of the seroprevalence of herpesviruses in humans and primates.