HSV-1 gD Research Articles

Herpes simplex virus with highly reduced gD levels can efficiently enter and spread between human keratinocytes.

The rapid spread of herpes simplex virus type 1 (HSV-1) in mucosal epithelia and neuronal tissue depends primarily on the ability of the virus to navigate within polarized cells and the tissues they constitute. To understand HSV entry and the spread of virus across cell junctions, we have previously characterized a human keratinocyte cell line, HaCaT. These cells appear to reflect cells infected in vivo more accurately than many of the cultured cells used to propagate HSV. HSV mutants lacking gE/gI are highly compromised in spread within epithelial and neuronal tissues and also show defects in cell-to-cell spread in HaCaT cells, but not in other, nonpolarized cells. HSV gD is normally considered absolutely essential for entry and cell-to-cell spread, both in cultured cells and in vivo. Here, an HSV-1 gD mutant virus, F-US6kan, was found to efficiently enter HaCaT cells and normal human keratinocytes and could spread from cell to cell without gD provided by complementing cells. By contrast, entry and spread into other cells, especially highly transformed cells commonly used to propagate HSV, were extremely inefficient. Further analyses of F-US6kan indicated that this mutant expressed extraordinarily low (1/500 wild-type) levels of gD. Neutralizing anti-gD monoclonal antibodies inhibited entry of F-US6kan, suggesting F-US6kan utilized this small amount of gD to enter cells. HaCaT cells expressed high levels of an HSV gD receptor, HveC, and entry of F-US6kan into HaCaT cells could also be inhibited with antibodies specific for HveC. Interestingly, anti-HveC antibodies were not fully able to inhibit entry of wild-type HSV-1 into HaCaT cells. These results help to uncover important properties of HSV and human keratinocytes. HSV, with exceedingly low levels of a crucial receptor-binding glycoprotein, can enter cells expressing high levels of receptor. In this case, surplus gD may be useful to avoid neutralization by anti-gD antibodies.

Varicella-zoster Virus gB and gE coexpression, but not gB or gE alone, leads to abundant fusion and syncytium formation equivalent to those from gH and gL coexpression.

Varicella-zoster virus (VZV) is distinguished from herpes simplex virus type 1 (HSV-1) by the fact that cell-to-cell fusion and syncytium formation require only gH and gL within a transient-expression system. In the HSV system, four glycoproteins, namely, gH, gL, gB, and gD, are required to induce a similar fusogenic event. VZV lacks a gD homologous protein. In this report, the role of VZV gB as a fusogen was investigated and compared to the gH-gL complex. First of all, the VZV gH-gL experiment was repeated under a different set of conditions; namely, gH and gL were cloned into the same vaccinia virus (VV) genome. Surprisingly, the new expression system demonstrated that a recombinant VV-gH+gL construct was even more fusogenic than seen in the prior experiment with two individual expression plasmids containing gH and gL (K. M. Duus and C. Grose, J. Virol. 70:8961-8971, 1996). Recombinant VV expressing VZV gB by itself, however, effected the formation of only small syncytia. When VZV gE and gB genes were cloned into one recombinant VV genome and another fusion assay was performed, extensive syncytium formation was observed. The degree of fusion with VZV gE-gB coexpression was comparable to that observed with VZV gH-gL: in both cases, >80% of the cells in a monolayer were fused. Thus, these studies established that VZV gE-gB coexpression greatly enhanced the fusogenic properties of gB. Control experiments documented that the fusion assay required a balance between the fusogenic potential of the VZV glycoproteins and the fusion-inhibitory effect of the VV infection itself.

Use of chimeric nectin-1(HveC)-related receptors to demonstrate that ability to bind alphaherpesvirus gD is not necessarily sufficient for viral entry.

Human nectin-1 (HveC, Prr1), a member of the immunoglobulin superfamily and a receptor for the entry of herpes simplex viruses 1 and 2 (HSV-1, HSV-2), pseudorabies virus (PRV), and bovine herpesvirus 1 (BHV-1), binds to viral gD. For HSV-1, HSV-2, and PRV, the gD-binding region of nectin-1 has been localized to the N-terminal V-like domain. To determine whether the two C-like domains of nectin-1 influenced gD binding and entry activity, genes encoding chimeric proteins were constructed. Portions of nectin-1 were replaced with homologous regions from nectin-2 (HveB, Prr2), a related protein with ability to mediate the entry of PRV, HSV-2, and Rid mutants of HSV-1, but not HSV-1 or BHV-1. Also, one or more domains of nectin-1 were fused to the two membrane-proximal Ig domains of CD4, a protein with no herpesvirus entry or gD-binding activity. The chimeric proteins were expressed in Chinese hamster ovary cells, which normally lack alphaherpesvirus entry receptors, and detected on the cell surface by one or more anti-nectin-1 monoclonal antibodies. One chimeric protein (nectin-1 amino acids 1-124 fused to CD4) failed to bind to soluble forms of HSV-1, HSV-2, PRV, and BHV-1 gD and, as expected, also failed to mediate entry of the viruses from which these gDs were derived. The other chimeric receptors bound all forms of gD. Some mediated the entry of all the viruses tested but others mediated entry of some but not all the viruses. We conclude that binding of gD to the nectin-1 V domain is not sufficient for entry activity, that there are structural requirements for entry activity independent of gD binding, and that these requirements are different for the several alphaherpesviruses that can use nectin-1 as a receptor.

Glycoprotein D Homologs in Herpes Simplex Virus Type 1, Pseudorabies Virus, and Bovine Herpes Virus Type 1 Bind Directly to Human HveC (Nectin-1) with Different Affinities

Distinct subsets of human receptors for alphaherpesviruses mediate the entry of herpes simplex virus (HSV), pseudorabies virus (PrV), or bovine herpes virus type 1 (BHV-1) into cells. Glycoprotein D (gD) is essential for receptor-mediated entry of all three viruses into cells. However, the gD homologs of these viruses share only 22–33% amino acid identity. Several entry receptors for HSV have been identified. Two of these, HveA (HVEM) and HveC (nectin-1), mediate entry of most HSV-1 and HSV-2 strains and are bound directly by HSV gD. A third receptor, HveB (nectin-2), mediates entry of HSV-2 and only a limited number of HSV-1 strains. HveB and HveC can also serve as entry receptors for PrV, whereas only HveC can serve this function for BHV-1. We show here that gD from PrV and BHV-1 binds directly to the human receptors that mediate PrV and BHV-1 entry. We expressed soluble forms of PrV gD and BHV-1 gD using recombinant baculoviruses and purified each protein. Using ELISA, we detected direct binding of PrV gD to HveB and HveC and direct binding of BHV-1 gD to HveC. Biosensor analysis revealed that PrV gD had a 10-fold higher affinity than HSV-1 gD for human HveC. In contrast, the binding of BHV-1 gD to HveC was weak. PrV gD and HSV-1 gD competed for binding to the V domain of HveC and both inhibited entry of the homologous and heterologous viruses. These data suggest that the two forms of gD bind to a common region on human HveC despite their low amino acid similarity. Based on affinities for human HveC, we predict a porcine HveC homolog may be important for PrV infection in its natural host, whereas a BHV-1 infection in its natural host may be mediated by a receptor other than a bovine HveC homolog.

Nectin2alpha (PRR2alpha or HveB) and nectin2delta are low-efficiency mediators for entry of herpes simplex virus mutants carrying the Leu25Pro substitution in glycoprotein D.

The receptors for entry of herpes simplex viruses 1 and 2 (HSV-1 and -2), widely expressed in human cell lines, are members of a subset of the immunoglobulin superfamily exemplified by herpesvirus entry mediator C (HveC) and the herpesvirus immunoglobulin-like receptor (HIgR). This report focuses on two members of this subset, herpesvirus entry mediator B (HveB), recently designated nectin2/PRR2alpha, and its splice variant isoform, nectin2/PRR2delta. Nectin2alpha and -delta share the ectodomain but differ in the transmembrane and cytoplasmic regions. HveB was reported to enable entry of HSV-1 carrying mutations in glycoprotein D (gD) and of HSV-2, but not of wild-type (wt) HSV-1. We report that (i) both nectin2alpha and -delta served as receptors for the entry of HSV-1 mutant viruses HSV-1(U10) and -(U21) and AP7(r) that carry the Leu25Pro substitution in gD but not for HSV-1 mutants U30 and R5000 that carry the Ser140 or Ala185 substitution in gD. All of these mutants were able to overcome the block to entry mediated by expression of wt gD. (ii) Infection of cells expressing nectin2alpha or -delta required exposure to multiplicities of infection about 100-fold higher than those required to infect cells expressing HveC or HIgR. (iii) gD from HSV-1(U21) bound in vitro soluble forms of nectin2. The association was weaker than that to the soluble form of HveC/HIgR. Binding of wt HSV-1 gD to soluble nectin2 was not detectable. (iv) A major region of nectin2 functional in virus entry mapped to the V domain, located at the N terminus.

Varicella-Zoster Virus (VZV) Does Not Encode a Complete Herpes Simplex Virus (HSV) Glycoprotein D (gD) Homologue

VZV expresses homologues to all of the major glycoproteins of HSV, except gD. We previously identified in VZV a highly conserved DNA coding region for a 19 amino acid (aa) sequence of a major HSV-1 gD epitope. Additional gD coding sequences are not in the published VZV sequence.

Polymeric display of immunogenic epitopes from herpes simplex virus and transmissible gastroenteritis virus surface proteins on an enteroadherent fimbria.

The strong immunogenicity of bacterial fimbriae results from their polymeric and proteinaceous nature, and the protective role of these immunogens in experimental or commercial vaccines is associated with their capacity to induce antiadhesive antibodies. Fimbria-mediated intestinal colonization by enteropathogens typically leads to similar antibody responses. The possibility of taking advantage of these properties was investigated by determining whether enteroadhesive fimbriae, like the 987P fimbriae of enterotoxigenic Escherichia coli, can serve as carriers for foreign antigens without losing their adhesive characteristics. Random linker insertion mutagenesis of the fasA gene encoding the major 987P subunit identified five different mutants expressing wild-type levels of fimbriation. The linker insertion sites of these mutants were used to introduce three continuous segments of viral surface glycoproteins known to be accessible to antibodies. These segments encode residues 11 to 19 or 272 to 279 of herpes simplex virus type 1 (HSV-1) glycoprotein D [gD(11-19) and gD(272-279), respectively] or residues 379 to 388 of the transmissible gastroenteritis virus (TGEV) spike protein [S(379-388)]. Studies of bacteria expressing fimbriae incorporating mutated FasA subunits alone or together with wild-type FasA subunits (hybrid fimbriae) indicated that foreign epitopes were best exported and displayed on assembled fimbriae when they were inserted near the amino terminus of FasA. Fimbriated bacteria expressing FasA subunits carrying the HSV gD(11-19) or the TGEV S(379-388) epitope inserted between the second and third residues of mature FasA elicited high levels of foreign epitope antibodies in all rabbits immunized parenterally. Antibodies against the HSV epitope were also shown to recognize the epitope in the context of the whole gD protein. Because the 987P adhesive subunit FasG was shown to be present on mutated fimbriae and to mediate bacterial attachment to porcine intestinal receptors, polymeric display of foreign epitopes on 987P offers new opportunities to test the potential beneficial effect of enteroadhesion for mucosal immunization and protection against various enteric pathogens.

Enhancement of protective humoral (Th2) and cell-mediated (Th1) immune responses against herpes simplex virus-2 through co-delivery of granulocyte-macrophage colony-stimulating factor expression cassettes.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) could in theory attract antigen-presenting cells in muscle following intramuscular DNA immunization, resulting in enhanced antigen-specific immune responses. Thus, such adjuvants could constitute an important addition to a herpes vaccine by amplifying specific immune responses. Here we investigate the utility of GM-CSF cDNA as a vaccine adjuvant for herpes simplex virus (HSV)-2 in a mouse challenge model. GM-CSF cDNA co-injection enhanced levels of specific IgG, IgE and IgA against HSV-2 gD protein significantly higher than gD plasmid vaccination alone. Moreover, GM-CSF co-injection induced a dramatic increase in IgG1 levels, as compared to IgG2a levels, suggesting a Th2 bias in the response. T helper cell proliferation and secretion of cytokines (IL-2 and IFN-gamma) were significantly increased by GM-CSF cDNA co-injection. When challenged with a lethal dose of HSV-2, GM-CSF co-injection increased survival rates to 90%, an improvement as compared to gD vaccination alone (60-63%). Furthermore, GM-CSF cDNA co-injection reduced herpetic lesions and resulted in a faster recovery from lesions. These data indicate that GM-CSF cDNA enhances both humoral and cellular immune responses and enhances vaccine efficacy, resulting in reduced HSV-2-derived morbidity as well as mortality.

Varicella-zoster Virus (VZV) does not Encode a Complete Herpes Simplex Virus(HSV) Glycoprotein D (gD) homologue 862

VZV expresses homologues to all of the major glycoproteins of HSV, except gD. We previously identified in VZV a highly conserved DNA coding region for a 19 amino acid (aa) sequence of a major HSV-1 gD epitope. Additional gD coding sequences are not in the published VZV sequence.

Herpes simplex virus type 1 glycoproteins gB, gC and gD are major targets for CD4 T-lymphocyte cytotoxicity in HLA-DR expressing human epidermal keratinocytes.

T lymphocytes are the main mediators of the protective immune response in recurrent herpes simplex. Early in the development of recurrent lesions, macrophages and CD4 T lymphocytes predominate in the mononuclear infiltrate surrounding infected epidermal cells. Human epidermal keratinocytes allow herpes simplex virus type 1 (HSV-1) replication and human leukocyte antigen (HLA)-DR is strongly expressed in vivo. In vitro, their pretreatment with IFN-gamma induced HLA-DR expression and partially reversed major histocompatibility complex class I down-regulation by the virus. Mononuclear cell cytotoxicity for these cells was mediated predominantly by CD4 and also by CD8 T cells. Late HSV-1 proteins were the major targets for CD4 CTL, while CD8 CTL predominantly targeted early HSV-1 proteins. Here it is shown that both mononuclear and CD4 CTL consistently recognized the major HSV-1 glycoproteins, gB, gC, gD and gH, using IFN-gamma-pretreated keratinocytes infected with vaccinia virus-HSV glycoprotein recombinants (VvgB, VvgC, VvgD or VvgH). CD4 cytotoxicity was highest for VvgD-infected keratinocytes, followed by VvgB or VvgC and then VvgH in seven patients. CD4 CTL from two of 13 patients also recognized an epitope in the HSV tegument protein VP16, demonstrated by comparing cytotoxicity for the partial deletion mutants RP3 or RP4 and the parental RP1 HSV strain. In summary, the major HSV glycoproteins gB, gC and gD were consistently the major targets for CD4 CTL in VvgB-, VvgC-, VvgD- and VvgH-infected, IFN-gamma-pretreated human epidermal keratinocytes in vitro.

LIGHT, a New Member of the TNF Superfamily, and Lymphotoxin α Are Ligands for Herpesvirus Entry Mediator

Herpes simplex virus (HSV) 1 and 2 infect activated T lymphocytes by attachment of the HSV envelope glycoprotein D (gD) to the cellular herpesvirus entry mediator (HVEM), an orphan member of the tumor necrosis factor receptor superfamily. Here, we demonstrate that HVEM binds two cellular ligands, secreted lymphotoxin α (LTα) and LIGHT, a new member of the TNF superfamily. LIGHT is a 29 kDa type II transmembrane protein produced by activated T cells that also engages the receptor for the LTαβ heterotrimer but does not form complexes with either LTα or LTβ. HSV1 gD inhibits the interaction of HVEM with LIGHT, and LIGHT and gD interfere with HVEM-dependent cell entry by HSV1. This characterizes herpesvirus gD as a membrane-bound viokine and establishes LIGHT-HVEM as integral components of the lymphotoxin cytokine-receptor system. 8 These authors made equal contributions.

Crystallization and preliminary X-ray analysis of herpes simplex virus neutralizing antibody Fab fragment DL11.

An Fab fragment of a virus-neutralizing monoclonal antibody (DL11) that binds to herpes simplex virus glycoprotein D (HSV gD) has been purified, sequenced and crystallized. The biological activity of the purified Fab was verified by enzyme-linked immunosorbant assay, flow cytometry and by neutralization of HSV infectivity. The crystals have the space group P1 with cell dimensions a = 40.2, b = 49.2, c = 63.9 A, alpha = 76.1, beta = 77.4, gamma = 71.6 degrees. The unit-cell volume is consistent with it containing a single Fab molecule. The crystals grow to a maximum size of 0.7 x 0.3 x 0.3 mm and diffract X-rays to greater than 2.2 A resolution. The amino-acid sequences of the variable regions of the heavy and light chains of DL11 have been determined. These have been compared to those for other known Fab structures in the Protein Data Bank for selection of a starting model for crystallographic refinement by the molecular-replacement method.

Anti-idiotypic antibodies mimicking glycoprotein D of herpes simplex virus identify a cellular protein required for virus spread from cell to cell and virus-induced polykaryocytosis.

Glycoprotein D (gD) of herpes simplex virus 1 (HSV-1) is required for stable attachment and penetration of the virus into susceptible cells after initial binding. We derived anti-idiotypic antibodies to the neutralizing monoclonal antibody HD1 to gD of HSV-1. These antibodies have the properties expected of antibodies against a gD receptor. Specifically, they bind to the surface of HEp-2, Vero, and HeLa cells susceptible to HSV infection and specifically react with a Mr 62,000 protein in these and other (143TK- and BHK) cell lines. They neutralize virion infectivity, drastically decrease plaque formation by impairing cell-to-cell spread of virions, and reduce polykaryocytosis induced by strain HFEM, which carries a syncytial (syn-) mutation. They do not affect HSV growth in a single-step cycle and plaque formation by an unrelated virus, indicating that they specifically affect the interaction of HSV gD) with a cell surface receptor. We conclude that the Mr 62,000 cell surface protein interacts with gD to enable spread of HSV-1 from cell to cell and virus-induced polykaryocytosis.

Analysis of herpes simplex virus type 1 glycoprotein D nucleotide sequence in human herpes simplex encephalitis.

Viral factors responsible for HSV neurovirulence in humans are still unknown. The aim of this work was to investigate the hypothesis that viral variants might contribute to the specific neurovirulence of some HSV strains. HSV-1 DNA was recovered from cerebrospinal fluid (CSF) in ten patients with HSV encephalitis (HSE) and the regions of HSV-1 gD gene corresponding to known antigenic sites were analyzed by direct sequencing of PCR products. Twenty-two mutations were found among a total of 6580 bp analyzed over a portion of 1000 bp of gD gene, of which 20 were silent whereas two conferred amino acid substitution. One missense mutation (E117D) was found in two CSF samples as well as in two control laboratory strains. The other one (A269T) was found in a single CSF sample, and lies within a region corresponding to a functionally essential antigenic site. These are the first mutations of the gene encoding gD of HSV identified in vivo in human encephalitis samples. Overall, the results argue against the role of gD in neurovirulence in humans.

Herpes simplex type 1: lacZ recombinant viruses. I. Characterization and application to defining the mechanisms of action of known antiherpes agents

Recombinant viruses with the lacZ gene placed under the control of the HSV-1 ICP4, TK and gD regulatory regions were constructed by recombination into the TK locus of HSV-1. Difficulty in isolating ICP4 and gD recombinant viruses with high level, regulated expression of β-galactosidase was overcome by the use of HSV-1 translational initiation sequences of these genes in place of vector-derived sequences. β-Galactosidase expression displayed the kinetics particular to each viral class. The maximal expression of β-galactosidase from the recombinant viruses within a 22-h period (m.o.i. 5) (relative to the ICP4 virus) was gD(3) > gC(2) > ICP4(1) > TK(0.5). The ICP4 virus produces easily quantifiable levels of β-galactosidase activity for multiplicities of infection from 5 × 10 −4 through 5 over 48 h postinfection. At multiplicities of infection between 2 and 5, ICP4-driven activity was measurable within 2 h postinfection from a monolayer of 3 × 10 4 Vero cells in microtiter wells. Mechanisms of inhibition of several antivirals were probed by using the regulated expression of β-galactosidase from the ICP4 virus as a marker for viral growth. An experimental antiviral (E3925, IC 50 1 μg/ml) and a neutralizing gD MAb (DUP55306, IC 50 0.6 μg/ml) acted prior to immediate early synthesis, consistent with inhibition of viral entry or uncoating. IFN-γ inhibited expression of immediate-early synthesis, while having no effect on viral entry. IC 50 values for E3925 obtained using either the ICP4 or gD viruses at m.o.i. 0.005, were in good agreement with those obtained by standard plaque assays, but were determined in only 1 day, using a microtiter plate format. Thus, these reporter viruses are useful tools for defining the mechanisms of action of antiherpes agents, while quantitatively reproducing the results for IC 50 determinations from standard plaque assays within 24 h in a microtiter plate format.

Viral determinants of the variable sensitivity of herpes simplex virus strains to gD-mediated interference.

Cells that express glycoprotein D (gD) of herpes simplex virus type 1 (HSV-1) resist infection by HSV-1 and HSV-2 because of interference with viral penetration. The results presented here show that both HSV-1 and HSV-2 gD can mediate interference and that various HSV-1 and HSV-2 strains differ in sensitivity to this interference. The relative degree of sensitivity was not necessarily dependent on whether the cell expressed the heterologous or homologous form of gD but rather on the properties of the virus. Marker transfer experiments revealed that the allele of gD expressed by the virus was a major determinant of sensitivity to interference. Amino acid substitutions in the most distal part of the gD ectodomain had a major effect, but substitutions solely in the cytoplasmic domain also influenced sensitivity to interference. In addition, evidence was obtained that another viral gene(s) in addition to the one encoding gD can influence sensitivity to interference. The results indicate that HSV-1 and HSV-2 gD share determinants required to mediate interference with infection by HSV of either serotype and that the pathway of HSV entry that is blocked by expression of cell-associated gD can be cleared or bypassed through subtle alterations in virion-associated proteins, particularly gD.

Protein-Specific Cervical Antibody Responses to Primary Genital Herpes Simplex Virus Type 2 Infections

Antibodies to herpes simplex virus (HSV) have been demonstrated in cervicovaginal secretions but have not been analyzed for their viral protein targets, prevalence, isotype, or kinetics of development. A method was devised to collect cervical secretions from women with primary genital HSV-2. By Western blot, cervical IgG and IgA responses to HSV-2 proteins VP5, gB, and gD were detected in most patients within 2 weeks of onset and to gC/gE within 3 weeks. Cervical IgM and IgG responses to gG, VP16, and ICP35 developed later and were more variable. Cervical IgM to most proteins appeared within 6-10 days. Cervical IgA and IgG persisted for weeks, but cervical IgM waned. Western blot profiles of serum IgG and cervical IgG to individual HSV-2 proteins were similar; those of serum IgA and cervical IgA differed. These findings suggest a universal, complex immune response to HSV-2 infection in the female genital tract.

Chromatographic characterization of HSV-1 gD 268–284 and IL-6 179–185 synthetic oligopeptides by reversed-phase high-performance liquid chromatography, automated Edman degradation and mass spectrometric analysis

Two groups of synthetic oligopeptides ( n amino acid = 7 and 17) were prepared by solid-phase peptide synthesis using the Boc-polystyrene strategy. After deprotection, cleavage and gel permeation, the crude products were analysed by conventional RP-HPLC methods. Separation and isolation of major components were performed on a semi-preparative RP-HPLC column. In order to clarify the primary structure of these products, amino acid analysis, Edman degradation sequence determination and analytical RP-HPLC characterization were applied. The isolated fractions were further assessed by direct molar mass investigation utilizing the fast atom bombardment and 252Cf plasma desorption mass spectrometry. The results with an interleukin-6 oligopeptide corresponding to the 179LRALRQM 185 sequence indicate that the single peak product obtained by RP-HPLC separation contains only one component, as verified by amino acid analysis and mass spectrometry. In contrast, the analysis of 268LAPEDPEDSALLEDPVG 284-NH 2 from HSV-1 gD protein suggests that this large peptide amide showing a single peak after repeated purification by RP-HPLC contains microheterogeneities as revealed by mass spectrometry and sequencing, but not by amino acid analysis.

Gene mapping and sequence analysis of the unique short region of the simian herpesvirus SA 8 genome.

A 10.5 kbp BamHI restriction fragment representing most of the unique short (Us) region of the genome of the simian alpha-herpesvirus SA8 was identified and cloned. Partial sequencing of this DNA fragment identified regions of sequence homology with eight open reading frames (ORFs) of HSV1 and/or HSV2. Sequence and size analysis of subcloned fragments of the SA8 Us region and comparison with homologous HSV Us sequences determined that the number, order, size, and orientation of SA8 Us ORFs are comparable to those of HSV. Based on the location of transcriptional control elements, transcription of SA8 Us genes appears to be organized into 3' co-terminal mRNA sets as in HSV, although the grouping of the gene sets is different. The SA8 US4 (gG) ORF is more similar to that of HSV2 than HSV1, both in size and predicted amino acid sequence. Complete sequences were determined for five SA8 genes which represent homologs of the HSV gD, gE, gI, US5, and US9 genes. The predicted polypeptides encoded by SA8 are similar to the corresponding HSV polypeptides. All SA8 Us genes were more closely related to those of HSV than to related gene homologs of other mammalian alpha-herpesviruses.

Soluble glycoprotein D blocks herpes simplex virus type 1 infection of rat eyes.

Herpes simplex virus type 1 (HSV-1) ocular infection in rats was blocked by treating the eyes with UV-inactivated virions containing glycoprotein D (gD) prior to ocular challenge. In contrast, rats treated with UV-inactivated virions lacking gD were not protected. A soluble, truncated form of HSV-2 gD (gD-2t) also protected against ocular infection. Treatment with gD-2t not only reduced mortality but also restricted progression of pathology and reduced the amount of viral antigen in the cornea. Host antibody or alpha/beta interferon responses to the gD-2t treatment were not detected. These results are similar to those observed in cell culture (D. C. Johnson, R. L. Burke, and T. Gregory, J. Virol. 64:2569-2576, 1990). The in vivo effect of exogenous gD is consistent with blocking of a cell surface gD receptor or with an inhibitory interaction of gD with virions.