Human T-lymphocyte response in vitro to synthetic peptides of herpes simplex virus glycoprotein D

Antibody to HSV gD peptide induced by vaccination does not protect against HSV-2 infection in HSV-2 seronegative women

BACKGROUND

In the HIV-1 vaccine trial RV144, ALVAC-HIV prime with an AIDSVAX® B/E boost reduced HIV-1 acquisition by 31% at 42 months post first vaccination. The bivalent AIDSVAX® B/E vaccine contains two gp120 envelope glycoproteins, one from the subtype B HIV-1 MN isolate and one from the subtype CRF01_AE A244 isolate. Each envelope glycoprotein harbors a highly conserved 27-amino acid HSV-1 glycoprotein D (gD) tag sequence that shares 93% sequence identity with the HSV-2 gD sequence. We assessed whether vaccine-induced anti-gD antibodies protected females against HSV-2 acquisition in RV144.

METHODS

Of the women enrolled in RV144, 777 vaccine and 807 placebo recipients were eligible and randomly selected according to their pre-vaccination HSV-1 and HSV-2 serostatus for analysis. Immunoglobulin G (IgG) and IgA responses to gD were determined by a binding antibody multiplex assay and HSV-2 serostatus was determined by Western blot analysis. Ninety-three percent and 75% of the vaccine recipients had anti-gD IgG and IgA responses two weeks post last vaccination, respectively. There was no evidence of reduction in HSV-2 infection by vaccination compared to placebo recipients over 78 weeks of follow-up. The annual incidence of HSV-2 infection in individuals who were HSV-2 negative at baseline or HSV-1 positive and HSV-2 indeterminate at baseline were 4.38/100 person-years (py) and 3.28/100 py in the vaccine and placebo groups, respectively. Baseline HSV-1 status did not affect subsequent HSV-2 acquisition. Specifically, the estimated odds ratio of HSV-2 infection by Week 78 for female placebo recipients who were baseline HSV-1 positive (n = 422) vs. negative (n = 1120) was 1.14 [95% confidence interval 0.66 to 1.94, p = 0.64)]. No evidence of reduction in the incidence of HSV-2 infection by vaccination was detected.

CONCLUSIONS

AIDSVAX® B/E containing gD did not confer protection from HSV-2 acquisition in HSV-2 seronegative women, despite eliciting anti-gD serum antibodies.

Liposomal gD ectodomain (gD1-306) vaccine protects against HSV2 genital or rectal infection of female and male mice

Herpes simplex virus type 2 (HSV2) is the most common causative agent of genital herpes, with infection rates as high as 1 in 6 adults. The present studies were done to evaluate the efficacy of a liposomal HSV2 gD(1-306) vaccine (L-gD(1-306)-HD) in an acute murine HSV2 infection model of intravaginal (female) or intrarectal (male or female) challenge. Two doses of L-gD(1-306)-HD containing 60 microg gD(1-306)-HD and 15 microg monophosphoryl lipid A (MPL) per dose provided protection against HSV2 intravaginal challenge (86-100% survival, P< or =0.0003 vs. control liposomes; P=0.06 vs. L-gD(1-306)-HD without MPL). Both male and female mice (BALB/c and C57BL/6) immunized with L-gD(1-306)-HD/MPL were significantly protected against HSV2 intrarectal challenge, with higher survival rates compared to controls (71-100%, P< or =0.007). L-gD(1-306)-HD/MPL also provided increased survival when compared to a liposomal peptide vaccine, L-gD(264-285)-HD/MPL (male BALB/c, P</=0.001; female BALB/c and male C57BL/6, P=0.06). Mice given L-gD(1-306)-HD/MPL also had minimal disease signs, reduced viral burden in their spinal cords and elevated neutralizing antibody titers in the females. The vaccine also stimulated gD(1-306)-HD specific splenocytes of both male and female mice with significantly elevated levels of IFN-gamma compared to IL-4 (P< or =0.01) indicating that there was an enhanced Th1 response. These results provide the first evidence that the L-gD(1-306)-HD vaccine can protect both male and female mice against intrarectal HSV2 challenge.

Immunodominant epitopes in herpes simplex virus type 2 glycoprotein D are recognized by CD4 lymphocytes from both HSV-1 and HSV-2 seropositive subjects

In human recurrent cutaneous herpes simplex, there is a sequential infiltrate of CD4 and then CD8 lymphocytes into lesions. CD4 lymphocytes are the major producers of the key cytokine IFN-gamma in lesions. They recognize mainly structural proteins and especially glycoproteins D and B (gD and gB) when restimulated in vitro. Recent human vaccine trials using recombinant gD showed partial protection of HSV seronegative women against genital herpes disease and also, in placebo recipients, showed protection by prior HSV1 infection. In this study, we have defined immunodominant peptide epitopes recognized by 8 HSV1(+) and/or 16 HSV2(+) patients using (51)Cr-release cytotoxicity and IFN-gamma ELISPOT assays. Using a set of 39 overlapping 20-mer peptides, more than six immunodominant epitopes were defined in gD2 (two to six peptide epitopes were recognized for each subject). Further fine mapping of these responses for 4 of the 20-mers, using a panel of 9 internal 12-mers for each 20-mers, combined with MHC II typing and also direct in vitro binding assay of these peptides to individual DR molecules, showed more than one epitope per 20-mers and promiscuous binding of individual 20-mers and 12-mers to multiple DR types. All four 20-mer peptides were cross-recognized by both HSV1(+)/HSV2(-) and HSV1(-)/HSV2(+) subjects, but the sites of recognition differed within the 20-mers where their sequences were divergent. This work provides a basis for CD4 lymphocyte cross-recognition of gD2 and possibly cross-protection observed in previous clinical studies and in vaccine trials.

Gender-dependent HLA-DR-restricted epitopes identified from herpes simplex virus type 1 glycoprotein D

In recent clinical trials, a herpes simplex virus (HSV) recombinant glycoprotein D (gD) vaccine was more efficacious in woman than in men. Here we report six HLA-DR-restricted T-cell gD epitope peptides that bind to multiple HLA-DR (DR1, DR4, DR7, DR13, DR15, and DRB5) molecules that represent a large proportion of the human population. Four of these peptides recalled naturally primed CD4(+) T cells in up to 45% of the 46 HSV-seropositive, asymptomatic individuals studied. For the gD(49-82), gD(77-104), and gD(121-152) peptides, the CD4(+) T-cell responses detected in HSV-seropositive, asymptomatic women were higher and more frequent than the responses detected in men. Immunization of susceptible DRB1*0101 transgenic mice with a mixture of three newly identified, gender-dependent, immunodominant epitope peptides (gD(49-82), gD(77-104), and gD(121-152)) induced a gender- and CD4(+) T-cell-dependent immunity against ocular HSV type 1 challenge. These results revealed a gender-dependent T-cell response to a discrete set of gD epitopes and suggest that while a T-cell epitope-based HSV vaccine that targets a large percentage of the human population may be feasible with a limited number of immunodominant promiscuous HLA-DR-restricted epitopes, gender should be taken into account during evaluations of such vaccines.

Protective immunity to genital herpes simplex virus type 1 and type 2 provided by self-adjuvanting lipopeptides that drive dendritic cell maturation and elicit a polarized Th1 immune response

Genital herpes simplex virus type 1 and type 2 (HSV-1 and HSV-2) infections are a significant health problem worldwide. While it is believed that CD4+ Th1 cells are among the effectors to herpes immunity, developing an epitope-based clinical vaccine capable of inducing an effective anti-herpes CD4+ Th1-mediated protection is still under investigation. Few molecules achieve this target without the aid of external immuno-adjuvant. The present study was undertaken to examine the immunogenicity in mice of five CD4+ T cell epitope peptides (gD1-29, gD49-82, gD146-179, gD228-257, and gD332-358), recently identified from the HSV-1 glycoprotein D (gD), covalently linked to a palmitic acid moiety (lipopeptides) using the high-yielding chemoselective ligation method and delivered subcutaneously in free-adjuvant saline. Their protective efficacy was evaluated in a progestin-induced susceptibility mouse model of genital herpes following intravaginal challenge with either HSV-1 or HSV-2. Four out of five gD lipopeptides effectively induced virus-specific CD4+ Th1 responses associated with a reduction of virus replication in the genital tract and protection from overt signs of genital disease. A cocktail of three highly immunogenic lipopeptides provoked maturation of dendritic cells, induced interferon gamma (IFN-gamma)-producing CD4+ T cells, and protected against both HSV- 1 and HSV-2 infections. Depletion of specific T cell subsets from lipopeptideimmunized mice before intravaginal HSV challenges demonstrated that CD4+ T cells were primarily responsible for this protection. The strength of induced T cell immunity, together with the ease of construction and safety of these totally synthetic self-adjuvanting lipopeptides, provide a molecularly defined formulation that could combat genital herpes and other human viral infections for which induction of Th1 immunity is crucial.

Identification of novel immunodominant CD4+ Th1-type T-cell peptide epitopes from herpes simplex virus glycoprotein D that confer protective immunity

The molecular characterization of the epitope repertoire on herpes simplex virus (HSV) antigens would greatly expand our knowledge of HSV immunity and improve immune interventions against herpesvirus infections. HSV glycoprotein D (gD) is an immunodominant viral coat protein and is considered an excellent vaccine candidate antigen. By using the TEPITOPE prediction algorithm, we have identified and characterized a total of 12 regions within the HSV type 1 (HSV-1) gD bearing potential CD4(+) T-cell epitopes, each 27 to 34 amino acids in length. Immunogenicity studies of the corresponding medium-sized peptides confirmed all previously known gD epitopes and additionally revealed four new immunodominant regions (gD(49-82), gD(146-179), gD(228-257), and gD(332-358)), each containing naturally processed epitopes. These epitopes elicited potent T-cell responses in mice of diverse major histocompatibility complex backgrounds. Each of the four new immunodominant peptide epitopes generated strong CD4(+) Th1 T cells that were biologically active against HSV-1-infected bone marrow-derived dendritic cells. Importantly, immunization of H-2(d) mice with the four newly identified CD4(+) Th1 peptide epitopes but not with four CD4(+) Th2 peptide epitopes induced a robust protective immunity against lethal ocular HSV-1 challenge. These peptide epitopes may prove to be important components of an effective immunoprophylactic strategy against herpes.

Lipopeptide vaccines--yesterday, today, and tomorrow

Peptide-based vaccines offer several potential advantages over the conventional whole proteins (or whole gene, in the case of genetic immunisation) in terms of purity and a high specificity in eliciting immune responses. However, concerns about toxic adjuvants, which are critical for immunogenicity of synthetic peptides, still remain. Lipopeptides, a form of peptide vaccine, discovered more then a decade ago, are currently under intensive investigation because they can generate comprehensive immune responses, without the use of adjuvants. In this review, we address the past of lipopeptide vaccines, highlight the progress made toward their optimisation, and stress future challenges and issues related to their synthesis, formulation, and delivery. In particular, the recent development of mucosal application of lipopeptide vaccines may present an ideal strategy against many pathogens that infect mucosal surfaces.

Immunodominant T-cell epitopes of rubella virus structural proteins defined by synthetic peptides

Sets of overlapping synthetic peptides containing predicted T-cell epitope motifs were designed from the murine monoclonal antibody-defined map of linear B-cell epitope domains within each of the structural proteins of rubella virus (RV). The peptides represented well-defined subsequences of two capsid domains (C1 to C29 and C64 to C97), of a domain of glycoprotein E1 containing neutralizing determinants (E1(202) to E1(283), and of a domain of glycoprotein E2 (E2(31) to E2(105). With the exception of peptides representing C64 to C97, each set of peptides stimulated varied but individually specific lymphoproliferative responses in peripheral blood mononuclear cells from 25 to 50% of a representatively large number of normal, RV-immune human donors with diverse human leukocyte antigen (HLA) backgrounds. Responses were mediated by CD4+ T cells in association with HLA class II antigens, though lymphoproliferative responses to a given peptide were usually not HLA-DR allele specific. Correlation analysis of responses to overlapping peptides suggests that there is an immunodominant T-proliferative epitope within C14 to C29 recognized by approximately 50% of the donor population. However, limiting-dilution analysis indicated much variability between individuals in lymphocyte recognition of this T-cell determinant, even within similar HLA-DR contexts. Thus, the fine specificity of relatively immunodominant T-cell epitopes may vary from individual to individual. Synthetic peptides with predicted T-cell motifs have proved to be useful probes of the molecular determinants of cellular immunity to RV and should expand the rational basis for the design of synthetic RV vaccines.

Analysis of T- and B-cell epitopes of capsid protein of rubella virus by using synthetic peptides

A nested set of 11 overlapping synthetic peptides covering the entire sequence of rubella virus capsid protein was synthesized, purified, and tested against human rubella virus-specific T-cell lines and rubella virus-seropositive sera. T-cell lines derived from four donors responded strongly to four synthetic peptides containing residues 96 to 123, 119 to 152, 205 to 233, and 255 to 280. Only one peptide (residues 255 to 280) was recognized by all four T-cell lines. Two human immunodominant linear B-cell epitopes were mapped to residues 1 to 30 and 96 to 123 by using peptide-specific enzyme-linked immunosorbent assay. All 11 synthetic peptides were highly immunogenic and induced strong antibody responses in rabbits against the respective immunized peptides. Seven of the 11 rabbit antipeptide antisera (anti-1-30, -74-100, -96-123, -119-152, -205-233, -231-257, and -255-280) specifically recognized the capsid protein on immunoblots. Identification of these T- and B-cell epitopes represents the first step toward rational design of synthetic vaccines against rubella.

Analysis of the role of antibody-dependent cellular cytotoxic antibody activity in murine neonatal herpes simplex virus infection with antibodies to synthetic peptides of glycoprotein D and monoclonal antibodies to glycoprotein B

The role of antibody in neonatal herpes simplex virus (HSV) infection remains controversial. A battery of well-characterized monoclonal antibodies to HSV glycoprotein B (gB), and polyclonal antibodies against synthetic peptides of predicted epitopes of HSV glycoprotein D (gD) were used to determine in vitro functional activity and association with protection against lethal infection in a murine model of neonatal HSV disease. Antiviral neutralization activity of HSV was not associated with antibody-dependent cellular cytotoxicity (ADCC) activity to HSV-infected cells in vitro. In a model of high dose challenge (10(4) PFU), protection was not afforded by any antibody alone, but was by antibody plus human mononuclear cells, and highly associated with ADCC functional activity (P less than 0.001). In a low dose challenge model, neutralizing activity of antibody alone was associated with protection in vivo (P less than 0.001). Of the nine neutralizing epitopes of gD in vitro, eight were predicted surface regions. Four of the five epitopic sites of gD (2-21, 267-276, 288-297, and 303-312) that were determined to be important targets of ADCC and in vivo protection were also predicted to be surface regions. The only exception was the antiserum to region 52-61 which was predicted to be buried and also showed these activities. ADCC as well as neutralizing antibody activity are important in protection against neonatal HSV infection.

T-cell responses to predicted amphipathic peptides of varicella-zoster virus glycoproteins II and IV

Four peptides from the predicted amino acid sequences of varicella-zoster virus (VZV) glycoproteins II and IV selected for potential amphipathicity and a terminal lysine residue were synthesized. The peptides elicited weak proliferative responses by T cells with the CD4+ UCHL1+ CD45R- phenotype from the blood of VZV-immune individuals. The frequency of responder cells in individuals with specific response to peptides was 1:80,000 or fewer blood mononuclear cells, and the number of peptides responded to did not correlate with the proliferative response to VZV antigen. Of 40 peptide-specific T-cell clones obtained by limiting dilution, 10 were restimulated by extracted VZV antigen in the presence of autologous antigen-presenting cells. A total of 50% of these clones lysed HLA class II-positive lymphoblasts which had been preincubated with the appropriate peptide, and 2 of 15 cytotoxic clones lysed lymphoblast targets superinfected with VZV. The data indicated that T cells with specificity for putative VZV peptides may readily be cultured from the subset of blood mononuclear cells which bears the phenotype associated with memory.

Influence of peptide acylation, liposome incorporation, and synthetic immunomodulators on the immunogenicity of a 1-23 peptide of glycoprotein D of herpes simplex virus: implications for subunit vaccines

A peptide corresponding to residues 1 to 23 of glycoprotein D of herpes simplex virus type 1 was chemically synthesized and coupled to a fatty acid carrier by standard Merrifield synthesis procedures. The resulting peptide-palmitic acid conjugate (acylpeptide) exhibited enhanced immunogenicity in mice as compared with that exhibited by the free form of the peptide. Incorporation of the acylpeptide into liposomes further increased the immunogenicity of the peptide, while inclusion of the immunomodulators muramyl tripeptide phosphatidylethanolamine and monophosphoryl lipid A into the same liposome stimulated the strongest response. The humoral immune responses induced by the acylpeptide-liposome construct were greater than those induced by peptide in Freund complete adjuvant, and cellular responses were equal. The acylpeptide-immunomodulator-liposome formulation also induced significant levels of protective immunity, although the immunity was less than that induced by herpes simplex virus infection. Acylated peptides, especially in liposomes, were taken up more effectively by draining lymph nodes, which possibly accounts in part for the enhanced immunogenicity of the peptides. Since the acylpeptide-immunoliposome formulation used was nontoxic, it could represent a useful way to enhance immunogenicity of subunit peptides used for vaccine purpose in humans and animals.

Fine mapping of antigenic site II of herpes simplex virus glycoprotein D

Glycoprotein D (gD) is a virion envelope component of herpes simplex virus types 1 (HSV-1) and 2 (HSV-2) which plays an important role in viral infection and pathogenesis. Previously, anti-gD monoclonal antibodies (MAbs) were arranged into groups which recognize distinct type-common and type-specific sites on HSV-1 gD (gD-1) and HSV-2 gD (gD-2). Several groups recognize discontinuous epitopes which are dependent on tertiary structure. Three groups, VII, II, and V, recognize continuous epitopes present in both native and denatured gD. Previously, group II consisted of a single MAb, DL6, whose epitope was localized between amino acids 268 and 287. In the study reported here, we extended our analysis of the antigenic structure of gD, concentrating on continuous epitopes. The DL6 epitope was localized with greater precision to residues 272 to 279. Four additional MAbs including BD78 were identified, each of which recognizes an epitope within residues 264 to 275. BD78 and DL6 blocked each other in binding to gD. In addition, a mutant form of gD was constructed in which the proline at 273 was replaced by serine. This change removes a predicted beta turn in gD. Neither antibody reacted with this mutant, indicating that the BD78 and DL6 epitopes overlap and constitute an antigenic site (site II) within residues 264 to 279. A separate antigenic site (site XI) was recognized by MAb BD66 (residues 284 to 301). This site was only six amino acids downstream of site II, but was distinct as demonstrated by blocking studies. Synthetic peptides mimicking these and other regions of gD were screened with polyclonal antisera to native gD-1 or gD-2. The results indicate that sites II, V, VII, and XI, as well as the carboxy terminus, are the major continuous antigenic determinants on gD. In addition, the results show that the region from residues 264 through 369, except the transmembrane anchor, contains a series of continuous epitopes.

Mapping an antibody-binding site and a T-cell-stimulating site on the 1A protein of respiratory syncytial virus

A synthetic peptide modeled on residues 45 to 60 of the 1A protein of respiratory syncytial (RS) virus [1A(45-60)] was constructed and used for immunization of mice and rabbits. The immunoglobulin G fraction of the resulting rabbit antibody, purified on protein A-Sepharose, immunoprecipitated from RS-infected HEp-2 cells a protein with a molecular size of approximately 9.5 kilodaltons, which corresponds to the previously published molecular size of the 1A protein (Y. T. Huang, P. L. Collins, and G. W. Wertz, Virus Res. 2:157-173, 1985). To investigate the T-cell-inducing properties of 1A(45-60), six strains of mice were immunized and their popliteal lymph node cells were tested for proliferation upon restimulation with peptide in vitro. The lymph node cells of all six strains of mice were responsive to restimulation with 1A(45-60) and showed high- and low-responder strain variation. These peptide-primed lymph node cells also proliferated upon in vitro restimulation with RS virus-infected cells. Correlation of proliferation with interleukin 2 production suggested that the responding lymphocytes were T-helper cells. The antibody-binding and T-cell-stimulating sites of 1A were mapped by constructing a series of overlapping synthetic peptides and testing each for ability to react with antiserum prepared by immunization of BALB/C mice with free peptide 1A(45-60) or for ability to restimulate proliferation in 1A(45-60)-primed lymph node cells of BALB/C mice. Human antibody, obtained during confirmed RS virus infection, was similarly tested with the truncated peptides. Antibody-binding activity was reduced after truncation from the carboxy terminus, and a binding site was mapped to residues 51 through 60, the smallest peptide tested. T-cell-stimulating activity in mice was relatively resistant to truncation from the carboxy terminus and sensitive to truncation from the amino terminus. The smallest region which retained significant T-cell-stimulating activity mapped to residues 46 through 56. However, addition of the naturally occurring Cys at residue 45 and extension of the C terminus to residue 62 resulted in maximum T-cell-stimulating activity of the peptide. These data define both a T-cell epitope and a B-cell epitope of the 1A protein of RS virus and suggest that the carboxy terminus of 1A contains a B-cell epitope, involving residues 51 through 60, which is recognized during natural human infection.

Use of synthetic peptides to map the antigenic determinants of glycoprotein D of herpes simplex virus

The predictive algorithm Surfaceplot (J.M.R. Parker, D. Guo, and R.S. Hodges, Biochemistry 25:5425-5432, 1986) was used to examine glycoprotein D of herpes simplex virus type 1 (HSV-1) for amino acid residues with a high probability of being exposed on the molecular surface. Based on these data, 11 different peptides corresponding to 10-residue segments in the primary sequence of glycoprotein D and one 20-residue segment were synthesized, conjugated to carrier proteins, and used to generate specific antisera in rabbits. Two synthetic peptides predicted not to be on the surface of glycoprotein D were included as negative controls. The polyclonal antisera against individual synthetic peptide conjugates were in turn evaluated for their ability to recognize both isolated glycoprotein D and intact HSV-1 virions in an enzyme-linked immunosorbent assay. Based on Surfaceplot predictions, eight linear antigenic sites on glycoprotein D were thereby defined from the 12 antipeptide antisera prepared. Four of these sites contained epitopes to which complement-independent neutralizing antibodies could be generated. The latter sites corresponded to sequences 12 to 21, 267 to 276, 288 to 297, and 314 to 323 of the mature protein. An additional peptide sequence, 2 to 21, was found to generate antisera which had potent virus-neutralizing capacity in the presence of complement. Identification of a neutralizing epitope in the sequence 314 to 323 makes it likely that the membrane-spanning region of glycoprotein D is within the subsequent sequence, 323 to 339. Antipeptide antisera prepared in this study from 12 synthetic peptides contained 13 surface sites predicted by Surfaceplot, of which 7 were not predicted by the parameters of Hopp and Woods (Proc. Natl. Acad. Sci. USA 78:3824-3828, 1981). Of these seven sites not predicted by the Hopp and Woods plot, all generated antipeptide antibodies that bound to HSV-1 virions and three of these seven sites generated neutralizing antibodies. In total, 8 of 12 synthetic peptides containing surface regions produced antipeptide antibodies that bound to HSV-1 virions and 5 of these generated neutralizing antibodies. These results suggest the advantages of Surfaceplot in mapping antigenic determinants in proteins.

Biological characterization of a simian immunodeficiency virus-like retrovirus (HTLV-IV): evidence for CD4-associated molecules required for infection

We have analyzed a number of biological features of HTLV-IV, a retrovirus indistinguishable from a macaque isolate of simian immunodeficiency virus (SIV), and compared this virus with several strains of human immunodeficiency virus type 1 (HIV-1). Although HTLV-IV was found to be similar to HIV-1 in its tropism for CD4+ lymphocytes, its effects on CD4 expression and the ability of its externalized envelope molecule to form a complex directly with the CD4 molecule, a number of striking differences were noted. Unlike with HIV-1, the range of cells susceptible to HTLV-IV infection and syncytia formation was restricted to a subset of CD4+ cell lines, particularly those that coexpressed CD4 with human leukocyte antigen (HLA) class II antigens. An analysis of the patterns of HTLV-IV infection with B x T somatic cell hybrids indicated that for this virus, molecules in addition to CD4 were probably required to facilitate infection and cell fusion. Additional studies of HTLV-IV infection of Sup-T1 cells, which are exquisitely sensitive to cytopathic effects induced by HIV-1, demonstrated that HTLV-IV infection could occur in the absence of cytopathic effects and, remarkably, with minimal or no downmodulation of the CD4 molecule from the cell surface. The failure of HTLV-IV infection to reduce the expression of several CD4 epitopes suggested that the HTLV-IV envelope produced by Sup-T1 cells was altered in its ability to interact with or bind to CD4. Additional differences were also noted in the size of the transmembrane envelope molecule of HTLV-IV produced by Sup-T1 cells, indicating that cell-specific alterations in processing of the HTLV-IV envelope occurred during the production of virus in this cell line. Understanding the basis for these biological differences between HTLV-IV and the HIV-1 viruses may help to elucidate more general mechanisms for pathogenesis of other members of the SIV and HIV families of retroviruses.

Cellular and humoral immune responses to synthetic peptides deduced from the amino-acid sequences of Epstein-Barr virus-encoded proteins in EBV-transformed cells

Ten synthetic peptides containing 18-22 residues deduced from the amino-acid sequences of the EBV-encoded latent-infection-associated membrane protein (LMP) and the 2 principal nuclear antigens, EBNA-1 and EBNA-2, were tested for their ability to induce lymphokine release from sensitized T-cells of EBV-seropositive donors, as measured by the leukocyte migration inhibition assay (LMI). Only one of the 10 free peptides induced EBV-specific LMI. After Sepharose-coupling, 4 additional peptides were regularly active. In parallel, the sera of the same and other donors were screened for synthetic peptide-binding antibodies, as measured by an ELISA assay. Antibodies to 9 of the 10 peptides were detected in 25-80% of EBV-antibody-positive, but not in EBV-antibody-negative sera. A comparison of the two responses indicates that the humoral immune system tends to react with more epitopes on a given protein than the cellular immune system. Furthermore, the antibody reactivity pattern to different epitopes is more variable from individual to individual than the T-cell response. Also, the epitopes detected by antibodies and sensitized T-cells are often not identical.

Cells expressing herpes simplex virus glycoprotein gC but not gB, gD, or gE are recognized by murine virus-specific cytotoxic T lymphocytes

To determine which viral molecule(s) is recognized by herpes simplex virus (HSV)-specific cytotoxic T lymphocytes (CTL), target cells were constructed which express individual HSV glycoproteins. A mouse L cell line, Z4/6, which constitutively expressed high levels of HSV type 2 (HSV-2) gD (gD-2) was isolated and characterized previously (D. C. Johnson and J. R. Smiley, J. Virol. 54:682-689, 1985). Despite the expression of gD on the surface of Z4/6 cells, these cells were not killed by anti-HSV-2 CTL generated following intravaginal infection of syngeneic mice. In contrast, parental Z4 or Z4/6 cells infected with HSV-2 were lysed. Furthermore, unlabeled Z4/6 cells were unable to block the lysis of HSV-2-infected labeled target cells. Cells which express HSV-1 gB (gB-1) were isolated by transfecting L cells with the recombinant plasmid pSV2gBneo, which contains the HSV-1 gB structural sequences and the neomycin resistance gene coupled to the simian virus 40 early promoter and selecting G418-resistant cell lines. One such cell line, Lta/gB15, expressed gB which was detected by immunoprecipitation and at the cell surface by immunofluorescence. Additionally, cells expressing HSV-1 gC (gC-1) or gE (gE-1) were isolated by transfecting Z4 cells, which are L cells expressing ICP4 and ICP47, with either the recombinant plasmid pGE15neo, which contains the gE structural sequences and the neomycin resistance gene, or pDC17, which contains the gC structural gene coupled to the gD-1 promoter. A number of G418-resistant cell lines were isolated which expressed gC-1 or gE-1 at the cell surface. Anti-HSV-1 CTL generated following footpad infection of syngeneic mice were unable to lyse target cells expressing gB-1 or gE-1. In contrast, target cells expressing very low levels of gC-1 were killed as well as HSV-1-infected target cells. Furthermore, infection of gC-1-transformed target cells with wild-type HSV-1 or a strain of HSV-1 that does not express gC did not result in a marked increase in susceptibility to lysis. These results suggest that murine class I major histocompatibility complex-restricted anti-HSV CTL recognize gC-1 but do not recognize gB, gD, or gE as these molecules are expressed in transfected syngeneic target cells. The results are discussed in terms of recent evidence concerning the specificity of antiviral CTL.

Native and recombinant herpes simplex virus type 1 envelope proteins induce human immune T-lymphocyte responses

The abilities of whole herpes simplex virus type 1 (HSV-1) antigen (HSV-ag) and purified HSV-1 native and recombinant envelope proteins to stimulate in vitro T-lymphocyte responses were compared in patients with recurrent herpes labialis. Immunochemically purified preparations of native glycoproteins B, C, and D (ngB, ngC, ngD) from cultured HSV-1 as well as expressed recombinant plasmid preparations of gD (rgD-1t, rgD-45K) elicited lymphocyte proliferation (LT) and production of gamma interferon (IFN-gamma) and interleukin-2 (IL-2) only in seropositive individuals. The IFN-gamma induced by rgD-1t correlated with the time to the next herpetic lesion in 19 volunteers followed to recurrence (r = 0.69, P less than 0.008), although the magnitude and frequency of LT and IFN-gamma responses were lower with either recombinant or native purified antigens than with the whole-virus antigen. Combinations of ngB plus ngD or ngB plus ngC plus ngD stimulated more IFN-gamma, equivalent to whole-virus-antigen responses. Recombinant-derived human IL-2 also specifically increased LT and IFN-gamma responses in antigen-driven cultures. ngD stimulated IL-2 and LT responses similar to those of whole-virus antigen and higher than those of ngC. HSV-ag and ngB induced significantly higher titers of total IFN than could be accounted for by IFN-gamma; this was not seen for the other antigens, which induced only IFN-gamma. HSV-ag-driven Leu 2a-, plastic-nonadherent blood cells, unlike whole peripheral blood mononuclear cells, showed evidence of an increase and then a decline in the frequency of HSV-responsive cells after a lesion recurrence. These studies suggest that HSV-1 envelope proteins are capable of stimulating an immune T-helper-cell response which is associated with the prevention of human herpes simplex lesion recurrence. Although the whole virus probably contains additional important antigens, increasing concentrations or combinations of certain purified glycoproteins or the addition of nonspecific enhancers of T-lymphocyte function can drive in vitro immune responses to the same level as the complete set of viral antigens.

Regulation of interleukin 2 receptors on T cells from multiple sclerosis patients

Receptors for interleukin 2 (IL-2) are absent on resting T lymphocytes and are induced by antigenic and mitogenic stimulation. After a limited time (8-12 days), these receptors on normal T cells are down-regulated despite the presence of receptor-saturating concentrations of IL-2. We report here that both antigen- and mitogen-induced T-cell lines and clones obtained from peripheral blood and cerebrospinal fluid of multiple sclerosis patients show prolonged expression of IL-2 receptors. This expression is coincident with a prolonged responsiveness to the proliferative effects of IL-2. In addition, Leu 3+, IL-2 receptor-positive T-cell clone from the cerebrospinal fluid of a multiple sclerosis patient has been established and maintained for more than 1 year without IL-2. This clone has some morphologic and histochemical properties of T cells transformed or infected by human T-lymphotropic virus type I.

Synthetic glycoprotein D-related peptides protect mice against herpes simplex virus challenge

Glycoprotein D (gD) of herpes simplex virus (HSV) protects mice from a lethal challenge by either HSV type 1 (HSV-1; oral) or HSV-2 (genital). We evaluated whether synthetic peptides representing residues 1 through 23 of gD (mature protein) can be used as a potential synthetic herpesvirus vaccine. The immunogenicity of the peptides was demonstrated by the biological reactivity of antipeptide sera in immunoprecipitation and neutralization assays. All sera which immunoprecipitated gD had neutralizing against both HSV-1 and HSV-2. The highest titers were found in animals immunized with the longest peptides. The region of residues 1 through 23 was immunogenic regardless of whether the type 1 or type 2 sequence was presented to the animal. Immunization of mice with gD or synthetic peptides conferred solid protection against a footpad challenge with HSV-2. However, the peptides were not as effective as gD in protection against an intraperitoneal challenge. The results suggested that synthetic vaccines based on gD show promise and should be more rigorously tested in a variety of animal models.