Membrane proteins specified by herpes simplex viruses. I. Identification of four glycoprotein precursors and their products in type 1-infected cells

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.

Conservation of a gene cluster including glycoprotein B in bovine herpesvirus type 2 (BHV-2) and herpes simplex virus type 1 (HSV-1)

A library of subgenomic fragments of bovine herpesvirus type 2 (BHV-2) DNA was constructed in the expression cloning vector lambda gt11 and screened with monoclonal antibodies to the glycoprotein gb BHV-2, which is homologous to glycoprotein gB (gB-1) of herpes simplex virus type 1 (HSV-1). Lambda gt11 clones containing gB BHV-2-specific sequences were used to identify lambda EMBL3 vectors with DNA inserts which contained the complete gB BHV-2 gene. Nucleotide sequencing revealed that the gB BHV-2 gene is highly conserved compared to gB-1. The amino acid sequences and the predicted secondary structures of both glycoproteins are very similar. Two further open reading frames (ORF) in close vicinity to the gene encoding gB BHV-2 showed considerable homology to HSV-1 genes. They code for the major DNA-binding protein (dbp) of BHV-2 and a putative 72-kDa polypeptide. The gene of the latter protein corresponding to ICP18.5 of HSV-1 is interspersed between the ORFs of gB BHV-2 and the dbp of BHV-2. All three genes map in the unique long region of the genome. Their homology and the colinear arrangement compared to HSV-1 indicate a close relationship between the two viruses.

Expression of herpes simplex virus type 1 glycoprotein D deletion mutants in mammalian cells

Glycoprotein D (gD) is a viron envelope component of herpes simplex virus types 1 and 2. We have previously defined seven monoclonal antibody (MAb) groups which recognize distinct epitopes on the mature gD-1 protein of 369 amino acids. MAb groups VII, II, and V recognize continuous epitopes at residues 11-19, 272-279, and 340-356, respectively. MAb groups I, III, IV, and VI recognize discontinuous epitopes. Recent studies have focused on epitopes I, III, and VI. Using truncated forms of gD generated by recombinant DNA methods and proteolysis, epitopes III, IV, and VI were located within amino acids 1-233. A portion of discontinuous epitope I was located in a region within residues 233-275. For this study, we used recombinant DNA methods to create mutations in the gD-1 gene and studied the effects of those mutations on gD as expressed in mammalian cells. Plasmid pRE4, containing the coding sequence of gD-1 and the Rous sarcoma virus long terminal repeat promoter, was transfected into mammalian cells. The expressed protein, gD-1-(pRE4), was identical in size and antigenic properties to gD-1 from infected cells. Six in-frame deletion mutations were subsequently constructed by using restriction enzymes to excise portions of the gD-1 gene. Plasmids carrying these mutated forms were transfected into cells, and the corresponding proteins were examined at 48 h posttransfection for antigenicity and glycosylation patterns. Three deletions of varying size were located downstream of residue 233. Analysis of these mutants showed that amino acids within the region 234-244 were critical for binding of DL11 (group I), but not for other MAb groups. Three other deletion mutants lost all ability to bind MAbs which recognize discontinuous epitopes. In addition, much of the gD expressed by these mutants was observed to migrate as high-molecular-weight aggregated forms in nondenaturing gels. Each of these mutations involved the loss of a cysteine residue, suggesting that disulfide linkages play an essential role in the formation of discontinuous epitopes. The extent of glycosylation of the mutant gD molecules accumulated at 48 h posttransfection suggested altered carbohydrate processing. In one case, there was evidence for increased O-linked glycosylation. Those proteins which had lost a cysteine residue as part of the deletion did not accumulate molecules processed beyond the high-mannose stage. The results suggest that carbohydrate processing during synthesis of gD is very sensitive to alterations in structure, particularly changes involving cysteine residues.

The cytoplasmic domain of herpes simplex virus type 1 glycoprotein C is required for membrane anchoring

The herpes simplex virus type 1 (HSV-1) glycoprotein C (gC) gene was altered so that it encoded a truncated glycoprotein lacking a cytoplasmic domain but retaining 20 of 23 amino acids of the transmembrane domain. No additional amino acid residues were introduced into the glycoprotein encoded by the altered gene. The gene was recombined into the HSV-1 genome by marker transfer. Two recombinant viruses, dl1 and dl2, that expressed the mutant gene were isolated. Characterization of these viruses showed that a substantial fraction of the mutant glycoprotein was secreted from infected cells. Pulse-chase experiments showed that the kinetics of posttranslational modification of the mutant glycoprotein were similar to those of the wild type. However, comparison of the kinetics of secretion of gC by dl2 and gC-3, a gC mutant lacking both the transmembrane and cytoplasmic domains, showed that dl2 gC was secreted much more slowly than gC-3 gC. Iodination of plasma membrane glycoproteins showed that dl2 gC was initially expressed on the cell surface as a membrane protein and subsequently was slowly released from the membrane into the medium. These data indicate that a major function of the cytoplasmic domain of gC is to ensure the stable anchoring of the glycoprotein in plasma membranes. In contrast to these major changes in the membrane-anchoring properties of gC, characterization of the virions produced by dl1 and dl2 showed that they contain significant amounts of gC. Thus the cytoplasmic domain does not appear to be essential for incorporation of this glycoprotein into virions.

Individual herpes simplex virus 1 glycoproteins display characteristic rates of maturation from precursor to mature form both in infected cells and in cells that constitutively express the glycoproteins

Pulse-chase experiments in conjunction with quantitative immunoprecipitation have been used to study the time-course of conversion from precursor to mature form of herpes simplex virus 1 glycoproteins C, D and B (gC, gD, and gB). The experimental systems employed were two infected cell lines and cells that constitutively express gD or gB. The relative rates of conversion among the glycoproteins did not vary in the systems used; the rate of maturation of gC was about two-fold higher than that of gD which, in turn, was about one and a half-fold higher than that of gB. Treatment with phosphonoacetate which inhibits viral DNA synthesis and hence virion morphogenesis induced a striking increase in the time course of conversion of immature gC, gD, and gB to fully glycosylated forms when measured late in the infection. The model of HSV glycoproteins maturation as integral components of the virion envelope is discussed.

HSV-specific IgA from tears blocks virus attachment to the cell membrane

The results of this investigation demonstrate that the IgA antibody in tears inhibits the attachment of herpes simplex virus (HSV) to cells and implicate immunoglobulin A (IgA) isotype antibody in the protection of the ocular surface. Tears were collected from the eyes of infected and uninfected rabbits and tested for the presence of infectious virus, for viral neutralization titer, and in an enzyme-linked immunoassay (ELISA) for antibody to HSV. Neither the tears from the uninfected rabbits nor the tears from the infected rabbits produced viral cytopathic effects on indicator cells in vitro. Tears from uninfected rabbits had no virus neutralization capacity while the tears from infected rabbits had titers of 1:10 to 1:40. Tears collected from HSV-1 infected rabbits, but not uninfected rabbits, had anti-HSV antibody titers as determined by the enzyme-linked immunosorbent assay. Lectin affinity column enrichment of IgA from the tears of uninfected and infected rabbits was examined for the capacity to block viral adsorption to cells using 32P-labeled virus. It was found that exposure of the radio-actively-labeled virus to the purified IgA fraction of tears from infected rabbits reduced the amount of virus binding to Vero cells, whereas the purified IgA obtained from uninfected tears had minimal activity. These results may imply a role for the IgA-containing fraction of tears from HSV-infected animals in preventing viral attachment to cells and suggest that antibody of this isotype plays a protective role at the ocular surface.

Entry of herpes simplex virus 1 in BJ cells that constitutively express viral glycoprotein D is by endocytosis and results in degradation of the virus

The BJ cell line which constitutively expresses herpes simplex virus 1 glycoprotein D is resistant to infection with herpes simplex viruses. Analysis of clonal lines indicated that resistance to superinfecting virus correlates with the expression of glycoprotein D. Resistance was not due to a failure of attachment to cells, since the superinfecting virus absorbed to the BJ cells. Electron microscopic studies showed that the virions are juxtaposed to coated pits and are then taken up into endocytic vesicles. The virus particles contained in the vesicles were in various stages of degradation. Viral DNA that reached the nucleus was present in fewer copies per BJ cell than that in the parental BHKtk- cells infected at the same multiplicity. Moreover, unlike the viral DNA in BHKtk- cells which was amplified, that in BJ cells decreased in copy number. The results suggest that the glycoprotein D expressed in the BJ cell line interfered with fusion of the virion envelope with the plasma membrane but not with the adsorption of the virus to cells and that the viral proteins that mediate adsorption to and fusion of membranes appear to be distinct.

Release of a virus coded glycoprotein from herpes simplex virus type 1 infected cells

HEp-2 cells, which were infected with HSV-1, excrete besides other proteins a soluble glycoprotein (Mr 125,000-130,000) related to the virus protein gC. The excretion of the glycoprotein and the production of extracellular virus particles is reduced to a similar extent when the cells were treated with monensin. Possible consequences of the excretion of soluble viral proteins to a modulation of the immune response are discussed.

Immunogenic glycoproteins of infectious laryngotracheitis herpesvirus

The viral glycoproteins produced in cells infected with either vaccine strain or virulent isolates of infectious laryngotracheitis virus, an avian herpesvirus, were identified by in vitro labeling using [14C]glucosamine and [14C]mannose. Chicken antisera to the vaccine strain and to a virulent isolate, and rabbit antisera to the vaccine strain, immunoprecipitated four major viral glycoproteins of 205, 115, 90, and 60K mol wt. Additional glycoprotein bands were recognized by immune chicken and rabbit sera in Western blotting using a glycoprotein fraction purified from extracts of virus-infected cells. Monoclonal antibodies to the immunogenic glycoproteins were produced and characterized by immunoprecipitation and Western blotting. One group of monoclonal antibodies reacted only with the 60K glycoprotein, by both techniques, while a second group reacted with the 205, 115, and 90K glycoproteins in immunoprecipitation and with additional bands of 85 and 160K in Western blotting.

Herpes simplex virus glycoproteins gC-1 and gC-2 bind to the third component of complement and provide protection against complement-mediated neutralization of viral infectivity

Cells infected with herpes simplex virus type 1 (HSV-1) form rosettes with C3b-coated erythrocytes, whereas cells infected with herpes simplex virus type 2 (HSV-2) or other herpes viruses do not. It was reported that glycoprotein C of HSV-1 (gC-1) mediates the binding of C3b-coated erythrocytes to infected cells and has regulatory (decay-accelerating) activity for the alternative pathway C3 convertase of human complement. We show here that solubilized gC-1 binds to iC3-Sepharose affinity columns. We also report that solubilized gC-2, the genetically related glycoprotein specified by HSV-2, binds to iC3-Sepharose. mAb specific for gC-1 or gC-2 and mutant viral strains were used to identify the C3-binding glycoproteins. In other experiments, HSV-1 mutant strains and recombinants, differing only in their expression of gC, were tested for sensitivity to neutralization by human complement in the presence or absence of antibodies specific for HSV gD. In either case the gC- strain was most sensitive. Expression of gC-1 or gC-2 by isogenic insertion mutants provided protection against complement-mediated neutralization. These results indicate that the genetically and structurally related gC-1 and gC-2 share the functional activity of binding to human C3 and enhance viral infectivity.

Neutralizing monoclonal antibodies specific for herpes simplex virus glycoprotein D inhibit virus penetration

Nine monoclonal antibodies specific for glycoprotein D (gD) of herpes simplex virus type 1 were selected for their ability to neutralize virus in the presence of complement. Four of these antibodies exhibited significant neutralization titers in the absence of complement, suggesting that their epitope specificities are localized to site(s) which contribute to the role of gD in virus infectivity. Each of these antibodies was shown to effectively neutralize virus after virion adsorption to cell surfaces, indicating that neutralization did not involve inhibition of virus attachment. Although some of the monoclonal antibodies partially inhibited adsorption of radiolabeled virions, this effect was only observed at concentrations much higher than that required to neutralize virus and did not correlate with complement-independent virus-neutralizing activity. All of the monoclonal antibodies slowed the rate at which virus entered cells, further suggesting that antibody binding of gD inhibits virus penetration. Experiments were carried out to determine the number of different epitopes recognized by the panel of monoclonal antibodies and to identify epitopes involved in complement-independent virus neutralization. Monoclonal antibody-resistant (mar) mutants were selected by escape from neutralization with individual gD-specific monoclonal antibodies. The reactivity patterns of the mutants and antibodies were then used to construct an operational antigenic map for gD. This analysis identified a minimum of six epitopes on gD that could be grouped into four antigenic sites. Antibodies recognizing four distinct epitopes contained in three antigenic sites were found to neutralize virus in a complement-independent fashion. Moreover, mar mutations in these sites did not affect the processing of gD, rate of virus penetration, or the ability of the virus to replicate at high temperature (39 degrees C). Taken together, these results (i) confirm that gD is a major target antigen for neutralizing antibody, (ii) indicate that the mechanism of neutralization can involve inhibition of virus penetration of the cell surface membrane, and (iii) strongly suggest that gD plays a direct role in the virus entry process.

Characterization of herpesvirus sylvilagus glycoproteins released into the culture medium of infected cells: antisera to gp13 and gp32 neutralize viral infectivity in vitro and identify antigens on plasma membranes of infected cells

Polypeptides released into the culture medium of herpesvirus sylvilagus-infected cells were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of extracellular fluid from [35S]methionine- and [3H]glucosamine-labeled cell cultures. Virus-induced glycoproteins 31, 32, and 33 (molecular weights of 62,000, 59,000, and 54,000, respectively) were the most abundant species and appeared predominantly in the culture medium. This observation, together with the known cell-associated nature of herpesvirus sylvilagus, suggested that virus-induced glycoproteins 31, 32, and 33 were specifically released. Immunization of rabbits with virus-induced glycoproteins 13 (molecular weight of 130,000) and 32 resulted in the production of antibodies that neutralized viral infectivity in vitro. Both antiserum to gp13 and antiserum to gp32 immunoprecipitated gp13, gp26, gp33a, gp45, and virus-induced polypeptide 39 (molecular weights of 130,000, 77,000, 49,000, 27,000, and 36,000, respectively) from [35S]methionine-labeled cell extracts as well as virus-induced glycoproteins 31, 32, and 33 from the culture medium. In addition, membrane immunofluorescence assays indicate that an antigen(s) reactive with anti-gp13/32 serum was located on the plasma membrane of infected cells.

Analysis of the IgM and IgG antibody response against herpes simplex virus type 1 (HSV-1) structural and nonstructural proteins

In the present study the reactivity of IgG and IgM antibodies against HSV-1 structural and nonstructural proteins was analyzed by Western blot analysis (WBA) and radioimmunoprecipitation followed by polyacrylamide gel electrophoresis (RIPA-PAGE). It was demonstrated that IgM and IgG antibodies were directed against viral immediate-early, early, and late proteins. Following acute primary HSV infection, the early IgM antibody response in general was found to be directed against nonglycosylated structural proteins, viral early and immediate-early polypeptides. IgM antibodies against viral glycoproteins were found inconsistently. IgG antibodies against viral glycoproteins and other structural proteins with an apparent molecular weight of 56 kD, 45 kD, and 39 kD could be detected early in infection. Viral early and immediate-early proteins were poorly recognized by IgG antibodies in acute primary infections. In recurrent HSV infections, IgM antibodies revealed a less complex reaction with viral polypeptides. Thus, such IgM antibodies reacted predominantly with viral nonglycosylated structural proteins. In contrast, IgG antibodies from patients with recurrent infections strongly recognized viral structural, early, and immediate-early proteins. In seropositive individuals without obvious symptoms of acute infection, the most prominent antibody response was directed against gB and gD.

Inactivation of herpes simplex virus by protein components of bovine neutrophil granules

From an acid extract of granules of bovine neutrophils we isolated fractions of cationic proteins, exhibiting significant anti-herpesvirus activity at concentrations which were devoid of cytotoxicity and of activity against a picornavirus (rhinovirus). The mechanism of action seems to involve a direct neutralization of the virions. Two antiviral peptides with an approximate MW 7500 were purified to homogeneity by reversed phase high-performance liquid chromatography. Proline and arginine accounted for about 43% and 26-27% of their amino acid residues. One of these peptides (IIIa2 beta) had an MIC of 2 microM.

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.

Limiting dilution analysis of specific in vitro anti-herpes simplex virus antibody production by human lymphocytes

An enzyme linked immunosorbent assay (ELISA) system to study specific anti-herpes simplex virus (HSV) antibody production in vitro by human peripheral blood mononuclear cells (PBMC) has been developed. HSV specific antibody production was detected in culture supernatants of PBMC from HSV seropositive healthy individuals by stimulating with optimal concentrations of HSV antigen without mitogens. To investigate the specificity of the resulting antibody, a limiting dilution analysis was performed as follows. PBMC from HSV-1 seropositive and HSV-2 seronegative individuals were stimulated by wild type HSV-1 (KOS), glycoprotein C deletion mutant of HSV-1 (MP), and wild type HSV-2 (186), and the precursor frequencies of B cells which produce antibodies to HSV-1 (KOS), HSV-1 (MP) and HSV-2 (186) were then estimated. When PBMC from five individuals were stimulated by HSV-1 (KOS), the estimated precursor frequencies of B cells which produced antibodies to HSV-1 (KOS), HSV-1 (MP), and HSV-2 (186) were 1/79,000 to 1/37,000, 1/104,000 to 1/52,000. and 1/78,000 to 1/101,000, respectively. On the other hand, when PBMC were stimulated by HSV-1 (MP) and HSV-2 (186), the precursor frequencies of B cells which produced antibody to HSV-1 (KOS) were the same as those to HSV-1 (MP) and HSV-2 (186), respectively. By using the experimental systems reported here, it became possible to determine clearly the immune status to HSV type-specific and type-common antigens and to each viral glycoprotein.

Herpes simplex-specific IgG subclass response in herpetic keratitis

The measurement of the local IgG response in ocular Herpes simplex virus infection presents particular problems due to the difficulty in obtaining sufficient tear samples and the possible transudation of IgG from the serum to the inflamed eye. Using specific monoclonal antibodies to Human IgG subclasses in an enzyme-linked immunoabsorbant assay (ELISA) the local IgG antibody response in Herpes simplex keratitis was analysed. All serum samples from patients and controls contained quantifiable levels of HSV specific IgG1 and IgG4 antibody. Comparison of serum antibody levels with tear levels for patients showed that HSV specific IgG1 serum concentrations were 16.1 fold or more higher than in tears, whereas IgG4 concentrations were only 6.5 fold higher in serum than in tears. This difference was not apparent in the control group. Radioimmunoprecipitation assay of 35S-methionine labelled HSV antigens revealed only minor differences in the protein profiles produced by immunoprecipitation using serum or tear antibody. These results suggest a role for IgG4 antibodies in mucosal immunity in the eye as has been suggested for the mucosal surface of the lung.

The nucleotide sequence of the gB glycoprotein gene of HSV-2 and comparison with the corresponding gene of HSV-1

The nucleotide sequence of the gB glycoprotein gene of HSV-2 has been determined and compared with the homologous gene of HSV-1. The two genes are specified by the same total number of codons (904); eight additional codons of the HSV-1 gene are found within the signal sequence, and eight additional codons of the HSV-2 gene are found at three different sites in the gene. The signal cleavage, membrane-spanning, and eight potential N-linked oligosaccharide sites, as well as 5'- and 3'-regulatory signals are largely conserved. The overall amino acid homology is 85%; least conserved are the N- and C-terminal regions of the protein. Secondary structure plots were determined for the two proteins, and the structures were compared with each other and with alterations in structure due to several mutations in the HSV-1 gB gene for which sequence analysis is available. The high homology in primary and secondary structure suggests a conserved, essential function for the gene.

Binding of complement component C3b to glycoprotein gC of herpes simplex virus type 1: mapping of gC-binding sites and demonstration of conserved C3b binding in low-passage clinical isolates

The sites on glycoprotein gC of herpes simplex virus type 1 (HSV-1) which bind complement component C3b were evaluated by using anti-gC monoclonal antibodies and mutants which have alterations at defined regions of the glycoprotein. Monoclonal antibodies were incubated with HSV-1-infected cells in a competitive assay to block C3b binding. Each of 12 different monoclonals, which recognize the four major antigenic sites of gC, completely inhibited C3b binding. With this approach, no one antigenic group on gC could be assigned as the C3b-binding region. Next, 21 gC mutants were evaluated for C3b binding, including 1 which failed to synthesize gC, 4 which synthesized truncated forms of the glycoprotein such that gC did not insert into the cell's membrane, and 16 which expressed gC on the cell's surface but which had mutations in various antigenic groups. Eleven strains did not bind C3b. This included the 1 strain which did not synthesize gC, the 4 strains which secreted gC without inserting the glycoprotein into the cell membrane, and 6 of 16 strains which expressed gC on the cell surface. In these six strains, the mutations were at three different antigenic sites. One hypothesis to explain these findings is that C3b binding is modified by changes in the conformation of gC which develop either after antibodies bind to gC or as a result of mutations in the gC gene. Attachment of C3b to gC was also evaluated in 31 low-passage clinical isolates of HSV-1. Binding was detected with each HSV-1 isolate, but not with nine HSV-2 isolates. Therefore, although mutants that lack C3b binding are readily selected in vitro, the C3b-binding function of gC is maintained in vivo. These results indicate that the sites on gC that bind C3b are different from those that bind monoclonal antibodies, that antibodies directed against all sites on gC block C3b binding, and that C3b binding is a conserved function of gC in vivo.

Oligomerization of herpes simplex virus glycoprotein B

Glycoprotein B (gB) specified by herpes simplex virus can be extracted from virions or infected cells in the form of detergent-stable, heat-dissociable oligomers. The composition of the oligomers and requirements for their formation were investigated. Evidence is presented that the faster-migrating forms of the oligomers are homodimers of gB. Dimerization was shown to occur within minutes of polypeptide synthesis and did not depend on glycosylation, the expression of other viral proteins, or virion morphogenesis. The multiple, electrophoretically distinct forms of gB dimers differ in extent or rate of N-linked oligosaccharide processing and also have other differences that influence electrophoretic mobility.

Localization of discontinuous epitopes of herpes simplex virus glycoprotein D: use of a nondenaturing ("native" gel) system of polyacrylamide gel electrophoresis coupled with Western blotting

Previously, a panel of monoclonal antibodies (MCAb) was used to define specific epitopes of herpes simplex virus glycoprotein D (gD) (R. J. Eisenberg et al., J. Virol. 53:634-644, 1985). Three groups of antibodies recognized continuous epitopes; group VII reacted with residues 11 to 19 of the mature protein (residues 36 to 44 of the predicted sequence), group II reacted with residues 272 to 279, and group V reacted with residues 340 to 356. Four additional antibody groups recognized discontinuous epitopes of gD, since their reactivity was lost when the glycoprotein was denatured by reduction and alkylation. Our goal in this study was to localize more precisely the discontinuous epitopes of gD. Using a nondenaturing system of polyacrylamide gel electrophoresis ("native" gel electrophoresis) coupled to Western blotting, we analyzed the antigenic activity of truncated forms of gD. These fragments were generated either by recombinant DNA methods or by cleavage of purified native gD-1 (gD obtained from herpes simplex virus type 1) and gD-2 (gD obtained from herpes simplex virus type 2) with Staphylococcus aureus protease V8. Antibodies in groups III, IV, and VI recognized three truncated forms of gD-1 produced by recombinant DNA methods, residues 1 to 287, 1 to 275, and 1 to 233. Antibodies in group I recognized the two larger forms but did not react with the gD-1 fragment of residues 1 to 233. On the basis of these and previous results, we concluded that a protion of epitope I was located within residues 233 to 259 and that epitopes III, IV, and VI were upstream of residue 233. Antibodies to continuous epitopes identified protease V8 fragments of gD-1 and gD-2 that contained portions of either the amino or carboxy regions of the proteins. None of the V8 fragments, including a 34K polypeptide containing residues 227 to 369, reacted with group I antibodies. This result indicated that a second portion of epitope I was located upstream of residue 227. Two amino-terminal fragments of gD-1, 33K and 30K, reacted with group III, IV, and VI antibodies. A 33K fragment of gD-2 reacted with group III antibodies. Based on their size and reactivity with endo-beta-N-acetylglycosaminidase F, we hypothesized that the 33K and 30K molecules represented residues 1 to 226 and 1 to 182 of gD-1, respectively. These results suggest that epitopes III, IV, and VI are located within the first 182 residues of gD.(ABSTRACT TRUNCATED AT 400 WORDS)

In vitro cytopathology and pathogenicity to inbred mice shown by five variants of a laboratory strain of type 1 herpes simplex virus

The in vitro cytopathology and the neurovirulence to inbred mice demonstrated by five variants originally derived from one laboratory strain (Miyama) of type 1 herpes simplex virus (HSV-1) were studied comparatively. Three of the variants are syncytial [+GC (LPV), +GC (SPV), +GC (81)] and two are non-syncytial [-GCr and -GCf]. The size of plaques produced by the five variants was found to be in the order of +GC (LPV) greater than +GC (81) greater than +GC (SPV) greater than -GCf greater than -GCr. The pathogenicity of these variants was compared in three kinds of inbred mice (AKR, C 3 H/He and C 57 BL) after intraperitoneal (IP) or intracerebral (IC) inoculation. The +GC (LPV) variant was the most virulent as shown by the highest mortality of mice by either route of inoculation. The other four variants caused death of mice only after IC inoculation, and among these variants, +GC (81) was shown to be the most virulent. These data indicate that so far as these five variants of the Miyama strain of HSV-1 are concerned, neurovirulence is positively correlated with their cell fusion activity or the size of plaques which they produce. Pre-IP-inoculation with any of the less virulent variants [-GCr, +GC (SPV) and +GC (81)] protected mice from subsequent lethal infection with +GC (LPV) by the same route of inoculation.

Further characterization of virus obtained from herpes simplex virus type 1 recurrences and primary infections. Influence of the temperature of incubation upon glycoprotein synthesis and virus release. Brief report

The virus contained in clinical isolates of herpes simplex virus type 1 (HSV-1) which have not undergone previous in vitro passages (new isolates) differs from HSV-1 prototype strains with respect to infected cell glycoprotein pattern, and, most probably efficiency of virus egress at 37 degrees C. The differences can be abolished by lowering the temperature of incubation to 33 degrees C. A few tissue culture passages cause the conversion of the original virus to a virus undistinguishable from HSV-1 prototype strains with respect to the parameters mentioned above.

Synthesis and processing of bovine herpesvirus 1 glycoproteins

Four unique glycoproteins or glycoprotein complexes were recognized by a panel of monoclonal antibodies to bovine herpesvirus 1 (BHV-1), i.e., GVP 6/11a/16 (130,000-molecular-weight glycoprotein [130K glycoprotein]/74K/55K), GVP 7 (108K), GVP 3/9 (180K/91K), and GVP 11b (71K). The absence of any antigenic or structural relationship between GVP 11a and GVP 11b, which were previously identified as one glycoprotein, GVP 11, demonstrated that these two GVP 11 species are unique glycoproteins. GVP 3 and GVP 9 showed complete sequence homology, as shown by the identity of their antigenic determinants and by partial peptide mapping. This observation, as well as the ratio of their apparent molecular weights, indicated that GVP 3 (180K) is a dimeric form of GVP 9 (91K). GVP 6 and GVP 11a, as well as GVP 6 and GVP 16, showed at least partial sequence homology, since they shared several antigenic determinants and peptides. In addition, GVP 6, GVP 11a, and GVP 16 were derived from one primary precursor. These results, as well as the ratio of their apparent molecular weights, indicated that the GVP 6/11a/16 complex consists of two forms: one in which GVP 6 (130K) is uncleaved and the other one in which GVP 6 is cleaved and composed of GVP 11a (74K) and GVP 16 (55K), linked by disulfide bridges. An antigenically distinct precursor to each of the four BHV-1 glycoproteins or glycoprotein complexes was identified by monoclonal antibodies. These precursors, pGVP 6 (117K), pGVP 11a (62K), pGVP 7 (100K), pGVP 9 (69K), and pGVP 11b (63K) were sensitive to endo-beta-N-acetylglucosaminidase H treatment, indicating that they represent the partially glycosylated high-mannose-type intermediate forms generated by cotranslational glycosylation of the primary, unglycosylated precursors to GVP 6/11a/16, GVP 7, GVP 3/9, and GVP 11b, which were identified as having apparent molecular weights of 105,000, 90,000, 61,000, and 58,000, respectively. A new nomenclature for the BHV-1 glycoproteins, based on roman numerals, is proposed.

Antigenic variation (mar mutations) in herpes simplex virus glycoprotein B can induce temperature-dependent alterations in gB processing and virus production

Monoclonal antibody-resistant (mar) mutants altered in the antigenic structure of glycoprotein B (gB) of herpes simplex virus type 1, strain KOS-321, were selected by neutralization with each of six independently derived gB-specific monoclonal antibodies. Analysis of the reactivity patterns of these mar mutants with a panel of 16 virus-neutralizing monoclonal antibodies identified at least five nonoverlapping epitopes on this antigen, designated groups I through V. Multiple mar mutations were also introduced into the gB structural gene by recombination and sequential antibody selection to produce a set of mar mutants with double, triple, and quadruple epitope alterations. Group II (B2) and group III (B4) antibodies were used to select the corresponding mutants, mar B2.1 and mar B4.1, which in addition to carrying the mar phenotype were temperature sensitive (ts) for processing of the major partially glycosylated precursor of gB, pgB (Mr = 107,000), to mature gB (Mr = 126,000) and showed reduced levels of gB on the cell surface at high temperature (39 degrees C). These mutants were not, however, ts for production of infectious progeny. A recombinant virus, mar B2/4.1, carrying both of these alterations was ts for virus production and failed to produce and transport any detectable mature gB to the cell surface at 39 degrees C. Rather, pgB accumulated in the infected cell. Revertants of the ts phenotype, isolated from virus plaques at 39 degrees C, regained the B2 but not the B4 epitope and were phenotypically indistinguishable from the mar B4.1 parent. Finally, it was shown that group II (B5) and group III (B4) antibodies failed to immunoprecipitate pgB (39 degrees C) produced by ts gB mutants of herpes simplex virus type 1 which were not selected with monoclonal antibodies. Taken together, our findings indicate that (i) mar mutations can alter antigenic as well as other functional domains of gB, namely, the domain(s) involved in processing and infectivity, and (ii) group II and group III epitopes lie within an essential functional domain of gB which is a target for ts gB mutations.

Studies on herpes simplex virus type 1 glycoproteins using monoclonal antibodies

Monoclonal antibodies against herpes simplex virus type 1 glycoproteins were isolated and utilized to study the synthesis and processing of glycoproteins B, C, and D (gB, gC, gD, respectively). Monoclonal antibodies against both gB and gD had higher virus-neutralizing activity when compared to that of gC. Differences among these glycoproteins were observed in their time of appearance in the virus-infected cells. The presence of gD was detected at a very early stage of infection when compared to gB and gC. The localization of these glycoproteins during their synthesis and processing was studied.

Expression and regulation of glycoprotein C gene of herpes simplex virus 1 resident in a clonal L-cell line

Ltk- cells were transfected with a plasmid containing the entire domain of glycoprotein C (gC), a true gamma or gamma 2 gene of herpes simplex virus 1 (HSV-1) and the methotrexate-resistant mouse dihydrofolate reductase mutant gene. The resulting methotrexate-resistant cell line was cloned; of the 39 clonal lines tested only 1, L3153(28), expressed gC after infection with HSV-1(MP), a gC- mutant, and none expressed gC constitutively. The induction of gC was optimal at multiplicities ranging between 0.5 and 2 PFU per cell, and the quantities produced were equivalent to or higher than those made by methotrexate-resistant gC- L cells infected with wild-type (gC+) virus. The gC gene resident in the L3153(28) cells was regulated as a beta gene inasmuch as the amounts of gC made in infected L3153(28) cells exposed to concentrations of phosphonoacetate that inhibited viral DNA synthesis were higher than those made in the absence of the drug, gC was induced at both permissive and nonpermissive temperatures by the DNA- mutant tsHA1 carrying a lesion in the gene specifying the major DNA-binding protein and which does not express gamma 2 genes at the nonpermissive temperature, and gC was induced only at the permissive temperature in cells infected with ts502 containing a mutation in the alpha 4 gene. The gC induced in L3153(28) cells was made earlier and processed faster to the mature form than that induced in a gC- clone of methotrexate-resistant cells infected with wild-type virus. Unlike virus stocks made in gC- cells, HSV-1(MP) made in L3153(28) cells was susceptible to neutralization by anti-gC monoclonal antibody.

Identification, properties, and gene location of a novel glycoprotein specified by herpes simplex virus 1

We report the identification of a novel herpes simplex virus 1 (HSV-1) glycoprotein reactive with type specific monoclonal antibody H1379. The monoclonal antibody reacted with two broad bands with apparent mol wt of 60K to 68K and 44K to 48K formed by infected cell lysates subjected to electrophoresis in denaturing polyacrylamide gels and electrically transferred to a nitrocellulose sheet. Early in infection the H1379 reactive protein was found in the faster migrating band. The rate of accumulation was highest late in infection and only the slower migrating form incorporates significant amounts of glucosamine. The epitopic site recognized by H1379 was not uniformly distributed among strains. Analyses of HSV-1 X HSV-2 recombinants with monoclonal antibodies to HSV-1 and HSV-2 glycoproteins mapping in the S component of the HSV genomes and marker transfer experiments indicated that the gene specifying the H1379 reactive protein maps within BamHI fragment J to the left of gD most probably within the open reading frame designated as US4 (D. J. McGeoch, A Dolan, S. Donald, and F. J. Rixon, 1985, J. Mol. Biol. 181, 1-13). The gene specifying a recently discovered HSV-2 glycoprotein designated as gG-2 (B. Roizman, B. Norrild, C. Chan, and L. Pereira, 1984, Virology 133, 242-247) maps in the corresponding domain of the HSV-2 genome and marker transfer experiments suggest that the H1379 reactive protein and gG-2 are collinear. We have therefore designated the novel HSV-1 glycoprotein as gG-1.

Characterization and mapping of a nonessential pseudorabies virus glycoprotein

Antigenic variants of pseudorabies virus (PRV) containing mutations in a viral glycoprotein with a molecular weight of 82,000 (gIII) were isolated by selecting for resistance to a complement-dependent neutralizing monoclonal antibody (MCA82-2) directed against gIII. These mutants were completely resistant to neutralization with MCA82-2 in the presence of complement. Two mutants selected for further studies either did not express gIII or expressed an improperly processed form of the glycoprotein. The mutations were also associated with an altered plaque morphology (syncytium formation). The gIII gene was mapped by marker rescue of a gIII- mutant with cloned restriction enzyme fragments to the long unique region of the PRV genome between 0.376 and 0.383 map units. This corresponds to the map location of a glycoprotein described by Robbins et al. (J. Mol. Appl. Gen. 2:485-496, 1984). Since gIII is nonessential for viral replication in cell culture and has several other characteristics in common with the herpes simplex virus glycoprotein gC, gIII may represent the PRV equivalent to herpes simplex virus gC.

Immunogenicity of purified glycoprotein gB of herpes simplex virus

The efficacy of a herpes simplex virus (HSV) component vaccine consisting of viral glycoprotein gB was examined in a mouse system. Immunization of mice with HSV type 1 (HSV-1) gB emulsified in Freund's complete adjuvant or with HSV-1 gB adsorbed to aluminum gel was fully protective against subsequent challenge with HSV-1 or HSV type 2. Latent infection in the trigeminal ganglion was also prevented by immunization with gB.

Detection of herpes simplex virus proteins in cultured cells by monoclonal antibodies and the avidin-biotin-immunoperoxidase complex method

The distribution of 5 proteins of herpes simplex virus Type 1 was observed in cells that had been infected for various periods. The cells were stained with monoclonal antibodies to ICP4, ICP5, ICP6, ICP8, and gB, using the avidin-biotin-peroxidase complex (ABC) method. Each protein had a characteristic pattern of time of appearance and translocation by which it could be distinguished from the others. The sensitivity of the ABC technique, its ease of use, and the permanence of the preparations make this method well suited for the study of viral proteins.

Comparison of the primate alphaherpesviruses. I. Characterization of two herpesviruses from spider monkeys and squirrel monkeys and viral polypeptides synthesized in infected cells

Biological and biochemical properties of two neurotropic herpesviruses of New World monkeys--Herpesvirus saimiri type 1 (HVS-1) and Herpesvirus ateles type 1 (HVA-1)--were examined and compared. HVS-1 and HVA-1 both exhibited a time course of replication similar to another primate herpesvirus, SA 8. Both viruses grew rapidly and high titers of infectious virus were readily produced. HVS-1 and HVA-1 were also able to replicate efficiently in cell lines derived from a number of primate and non-primate species. Analysis of proteins synthesized in infected cells revealed the presence of over 30 virus-specific proteins ranging from less than 30,000 to over 200,000 daltons apparent molecular weight. Both viruses specified synthesis of a major capsid polypeptide of 148,000 daltons. Pulse labeling of cells during infection demonstrated temporal differences in the kinetics of synthesis of individual viral proteins and post-translational modification of a number of viral polypeptides. Glycosylated polypeptides synthesized in HVS-1 and HVA-1 infected cells were identified which ranged from approximately 49,000 to 120,000 daltons. Structural polypeptides of HVA-1 and HVS-1 virions were identified by SDS-PAGE analysis of purified virions. Taken together with clinical data on the diseases caused by these viruses, these studies indicate that HVS-1 and HVA-1 appear similar in many respects to both the human herpes simplex viruses and alphaherpesviruses of other primates.

Identification of a new glycoprotein of herpes simplex virus type 1 and genetic mapping of the gene that codes for it

A type-specific monoclonal antibody, LP10, precipitated a glycoprotein with a molecular weight of approximately 59,000 from purified herpes simplex virus type 1. Although this glycoprotein was similar in size to glycoprotein D (gD), it was shown to be less abundant in both virions and infected cells, to migrate more rapidly in its precursor form, to incorporate glucosamine but not mannose, and to have a more stable precursor in tunicamycin-treated cells than the gD precursor (pgD). Immunoassays of cells infected with insertion recombinants and intertypic recombinants localized the gene coding for the target antigen of LP10 to the unique short (Us) region at map units 0.892 to 0.924 excluding gD. The target antigen of LP10 was then definitively mapped to the Us4 open reading frame by immunoprecipitation of a polypeptide synthesized by in vitro translation of a Us4-specific transcript prepared by using an SP6 cloning This newly identified glycoprotein product of the Us4 gene of herpes simplex virus type 1 is distinct from the previously identified gB1, gC1, gE1, and gH1.

Expression of herpes simplex virus glycoprotein B gene in yeast

The DNA sequence coding for herpes simplex virus type 1 glycoprotein B was placed under control of the acid phosphatase promoter of the yeast Saccharomyces cerevisiae in a plasmid capable of replicating in both yeast and Escherichia coli. Yeast transformed by the plasmid synthesized immunologically active glycoprotein B polypeptide.

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.

Effect of herpes simplex virus type 1 on cellular pools of oligosaccharide-lipid

Incorporation of [3H]mannose into cellular pools of mannosylphosphoryl dolichol (Man-P-Dol), oligosaccharide-lipid, and glycoprotein was measured and compared in herpes simplex virus type 1 (HSV-1)-infected cells and -uninfected cells. While mannose incorporation into the monosaccharide-dolichol fraction was similar in infected or uninfected Vero cells, incorporation into the oligosaccharide-lipid fraction was markedly reduced in HSV-1-infected cells (64% of control levels). In contrast, mannose incorporation into glycoprotein was significantly increased in virus-infected cells versus uninfected cells (194% of control levels). The kinetics of incorporation into the various fractions was examined and it was determined that there was minimal increase in mannose incorporation into oligosaccharide-lipid after 8 hr postinfection in virus-infected cells. This corresponded to the time at which nonglycosylated precursors of the HSV-1 glycoproteins were first detected in association with the nuclear fraction. These data suggest that there is an accelerated turnover of oligosaccharide-lipid in virus-infected Vero cells which is most likely due to extensive glycoprotein synthesis.

Humoral immune response to HSV-1 and HSV-2 viral proteins in patients with primary genital herpes

The humoral immune response to HSV-1 and HSV-2 proteins was examined in patients with primary first-episode genital herpes. Ten patients had culture-proven HSV-1 infections, 37 had HSV-2 infections, and all were seronegative to HSV proteins before developing their infections. Development of serum antibodies to individual HSV proteins and glycoproteins was determined by immunoprecipitation of radiolabeled HSV-1- and HSV-2-infected cell proteins and subsequent gel electrophoresis. In HSV-1 patients, a sequential development of antibodies to HSV-1 proteins was observed with early appearance of antibodies to the nucleocapsid protein p148 and to glycoproteins gB and gC. Seroconversion to gD and to a polypeptide of 88,000 molecular weight (p88) occurred next, and, finally, seroconversion to gE and to a nonglycosylated 66,000 dalton protein p66. In HSV-2 patients, antibodies to HSV-2 proteins p148, gB, and p88 appeared within 1 week of onset of symptoms. Seroconversion to p66, gD, and to a complex of glycoproteins gC and gE ("g80") occurred later, at a mean time of approximately 3 weeks. Seroconversion to HSV-1 gB, p88, and p66 occurred significantly later than seroconversion to the homologous counterparts. Seroconversion within 21 days of onset to HSV-2 gD, g80, and p66 was associated with a longer time to the first recurrence in HSV-2 patients, suggesting a possible role of these antibodies, alone or in combination, in the maintenance of HSV-2 latency in humans.

Sialylated oligosaccharides O-glycosidically linked to glycoprotein C from herpes simplex virus type 1

Glycoprotein C (gC) was purified by immunoabsorbent from herpes simplex virus type-1-infected BHK cells labeled with [14C]glucosamine for 11 h and chased for 3 h. Glycopeptides obtained by pronase digestion of gC were fractionated by Bio-Gel filtration and concanavalin A-Sepharose chromatography. Each glycopeptide fraction was analyzed for amino sugar composition by thin-layer chromatography. The majority of radioactivity was recovered as N-acetylglucosamine, but a significant amount of labeled N-acetylgalactosamine was detected and recovered preferentially in some glycopeptide species. Mild alkaline borohydride treatment of the glycopeptides resulted in the release of small degradation products which contained N-acetylgalactosaminitol as the major labeled component and a drastic reduction of N-acetylgalactosamine in the residual glycopeptides. These results demonstrated that gC carries O-glycosidically linked oligosaccharides in addition to the N-linked di- and triantennary glycans previously described (F. Serafini-Cessi, F. Dall'Olio, L. Pereira, and G. Campadelli-Fiume, J. Virol. 51:838-844, 1984). Chromatographic behavior on DEAE-Sephacel chromatography and neuraminidase digestion of O-linked oligosaccharides indicated the presence of two major sialylated species carrying one and two sialic acid residues, respectively. The characterization of a peculiar glycopeptide species supported the notion that some of the O-linked oligosaccharides are bound to a cluster of hydroxyamino acids located near an N-glycosylation site which carries one N-linked diantennary oligosaccharide.

Oligosaccharide chains of herpes simplex virus type 2 glycoprotein gG.2

gG.2 glycoprotein was purified by H966 monoclonal antibodies linked to Sepharose from herpes simplex virus type 2-infected HEp-2 cells labeled with [3H] glucosamine. The glycoprotein was subjected to Pronase digestion and the glycopeptides were fractionated by Con A-Sepharose in a major fraction (88.5% of total radioactivity) unbound to the lectin gel and in a minor species which bound to the lectin as a N-linked diantennary oligosaccharide. Mild and strong acid hydrolysis of Con A-unbound and Con A-bound fractions revealed that (i) both species were highly sialylated; (ii) the Con A-unbound fraction contained mainly labeled N-acetylgalactosamine, as is the case for O-linked oligosaccharides; and (iii) the Con A-bound fraction carried the vast majority of the labeled N-acetylglucosamine present in gG.2. Three size classes of oligosaccharides were separated from mild alkaline borohydride-treated Con A-unbound glycopeptides, which accounted for about 80% of the radioactivity present in the fraction. Galactosaminitol was recovered as the major labeled product in the strong acid hydrolyzates of the oligosaccharides generated by reductive beta-elimination, indicating that they were O-glycosidically linked to the peptide backbone. Thin-layer and DEAE-Sephacel chromatography of the three O-linked oligosaccharide species indicated that disialylated tetrasaccharides and monosialylated trisaccharides were the major components, whereas neutral disaccharide was a minor component. Digestion with neuraminidase and beta-galactosidase of the O-linked oligosaccharides supported the idea that the common disaccharide core was mainly of the structure beta-galactosyl-N-acetylgalactosamine. The large occurrence of O-linked oligosaccharides differentiates this type 2-specific herpes simplex virus glycoprotein from the type-common herpesvirus glycoproteins gB, gC, and gD.

Specificities of monoclonal and polyclonal antibodies that inhibit adsorption of herpes simplex virus to cells and lack of inhibition by potent neutralizing antibodies

Polyclonal and monoclonal antibodies to individual herpes simplex virus (HSV) glycoproteins were tested for ability to inhibit adsorption of radiolabeled HSV type 1 (HSV-1) strain HFEMsyn [HSV-1(HFEM)syn] to HEp-2 cell monolayers. Polyclonal rabbit antibodies specific for glycoprotein D (gD) or gC and three monoclonal mouse antibodies specific for gD-1 or gC-1 most effectively inhibited HSV-1 adsorption. Antibodies of other specificities had less or no inhibitory activity despite demonstrable binding of the antibodies to virions. Nonimmune rabbit immunoglobulin G and Fc fragments partially inhibited adsorption when used at relatively high concentrations. These results suggest involvement of gD, gC, and perhaps gE (the Fc-binding glycoprotein) in adsorption. The monoclonal anti-gD antibodies that were most effective at inhibiting HSV-1 adsorption had only weak neutralizing activity. The most potent anti-gD neutralizing antibodies had little effect on adsorption at concentrations significantly higher than those required for neutralization. This suggests that, although some anti-gD antibodies can neutralize virus by blocking adsorption, a more important mechanism of neutralization by anti-gD antibodies may be interference with a step subsequent to adsorption, possibly penetration.

Identification of a herpes simplex virus function that represses late gene expression from parental viral genomes

The expression of herpes simplex virus gamma 2 (late) genes is inhibited before the onset of viral DNA replication. We report that the block in the expression of certain gamma 2 genes is relieved, at least in part, by defects in the beta ICP8 protein. We have examined the expression of the gamma 2 gene encoding glycoprotein C (gC) in cells infected with a temperature-sensitive ICP8 mutant. Under conditions in which viral DNA replication is inhibited, cells infected with the ICP8 mutant overproduce the gC family of mRNAs relative to the level observed in cells infected with a wild-type virus. The gC mRNA synthesized in cells infected with the ICP8 mutant virus is correctly initiated and spliced and is translated with the same relative efficiency as in cells infected with a replicating wild-type virus. These results suggest that ICP8 is involved in the negative regulation of gamma 2 genes expressed from parental viral genomes. The level of gC expression was greatest in cells infected with a replicating wild-type virus. These data suggest that DNA replication and genome amplification are not absolute requirements for gamma 2 gene expression but may facilitate full-level expression of these genes.

Synthesis and processing of glycoprotein gG of herpes simplex virus type 2

Monoclonal antibody 13 alpha C5-1-A11 immunoprecipitated two major polypeptides of molecular weights 108,000 and 120,000 from extracts of herpes simplex virus type 2-infected BHK-21 cells labeled with [35S]methionine or [3H]glucosamine. In pulse-chase experiments, both labels were chased from the 120,000-molecular-weight peptide (120K peptide) into the 108K molecule. Endoglycosidase H (endo H) reduced the 120K peptide to a 112K peptide but did not affect the 108K peptide. Similar profiles were obtained with monoclonal antibody AP-1 which reacts with a 92K glycoprotein, gG, which maps to the short unique region of the genome. Cross-absorption experiments indicated that both antibodies reacted with the same peptides, suggesting that the 120K peptide is a partially glycosylated high-mannose-type precursor of gG (pgG1). Immunoprecipitation from monensin-treated cells indicated that pgG1(120K) may undergo peptide cleavage to form a 74K high-mannose-type peptide (pgG2) and that this 74K peptide may be further processed into an endo H-resistant 110K to 116K peptide. In the presence of tunicamycin, gG(108K) was replaced by 110K and 105K peptides which were resistant to both endo H and endoglycosidase F. The 105K peptide was the only molecule labeled by [3H]galactose or [3H]glucosamine in the presence of tunicamycin, and none of the peptides were labeled with [3H]mannose, indicating the probable presence of O-linked sugars in the 105K peptide. Our results imply that cotranslational glycosylation of the unglycosylated precursor 110K peptide results in the high-mannose-type pgG1(120K), which probably undergoes peptide cleavage. This putative cleavage product may then mature into gG (108K) by the trimming of sugars and the addition of complex and probably O-linked sugars; the high-mannose-type pgG2(74K) is probably an intermediate peptide formed in this process.

Intracellular transport of herpes simplex virus gD occurs more rapidly in uninfected cells than in infected cells

A mouse L cell line which expresses the herpex simplex virus type 1 immediate-early polypeptides ICP4 and ICP47 was cotransfected with a cloned copy of the BglII L fragment of herpes simplex virus type 2, which includes the gene for gD, and the plasmid pSV2neo, which contains the aminoglycosyl 3'-phosphotransferase (agpt) gene conferring resistance to the antibiotic G418. A G418-resistant transformed cell line was isolated which expressed herpes simplex virus type 2 gD at higher levels than were found in infected cells. The intracellular transport and processing of gD was compared in transformed and infected cells. In the transformed Z4/6 cells gD was rapidly processed and transported to the cell surface; in contrast, the processing and cell surface appearance of gD in infected parental Z4 cells occurred at a much slower rate, and gD accumulated in nuclear membrane to a greater extent. Thus, the movement of HSV-2 gD to the cell surface in infected cells is retarded as viral glycoproteins accumulate in the nuclear envelope, probably because they interact with other viral structural components.

Vaccinia virus recombinant expressing herpes simplex virus type 1 glycoprotein D prevents latent herpes in mice

In humans, herpes simplex virus causes a primary infection and then often a latent ganglionic infection that persists for life. Because these latent infections can recur periodically, vaccines are needed that can protect against both primary and latent herpes simplex infections. Infectious vaccinia virus recombinants that contain the herpes simplex virus type 1 (HSV-1) glycoprotein D gene under control of defined early or late vaccinia virus promoters were constructed. Tissue culture cells infected with these recombinant viruses synthesized a glycosylated protein that had the same mass (60,000 daltons) as the glycoprotein D produced by HSV-1. Immunization of mice with one of these recombinant viruses by intradermal, subcutaneous, or intraperitoneal routes resulted in the production of antibodies that neutralized HSV-1 and protected the mice against subsequent lethal challenge with HSV-1 or HSV-2. Immunization with the recombinant virus also protected the majority of the mice against the development of a latent HSV-1 infection of the trigeminal ganglia. This is the first demonstration that a genetically engineered vaccine can prevent the development of latency.

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

Immunization of mice with a synthetic peptide that corresponds to a murine antibody-defined immunodominant domain of herpes simplex virus (HSV) glycoprotein D (gD) induced neutralizing antibodies against HSV types 1 and 2 and protected animals against a lethal challenge with HSV type 2 (Dietzschold, B., Eisenberg, R., Ponce de Leon, M., Golub, E., Hudecz, F., Varicchio, A. & Cohen, G. (1984) J. Virol. 52, 431-435). We report here that human peripheral blood T cells from HSV-seropositive and -seronegative adult donors are activated by this synthetic peptide in vitro. Interleukin-2-dependent T-cell lines established from these cultures respond specifically to peptides containing residues 1-23 of HSV gD and to a panel of overlapping peptides within this domain. The T-cell proliferative response was maximal when the majority of interleukin-2-propagated T cells were of the helper phenotype and the peptides were at least 16 amino acids long. Peptides of 8 or 12 amino acids from the carboxyl terminus were nonstimulatory. Peptide-activated T-cell lines from sero-negative donors less than 11 years old could be established in vitro, but most cells were of the suppressor/cytotoxic phenotype and demonstrated no antigen-specificity when tested with the panel of synthetic peptides.

Isolation by high-performance liquid chromatography and partial characterization of a 57,000-dalton herpes simplex virus type 1 polypeptide

A Nonidet P-40 extract of HSV-1-purified virions was fractionated by reversed-phase high-performance liquid chromatography (RP-HPLC). The first peak fraction eluted at 25% organic solvent. Polyacrylamide gel electrophoresis showed that it contained a 57,000-dalton polypeptide. The polypeptide was characterized by determination of the amino acid composition and the N-terminal amino acid sequence. Adsorption of the detergent extract before RP-HPLC showed that the polypeptide reacted with monoclonal antibodies LP1 directed against herpes simplex virus polypeptide VP-16.

Effect of tunicamycin and monensin on biosynthesis, transport, and maturation of bovine herpesvirus type-1 glycoproteins

The effect of tunicamycin and monensin on the biosynthesis, intracellular transport, and maturation of bovine herpesvirus type-1 (BHV-1) glycoproteins was examined. Tunicamycin completely inhibited the production of infectious virus particles and significantly reduced the incorporation of [3H]glucosamine into viral glycoproteins. In the presence of monensin, reduced amounts of infectious virus particles were produced, which was mainly due to inhibition of virus release, rather than virus production. Monensin only slightly inhibited viral glycoprotein synthesis. The effects of these compounds on infectivity indicated that glycosylation is required for the production of infectious virus, though complete processing of the glycoproteins is not essential. In addition, egress of the virions from infected cells probably requires a functional Golgi complex. In the presence of tunicamycin or monensin various degrees of glycosylation of the major glycoproteins occurred, consequently their rates of migration differed from that of the normal glycoproteins. Tunicamycin completely blocked glycosylation of GVP 6/11a/16 and GVP 7. In contrast, GVP 3/9 and GVP 11b were partially glycosylated in the presence of tunicamycin. These results indicated that GVP 6/11a/16 and GVP 7 are N-linked glycoproteins, but GVP 3/9 and GVP 11b contain both N- and O-linked oligosaccharide side chains. Tunicamycin blocked the transport of all viral glycoproteins to the cell surface, suggesting that glycosylation is required for this process. In the presence of monensin, the viral glycoproteins were transported and expressed on the cell surface indicating that transport does not require complete processing of the glycoproteins and may occur via a Golgi-independent pathway. In addition, monensin-treated BHV-1 infected cells could act as target cells in an antibody-dependent cell cytotoxicity assay. Thus, complete glycosylation may not be essential for maintenance of antigenicity and participation in immune destruction.

Protection from genital herpes simplex virus type 2 infection by vaccination with cloned type 1 glycoprotein D

Guinea pigs were vaccinated with truncated herpes simplex virus type-1 (HSV-1) glycoprotein D produced in the genetically engineered mammalian cell line gD10.2. Vaccinated animals formed antibodies that neutralized both HSV-1 and herpes simplex virus type 2 (HSV-2) in an in vitro neutralization assay. Vaccinated animals were challenged with HSV-2 by intravaginal infection. Animals that received the immunogen in Freund's complete adjuvant were completely protected from the clinical manifestations of genital HSV-2 infection. Animals that received the immunogen incorporated in alum adjuvants were partly protected from clinical disease; the infections that did develop were significantly less severe than those that occurred in control animals injected with adjuvant alone. The results demonstrate that immunization with a purified viral protein can provide significant protection against primary genital infection by HSV-2 in guinea pigs.