Mechanisms of antiviral immunity induced by a vaccinia virus recombinant expressing herpes simplex virus type 1 glycoprotein D: cytotoxic T cells

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.

Vaccination with a HSV-2 UL24 mutant induces a protective immune response in murine and guinea pig vaginal infection models

The rational design and development of genetically attenuated HSV-2 mutant viruses represent an attractive approach for developing both prophylactic and therapeutic vaccines for genital herpes. Previously, HSV-2 UL24 was shown to be a virulence determinant in both murine and guinea pig vaginal infection models. An UL24-βgluc insertion mutant produced syncytial plaques and replicated to nearly wild type levels in tissue culture, but induced little or no pathological effects in recipient mice or guinea pigs following vaginal infection. Here we report that immunization of mice or guinea pigs with high or low doses of UL24-βgluc elicited a highly protective immune response. UL24-βgluc immunization via the vaginal or intramuscular routes was demonstrated to protect mice from a lethal vaginal challenge with wild type HSV-2. Moreover, antigen re-stimulated splenic lymphocytes harvested from immunized mice exhibited both HSV-2 specific CTL activity and IFN-γ expression. Humoral anti-HSV-2 responses in serum were Th1-polarized (IgG2a>IgG1) and contained high-titer anti-HSV-2 neutralizing activity. Guinea pigs vaccinated subcutaneously with UL24-βgluc or the more virulent parental strain (186) were challenged with a heterologous HSV-2 strain (MS). Acute disease scores were nearly indistinguishable in guinea pigs immunized with either virus. Recurrent disease scores were reduced in UL24-βgluc immunized animals but not to the same extent as those immunized with strain 186. In addition, challenge virus was not detected in 75% of guinea pigs subcutaneously immunized with UL24-βgluc. In conclusion, disruption of the UL24 gene is a prime target for the development of a genetically attenuated live HSV-2 vaccine.

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.

Recombinant vesicular stomatitis virus vectors expressing herpes simplex virus type 2 gD elicit robust CD4+ Th1 immune responses and are protective in mouse and guinea pig models of vaginal challenge

Recombinant vesicular stomatitis virus (rVSV) vectors offer an attractive approach for the induction of robust cellular and humoral immune responses directed against human pathogen target antigens. We evaluated rVSV vectors expressing full-length glycoprotein D (gD) from herpes simplex virus type 2 (HSV-2) in mice and guinea pigs for immunogenicity and protective efficacy against genital challenge with wild-type HSV-2. Robust Th1-polarized anti-gD immune responses were demonstrated in the murine model as measured by induction of gD-specific cytotoxic T lymphocytes and increased gamma interferon expression. The isotype makeup of the serum anti-gD immunoglobulin G (IgG) response was consistent with the presence of a Th1-CD4+ anti-gD response, characterized by a high IgG2a/IgG1 IgG subclass ratio. Functional anti-HSV-2 neutralizing serum antibody responses were readily demonstrated in both guinea pigs and mice that had been immunized with rVSV-gD vaccines. Furthermore, guinea pigs and mice were prophylactically protected from genital challenge with high doses of wild-type HSV-2. In addition, guinea pigs were highly protected against the establishment of latent infection as evidenced by low or absent HSV-2 genome copies in dorsal root ganglia after virus challenge. In summary, rVSV-gD vectors were successfully used to elicit potent anti-gD Th1-like cellular and humoral immune responses that were protective against HSV-2 disease in guinea pigs and mice.

Recent progress in herpes simplex virus immunobiology and vaccine research

Herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) cause prevalent, chronic infections that have serious outcomes in some individuals. Neonatal herpes may occur when the infant traverses the cervix during maternal genital herpes. Genital herpes is a major risk factor for human immunodeficiency virus type 1 transmission. Considerable efforts have been made to design and test vaccines for HSV, focusing on genital infection with HSV-2. Several protein subunit vaccines based on HSV-2 envelope glycoproteins have reached advanced-phase clinical trials. These antigens were chosen because they are the targets of neutralizing-antibody responses and because they elicit cellular immunity. Encouraging results have been reported in studies of treatment of HSV-seronegative women with a vaccine consisting of truncated glycoprotein D of HSV-2 and a novel adjuvant. Because most sexual HSV transmission occurs during asymptomatic shedding, it is important to evaluate the impact of vaccination on HSV-2 infection, clinically apparent genital herpes, and HSV shedding among vaccine recipients who acquire infection. There are several other attractive formats, including subunit vaccines that target cellular immune responses, live attenuated virus strains, and mutant strains that undergo incomplete lytic replication. HSV vaccines have also been evaluated for the immunotherapy of established HSV infection.

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.

DNA vaccines encoding interleukin-8 and RANTES enhance antigen-specific Th1-type CD4(+) T-cell-mediated protective immunity against herpes simplex virus type 2 in vivo

Chemokines are inflammatory molecules that act primarily as chemoattractants and as activators of leukocytes. Their role in antigen-specific immune responses is of importance, but their role in disease protection is unknown. Recently it has been suggested that chemokines modulate immunity along more classical Th1 and Th2 phenotypes. However, no data currently exist in an infectious challenge model system. We analyzed the modulatory effects of selected chemokines (interleukin-8 [IL-8], gamma interferon-inducible protein 10 [IP-10], RANTES, monocyte chemotactic protein 1 [MCP-1], and macrophage inflammatory protein 1 alpha [MIP-1 alpha]) on immune phenotype and protection against lethal challenge with herpes simplex virus type 2 (HSV-2). We observed that coinjection with IL-8 and RANTES plasmid DNAs dramatically enhanced antigen-specific Th1 type cellular immune responses and protection from lethal HSV-2 challenge. This enhanced protection appears to be mediated by CD4(+) T cells, as determined by in vitro and in vivo T-cell subset deletion. Thus, IL-8 and RANTES cDNAs used as DNA vaccine adjuvants drive antigen-specific Th1 type CD4(+) T-cell responses, which result in reduced HSV-2-derived morbidity, as well as reduced mortality. However, coinjection with DNAs expressing MCP-1, IP-10, and MIP-1 alpha increased mortality in the challenged mice. Chemokine DNA coinjection also modulated its own production as well as the production of cytokines. These studies demonstrate that chemokines can dominate and drive immune responses with defined phenotypes, playing an important role in the generation of protective antigen-specific immunity.

Interleukin 7 can enhance antigen-specific cytotoxic-T-lymphocyte and/or Th2-type immune responses in vivo

Interleukin 7 (IL-7) protein has been reported to be important in the development of cytotoxic-T-lymphocyte (CTL) responses. However, other studies also support a partial Th2 phenotype for this cytokine. In an effort to clarify this unusual conflict, we compared IL-7 along with IL-12 (Th1 control) and IL-10 (Th2 control) for its ability to induce antigen (Ag)-specific CTL and Th1- versus Th2-type immune responses using a well established DNA vaccine model. In particular, IL-7 codelivery showed a significant increase in immunoglobulin G1 (IgG1) levels compared to IgG2a levels. IL-7 coinjection also decreased production of Th1-type cytokine IL-2, gamma interferon, and the chemokine RANTES but increased production of the Th2-type cytokine IL-10 and the similarly biased chemokine MCP-1. In herpes simplex virus (HSV) challenge studies, IL-7 coinjection decreased the survival rate after lethal HSV type 2 (HSV-2) challenge compared with gD plasmid vaccine alone in a manner similar to IL-10 coinjection, whereas IL-12 coinjection enhanced the protection, further supporting that IL-7 drives immune responses to the Th2 type, resulting in reduced protection against HSV-2 challenge. Moreover, coinjection with human immunodeficiency virus type 1 env and gag/pol genes plus IL-12 or IL-7 cDNA enhanced Ag-specific CTLs, while coinjection with IL-10 cDNA failed to influence CTL induction. Thus, IL-7 could drive Ag-specific Th2-type cellular responses and/or CTL responses. These results support that CTLs could be induced by IL-7 in a Th2-type cytokine and chemokine environment in vivo. This property of IL-7 allows for an alternative pathway for CTL development which has important implications for host-pathogen responses.

Murine response to DNA encoding herpes simplex virus type-1 glycoprotein D targeted to the liver

Plasmid DNA encoding herpes simplex virus type-1 glycoprotein D (gD-1) was complexed with asialoorosomucoid conjugated to poly-L-lysine. Following its intravenous injection into BALB/c mice, this complex was targeted to the liver. Liver cells expressing gD-1 were detected immunohistochemically through day 6 post-immunization, while gD-1 DNA was detectable through 14 days post-immunization. Decline of gD-1 expression and detectable gD-1 DNA in the liver correlated with influx of T cells, predominantly CD4(+). The ASOR-poly-L-lysine DNA carrier system promotes hepatic expression of gD-1 and may be useful in vaccination against herpes simplex virus type-1.

A novel immunization method to induce cytotoxic T-lymphocyte responses (CTL) against plasmid-encoded herpes simplex virus type-1 glycoprotein D

DNA molecules complexed with an asialoglycoprotein-polycation conjugate, consisting of asialoorosomucoid (ASOR) coupled to poly-L-lysine, can enter hepatocytes which bear receptors for ASOR. We used this receptor-mediated DNA delivery system to deliver plasmid DNA encoding glycoprotein D (gD) of herpes simplex virus type 1 to ASOR-positive cells. Maximum expression of gD protein was seen at 3 days after injection of this preparation in approximately 13% of cells from BALB/c mice [hepatocytes from mice injected intravenously (i.v.) or peritoneal exudate cells from mice injected intraperitoneally (i.p.)]. In comparison with mice injected with either the plasmid vector alone or the gD-containing plasmid uncomplexed to ASOR, mice immunized with gD-containing plasmid complexed with ASOR-poly-L-lysine induced marked antigen-specific CTL responses. BALB/c mice immunized with gD-DNA developed a T-cell-mediated CTL response against target cells expressing gD and MHC class II glycoproteins, but not against cells expressing only gD and MHC class I molecules. In C3H mice, gD-DNA induced a T-cell-mediated CTL response against target cells expressing gD and class I MHC molecules. Serum anti-gD antibody in low titers were produced in both strains of mice. DNA complexed with ASOR-poly-L-lysine induced CTL responses in mice.

Role of Mucosal Immunity in Herpes Simplex Virus Infection

This study evaluates whether the vaginal mucosal surface of immunized mice can prevent invasion by herpes simplex virus (HSV) and aims to identify immune components that affect immunity after challenge at the vaginal mucosa. Despite the induction of both IgA and IgG vaginal Ab following immunization with recombinant vaccinia virus vectors expressing either glycoproteins B or D, viral infection occurred in most animals even after minimal viral dose challenge. Challenged immune animals, including those genetically unable to generate anti-HSV Ab, survived and showed few if any clinical signs of infection. Experiments with T cell subtype knockout animals and depletion with T cell subset-specific MAb indicated that immunity following vaginal challenge was principally dependent on the function of CD4+ T cells. Our results indicate that anti-HSV vaccines may not provide barrier immunity at the vaginal mucosal site but may be adequate to minimize clinical expression of disease.

Modulation of virus-induced delayed-type hypersensitivity by plasmid DNA encoding the cytokine interleukin-10

This report evaluates the efficacy of eukaryotic expression plasmids encoding cytokines at modulating the induction and expression of cutaneous delayed-type hypersensitivity (DTH) responses to virus infections. Mice given a single intramuscular administration of cytokine DNA were subsequently infected with either herpes simplex virus (HSV) or vaccinia virus, then tested for DTH. Responses in animals given interleukin-10 DNA were markedly suppressed for at least 5 weeks after pretreatment. Animals also expressed diminished T-cell proliferative responses and modest changes in the balance of T helper type 1 and 2 T-cell reactions. Treatment of animals already sensitized to express DTH, also showed inhibited responses, these taking 6-7 days after treatment to become apparent. Our results show the potency and convenience of plasmid DNA encoding cytokines to modulate inflammatory reactions. Advantages and risks of the cytokine DNA approach are briefly discussed.

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.

Immunomodulatory effects of HSV2 glycoprotein D in HSV1 infected mice: implications for immunotherapy of recurrent HSV infection

Immunological analyses in this laboratory and others have suggested that a nonrecurrent HSV seropositive immune status is more closely correlated with a type 1 T helper cell (Th1) response characterized by elevated levels of interferon-gamma and IL2 rather than high titers of virus-specific antibodies. Effective intervention with an immunotherapeutic vaccine may require modulation of the regulatory network of T helper cells such that there is selective restimulation and expansion of the Th1 response. We have established a murine model for assessing the immunomodulatory capacity of an HSV glycoprotein subunit vaccine in animals with pre-existing herpes immunity. Animals were infected with varying doses of HSV1 and then administered glycoprotein D (gD) vaccine adjuvanted with aluminum phosphate at 3-week intervals. Observed changes in serological and cellular responses indicated that administration of subunit vaccine adjuvanted with aluminum phosphate could shift a dominant Th1 response, induced by sensitization with live HSV, towards a Th2 profile of activity. These data suggest that use of aluminum based adjuvants will not selectively stimulate Th1-associated responses and alternative adjuvants may be required for effective use of subunit vaccine in an immunotherapeutic indication in humans.

Development and antigen specificity of the lymphoproliferation responses of pigs to pseudorabies virus: dichotomy between secondary B- and T-cell responses

To better understand the contribution of T cells to the immunity of pigs to pseudorabies virus (PRV), we examined the lymphoproliferation response to this virus. Depletion studies demonstrated that both CD2+CD8+ and CD2+CD4+ cells contributed to lymphoproliferation, but to varying degrees upon stimulation with live and ultraviolet (UV) light-inactivated PRV. Flow cytometric analysis revealed the emergence of both CD2+CD8+ and CD2+CD4+ lymphoblastoid cells. To examine the contribution of specific viral proteins, we prepared immortalized porcine B cells of haplotype d/d that stably expressed a single PRV protein, and used these cells for in vitro stimulation of lymphocytes from PRV-immune miniature pigs of the same haplotype. Cells expressing PRV gB or gC induced proliferation. An immunization/challenge experiment showed that the lymphoproliferation response was stronger upon immunization with the virulent NIA-3 strain than with the attenuated Bartha strain. Upon challenge inoculation, the NIA-3-immunized pigs were almost completely immune, in contrast to the Bartha-immunized pigs. Such poorly protected pigs showed secondary B- and T-cell immune responses upon challenge. In contrast, the better protected NIA-3-immunized pigs did not show a secondary B-cell response. However, they developed a secondary lymphoproliferation response, which was quicker and stronger than in the Bartha-immunized pigs. This dichotomy between secondary B- and T-cell responses indicates that an effective T-cell memory response is able to quickly eliminate challenge virus in immune pigs, so preventing a secondary B-cell response.

Expression of seven herpes simplex virus type 1 glycoproteins (gB, gC, gD, gE, gG, gH, and gI): comparative protection against lethal challenge in mice

We have constructed recombinant baculoviruses individually expressing seven of the herpes simplex virus type 1 (HSV-1) glycoproteins (gB, gC, gD, gE, gG, gH, and gI). Vaccination of mice with gB, gC, gD, gE, or gI resulted in production of high neutralizing antibody titers to HSV-1 and protection against intraperitoneal and ocular challenge with lethal doses of HSV-1. This protection was statistically significant and similar to the protection provided by vaccination with live nonvirulent HSV-1 (90 to 100% survival). In contrast, vaccination with gH produced low neutralizing antibody titers and no protection against lethal HSV-1 challenge. Vaccination with gG produced no significant neutralizing antibody titer and no protection against ocular challenge. However, gG did provide modest, but statistically significant, protection against lethal intraperitoneal challenge (75% protection). Compared with the other glycoproteins, gG and gH were also inefficient in preventing the establishment of latency. Delayed-type hypersensitivity responses to HSV-1 at day 3 were highest in gG-, gH-, and gE-vaccinated mice, while on day 6 mice vaccinated with gC, gE, and gI had the highest delayed-type hypersensitivity responses. All seven glycoproteins produced lymphocyte proliferation responses, with the highest response being seen with gG. The same five glycoproteins (gB, gC, gD, gE, and gI) that induced the highest neutralization titers and protection against lethal challenge also induced some killer cell activity. The results reported here therefore suggest that in the mouse protection against lethal HSV-1 challenge and the establishment of latency correlate best with high preexisting neutralizing antibody titers, although there may also be a correlation with killer cell activity.

Application of a transformed cell line constitutively expressing HSV-1 polypeptides for the detection of HSV antibodies in human sera by an enzyme immunoassay

We have previously reported the construction of a cell line BA4, constitutively producing the glycoproteins gD, gG, and alpha 4, the major regulatory protein of HSV-1. These cells have been selected in stepwise increasing concentrations of methotrexate and shown to produce much higher amounts of gD than non-selected cells. Extracts of the selected cells were used in an enzyme linked immunosorbent assay to detect HSV antibodies in human sera obtained from Greek blood donors. We report here that (i) the assay developed is able to distinguish HSV antibody positive from negative human sera and (ii) that its application in an epidemiological survey showed that the incidence of HSV infection in the general population in Greece is 90.4%.

Bovine x murine T-cell hybridomas specific for bovine herpesvirus 1 (BHV-1) glycoproteins

Difficulties in the isolation and long-term maintenance of bovine herpesvirus-1 (BHV-1) specific T-cell clones have hindered the analysis of bovine cell-mediated immune response to this virus. In an effort to identify the T-cell epitopes of the virus, bovine murine T-cell hybridomas specific for BHV-1 were generated as an alternative to T-cell clones. Peripheral blood lymphocytes from a calf immunized with BHV-1 were restimulated in vitro with the virus to generate bulk T-cell cultures. The antigen-specific T-cell-enriched bulk culture lymphocytes were fused with the T-cell receptor-deficient mutant of the murine thymoma cell line BW 5147. T-cell hybridomas were screened for their ability to produce interferon-gamma in response to BHV-1 stimulation. Hybridomas with various specificities were obtained. One of them was specific for the BHV-1 glycoprotein gI, two were specific for gIV, while three other hybridomas were specific for gIII. One hybridoma responded to stimulation with BHV-1, but not to any of the glycoproteins gI, gIII, or gIV, suggesting that proteins other than these major glycoproteins may be involved in the bovine T-cell response to BHV-1. Of these hybridomas, one was MHC Class I restricted, while all the others were Class II restricted.

Responses of ponies to equid herpesvirus-1 ISCOM vaccination and challenge with virus of the homologous strain

An experimental (ISCOM) vaccine previously shown to protect hamsters from lethal challenge with equid herpesvirus-1 (EHV-1), was tested in horses. Vaccination with EHV-1 ISCOMs induced serum antibodies to the major virus glycoproteins gp10, 13, 14, 17, 18 and 21/22a, whereas antibody responses to gp2 were weak or absent. High levels of virus neutralising antibody of long duration were induced, but did not prevent challenge infection with virus of the homologous strain. However, in the vaccinated ponies there was a significant reduction in clinical signs, nasal virus excretion and cell associated viraemia compared with age-matched unvaccinated controls. There was a strong correlation between pre-challenge levels of serum virus neutralising antibody and the duration and total amount of virus excreted from the nasopharynx.

Efficacy of the herpes simplex virus types 1 and 2 mutant viruses to confer protection against zosteriform spread in mice

Two mutant viruses, HSV-2 XD192 and HSV-1 1716, failed to generate zosteriform lesions when injected in high dose into BALB/c and C3H mice. Mice exposed to mutant viruses were solidly immune to challenge by wild-type homologous or heterologous virus. However, at lower immunizing doses protection was evident against lethality, but not skin lesions, especially in the case of mutant XD192. Protection could be conferred with lymphoid cells from mutant virus immune mice and again, protection against lethality was more frequent than prevention of skin lesions. On the basis of cell fractionation studies, protection against lethality was assumed to be principally the function of CD8+ T lymphocytes. The implications of the results in terms of vaccine development were briefly discussed.

Baculovirus-expressed herpes simplex virus type 2 glycoprotein D is immunogenic and protective against lethal HSV challenge

Herpes simplex virus type 2 glycoprotein D (gD2) was cloned and expressed in the baculovirus-Spodoptera frugiperda system. Milligram quantities of glycoprotein were recovered from suspension culture and subjected to purification by ion-exchange and immunoaffinity chromatography. The resultant purified gD existed as a homogeneous 57,500 MW monomeric species demonstrating reactivity with anti-gD monoclonal antibodies including those directed at a non-sequential neutralizing epitope of gD. Immunization of Balb/c mice with doses of 0.1-10.0 micrograms of AlPO4-absorbed gD resulted in elicitation of humoral and cellular responses to both HSV1 and HSV2 as well as to purified gD1 and gD2. Immunized mice receiving an infectious dose of 1 x 10(6) p.f.u. of HSV2 via the footpad route were significantly protected against infection at all doses tested when compared with unimmunized AlPO4 and uninoculated control animals.

The proportion of herpes simplex virus-specific cytotoxic T lymphocytes (Tc) that recognize glycoprotein C varies between individual mice and is dependent on the form of immunization

In mice the immune response to HSV-1 includes a brisk Tc response that is intimately associated with the control of infection. This report evaluated the Tc response to gC, one of the envelope glycoproteins of HSV-1. This protein was recognized as a target antigen for Tc from HSV-1 immune mice only if they expressed the H-2Kb MHC allele. However, even within these "responder" strains of mice the proportion of gC specific Tc was highly variable. The failure of HSV-induced Tc to recognize gC in the context of other class 1 MHC haplotypes (H-2d and H-2k) was demonstrable at the clonal level and could not be attributed to peculiarities of the recombinant constructs. Surprisingly, despite the inability of H-2k-restricted, HSV-1-induced Tc to recognize gC, when a vaccinia gC virus construct was used to immunize H-2k strains of mice it showed a variable ability to induce memory Tc populations capable of lysing HSV-1-infected autologous cells. Of added importance was the correlation of this induced Tc response with optimum protection against subsequent challenge with HSV-1. This demonstrated that despite the presence of suitable epitopes, the context of the immunogen would also influence its ability to induce Tc. Consequently, the potential repertoire of available HSV-1-specific Tc specificities is larger than indicated by studying animals immunized with HSV.

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.

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.

Human CD8+ herpes simplex virus-specific cytotoxic T-lymphocyte clones recognize diverse virion protein antigens

The role of the HLA class I-restricted, CD8+, herpes simplex virus (HSV)-specific cytotoxic T lymphocytes (CTL) in the control of human HSV infections is controversial because previous reports suggest that a substantial portion of the antigen-specific lytic response is mediated by CD4+ cells. To address this question directly, we isolated HSV-specific CD8+ CTL clones from a patient with recurrent genital herpes. These CTL were cloned by coculturing responder peripheral blood mononuclear cells (PBMC) with phytohemagglutinin-stimulated PBMC that had been infected with live HSV-2 and then irradiated prior to the addition of responder cells. After 1 week, CTL were cloned by limiting dilution using phytohemagglutinin stimulation and allogeneic feeder PBMC. Seven clones were isolated; all seven clones were CD8+ CD4- CD3+ DRbright, six lysed only HSV-2-infected targets, and one lysed both HSV-1- and HSV-2-infected targets. Antigen presentation was restricted by two to three different HLA class I loci. To determine the antigens recognized by these HSV-specific CTL, target cells were infected with HSV in the presence of acyclovir, 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole, or cycloheximide in a series of drug block/release protocols to limit the repertoire of viral gene expression to select transcriptional classes. Five of the clones exhibited a different pattern of cytotoxicity, suggesting that each recognized a distinct HSV antigen. One of the clones appears to be directed against an immediate-early antigen; six of the clones recognize virion proteins. Five of these clones recognized internal virion proteins that could be introduced into target cells by HSV infection in the absence of virus gene expression. Antigen specificity was further tested by using vaccinia virus vectors that express glycoproteins gD2 and gB2 or the tegument protein VP16. One clone lysed vaccinia virus/gD2-infected target cells; the remaining clones did not recognize any of these gene products. The diversity of the CD8+ response from a single individual indicated that several different antigens are recognized when presented in the context of a variety of class I HLA alleles, a pattern that markedly differs from that described for another human herpesvirus, cytomegalovirus.

Effects of in vivo depletion of immunocyte populations on herpes simplex virus glycoprotein D vaccine-induced resistance to HSV2 challenge

BALB/c mice, preimmunized with a protective dose of native herpes simplex virus type 1 glycoprotein D (ngD1) vaccine, were depleted of selected immunocyte populations in vivo using monoclonal antibodies directed at Thy1+, L3T4+, or Lyt2+ cells. Following immunization and depletion, animals were inoculated with varied challenge levels of herpes simplex virus type 2 (HSV2) in the footpad and were monitored for disease. Both depleted undepleted gD-immunized mice were significantly protected when compared with placebo controls. T-cell-independent protection in Thy1 and L3T4-depleted ngD1-immunized animals was effective at low and moderate levels of HSV2 challenge levels, high levels of HSV2 giving high symptom scores in immunized and depleted mice. Depletion of Lyt2+ cells had no significant effect on the outcome of HSV2 infection. Depleted and nondepleted animals also were assessed in parallel for cellular and humoral responsiveness to ngD1 and to HSV antigens in vitro. Lymphoproliferative responses were abrogated in gD-immunized mice treated with anti-Thy1 or anti-L3T4, anti-Lyt2 treatment having little effect. Postimmunization T-cell depletion did not undermine ELISA or neutralizing antibody responses. These findings suggest that at low to moderate levels of virus challenge vaccine-elicited antibody plays a primary role in limiting the severity of infection, T-cell-mediated protective responses being of enhanced significance only at high levels of virus challenge.

Intratypic variations in neutralizable epitopes among herpes simplex virus type 2 isolates

Intratypic variation among 94 isolates of herpes simplex virus type 2 (HSV-2) was investigated using 4 different monoclonal antibodies (MAbs). By neutralization test, these MAbs appeared to be directed to at least 2 distinct epitopes on the viral glycoprotein D (gD), i.e., 6G6.G9 and 6E8.F11 which did not require complement (C-MAb) and gD-105 and gD-110 whose neutralizing activities could be enhanced by complement (C+MAb). The C-MAb pairs each separately could detect significant intratypic variations among the isolates. Whether these variations also existed in the gD epitope(s) recognized by C+MAbs remains to be elucidated. The results suggested that intratypic variation occurred on at least one of the neutralizable (thus related to protective immunity) epitopes on gD of HSV-2.

Herpes simplex virus type 1-specific cytotoxic T lymphocytes recognize immediate-early protein ICP27

The identity of herpes simplex virus type 1 (HSV-1) antigens that serve as targets for cytotoxic T lymphocytes (CTL) and their ability to induce protective immunity remain uncertain. In this article, we report the identification of the immediate-early protein ICP27 as a CTL antigen in H-2d mice but not in H-2k or H-2b mice. Calculation of the frequencies of H-2d-restricted virus-specific CTL demonstrated that approximately one-fourth of the total HSV-1-specific response was directed against ICP27. To define the location of this CTL epitope, four truncated derivatives of the ICP27 gene which place the epitope in a 217-amino-acid region (amino acids 189 to 406) near the central portion of the protein were constructed. Mice immunized with ICP27 were able both to induce HSV-1-specific CTL and to survive a lethal intraperitoneal challenge with virulent HSV-1. However, neither appreciable antibody nor delayed-type hypersensitivity responses were induced in immunized mice, and they were also unable to clear a local epithelial virus challenge. It appears that ICP27, although capable of inducing several aspects of the immune response, is by itself unable to provide complete immunity.

Guanidine group specific ADP-ribosyltransferase in murine cells

We have identified a guanidine group specific ADP-ribosyltransferase activity, capable of transferring an ADP-ribose group from NAD to a low molecular weight guanidine compound [p-(nitrobenzylidine)amino]guanidine and proteins such as histone and poly-L-arginine, in a variety of murine cell lines. The enzyme activity appears to be associated with an integral membrane protein of apparent molecular weight 30-33 kDa. Incubation of the viable cells in isotonic phosphate buffered saline with [32P]NAD results in the incorporation of label into cellular proteins. Dimethyl sulfoxide treatment of the cells downregulates the transferase activity as well as the ADP-ribosylation of cell proteins with extracellular NAD.

CD4-positive T lymphocytes are required for the generation of the primary but not the secondary CD8-positive cytolytic T lymphocyte response to herpes simplex virus in C57BL/6 mice

To understand the cellular basis for recovery from HSV infection, it is critical to identify functional interactions between HSV-specific T lymphocyte subpopulations involved in the generation of the optimal response. To this end, the requirement for CD4+ (L3T4+) T lymphocytes in the development of the primary and secondary CD8+ (Lyt-2+) cytolytic T lymphocyte (CTL) response following HSV infection in C57BL/6 mice was investigated. It was found that chronic depletion of CD4+ cells in vivo by treatment with the mAb GK1.5, which resulted in greater than 95% depletion of peripheral CD4+ T lymphocytes in treated animals, caused a profound decrease in the levels of cytolytic activity obtained during the primary response in the draining popliteal lymph nodes of mice responding to infection in the hind footpads. However, treatment did not affect the levels of in vivo secondary CTL activity in the popliteal lymph nodes, nor the in vitro secondary response in the spleen. The decreased CTL activity observed during the primary response was not due to an inability to prime HSV-specific CTL precursors (CTLp), as full cytolytic activity was obtained following culture of lymphocytes in the presence of exogenous IL-2 and antigen, and the response could be reconstituted by treatment with recombinant IL-2 in vivo. Analysis of the secondary CTL response in the spleen indicated that CD4+ cells were not required for either the generation or maintenance of this aspect of the response. However, blockade of IL-2 utilization by CTL using anti-IL-2R antibodies indicated that this lymphokine was absolutely essential for secondary CTL expansion in vitro. Finally, mice that had been infected 12 months previously exhibited a decreased ability to generate secondary HSV-specific CTL in vitro following CD4-depletion in vivo. Taken together, these results suggest two distinct stages of CTL development during the response: an early primary stage dependent upon the presence of CD4+ cells, and a later, CD4-independent stage operative during the secondary response, which decays with time postinfection.

Identification of an immunodominant cytotoxic T-lymphocyte recognition site in glycoprotein B of herpes simplex virus by using recombinant adenovirus vectors and synthetic peptides

Cytotoxic T-lymphocyte (CTL) responses to herpes simplex virus (HSV) polypeptides play an important role in recovery from infection and in preventing latency. We have previously shown that glycoprotein B (gB) is a major target recognized by HSV-specific CTLs in C57BL/6 (H-2b) and BALB/c (H-2d) mice but not in CBA/J (H-2k) mice (L. A. Witmer, K. L. Rosenthal, F. L. Graham, H. M. Friedman, A. Yee, and D. C. Johnson, J. Gen. Virol. 71:387-396, 1990). In this report, we utilize adenovirus vectors expressing gB with various deletions to localize an immunodominant site in gB, recognized by H-2b-restricted anti-HSV CTLs, to a region between residues 462 and 594. Overlapping peptides spanning this region were synthesized and used to further localize the immunodominant site to residues 489 to 515, a region highly conserved in HSV type 1 (HSV-1) and HSV-2 strains. The 11-amino-acid peptide was apparently associated exclusively with the Kb major histocompatibility complex gene product and not the Db gene product. In contrast, H-2d-restricted CTLs recognized an immunodominant site between residues 233 and 379.

Native HSV glycoprotein D subunit vaccine: analysis of in vitro T-cell activation and antigen presentation

Native herpes simplex virus (HSV) glycoprotein D (ngD1) subunit vaccine, a potential human vaccine candidate, was examined to determine responsive murine lymphocyte populations in vitro. This vaccine preparation has been shown to protect against HSV challenge in mice and guinea pigs and to elicit humoral and cellular responses in rodents and primates. Immunized BALB/c mice were used in splenocyte lymphoproliferative studies to analyze the cellular response. After in vivo sensitization, the in vitro proliferative response observed appears to be resultant of Class II-restricted T-cell division in response to gD presented in the context of macrophage-expressed Ia.

Molecular and biological characterization of a herpes simplex virus type 1 (HSV-1) neuroinvasiveness gene

Pathogenetic studies of herpes simplex virus type 1 (HSV-1) strains ANG and its mouse brain-passaged descendant ANG path revealed no difference in neurovirulence but a significant difference in neuroinvasiveness. Thus, both viruses induced a fatal encephalitis in mice after direct injection into the brain, but only ANG path induced lethal neurologic disease after inoculation on rear footpads. The difference in neuroinvasiveness is not related to the capacity to replicate in mouse neural tissues or mouse cells in general, but is specifically related to virus entry into the peripheral nervous system in the footpad. Marker rescue experiments in which ANG path genes were used to confer neuroinvasiveness on ANG indicated that the gene that codes for glycoprotein D (gD) is responsible for the phenotypic difference. Analyses of the gD genes by dideoxy-sequencing techniques identified a base difference in the coding sequences and predicted that the ANG gD gene codes for alanine (GCC codon) at amino acid position 84 in the open reading frame and the ANG path gD gene codes for glycine (GGC codon) at this site. Using these data, an oligonucleotide probe predicted to be specific for the ANG path gD gene was prepared, and in Southern blot analyses, this probe revealed that neuroinvasiveness-rescued agents had incorporated the base change seen in the ANG path gD gene. We conclude that HSV-1 glycoprotein D functions to effect neuroinvasiveness and we discuss potential mechanisms that may be involved.

Immunogenicity of herpes simplex virus type 1 glycoproteins expressed in vaccinia virus recombinants

Vaccinia virus recombinants expressing glycoproteins B (vgB11), D (VgD52), E (gE/7.5 and gE/4B), G (gG-vac), H (gH-vac), and I (gI-vac) of HSV-1 were used to compare the protective response to these individual glycoproteins in the mouse. Glycoprotein D induced the best neutralizing antibody titers and the most increased rates of HSV clearance from the ear as well as good protection from the establishment of latent HSV infections in the sensory ganglia. Glycoprotein B also induced good neutralizing antibody titers and as great a protection from the establishment of latency as gD although the rate of virus clearance from the ear was not as great as after immunization with gD. Glycoprotein E induced weak neutralizing antibody but gG, gH, and gI did not show a neutralizing antibody response. At higher challenge doses of virus (10(6) PFU HSV-1 in the ear), gE induced a protective response by increasing the rate of virus clearance and reducing the acute infection of ganglia as compared to negative control immunized mice. However there was no protection from the establishment of latent infections after immunization with gE. No protective response was seen to gG, gH, or gl.

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.

Characterization of the gene and an antigenic determinant of equine herpesvirus type-1 glycoprotein 14 with homology to gB-equivalent glycoproteins of other herpesviruses

The gene encoding glycoprotein 14 (gp14) of equine herpesvirus type 1 was sequenced. Nucleotide sequence analysis revealed a complete transcription unit composed of a CAT box, a TATA box, a ribosome-binding sequence, a polyadenylation signal and an open reading frame (ORF) of 2940 bp transcribed from left to right. The amino acid (aa) sequence deduced from this ORF corresponded to that of a protein with 979 aa and had the characteristic features of membrane gp including a 20-aa signal sequence at the N terminus, a 743-aa surface domain, a 40-aa membrane anchoring region, a 108-aa hydrophilic cytoplasmic domain at the C terminus and eleven potential sites for N-linked glycosylation. An unusual feature of this protein was an exceptionally long (66aa) sequence, with a preponderance of hydrophilic residues, preceding the hydrophobic signal core. An antigenic determinant recognized by an anti-gp14 monoclonal antibody was present in the N terminus of the postulated surface domain. Comparison of gp 14 with the gp of other herpesviruses indicated that gp14 was highly homologous to corresponding gp of pseudorabies (gII), bovine herpesvirus (gI), varicella-zoster virus (gII), as well as of herpes simplex virus, Epstein-Barr virus and human cytomegalovirus (gB).

Intratypic variation of herpes simplex virus type 2 isolates detected by monoclonal antibodies against viral glycoproteins

Monoclonal antibodies (MAbs) to herpes simplex virus (HSV) glycoproteins gD, gG, gB, and gE were used to analyze antigenic variations of 128 genital HSV-2 isolates by an indirect enzyme-linked immunosorbent assay (ELISA). Isolates were considered significantly different from the standard HSV-2 strain 186 when their optical density (OD) in ELISA was less than half that of strain 186. This criterion gave 30 patterns of reactivity among the genital HSV-2 isolates. The MAbs to gB, gG, and 2 of the gD antibodies reacted with more than 90% of the isolates, suggesting that these MAbs recognized highly conserved epitopes. However, the gE MAb reacted with only 47% of the isolates, and one of the gD antibodies with only 39%. Thus, HSV-2 can readily tolerate modifications in some parts of the gD and gE molecules while remaining infectious.

Antigenic and functional analysis of a neutralization site of HSV-1 glycoprotein D

Herpes simplex virus glycoprotein D is a component of the virion envelope and appears to be involved in attachment, penetration, and cell fusion. Monoclonal antibodies (MAbs) against this protein can be arranged in groups, on the basis of a number of biological and biochemical properties. Group I antibodies are type-common, have high complement-independent neutralization titers, recognize discontinuous (conformational) epitopes, and block each other in a binding assay. The sum of their epitopes constitutes antigenic site I of gD. Using a panel of neutralization-resistant mutants, we previously found that group I MAbs can be divided into two subgroups, Ia and Ib, such that mutations selected with Ia antibodies have little or no effect on binding and neutralization by Ib antibodies, and vice versa. Antigenic site I therefore consists of two parts, Ia and Ib. We have now identified the point mutations which prevent neutralization. Two Ib MAbs (DL11 and 4S) selected a Ser to Asn change at residue 140; this alteration creates a new N-linked glycosylation site, which is used. A third Ib MAb (D2) selected a Gln to Leu change at 132. The mutation selected by the Ia MAb HD1 (Ser to Asn at residue 216) is identical to that selected by MAb LP2, another Ia antibody. By using oligonucleotide-directed mutagenesis, we have produced gD genes with combinations of the above mutations. Attempts to recombine these genes into the virus genome were unsuccessful, suggesting that the combinations are lethal. This was confirmed by a complementation assay which measures the ability of gD transiently expressed in transfected Vero cells to rescue the production of infectious virus by the gD-minus mutant F-gD beta.

Pseudorabies virus glycoprotein gIII is a major target antigen for murine and swine virus-specific cytotoxic T lymphocytes

Pseudorabies virus (PrV) is the etiological agent of Aujeszky's disease, a disease that causes heavy economic losses in the swine industry. A rational approach to the generation of an effective vaccine against this virus requires an understanding of the immune response induced by it and of the role of the various viral antigens in inducing such a response. We have constructed mutants of PrV [strain PrV (Ka)] that differ from each other only in expression of the viral nonessential glycoproteins gI, gp63, gX, and gIII (i.e., are otherwise isogenic). These mutants were used to ascertain the importance of each of the nonessential glycoproteins in eliciting a PrV-specific cytotoxic T-lymphocyte (CTL) response in mice and pigs. Immunization of DBA/2 mice and pigs with a thymidine kinase-deficient (TK-) mutant of PrV elicits the formation of cytotoxic cells that specifically lyse syngeneic infected target cells. These PrV-specific cytolytic cells have the phenotype of major histocompatibility complex class I antigen-restricted CTLs. The relative number of CTLs specific for glycoproteins gI, gp63, gX, and gIII induced in mice vaccinated with a TK- mutant of PrV was ascertained by comparing their levels of cytotoxicity against syngeneic cells infected with either wild-type virus or gI-/gp63-, gX-, or gIII- virus deletion mutants. The PrV-specific CLTs were significantly less effective in lysing gIII(-)-infected targets than in lysing gI-/gp63-, gX-, or wild-type-infected targets. The in vitro secondary CTL response of lymphocytes obtained from either mice or pigs 6 or more weeks after immunization with a TK- mutant of PrV was also tested. Lymphocytes obtained from these animals were cultured with different glycoprotein-deficient mutants of PrV, and their cytolytic activities against wild-type-infected targets were ascertained. The importance of each of the nonessential viral glycoproteins in eliciting CTLs was assessed from the effectiveness of each of the virus mutants to stimulate the secondary anti-PrV CTL response. Cultures of both murine or swine lymphocytes that had been stimulated with gIII- virus contained only approximately half as many lytic units as did those stimulated with either wild-type virus, a gX- virus mutant, or a gI-/gp63- virus mutant. Thus, a large proportion of the PrV-specific CTLs that are induced by immunization with PrV of both mice and pigs are directed against gIII. Furthermore, glycoproteins gI, gp63, and gX play at most a minor role in the CTL response of these animals to PrV.

Role of coexpression of IL-2 and herpes simplex virus proteins in recombinant vaccinia virus vectors on levels of induced immunity

Vaccinia virus recombinants co-expressing the genes for IL-2 and HSV-1 gC or gD were used to study the potential adjuvant effects of IL-2 on immunity to HSV-1. In addition, constructs were produced which, while expressing IL-2, encoded for reduced levels of HSV-1 gC. Studies with mice revealed that gC and gD could stimulate HSV-1 immunity as measured by neutralizing antibody (NA), lymphoproliferation and viral clearance. IL-2 enhancement of NA and lymphoproliferation was observed only in those groups of mice immunized with the sub-optimal gC construct which co-expressed IL-2. In no instance did the presence of IL-2 augment the ability of mice to clear an epithelial challenge of HSV-1.

Expression in recombinant vaccinia virus of the equine herpesvirus 1 gene encoding glycoprotein gp13 and protection of immunized animals

The equine herpesvirus 1 (EHV-1) gene encoding glycoprotein 13 (gp13) was cloned into the hemagglutinin (HA) locus of vaccinia virus (Copenhagen strain). Expression of the gp13 gene was driven by the early/late vaccinia virus H6 promoter. Metabolically radiolabeled polypeptides of approximately 47 and 44 kilodaltons and 90 kilodaltons (glycosylated form) were precipitated with both polyclonal and gp13-specific monoclonal antibodies. Presentation of gp13 on the cytoplasmic membrane of cells infected with the recombinant gp13 vaccinia virus was demonstrated by immunofluorescence of unfixed cells. Inoculation of the recombinant gp13 vaccinia virus into guinea pigs induced neutralizing antibodies to both EHV-1 and vaccinia virus. Hamsters vaccinated with the recombinant gp13 vaccinia virus survived a lethal challenge with the hamster-adapted Kentucky strain of EHV-1. These results indicate that expression in vaccinia virus vectors of EHV-1 gp13, the glycoprotein homolog of herpes simplex virus gC-1 and gC-2, pseudorabies virus gIII, and the varicella-zoster virus gpV may provide useful vaccine candidates for equine herpesvirus infections.