Expression of herpes simplex virus 1 glycoprotein B by a recombinant vaccinia virus and protection of mice against lethal herpes simplex virus 1 infection

Analysis of codon usage pattern of infectious laryngotracheitis virus immunogenic glycoproteins and its biological implications

Infectious laryngotracheitis virus (ILTV) is a highly contagious acute respiratory poultry pathogen. Modified live ILTV vaccines are the only control against ILT infections. Reversions and establishment of latent infections are the major concerns imparting the need to develop safer vaccines against ILTV infection. ILTV glycoprotein B and D (gB and gD) are major protective immunogens. The factors shaping synonymous codon usage bias and nucleotide composition in ILTV glycoprotein genes have not yet been reported. In the present study, we have analyzed the synonymous codon usage indices of ILTV gB and gD genes. Variation in the codon usage was seen in both the glycoproteins majorly by mutational pressure. The pattern was determined using the correspondence analysis, effective number of codon (Nc), GC3 plot and correlation analyses among different indices. The study is a comprehensive analysis of the codon usage patterns of ILTV glycoprotein genes. This will be helpful in understanding the codon usage bias of ILTV and related DNA viruses which could further explore its biology.

Use of Reporter Genes in the Generation of Vaccinia Virus-Derived Vectors

Vaccinia virus (VACV) is one of the most extensively-studied viruses of the Poxviridae family. It is easy to genetically modify, so it has become a key tool for many applications. In this context, reporter genes facilitate the study of the role of foreign genes introduced into the genome of VACV. In this review, we describe the type of reporter genes that have been used to generate reporter-expressing VACV and the applications of the recombinant viruses obtained. Reporter-expressing VACV are currently employed in basic and immunology research, in the development of vaccines and cancer treatment.

Evaluation of the Protection Efficacy of a Serotype 1 Marek's Disease Virus-Vectored Bivalent Vaccine Against Infectious Laryngotracheitis and Marek's Disease

Laryngotracheitis (LT) is a highly contagious respiratory disease of chickens that produces significant economic losses to the poultry industry. Traditionally, LT has been controlled by administration of modified live vaccines. In recent years, the use of recombinant DNA-derived vaccines using turkey herpesvirus (HVT) and fowlpox virus has expanded, as they protect not only against the vector used but also against LT. However, HVT-based vaccines confer limited protection against challenge, with emergent very virulent plus Marek's disease virus (vv+MDV). Serotype 1 vaccines have been proven to be the most efficient against vv+MDV. In particular, deletion of oncogene MEQ from the oncogenic vvMDV strain Md5 (BACδMEQ) resulted in a very efficient vaccine against vv+MDV. In this work, we have developed two recombinant vaccines against MD and LT by using BACδMEQ as a vector that carries either the LT virus (LTV) gene glycoprotein B (gB; BACΔMEQ-gB) or LTV gene glycoprotein J (gJ; BACδMEQ-gJ). We have evaluated the protection that these recombinant vaccines confer against MD and LT challenge when administered alone or in combination. Our results demonstrated that both bivalent vaccines (BACΔMEQ-gB and BACδMEQ-gJ) replicated in chickens and were safe to use in commercial meat-type chickens bearing maternal antibodies against MDV. BACΔMEQ-gB protected as well as a commercial recombinant (r)HVT-LT vaccine against challenge with LTV. However, BACδMEQ-gJ did not protect adequately against LT challenge or increase protection conferred by BACΔMEQ-gB when administered in combination. On the other hand, both BACΔMEQ-gB and BACδMEQ-gJ, administered alone or in combination, protected better against an early challenge with vv+MDV strain 648A than commercial strains of rHVT-LT or CVI988. Our results open a new avenue in the development of recombinant vaccines by using serotype 1 MDV as vectors.

Duck enteritis virus glycoprotein D and B DNA vaccines induce immune responses and immunoprotection in Pekin ducks

DNA vaccine is a promising strategy for protection against virus infection. However, little is known on the efficacy of vaccination with two plasmids for expressing the glycoprotein D (gD) and glycoprotein B (gB) of duck enteritis virus (DEV) in inducing immune response and immunoprotection against virulent virus infection in Pekin ducks. In this study, two eukaryotic expressing plasmids of pcDNA3.1-gB and pcDNA3.1-gD were constructed. Following transfection, the gB and gD expressions in DF1 cells were detected. Groups of ducks were vaccinated with pcDNA3.1-gB and/or pcDNA3.1-gD, and boosted with the same vaccine on day 14 post primary vaccination. We found that intramuscular vaccinations with pcDNA3.1-gB and/or pcDNA3.1-gD, but not control plasmid, stimulated a high frequency of CD4+ and CD8+ T cells in Pekin ducks, particularly with both plasmids. Similarly, vaccination with these plasmids, particularly with both plasmids, promoted higher levels of neutralization antibodies against DEV in Pekin ducks. More importantly, vaccination with both plasmids significantly reduced the virulent DEV-induced mortality in Pekin ducks. Our data indicated that vaccination with plasmids for expressing both gB and gD induced potent cellular and humoral immunity against DEV in Pekin ducks. Therefore, this vaccination strategy may be used for the prevention of DEV infection in Pekin ducks.

Discovery of potential diagnostic and vaccine antigens in herpes simplex virus 1 and 2 by proteome-wide antibody profiling

Routine serodiagnosis of herpes simplex virus (HSV) infections is currently performed using recombinant glycoprotein G (gG) antigens from herpes simplex virus 1 (HSV-1) and HSV-2. This is a single-antigen test and has only one diagnostic application. Relatively little is known about HSV antigenicity at the proteome-wide level, and the full potential of mining the antibody repertoire to identify antigens with other useful diagnostic properties and candidate vaccine antigens is yet to be realized. To this end we produced HSV-1 and -2 proteome microarrays in Escherichia coli and probed them against a panel of sera from patients serotyped using commercial gG-1 and gG-2 (gGs for HSV-1 and -2, respectively) enzyme-linked immunosorbent assays. We identified many reactive antigens in both HSV-1 and -2, some of which were type specific (i.e., recognized by HSV-1- or HSV-2-positive donors only) and others of which were nonspecific or cross-reactive (i.e., recognized by both HSV-1- and HSV-2-positive donors). Both membrane and nonmembrane virion proteins were antigenic, although type-specific antigens were enriched for membrane proteins, despite being expressed in E. coli.

Prospects for Developing an Effective Vaccine Against Ocular Herpes Simplex Virus Infection

One of the hallmarks of herpes simplex virus (HSV) infection is the establishment of a lifelong latent infection accompanied by periods of recurrent disease. Primary HSV infections or repeated clinical recurrences do not elicit immune responses capable of completely preventing recurrences of endogenous virus. It is therefore questionable if vaccination approaches that seek to mimic the immune response to natural infection will reduce infection or disease due to an exogenous viral challenge. Approaches to the induction of protective responses by altering or enhancing both innate and adaptive immunity, using novel vaccines specifically tested in models of HSV infections of the eye, such as recombinant viral vaccine vectors and DNA vaccines, are detailed in this review.

Viral sequestration of antigen subverts cross presentation to CD8(+) T cells

Virus-specific CD8⁺ T cells (T_CD8+) are initially triggered by peptide-MHC Class I complexes on the surface of professional antigen presenting cells (pAPC). Peptide-MHC complexes are produced by two spatially distinct pathways during virus infection. Endogenous antigens synthesized within virus-infected pAPC are presented via the direct-presentation pathway. Many viruses have developed strategies to subvert direct presentation. When direct presentation is blocked, the cross-presentation pathway, in which antigen is transferred from virus-infected cells to uninfected pAPC, is thought to compensate and allow the generation of effector T_CD8+. Direct presentation of vaccinia virus (VACV) antigens driven by late promoters does not occur, as an abortive infection of pAPC prevents production of these late antigens. This lack of direct presentation results in a greatly diminished or ablated T_CD8+ response to late antigens. We demonstrate that late poxvirus antigens do not enter the cross-presentation pathway, even when identical antigens driven by early promoters access this pathway efficiently. The mechanism mediating this novel means of viral modulation of antigen presentation involves the sequestration of late antigens within virus factories. Early antigens and cellular antigens are cross-presented from virus-infected cells, as are late antigens that are targeted to compartments outside of the virus factories. This virus-mediated blockade specifically targets the cross-presentation pathway, since late antigen that is not cross-presented efficiently enters the MHC Class II presentation pathway. These data are the first to describe an evasion mechanism employed by pathogens to prevent entry into the cross-presentation pathway. In the absence of direct presentation, this evasion mechanism leads to a complete ablation of the T_CD8+ response and a potential replicative advantage for the virus. Such mechanisms of viral modulation of antigen presentation must also be taken into account during the rational design of antiviral vaccines.

Understanding the pathways by which protective immunity is mediated against viral pathogens is essential to allow the design of effective vaccines. No effective vaccine has been designed to activate killer cells of the immune system expressing CD8, although CD8⁺ T cells are the most effective cells at modulating anti-viral immunity. We have studied the process that activates the CD8⁺ T cell to better understand how the cells are triggered so future vaccines might readily activate these cells. CD8⁺ T cells are activated following recognition of small peptides derived from a virus that binds to a cell surface MHC molecule. Many viruses have evolved to prevent the presentation of these peptide-MHC complexes to CD8⁺ T cells. However, the immune system avoids these viral “evasion” mechanisms by allowing virus-derived peptides to be generated from viral proteins that are taken up by uninfected cells, a process termed “cross presentation”. We have shown that a poxvirus can specifically prevent the presentation of its proteins by uninfected cells, the first demonstration of evasion of cross presentation. This knowledge is vital in the use of certain viral vectors during vaccine design and adds to the numerous ways in which viruses can evade the immune system.

Expression of herpes simplex virus type 1 DNA polymerase by recombinant vaccinia virus

We have studied expression of the catalytic subunit of a phosphonoacetic acid-resistant (PAA(r)) DNA polymerase (Pol) of herpes simplex virus type 1 (HSV-1) strain ANG by recombinant vaccinia virus (VV) engineered with the dominant Ecogpt selection system. In agreement with the vector construction recombinant Pol expression was regulated like a VV late function. De novo-synthesis of the 136-kDa Pol polypeptide was detectable as early as 6 h postinfection, peaked between 10 and 12 h, and correlated with specific polymerase activity. Compared with HSV-1 lytic infection, the recombinant Pol protein exhibited a reduced stability with a half-life of 7 h. Whereas the Pol-associated exonuclease activities, determined from lysates of recombinant VV- and HSV-1-infected cells, were almost identical, the polymerizing activity of recombinant Pol ceased after 10 min of incubation, in correlation with the fact that Pol depends on its cofactor for optimal chain elongation. Kinetics of cellular localization, tracked by a monospecific Pol antibody, revealed that the catalytic subunit initially assembled to a few dot-like nuclear sites, reminiscent of HSV-1 DNA replication compartments. Later during infection, the localization of recombinant Pol matched with that found in lytically HSV-1-infected cells. This study demonstrates that nuclear transport and localization of the Pol subunit is independent of herpesviral functions, and neither requires the presence of herpesviral DNA sequences. Recombinant VV provides a promising alternative to explore protein interactions of the herpesviral replication machinery in their authentic cellular environment.

Asymptomatic human CD4+ cytotoxic T-cell epitopes identified from herpes simplex virus glycoprotein B

The identification of "asymptomatic" (i.e., protective) epitopes recognized by T cells from herpes simplex virus (HSV)-seropositive healthy individuals is a prerequisite for an effective vaccine. Using the PepScan epitope mapping strategy, a library of 179 potential peptide epitopes (15-mers overlapping by 10 amino acids) was identified from HSV type 1 (HSV-1) glycoprotein B (gB), an antigen that induces protective immunity in both animal models and humans. Eighteen groups (G1 to G18) of 10 adjacent peptides each were first screened for T-cell antigenicity in 38 HSV-1-seropositive but HSV-2-seronegative individuals. Individual peptides within the two immunodominant groups (i.e., G4 and G14) were further screened with T cells from HLA-DR-genotyped and clinically defined symptomatic (n = 10) and asymptomatic (n = 10) HSV-1-seropositive healthy individuals. Peptides gB(161-175) and gB(166-180) within G4 and gB(661-675) within G14 recalled the strongest HLA-DR-dependent CD4(+) T-cell proliferation and gamma interferon production. gB(166-180), gB(661-675), and gB(666-680) elicited ex vivo CD4(+) cytotoxic T cells (CTLs) that lysed autologous HSV-1- and vaccinia virus (expressing gB)-infected lymphoblastoid cell lines. Interestingly, gB(166-180) and gB(666-680) peptide epitopes were strongly recognized by CD4(+) T cells from 10 of 10 asymptomatic patients but not by CD4(+) T cells from 10 of 10 symptomatic patients (P < 0.0001; analysis of variance posttest). Inversely, CD4(+) T cells from symptomatic patients preferentially recognized gB(661-675) (P < 0.0001). Thus, we identified three previously unrecognized CD4(+) CTL peptide epitopes in HSV-1 gB. Among these, gB(166-180) and gB(666-680) appear to be "asymptomatic" peptide epitopes and therefore should be considered in the design of future herpes vaccines.

Glycoprotein D adjuvant herpes simplex virus vaccine

Herpes simplex virus (HSV) Type-1 and -2 are common infections that can cause primary and recurrent herpes labialis and genitalis, as well as gingivostomatitis, keratoconjunctivitis, encephalitis, disseminated infections in immunocompromised persons and neonatal infections. Despite several decades of HSV vaccine development, no effective vaccine has been developed until recently. The following review of the genital HSV-2 glycoprotein D (gD2t, t is for truncated) subunit vaccine formulated with a new adjuvant (AS04) containing alum and 3-O deacylated monophosphoryl lipid A (MPL) provides a background in which to evaluate the vaccine as well as a brief review of other approaches to herpes vaccines. The gD2t-AS04 vaccine has been demonstrated to be safe in several large clinical trials. In two trials, the vaccine reduced genital herpes disease by 73 and 74%, but only in females with no previous HSV infection. A large ongoing trial in HSV seronegative females will provide additional data on protection from HSV disease and infection.

Developments in herpes simplex virus vaccines: old problems and new challenges

Vaccination has remained the best method for preventing virus spread. The herpes simplex virus (HSV) candidate vaccines tested till now were mostly purified subunit vaccines and/or recombinant envelope glycoproteins (such as gB and gD). In many experiments performed in mice, guinea pigs and rabbits, clear-cut protection against acute virus challenge was demonstrated along with the reduction of the extent of latency, when established in the immunized host. The immunotherapeutic effect of herpes vaccines seems less convincing. However, introduction of new adjuvants, which shift the cytokine production of helper T-cells toward stimulation of cytotoxic T-cells (TH1 type cytokine response), reveals a promising development. Mathematical analysis proved that overall prophylactic vaccination of seronegative women, even when eliciting 40-60 % antibody response only, would reduce the frequency of genital herpes within the vaccinated population. Even when partially effective, immunotherapeutic vaccination might represent a suitable alternative of chronic chemotherapy in recurrent labial and genital herpes.

A soluble divalent class I MHC/IgG1 fusion protein activates CD8+ T cells in vivo

CD8+ T lymphocytes recognize tumor and viral antigens bound to class I major histocompatibility complexes (MHC). Tumors and viruses may evade detection by preventing antigen presentation. The present study was designed to determine whether a soluble divalent fusion protein, containing the extracellular domains of a class I MHC molecule fused to beta2-microglobulin and the constant domains of IgG1, could induce an immune response in vivo. Administration to mice of the fusion protein loaded with a tumor peptide induced peptide-specific T cell activation and retarded tumor growth. Administration of the fusion protein loaded with a glycoprotein B (gB) peptide derived from herpes simplex virus type 1 (HSV-1) induced gB-specific cytotoxic T lymphocytes and protected mice from a lethal HSV-1 challenge. These data suggest that antigen-loaded MHC/IgG fusion proteins may enhance T cell immunity in conditions where antigen presentation is altered.

A locus on mouse chromosome 6 that determines resistance to herpes simplex virus also influences reactivation, while an unlinked locus augments resistance of female mice

During studies to determine a role for tumor necrosis factor (TNF) in herpes simplex virus type 1 (HSV-1) infection using TNF receptor null mutant mice, we discovered a genetic locus, closely linked to the TNF p55 receptor (Tnfrsf1a) gene on mouse chromosome 6 (c6), that determines resistance or susceptibility to HSV-1. We named this locus the herpes resistance locus, Hrl, and showed that it also mediates resistance to HSV-2. Hrl has at least two alleles, Hrl(r), expressed by resistant strains like C57BL/6 (B6), and Hrl(s), expressed by susceptible strains like 129S6 (129) and BALB/c. Although Hrl is inherited as an autosomal dominant gene, resistance to HSV-1 is strongly sex biased such that female mice are significantly more resistant than male mice. Analysis of backcrosses between resistant B6 and susceptible 129 mice revealed that a second locus, tentatively named the sex modifier locus, Sml, functions to augment resistance of female mice. Besides determining resistance, Hrl is one of several genes involved in the control of HSV-1 replication in the eye and ganglion. Remarkably, Hrl also affects reactivation of HSV-1, possibly by interaction with some unknown gene(s). We showed that Hrl is distinct from Cmv1, the gene that determines resistance to murine cytomegalovirus, which is encoded in the major NK cell complex just distal of p55 on c6. Hrl has been mapped to a roughly 5-centimorgan interval on c6, and current efforts are focused on obtaining a high-resolution map for Hrl.

Immune responses to replication-defective HSV-1 type vectors within the CNS: implications for gene therapy

Herpes simplex virus (HSV) is a naturally occurring double-stranded DNA virus that has been adapted into an efficient vector for in vivo gene transfer. HSV-based vectors exhibit wide tropism, large transgene size capacity, and moderately prolonged transgene expression profiles. Clinical implementation of HSV vector-based gene therapy for prevention and/or amelioration of human diseases eventually will be realized, but inherently this goal presents a series of significant challenges, one of which relates to issues of immune system involvement. Few experimental reports have detailed HSV vector-engendered immune responses and subsequent resolution events primarily within the confines of the central nervous system. Herein, we describe the immunobiology of HSV and its derived vector platforms, thus providing an initiation point from where to propose requisite experimental investigation and potential approaches to prevent and/or counter adverse antivector immune responses.

Development of HSV-specific CD4+ Th1 responses and CD8+ cytotoxic T lymphocytes with antiviral activity by vaccination with the HSV-2 mutant ICP10DeltaPK

A growth compromised herpes simplex virus type 2 (HSV-2) mutant which is deleted in the PK domain of the large subunit of ribonucleotide reductase (ICP10DeltaPK) protects from HSV-2 challenge in the mouse and guinea pig cutaneous and vaginal models and reduces the incidence and frequency of recurrent disease (Vaccine (17) (1999) 1951; Vaccine (19) (2001) 1879). The present studies were designed to identify the immune responses induced by ICP10DeltaPK and define the component responsible for protective activity. We found that ICP10DeltaPK elicits a predominant HSV-specific T helper type 1 (Th1) response, as evidenced by: (1) higher levels of HSV-specific IgG2a (Th1) than IgG1 (Th2) isotypes and (2) higher numbers of CD4+ IFN-gamma than IL-10 secreting T cells in popliteal lymph nodes. This Th1 response pattern was associated with a significant increase in the levels of IL-12 produced by dendritic cells from ICP10DeltaPK than HSV-2 immunized animals. Lymph node cells (LNCs) from ICP10DeltaPK immunized mice had significantly higher levels of HSV-2 specific cytolytic activity than LNCs from mice immunized with HSV-2 and it was mediated by CD8+ T cells. CD8+ CTL were not seen in LNCs from HSV-2 immunized mice. In adoptive transfer experiments, CD8+ T cells and, to a lower extent, CD4+ T cells from ICP10DeltaPK immunized mice inhibited HSV-2 replication, suggesting that they are involved in the protective immunity induced by ICP10DeltaPK vaccination.

Vaccine-induced serum immunoglobin contributes to protection from herpes simplex virus type 2 genital infection in the presence of immune T cells

Herpes simplex type virus 2 (HSV-2) is a sexually transmitted pathogen that causes genital lesions and spreads to the nervous system to establish acute and latent infections. Systemic but not mucosal cellular and humoral immune responses are elicited by immunization of mice with a replication-defective mutant of HSV-2, yet the mice are protected against disease caused by subsequent challenge of the genital mucosa with virulent HSV-2. In this study, we investigated the role of immune serum antibody generated by immunization with a replication-defective HSV-2 vaccine prototype strain in protection of the genital mucosa and the nervous system from HSV-2 infection. Passive transfer of replication-defective virus-immune serum at physiologic concentrations to SCID or B-cell-deficient mice had no effect on replication of challenge virus in the genital mucosa but did significantly reduce the incidence and severity of genital and neurologic disease. In contrast, B-cell-deficient mice immunized with replication-defective HSV-2 were able to control replication of challenge virus in the genital mucosa, but not until 3 days postchallenge, and were not completely protected against genital and neurologic disease. Passive transfer of physiologic amounts of immune serum to immunized, B-cell-deficient mice completely restored their capacity to limit replication of challenge virus in the genital mucosa and prevented signs of genital and systemic disease. In addition, the numbers of viral genomes in the lumbosacral dorsal root ganglia of immunized, B-cell-deficient mice were dramatically reduced by transfer of immune serum prior to challenge. These results suggest that there is an apparent synergism between immune serum antibody and immune T cells in achieving protection and that serum antibody induced by vaccination with replication-defective virus aids in reducing establishment of latent infection after genital infection with HSV-2.

Effects of preexisting immunity on the response to herpes simplex-based oncolytic viral therapy

Herpes simplex viruses (HSV) type 1 are the basis of a number of anticancer strategies that have proven efficacious in animal models. They are natural human pathogens and the majority of adults have anti-HSV immunity. The current study examined the effect of preexisting immunity on the response to herpes-based oncolytic viral treatment of hepatic metastatic cancer in a murine model designed to simulate a clinical approach likely to be utilized for nonneurological tumors. Specifically, the anticancer effects of NV1020 or G207, two multimutated HSV-1 oncolytic viruses, were tested in immunocompetent mice previously immunized with a wild-type herpes simplex type 1 virus. Mice were documented to have humoral as well as cell-mediated immunity to HSV-1. Tumor response to oncolytic therapy was not measurably abrogated by immunity to HSV at the doses tested. The influence of route of viral administration was also tested in models of regional hepatic arterial and intravenous therapy. Route of viral administration influenced efficacy, as virus delivered intravenously produced some detectable attenuation while hepatic arterial therapy remained unaffected. These results demonstrate that when given at appropriate doses and in reasonable proximity to tumor targets, HSV-based oncolytic therapy can still be expected to be effective treatment for patients with hepatic malignancies.

Evidence of selective processing of immunodominant epitopes in virally infected cells

Recent advances in clarifying the molecular mechanisms involved in Ag processing and presentation have relied heavily on the use of somatic cell mutants deficient in proteasome subunits, TAP transporter, and cell surface expression of MHC class I molecules. Of particular interest currently are those mutants that lack specific protease activity involved in the generation of antigenic peptides. It is theoretically possible that deficiencies of this nature could selectively prevent the cleavage of certain peptide bonds and thus generate only a subset of antigenic peptides. Gro29/Kb cell line is derived from the wild-type murine Ltk- cell line. This cell line is one example of a mutant that lacks specific protease activities. This deficiency manifests itself in an inability to generate a subset of immunodominant peptide epitopes derived from vesicular stomatitis virus and herpes simplex virus. This in turn leads to a general inability to present these viral epitopes to cytotoxic T lymphocytes (CTL). These studies describe a unique Ag processing deficiency and provide new insight into the role of proteasome-independent proteases in MHC class I-restricted peptide generation.

Protection against herpes B virus infection in rabbits with a recombinant vaccinia virus expressing glycoprotein D

Herpes B virus infects naturally monkeys of the macaque genus in whom it can cause recurrent oral and genital lesions. However, when the virus infects humans it causes a neurological illness with a high case fatality rate. Successful treatment is possible but this depends on diagnosis prior to the onset of respiratory arrest, and fatalities over the last 10 years have been the result of late or no diagnostic data on which to base anti-viral intervention. An effective vaccine would be an ideal way to combat the risk of herpes B virus disease in humans working with potentially infected monkeys or their tissues. A recombinant vaccinia virus expressing herpes B virus glycoprotein D (gD) was constructed and rabbits inoculated with the chimeric virus were tested for immunoglobulin responses to herpes B virus by virus neutralisation, ELISA and Western blot analyses. Anti-gD humoral responses were detected in all vaccinated animals by ELISA and Western blot but neutralising antibody was not detected prior to challenge with herpes B virus. Non-vaccinated rabbits died within 8 days of challenge while 10/11 vaccinated animals were protected against herpes B virus disease. No antibodies to herpes B virus proteins other than gD were detectable in surviving animals, suggesting minimal herpes B virus replication post challenge. Autopsies were carried out on 4/10 rabbits which had remained healthy at 31 days post challenge and the dorsal root ganglia adjacent to the inoculation site were removed. Attempts to detect herpes B virus DNA by PCR followed by hybridisation proved negative suggesting protection against latent herpes B virus infection.

Immunization with a single major histocompatibility complex class I-restricted cytotoxic T-lymphocyte recognition epitope of herpes simplex virus type 2 confers protective immunity

We have evaluated the potential of conferring protective immunity to herpes simplex virus type 2 (HSV-2) by selectively inducing an HSV-specific CD8(+) cytotoxic T-lymphocyte (CTL) response directed against a single major histocompatibility complex class I-restricted CTL recognition epitope. We generated a recombinant vaccinia virus (rVV-ES-gB498-505) which expresses the H-2Kb-restricted, HSV-1/2-cross-reactive CTL recognition epitope, HSV glycoprotein B residues 498 to 505 (SSIEFARL) (gB498-505), fused to the adenovirus type 5 E3/19K endoplasmic reticulum insertion sequence (ES). Mucosal immunization of C57BL/6 mice with this recombinant vaccinia virus induced both a primary CTL response in the draining lymph nodes and a splenic memory CTL response directed against HSV gB498-505. To determine the ability of the gB498-505-specific memory CTL response to provide protection from HSV infection, immunized mice were challenged with a lethal dose of HSV-2 strain 186 by the intranasal (i.n.) route. Development of the gB498-505-specific CTL response conferred resistance in 60 to 75% of mice challenged with a lethal dose of HSV-2 and significantly reduced the levels of infectious virus in the brains and trigeminal ganglia of challenged mice. Finally, i.n. immunization of C57BL/6 mice with either a recombinant influenza virus or a recombinant vaccinia virus expressing HSV gB498-505 without the ES was also demonstrated to induce an HSV-specific CTL response and provide protection from HSV infection. This finding confirms that the induction of an HSV-specific CTL response directed against a single epitope is sufficient for conferring protective immunity to HSV. Our findings support the role of CD8(+) T cells in the control of HSV infection of the central nervous system and suggest the potential importance of eliciting HSV-specific mucosal CD8(+) CTL in HSV vaccine design.

Cytotoxic T lymphocyte response in chickens immunized with a recombinant fowlpox virus expressing Marek's disease herpesvirus glycoprotein B

Previously, we demonstrated that cytotoxic T lymphocytes (CTLs) from MHC: B19B19 and MHC: B21B21 chickens inoculated with a non-oncogenic Marek's disease virus (MDV) vaccine strain, SB-1/12 can lyse syngeneic reticuloendotheliosis virus (REV)-transformed cell lines expressing MDV pp38 or gB genes. In this study, we report the characterization of MDV gB-specific CTLs in chickens immunized with recombinant fowlpox virus expressing MDV gB gene (rFPV-gB). Spleen cells from rFPV-gB inoculated chickens (MHC: B19B19), depleted for CD4+, CD8+, TCR gamma delta+, TCR alpha beta 1+ or TCR alpha beta 2+ cells were used as effector cells in chromium release assays. Effector cells depleted of CD8+ or TCR alpha beta 1+, but not CD4+, TCR gamma delta+ or TCR alpha beta 2+ markedly reduced the percentage of specific release (%SR). Compared to the %SR caused by the SB-1/12-sensitized CTLs, the %SR caused by rFPV-gB-sensitized CTLs was low, but statistically significant. This is a first report on the induction of MDV gB-specific CD8+ CTLs in chickens immunized with rFPV-gB vaccine.

Immunization with a replication-deficient mutant of herpes simplex virus type 1 (HSV-1) induces a CD8+ cytotoxic T-lymphocyte response and confers a level of protection comparable to that of wild-type HSV-1

Replication-deficient viruses provide an attractive alternative to conventional approaches used in the induction of antiviral immunity. We have quantitatively evaluated both the primary and memory cytotoxic T-lymphocyte (CTL) responses elicited by immunization with a replication-deficient mutant of herpes simplex virus type 1 (HSV-1). In addition, we have examined the potential role of these CTL in protection against HSV infection. Using bulk culture analysis and limiting-dilution analysis, we have shown that a replication-deficient virus, d301, generates a strong primary CTL response that is comparable to the response induced by the wild type-strain, KOS1.1. Furthermore, the CTL induced by d301 immunization recognized the immunodominant, H-2Kb-restricted, CTL recognition epitope gB498-505 to a level similar to that for CTL from KOS1.1-immunized mice. The memory CTL response evoked by d301 was strong and persistent, even though the frequencies of CTL were slightly lower than the frequencies of CTL induced by KOS1.1. Adoptive transfer studies indicated that both the CD8+ and the CD4+ T-cell responses generated by immunization with d301 and KOS1.1 were able to limit the extent of a cutaneous HSV infection to comparable levels. Overall, these results indicate that viral replication is not necessary to elicit a potent and durable HSV-specific immune response and suggest that replication-deficient viruses may be effective in eliciting protection against viral pathogens.

Long-lived cytotoxic T lymphocyte memory in mucosal tissues after mucosal but not systemic immunization

The induction and maintenance of long-term CTL memory at mucosal surfaces may be a critical component of protection against mucosal pathogens and is one goal towards development of effective mucosal vaccines. In these studies we have functionally evaluated short and long-term CTL memory in systemic and respiratory or genital-associated lymphoid tissues following mucosal or systemic routes of immunization. Our results indicate that shortly after immunizing mice with a recombinant adenovirus vector expressing glycoprotein B (gB) of herpes simplex virus (AdgB8), gB-specific CTL memory responses were observed in systemic and mucosal immune compartments regardless of the route of inoculation. In contrast, several months after immunization, anamnestic CTL responses compartmentalized exclusively to mucosal or systemic lymphoid tissues after mucosal or systemic immunization, respectively. Furthermore, the compartmentalized CTL memory responses in mucosal tissues were functionally observed for longer than 1.5 yr after intranasal immunization, and CTL precursor frequencies one year after immunization were comparable to those seen shortly after immunization. Therefore, to our knowledge, this is the first functional demonstration that the maintenance of anti-viral memory CTL in mucosal tissues is dependent on the route of immunization and the time of assessment. These results have important implications for our understanding of the development, maintenance, and compartmentalization of functional T cell memory and the development and evaluation of vaccines for mucosal pathogens, such as HSV and HIV.

Immunization with DNA vaccines encoding glycoprotein D or glycoprotein B, alone or in combination, induces protective immunity in animal models of herpes simplex virus-2 disease

DNA vaccines expressing herpes simplex virus type 2 (HSV-2) full-length glycoprotein D (gD), or a truncated form of HSV-2 glycoprotein B (gB) were evaluated for protective efficacy in two experimental models of HSV-2 infection. Intramuscular (i.m.) injection of mice showed that each construction induced neutralizing serum antibodies and protected the mice from lethal HSV-2 infection. Dose-titration studies showed that low doses (< or = 1 microgram) of either DNA construction induced protective immunity, and that a single immunization with the gD construction was effective. The two DNAs were then tested in a low-dosage combination in guinea pigs. Immune sera from DNA-injected animals had antibodies to both gD and gB, and virus neutralizing activity. When challenged by vaginal infection with HSV-2, the DNA-immunized animals were significantly protected from primary genital disease.

Deletion of the carboxy-terminus of herpes simplex virus type 1 (HSV-1) glycoprotein B does not affect oligomerization, heparin-binding activity, or its ability to protect against HSV challenge

A recombinant vaccinia virus designated VgBt which expresses a truncated secreted herpes simplex virus gB (gBt) was constructed and compared to V11gB, a vaccinia recombinant previously studied which expresses gB exclusively on the surface of infected cells. Indirect immunofluorescence assay (IFA) revealed that gBt was strongly associated with the surface of infected cells despite being released slowly into the cell culture medium. Both gB and gBt existed as oligomers, and both membrane bound and secreted forms of gBt exhibited heparin-binding activity. In protection studies VgBt and V11gB conferred equivalent protection against both homologous (HSV-1) and heterologous (HSV-2) challenge with HSV.

Locations of herpes simplex virus type 2 glycoprotein B epitopes recognized by human serum immunoglobulin G antibodies

Herpes simplex virus type 2 (HSV-2) glycoprotein B (gB-2) gene segments were expressed as recombinant proteins in Escherichia coli. gB-2 recombinant proteins were reacted with human serum immunoglobulin G (IgG) antibodies in Western immunoblot assays. Initially, samples were tested for the presence of HSV-1-specific antibodies and HSV-2-specific antibodies by using HSV-infected cell lysates as antigen targets in Western blot assays. Serum samples that contained HSV-2-specific IgG (n = 58), HSV-1-specific IgG (n = 33), or no detectable HSV antibodies (n = 31) were tested for reactivities with the gB-2 recombinant proteins. In 58 of 58 samples that contained HSV-2-specific IgG, antibodies were present that reacted strongly with a gB-2 amino-proximal segment between amino acids (aa) 18 and 75. Three of 33 serum samples that contained HSV-1- and not HSV-2-specific IgG (as defined by the HSV lysate Western blot assay) reacted with this segment. Both HSV-2 antibodies and HSV-1 antibodies reacted strongly with a carboxy-terminal gB-2 segment between aa 819 and 904; a second minor cross-reactive region was mapped to a gB-2 segment between aa 564 and 626. The gB-2 segment from aa 18 to 75 may constitute a useful reagent for the virus type-specific serodiagnosis of HSV-2 infections. Further studies will be required to determine the relative sensitivities and specificities of the assay for gB-2 aa 18 to 75, HSV gG assays, and HSV lysate Western blot assays for detecting virus type-specific antibody responses in acute and chronic HSV-2 infections.

Virus-neutralization domains on the oligomeric (230 kDa) forms of antigen B of herpesvirus of turkeys and Marek's disease virus differ in cross-serotypic activity

Herpesvirus of turkeys (HVT) is frequently used to protect chickens against Marek's disease (MD). The HVT and MDV native antigen B complex shares common epitopes. To determine whether these oligomers present virus-neutralizing domains, monospecific antibodies to the HVT and MDV native 230 kDa oligomers were produced. The monospecific antibody immunopurified from an anti-HVT avian serum neutralized the in vitro infectivity of the oncogenic isolate MDV-B and the vaccine strains CVI988, SB1 and HVT and immunoblotted the 230 kDa oligomers of HVT and CVI988. As a result of the immunofluorescence analysis on infected cells, the monospecific antibody revealed foci of diffuse cytoplasmic immunofluorescence. A second monospecific antibody to the heat-stable 130 kDa monomer of HVT had limited neutralizing activity against HVT and CVI988 only, immunoblotted only the native HVT oligomer, and was not active in immunofluorescence. The monospecific antibody to the MDV-B 230 kDa oligomer neutralized and immunoblotted only the two MDV-1 strains but stained cells infected with MDVs of the three serotypes in immunofluorescence. It is concluded that the cross-protective neutralizing epitopes of HVT are located on heat-labile oligomeric forms of antigen B.

Analysis of the cytolytic T-lymphocyte response to herpes simplex virus type 1 glycoprotein B during primary and secondary infection

The immune response to herpes simplex virus type 1 (HSV-1) infection in C57BL/6 mice includes a population of major histocompatibility complex class I-restricted cytolytic T lymphocytes (CTL) that recognize the structural glycoprotein gB. To gain insight into the importance of this CTL subpopulation in vivo, gB-specific CTL present in the regional lymph nodes after a primary infection and after a reinfection of convalescent animals were analyzed. In a primary infection, gB-specific CTL precursors (CTLp) that recognized either a cell line constitutively expressing gB or cells pulsed with the optimal Kb-restricted gB epitope 498SSIEFARL505 were present at an estimated frequency of 1/12,000 compared with a frequency of 1/3,000 for CTLp which recognized cells infected with HSV-1 itself. In convalescent mice responding to reinfection, HSV-specific CTLp were present at an estimated frequency of 1/4,000 to 1/14,000. However, gB-specific CTLp could not be detected at this site. These findings suggest that CTL specific for an immunodominant epitope contribute substantially to the primary response but may not be a component of the HSV-specific CTL population that responds rapidly to reinfection in vivo.

A vaccinia virus--herpes simplex virus (HSV) glycoprotein B1 recombinant or an HSV vaccine overcome the HSV type 2 induced humoral immunosuppression and protect against vaginal challenge in BALB/c mice

Primary infections with herpes simplex virus type 2 (HSV-2) suppress the antibody response to secondary HSV-1 and -2 infections in the BALB/c mouse. In contrast, a challenge by the i.p. route using a vaccinia virus-HSV-1 glycoprotein B (VV gB1) recombinant induces a significant enhancement of the antibody response. This booster reaction is also observed if a challenge with a formalin-inactivated HSV-1 vaccine is performed. Although no or low humoral and vaginal antibodies are detectable after a single i.p. infection with the VV gB1 recombinant or the HSV-1 vaccine, protection against vaginal challenge with HSV-2 is induced. This points to the important role of cellular immunity for vaginal infections.

Induction of primary, antiviral cytotoxic, and proliferative responses with antigens administered via dendritic cells

Cytotoxic T lymphocytes (CTL) play an essential role in recovery from viral infections, but induction of CTL responses with nonreplicating antigens is difficult to achieve. Exogenous antigens, such as viral proteins and peptides, normally induce CD4+ T-cell responses unless appropriately delivered to the major histocompatibility complex class I antigen presentation pathway. In vitro studies performed to address this issue revealed a similar scenario, and primary CTL induction with nonreplicating antigens has rarely been reported. This study demonstrated primary antiviral CTL induction in vitro with exogenous antigens delivered in vivo to dendritic cells. This study also evaluated the efficacy of glycoprotein B peptide (free or encapsulated in liposomes), peptide-tripalmitoyl-S-glyceryl cysteinyl conjugate (acylpeptide), and glycoprotein B protein encapsulated in pH-sensitive liposomes as antigen delivery vehicles. Our results show that higher levels of cytotoxicity against herpes simplex virus type 1 resulted from exposure of dendritic cells to peptide-tripalmitoyl-S-glyceryl cysteinyl in liposomes. Macrophages treated in a similar manner were not effective stimulators for primary CTL induction. Our data have relevance to the understanding of mechanisms of antigen processing and presentation and the design of antiviral vaccines.

Replication-defective mutants of herpes simplex virus (HSV) induce cellular immunity and protect against lethal HSV infection

Live viruses and live virus vaccines induce cellular immunity more readily than do inactivated viruses or purified proteins, but the mechanism by which this process occurs is unknown. A trivial explanation would relate to the ability of live viruses to spread and infect more cells than can inactivated virus. We have used live but replication-defective mutants to investigate this question. Our studies indicate that the immune responses of mice to live virus differ greatly from the responses to inactivated virus even when the virus does not complete a replicative cycle. Further, these studies indicate that herpes simplex virus-specific T-cell responses can be generated by infection with replication-defective mutant viruses. These data indicate that the magnitude of the cellular immunity to herpes simplex virus may be proportional to the number or quantity of different viral gene products expressed by an immunizing virus.

Expression of the Marek's disease virus (MDV) homolog of glycoprotein B of herpes simplex virus by a recombinant baculovirus and its identification as the B antigen (gp100, gp60, gp49) of MDV

A gene encoding a homolog of glycoprotein B of herpes simplex virus (gB homolog) has been identified on the Marek's disease virus (MDV) genome (L. J. N. Ross, M. Sanderson, S. D. Scott, M. M. Binns, T. Doel, and B. Milne, J. Gen. Virol. 70:1789-1804, 1989); however, the molecular and immunological characteristics of the gene product(s) are still not clear. In the present study, the gB homolog of MDV was expressed in insect cells by a recombinant baculovirus, and it was characterized to determine its molecular and antigenic properties. The expressed recombinant protein had three molecular sizes (88 to 110, 58, and 49 kDa) and was recognized by antisera from chickens inoculated with each of the three serotypes of MDV. By immunofluorescence analysis, it was shown that the protein was expressed in the cytoplasm and on the surface of the recombinant baculovirus-infected cells. The gB homolog of MDV was processed similarly to pseudorabies virus and varicella-zoster virus with respect to cleavage and the intramolecular disulfide bond between the cleaved products. Interestingly, the expressed protein reacted with monoclonal antibody M51, specific to the B antigen (gp100, gp60, gp49) of MDV, although the locations of the gene encoding the B antigen and of the gene encoding the gB homolog were reported to be different. Moreover, competitive experiments revealed that anti-gB homolog serum and monoclonal antibody M51 recognized the same molecules. From these results, the gB homolog and the B antigen of MDV seem to be the same glycoprotein.

Identification and nucleotide sequence of a gene in feline herpesvirus type 1 homologous to the herpes simplex virus gene encoding the glycoprotein B

The nucleotide sequence of the glycoprotein B (gB) homologous gene of feline herpesvirus type 1 (FHV-1) was determined. The gene was found to be located within a 9.6 kbp SalI fragment by Southern-blot hybridization with a probe derived from the herpes simplex virus type 1 (HSV-1) gB DNA sequence. Furthermore, the predominant portion of the coding sequences was mapped to a 1.9 kbp Hin cII-EcoRI and its flanking 2.7 kbp Eco RI-Eco RI subfragments in the 9.6 kbp SalI fragment. The entire nucleotide sequence revealed that the FHV-1 gB homologous gene is capable of encoding a polypeptide of 948 amino acids. The predicted precursor polypeptide derived from this open reading frame could have a calculated M(r) of 106 kDa in unglycosylated form and contains ten potential N-linked glycosylation sites and a probable internal proteolytic cleavage site. By Northern-blot analysis using portions of the open reading frame as a probe, 3.9 and 3.3 kb RNA transcripts were identified in FHV-1 infected cells. The alignment of the amino acid sequence of the FHV-1 gB homologue with those of 14 other herpesviruses revealed that 10 cysteine residues were completely conserved. Meanwhile, when evolutionary trees were generated among these herpesvirus gB counterparts, the FHV-1 gB homologous nucleotide sequence seems to be closely related to equine herpesvirus type 4 and its amino acid sequence to pseudorabies virus.

Protection against Marek's disease by a fowlpox virus recombinant expressing the glycoprotein B of Marek's disease virus

Fowlpox virus (FPV) recombinants expressing the glycoprotein B and the phosphorylated protein (pp38) of the GA strain of Marek's disease virus (MDV) were assayed for their ability to protect chickens against challenge with virulent MDV. The recombinant FPV expressing the glycoprotein B gene elicited neutralizing antibodies against MDV, significantly reduced the level of cell-associated viremia, and, similar to the conventional herpesvirus of turkeys, protected chickens against challenge with the GA strain and the highly virulent RB1B and Md5 strains of MDV. The recombinant FPV expressing the pp38 gene failed to either elicit neutralizing antibodies against MDV or protect the vaccinated chickens against challenge with MDV.

Increased expression in vivo and in vitro of foreign genes directed by A-type inclusion body hybrid promoters in recombinant vaccinia viruses

We constructed A-type inclusion body (ATI) hybrid promoters, that is, late ATI promoters followed by tandemly repeated early regions of the promoter for the 7.5-kDa protein (the 7.5-kDa promoter). The repetition of the whole early promoter sequence of the 7.5-kDa gene, including the upstream consensus sequence and initiation region, efficiently increased the early expression of the bacterial chloramphenicol acetyltransferase gene in recombinant vaccinia virus. Recombinant vaccinia virus could express influenza virus hemagglutinin via the hybrid promoter more efficiently, induced higher levels of neutralizing antibody and cytotoxic T lymphocytes, and consequently protected mice more efficiently against challenge with influenza virus than did recombinant vaccinia virus containing the widely used 7.5-kDa promoter.

A comparison of T cell responses to glycoprotein B (gB-1) of herpes simplex virus type 1 and its non-glycosylated precursor protein, pgB-1

The ability of non-glycosylated precursor glycoprotein B (pgB) to induce T cell responses in herpes simplex virus (HSV) infected mice was compared with fully glycosylated glycoprotein B (gB) and with whole virus. pgB was as effective as gB in priming for virus- and glycoprotein-specific T cells. pgB could also re-stimulate virus or glycoprotein primed cells in vitro as efficiently as gB. In addition, priming with pgB protected mice against a lethal challenge with HSV type 1 (HSV-1) and could induce the early in vivo production of IL-2 and IL-3 in infected mice. In all of these responses, pgB was as effective as gB. Thus, the carbohydrate side chains on gB do not appear to be necessary for T cell recognition of this protein.

Herpes simplex virus type 1-specific immunity induced by peptides corresponding to an antigenic site of glycoprotein B

Herpes simplex virus (HSV) envelope glycoproteins are the prime targets of adaptive antiviral immunity. Previous investigation identified a protective, neutralizing, glycoprotein B1 (gB-1)-reactive monoclonal antibody (MAb B6) and localized the linear epitope recognized by the MAb to residue 84 of gB-1. Three overlapping peptides (two 20-mers and one 18-mer), together spanning amino acids 63 to 110 of the wild-type sequence of gB-1, were synthesized and analyzed for their ability to stimulate immunity which cross-reacts with HSV-1. All stimulated some level of response. Two peptides, the gB 18-mer and 20.1-mer, were recognized by MAb B6 and HSV-immune antibody but were unable to stimulate virus-neutralizing antibody or serum able to protect against zosteriform spread in vivo. The 20.2-mer peptide, however, which was not recognized by MAb B6 or HSV-generated immune antibody, stimulated the production of neutralizing antibody and serum able to protect against zosteriform spread. Immunization with all of the peptides was able to enhance viral clearance of a low dose of HSV-1 in an ear challenge model and induce antibody reactive in antibody-dependent complement-mediated lysis of HSV-1-infected cells in vitro. These results are the first report of HSV immunity induced by peptides corresponding to gB and indicate that the best immunogen, in terms of stimulating neutralizing antiserum able to protect in vivo against HSV-1, was a peptide not recognized by HSV-immune mechanisms or by the MAb used to localize it.

Antigens of infectious laryngotracheitis herpesvirus defined by monoclonal antibodies

Monoclonal antibodies to glycoprotein and protein antigens of infectious laryngotracheitis virus (ILTV) were divided into five groups on the basis of their reactivity in immunofluorescence and Western blotting. Group I antibodies recognised a single band of 60 K and Group II antibodies recognised bands of 205, 160, 115, 90 and 85 k in Western blotting. In immunofluorescence both these groups of antibodies reacted with antigens located in the cytoplasm of fixed virus-infected cells and they also reacted with unfixed cells, suggesting that these antigens are on the surface of virus-infected cells. While Group I monoclonal antibodies did not react with extracts of tunicamycin-treated cells, some Group II antibodies recognised bands of decreased molecular weight compared to those present in untreated cells. The reactivity of the Group II antibodies with extracts of tunicamycin-treated cells suggested that they recognised at least three different epitopes which was confirmed by ELISA additivity assays. Monoclonal antibodies of Group III, Group IV and Group V recognised several low molecular weight proteins from 45 to 24 k. Immunofluorescence studies showed that these were nuclear and cytoplasmic antigens that were not present on the surface of virus-infected cells.

Coexpression by vaccinia virus recombinants of equine herpesvirus 1 glycoproteins gp13 and gp14 results in potentiated immunity

The equine herpesvirus 1 glycoprotein 14 (EHV-1 gp14) gene was cloned, sequenced, and expressed by vaccinia virus recombinants. Recombinant virus vP613 elicited the production of EHV-1-neutralizing antibodies in guinea pigs and was effective in protecting hamsters from subsequent lethal EHV-1 challenge. Coexpression of EHV-1 gp14 in vaccinia virus recombinant vP634 along with EHV-1 gp13 (P. Guo, S. Goebel, S. Davis, M. E. Perkus, B. Languet, P. Desmettre, G. Allen, and E. Paoletti, J. Virol. 63:4189-4198, 1989) greatly enhanced the protective efficacy in the hamster challenge model over that obtained with single recombinants. The inoculum doses (log10) required for protection of 50% of hamsters were 6.1 (EHV-1 gp13), 5.2 (EHV-1 gp14), and less than 3.6 (vaccinia virus recombinant expressing both EHV-1 glycoproteins [gp13 and gp14]).

Vaccinia virus vectors: new strategies for producing recombinant vaccines

The development and continued refinement of techniques for the efficient insertion and expression of heterologous DNA sequences from within the genomic context of infectious vaccinia virus recombinants are among the most promising current approaches towards effective immunoprophylaxis against a variety of protozoan, viral, and bacterial human pathogens. Because of its medical relevance, this area is the subject of intense research interest and has evolved rapidly during the past several years. This review (i) provides an updated overview of the technology that exists for assembling recombinant vaccinia virus strains, (ii) discusses the advantages and disadvantages of these approaches, (iii) outlines the areas of outgoing research directed towards overcoming the limitations of current techniques, and (iv) provides some insight (i.e., speculation) about probable future refinements in the use of vaccinia virus as a vector.

Serologic specificity of antibodies to herpes simplex virus glycoprotein B present in human sera. Analysis by transient expression of glycoprotein B-derivatives

Glycoprotein B (gB) is an essential glycoprotein of herpes simplex virus (HSV) and a major target for cellular and humoral immune response in the infected host. In the present study, we have analyzed the pattern of reactivity of a panel of 23 HSV-seropositive patient sera using as test antigens gB derivatives made in COS cells in a transient expression assay. Our results show that nearly all the sera tested, reacted with wild-type gB or tgB (772) (that lacks 102 amino acids cytoplasmic domain). However, when tgB (477 amino acids) or gBdl (an inframe deletion between amino acids 477-772) were used as test antigens only 12 out of 23 sera tested positive. Further analysis using competition assays revealed that these sera can be classified into at least two groups: (i) that contain gB-reactive antibodies reactive to intact gB or tgB (772); (ii) that contain antibodies that recognize all forms of gB-derivatives tested. The results presented here underscore the potential limitations in using certain truncated forms of gB as antigens for subunit vaccine or in the serodiagnosis of HSV infection.