Protection of guinea pigs from primary and recurrent herpes simplex virus (HSV) type 2 cutaneous disease with vaccinia virus recombinants expressing HSV glycoprotein D

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.

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.

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.

Therapeutic vaccination against chronic viral infections

Chronic viral infections such as those caused by hepatitis B virus, human papilloma virus, herpes simplex virus, and HIV, in theory, present logical targets of active specific immunotherapy. Indeed, immunological mechanisms are involved in several aspects of their pathogenesis and natural course, such as virus persistence, destruction of infected cells and control of viral replication. Therapeutic vaccination could therefore be an adequate replacement for, or adjunct to, existing therapies. Almost all approaches to therapeutic vaccination have been evaluated in those four disease areas. Despite encouraging results in animals none of these attempts has, so far, been completely successful in the human setting. However, with a better understanding of the immunological mechanisms involved in the control of disease successful therapeutic vaccines, used alone or in combination with other therapies, are an achievable goal.

Design and selection of vaccine adjuvants: animal models and human trials

The availability of hundreds of different adjuvants has prompted a need for identifying rational standards for selection of adjuvant formulations based on safety and sound immunological principles for human vaccines. Although many of the mechanisms of adjuvants have been elucidated, meaningful comparisons between different adjuvants derived from in vitro studies, or from studies using adjuvants in rodents or other animals, are often not predictive for safety, adjuvant effects, or vaccine efficacy in humans. A highly efficient and cost-effective method for comparison of adjuvants with a new antigen is to conduct multiple small-scale, phase 1, comparative studies in humans with a new antigen, using adjuvants previously found to be safe with other antigens in human trials. Studies in which highly immunogenic and safe adjuvant formulations have been evaluated in comparative adjuvant trials in humans using a single candidate vaccine antigen against malaria, HIV, and prostate cancer with multiple adjuvants are reviewed.

A growth and latency compromised herpes simplex virus type 2 mutant (ICP10DeltaPK) has prophylactic and therapeutic protective activity in guinea pigs

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 fatal HSV-2 challenge in the mouse model (Aurelian L, Kokuba H, Smith CC. Vaccine potential of a Herpes Simplex Virus type 2 mutant deleted in the PK domain of the large subunit of ribonucleotide reductase (ICP10). Vaccine 1999;17:1951-1963). Here we report the results of our studies with ICP10DeltaPK in the guinea pig model of recurrent HSV-2 disease. ICP10DeltaPK was also compromised for growth and disease causation in this model. It was not isolated from latently infected ganglia by explant co-cultivation. The proportions of latently infected ganglia were significantly lower for ICP10DeltaPK than HSV-2 [3/25 (12%) and 7/10 (70%), respectively]. Similar results were obtained for the levels of viral DNA (8 x 10(3) and 2 x 10(5) molecules/ganglion for ICP10DeltaPK and HSV-2, respectively]. ICP10DeltaPK immunization caused a significant (P< or = 0.001) decrease in the proportion of animals with primary [1/14 (6%) and 16/16 (100%) for ICP10DeltaPK and PBS, respectively) and recurrent [1/14 (6%) and 11/14 (79%) for ICP10DeltaPK and PBS, respectively) HSV-2 skin lesions. It also protected from genital HSV-2 disease [1/10 and 10/10 for ICP10DeltaPK and PBS, respectively] and decreased the severity of the lesions in both models. Quantitative PCR (Q-PCR) with primers that distinguish between HSV-2 and ICP10DeltaPK indicated that immunization reduced the proportion of ganglia positive for HSV-2 DNA [8/25 (32%) and 7/10 (70%) for ICP10DeltaPK and PBS, respectively) and its levels [3 x 10(3) and 2 x 10(5) molecules/ganglion for ICP10DeltaPK and PBS, respectively]. The proportion of HSV-2 infected animals with recurrent disease was also significantly (P < or = 0.001) decreased by immunization with ICP10DeltaPK [1/15 (7%) and 11/14 (79%) with recurrent disease for ICP10DeltaPK and PBS, respectively], suggesting that ICP10DeltaPK has prophylactic and therapeutic activity in the guinea pig.

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 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.

NYVAC-Pf7: a poxvirus-vectored, multiantigen, multistage vaccine candidate for Plasmodium falciparum malaria

The highly attenuated NYVAC vaccinia virus strain has been utilized to develop a multiantigen, multistage vaccine candidate for malaria, a disease that remains a serious global health problem and for which no highly effective vaccine exists. Genes encoding seven Plasmodium falciparum antigens derived from the sporozoite (circumsporozoite protein and sporozoite surface protein 2), liver (liver stage antigen 1), blood (merozoite surface protein 1, serine repeat antigen, and apical membrane antigen 1), and sexual (25-kDa sexual-stage antigen) stages of the parasite life cycle were inserted into a single NYVAC genome to generate NYVAC-Pf7. Each of the seven antigens was expressed in NYVAC-Pf7-infected culture cells, and the genotypic and phenotypic stability of the recombinant virus was demonstrated. When inoculated into rhesus monkeys, NYVAC-Pf7 was safe and well tolerated. Antibodies that recognize sporozoites, liver, blood, and sexual stages of P. falciparum were elicited. Specific antibody responses against four of the P.falciparum antigens (circumsporozoite protein, sporozoite surface protein 2, merozoite surface protein 1, and 25-kDa sexual-stage antigen) were characterized. The results demonstrate that NYVAC-Pf7 is an appropriate candidate vaccine for further evaluation in human clinical trials.

Attenuated vaccinia virus-circumsporozoite protein recombinants confer protection against rodent malaria

NYVAC-based vaccinia virus recombinants expressing the circumsporozoite protein (CSP) were evaluated in the Plasmodium berghei rodent malaria model system. Immunization of mice with a NYVAC-based CSP recombinant elicited a high level of protection (60 to 100%). Protection did not correlate with CS repeat-specific antibody responses and was abrogated by in vivo CD8+ T-cell depletion. Protection was not enhanced by modification of the subcellular localization of CSP. These results suggest the potential of poxvirus-based vectors for the development of vaccine candidates for human malaria.

Immunization with recombinant varicella-zoster virus expressing herpes simplex virus type 2 glycoprotein D reduces the severity of genital herpes in guinea pigs

Varicella-zoster virus (VZV) is an attractive candidate for a live-virus vector for the delivery of foreign antigens. The Oka vaccine strain of VZV is safe and effective in humans, and recombinant Oka VZV (ROka) can be generated by transfecting cells with a set of overlapping cosmid DNAs. By this method, the herpes simplex virus type 2 (HSV-2) glycoprotein D (gD2) gene was inserted into an intergenic site in the unique short region of the Oka VZV genome. Expression of gD2 in cells infected with the recombinant Oka strain VZV (ROka-gD2) was confirmed by antibody staining of fixed cells and by immunoblot analysis. Immune electron microscopy demonstrated the presence of gD2 in the envelope of ROka-gD2 virions. The ability of ROka-gD2 to protect guinea pigs against HSV-2 challenge was assessed by inoculating animals with three doses of uninfected human fibroblasts, fibroblasts infected with ROka VZV, or fibroblasts infected with ROka-gD2. Neutralizing antibodies specific for HSV-2 developed in animals immunized with ROka-gD2. Forty days after the third inoculation, animals were challenged intravaginally with HSV-2. Inoculation of guinea pigs with ROka-gD2 significantly reduced the severity of primary HSV-2 infection (P < 0.001). These experiments demonstrate that the Oka strain of VZV can be used as a live virus vector to protect animals from disease with a heterologous virus.

Immunization of mice with HPV vaccinia virus recombinants generates serum IgG, IgM, and mucosal IgA antibodies

To assess the utility of vaccinia virus recombinants in the development of an immune response against HPV capsid antigens, 5-week-old C57B16 female mice were administered either purified HPV 1 capsids produced by a vaccinia virus recombinant or the recombinant vaccinia virus itself. Animals were boosted at Week 4 with either agent. Mice developed a serum IgG antibody response in all the administration protocols that was directed mainly against native L1 epitopes. Mice injected initially with the vaccinia virus recombinant and boosted with purified capsids had a higher titer antibody response (P = 0.024) with more mice responding to a greater extent. All mice produced a serum IgM response that preceded the IgG response by approximately 2 weeks and lasted 1-3 weeks. The IgM response was directed against native L1 epitopes. Although no serum IgA was detected, IgA could be detected in vaginal secretions of mice that were immunized or boosted with the vaccinia virus vector. These results indicate that an extensive humoral immune response to HPV can be elicited using vaccinia virus recombinants.

Vaccinating guinea pigs with recombinant glycoprotein D of herpes simplex virus in an efficacious adjuvant formulation elicits protection against vaginal infection

Guinea pigs were immunized with glycoprotein gD-2t in SAF-m or saline, then challenged with herpes simplex virus, type 2 (HSV-2). Animals given gD-2t in SAF-m had higher anti-gD-2t antibodies, fewer and less severe vaginal lesions, and decreased ganglionic latency compared to animals given gD-2t in saline. Leucocytes from animals vaccinated with gD-2t in SAF-m had greater proliferative responses to gD-2t in vitro than cells from control animals. MHC II-restricted, gD-2t-specific cytotoxic T cells were induced in guinea pigs vaccinated with gD-2t in SAF-m. Thus, immunization of guinea pigs with gD-2t in SAF-m markedly reduced the incidence and severity of primary HSV-2 by eliciting both humoral and cell-mediated responses.

Vaccine therapy for HIV: a historical review of the treatment of infectious diseases by active specific immunization with microbe-derived antigens

A review of the history of 'vaccine therapy' for infectious diseases is presented. The concept originated when Auzias-Turenne introduced 'syphilitic vaccination' or 'syphilization' as a treatment for syphilis in Paris in the mid-1800s; his clinical studies probably influenced Pasteur's successful rabies postexposure vaccine trials. Robert Koch in Berlin in the 1890s observed that inoculation of tuberculin into patients with tuberculosis induced an inflammatory response in affected tissues, and advocated 'tuberculin therapy'. Sir Almroth Wright in London in the early 20th century devised methods to measure changes in serum 'opsonizing' activity in response to therapeutic inoculations with microbe-derived vaccines. Since the advent of antibiotics, active specific immunization with microbe-derived antigens (vaccine therapy) has been largely forgotten as a strategy for treatment of infectious diseases. Advances in antigen production and in molecular immunology now permit new tactics to probe, analyse and selectively alter in vivo human immune responses to infectious microbes. Our recent demonstration that vaccine therapy can boost natural immunity to HIV in infected patients should rekindle interest in this approach.

Protection from herpes simplex virus type 2 is associated with T cells involved in delayed type hypersensitivity that recognize glycosylation-related epitopes on glycoprotein D

Immunization of mice with a vaccinia recombinant (VP176) that expresses a fully glycosylated herpes simplex virus (HSV) glycoprotein D (gD) induces long-term (greater than or equal to 50 days) HSV-specific lymphoproliferation and delayed type hypersensitivity (DTH) responses, the ability to eliminate a high challenge dose of HSV-2 from the epidermis and protection from fatal disease due to HSV replication in the nervous system. Adoptive transfer studies indicate that protection is mediated by the DTH functions of L3T4+ cells and requires the contribution of a non-specific irradiation-sensitive cell. Long-term protection (defined as that seen at greater than or equal to 50 days after immunization) from fatal HSV-2 challenge, virus clearance from the epidermis, and HSV-specific T-cell responses are not induced by a partially glycosylated gD expressed by a vaccinia recombinant (VP254) in which gD is controlled by a late vaccinia virus promoter. However, mice immunized with VP254 are protected from HSV-2 challenge early (day 10) after immunization. The VP254-induced protection is HSV-specific, but it is not mediated by L3T4+ and Lyt2+ cells. The findings are discussed within the context of future developments of anti-HSV vaccines.

Efficacy of HSV-1 ISCOM vaccine in the guinea-pig model of HSV-2 infection

The capability of a herpes simplex virus (HSV)-1 ISCOM vaccine to protect against intravaginal HSV-2 challenge infection in guinea-pigs is described. The protective efficacy of the HSV-1 ISCOM vaccine is compared with that of a purified, aqueous HSV-1 antigen preparation administered using a similar immunization schedule. The results show that female guinea-pigs immunized with two doses of HSV-1 ISCOM vaccine, each consisting of 20 micrograms of protein given 2 weeks apart responded with high ELISA and neutralization antibody titres, and are almost completely protected against the clinical effects of intravaginal challenge with 10(5.2) TCID50 of HSV-2. This cross-protection is significantly greater than that observed in guinea-pigs immunized with a single dose of HSV-1 ISCOM vaccine, two doses of aqueous HSV-1 antigen preparation or two doses of a mock ISCOM vaccine. However, none of the vaccine preparations completely prevented HSV-2 replication following challenge. Western blot and radioimmunoprecipitation of sera from immunized guinea-pigs show the HSV-1 ISCOM vaccine preparation to contain the major HSV-1 glycoproteins. These findings are discussed in relation to the value and potential use of HSV-1 ISCOM vaccine in humans.

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.

Comparative studies of HSV-1 antigens solubilised from infected cells by using non-ionic or zwitterionic detergents

HSV-1 antigen preparations solubilised from Vero cells by using either the non-ionic detergent Nonidet P40 or the zwitterionic detergent Empigen BB, and purified on sucrose density gradients or over a sucrose cushion, were tested by ELISA with anti-HSV-1 glycoprotein monoclonal antibodies and by radioimmunoprecipitation (RIP) with polyclonal HSV-1 antiserum. Amongst several proteins detected in these preparations, the four major HSV-1 glycoproteins, gB, gC, gD, and gE, were found to be present. Differences between NP40 or Empigen-solubilised HSV-1 antigen preparations with respect to two of these glycoproteins, gB and gE, were detected by using a small panel of monoclonal antibodies. Comparative studies in mice showed the Empigen-solubilised HSV-1 antigen preparations elicited greater antibody responses and greater protection against lethal HSV-1 challenge infection than the NP40-solubilised preparation.

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]).

Antibody response to herpes simplex virus glycoproteins gB and gD

The antibody response to herpes simplex virus (HSV) glycoproteins B and D was evaluated using these cloned glycoproteins in an ELISA assay and compared to a standard Western blotting procedure. The ELISA assay appeared to be more sensitive for detecting gB and gD antibodies. Antibodies to gB but not gD were detected in the acute sera of patients presenting with their first episode of true primary genital herpes. The geometric mean HSV gB titer (log 2) was also significantly higher than the geometric mean gD titer in the convalescent sera of these patients (7.9 +/- 0.7 vs. 5.5 +/- 0.9, P less than .003). A cross-reaction between HSV gB and varicella zoster virus (VZV) gp II was demonstrated. Thus, it is possible that a previous VZV infection could prime the immune system to respond rapidly and more vigorously to HSV gB. Indeed, in this report we demonstrated a significant correlation between the VZV ELISA absorbance and the titer to HSV gB and also detected a higher VZV ELISA absorbance and HSV gB titer in the acute sera of patients with a true primary HSV infection compared to other HSV seronegative VZV seropositive patients. Use of this quantitative assay should allow further investigation into the relationship of the immune response to these important targets and the clinical course of HSV disease.

Immunological properties of multiple repeats of a linear epitope of herpes simplex virus type 1 glycoprotein D

Several peptides containing the amino acid sequence 9-21 of glycoprotein D of herpes simplex virus type 1 (HSV-1) were synthesized and investigated for reactivity with monoclonal antibody LP14 in a competition enzyme-linked immunosorbent assay (ELISA). Peptides containing two or four repeats of sequence 9-21 reacted at least one order of magnitude better with LP14 than with the monomeric form of sequence 9-21. Dimers in which one of the repeats of one or more essential residues were absent did not show this increased reactivity. Antisera obtained from rabbits immunized with a peptide containing two repeats of sequence 9-21 coupled to bovine serum albumin showed high antipeptide antibody titers with this peptide and were able to neutralize virus infectivity in vitro. Sera obtained from rabbits immunized with the free dimer could not neutralize virus infectivity.

The influence of different adjuvants on the immune response to a synthetic peptide comprising amino acid residues 9-21 of herpes simplex virus type 1 glycoprotein D

The immuno-modulating properties of different adjuvant systems on the murine humoral and cellular immune response to a synthetic peptide comprising amino acid residues 9-21 of glycoprotein D of herpes simplex virus type 1 (HSV-1) were investigated. For immunization, the peptide was conjugated to ovalbumin or bovine serum albumin by glutaraldehyde and the adjuvants used in this study were Freund's complete adjuvant (FCA), aluminium hydroxide, the Ribi adjuvant system (RAS) and two non-ionic block polymer surfactants, viz. L101 and 31R1, in oil in water emulsions. High anti-peptide antibody titers were obtained after immunization with FCA, aluminium hydroxide, RAS and L101. All adjuvants, except RAS, stimulated the induction of delayed type hypersensitivity obtained after immunization with peptide 9-21 coupled to ovalbumin and elicited by injection of purified HSV-1 virions in the footpad. Challenge with a lethal dose of HSV-1 showed that mice immunized with peptide 9-21 coupled to ovalbumin in combination with FCA, RAS and L101, respectively, were significantly protected. Although immunization with peptide 9-21 coupled to ovalbumin combined with aluminium hydroxide stimulated induction of delayed type hypersensitivity, no significant protective immunity against the challenge was generated.

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.

Cloning and expression of foreign genes in vaccinia virus, using a host range selection system

A simple selection system has been developed for the cloning and expression of open reading frames in vaccinia virus. The selection system is based on a conditional lethal (host range) mutant of vaccinia virus. A deletion mutant of the vaccinia virus WR strain was generated by insertion of the neomycin resistance gene from transposon Tn5 and selection with the antibiotic G418. This deletion recombinant, vP293, lacked approximately 21.7 kilobases of DNA beginning 3.8 kilobases from the left end of the genome, vP293, was capable of plaquing on primary chicken embryo fibroblasts and two monkey cell lines (BSC-40 and Vero) but was defective in replication in the human cell line MRC-5. Insertion of the host range gene K1L into vP293 restored the ability to grow on MRC-5 cells. A series of plasmids were constructed which in addition to the K1L gene contained a vaccinia virus early-late promoter, H6, followed by a unique polylinker sequence, translational initiation and termination signals, and an early transcription termination signal. These plasmids, pHES1 through 4, allowed for rapid single-step cloning and expression of any open reading frame when recombined in vivo with vP293 and scored for growth on MRC-5 cells.

Antibody to cloned HSV glycoproteins B and D plus adult human leukocytes protect neonatal mice from lethal HSV infection

Antisera produced by HSV infection or following vaccination of guinea pigs with the cloned herpes simplex virus (HSV) glycoproteins gB and gD were compared for in vitro antibody-dependent cellular cytotoxicity (ADCC) activity and for in vivo protection. Antibody from guinea pigs was able to participate in ADCC with human mononuclear cells in vitro, anti-gBgD serum being equivalent to HSV convalescent sera. In vivo, each of the guinea pig sera was able to protect neonatal mice from a fatal HSV-1 infection when given with human mononuclear cells but not when given alone. The anti-gBgD serum was the most effective in vivo, protecting 15 of 17 (88%) neonatal mice when given at a 10(-4) dilution with human mononuclear cells and was the only guinea pig serum protective at a 10(-6) dilution (5 of 7 neonatal mice).

Expression of herpes simplex virus glycoprotein D on antigen presenting cells infected with vaccinia recombinants and protective immunity

We studied the effect of the temporal regulation of herpes simplex virus (HSV) type 1 glycoprotein D (gD-1) expression in Ia+ epidermal cells (EC) and macrophages on virus specific immunity and protection from HSV-2 challenge. gD-1 was expressed on the surface of cells infected with a vaccinia recombinant containing gD-1 under the control of an early vaccinia virus promoter (VP176). It was not expressed in cells infected with a recombinant (VP254) in which gD-1 is controlled by a late vaccinia virus promoter. BALB/c mice immunized with both recombinants seroconverted to HSV-2 as determined by neutralization. However, HSV specific delayed type hypersensitivity (DTH) responses were significantly (p less than 0.025) higher in VP176 than VP254 immunized animals. Both VP176 and VP254 immunized mice were protected from severe neurological disease due to HSV-2 challenge at 14 days post immunization, but long term protection was observed only in VP176 immunized mice.

Epitope specificity and protective efficacy of the bovine immune response to bovine herpesvirus-1 glycoprotein vaccines

Bovine herpesvirus-1 (BHV-1) envelope glycoproteins gI, gIII and gIV were individually purified on monoclonal antibody affinity columns and injected intradermally into BHV-1 seronegative calves. The calves developed serum neutralizing antibodies that monospecifically precipitated the immunizing glycoprotein from a preparation of 125I-labelled BHV-1 envelope proteins. A competitive radioimmunoassay using the bovine antisera demonstrated that known functional epitopes had been retained in the glycoprotein vaccines. Calves immunized with the gI, gIII or gIV glycoproteins were not protected from intranasal challenge with BHV-1 and had levels and duration of viral shedding in their nasal secretions similar to those of non-immunized control calves.