Characterization of a herpes simplex virus type 2 75,000-molecular-weight glycoprotein antigenically related to herpes simplex virus type 1 glycoprotein C.

Evidence is presented that the herpes simplex virus type 2 glycoprotein previously designated gF is antigenically related to herpes simplex virus type 1 gC (gC-1). An antiserum prepared against type 1 virion envelope proteins immunoprecipitated gF of type 2 (gF-2), and competition experiments revealed that the anti-gC-1 component of the antiserum was responsible for the anti-gF-2 cross-reactivity. An antiserum prepared against fully denatured purified gF-2, however, and three anti-gF-2 monoclonal antibodies failed to precipitate any type 1 antigen, indicating that the extent of cross-reactivity between gC-1 and gF-2 may be limited. Several aspects of gF-2 synthesis and processing were investigated. Use of the enzymes endo-beta-N-acetylglucosaminidase H and alpha-D-N-acetylgalactosaminyl oligosaccharidase revealed that the fully processed form of gF-2 (about 75,000 [75K] apparent molecular weight) had both complex-type N-linked and O-linked oligosaccharides, whereas newly synthesized forms (67K and 69K) had only high-mannose N-linked oligosaccharides. These last two forms were both reduced in size to 54K by treatment with endo-beta-N-acetylglucosaminidase H and therefore appear to differ only in the number of N-linked chains. Neutralization tests and radioiodination experiments revealed that gF-2 is exposed on the surfaces of virions and that the 75K form of gF-2 is exposed on cell surfaces. The similarities and differences of gF-2 and gC-1 are discussed in light of recent mapping results which suggest collinearity of their respective genes.     

Extensive homology between the herpes simplex virus type 2 glycoprotein F gene and the herpes simplex virus type 1 glycoprotein C gene.

The region of the herpes simplex virus type 2 (HSV-2) genome which maps colinearly with the HSV-1 glycoprotein C (gC) gene has been cloned, and the DNA sequence of a 2.29-kilobase region has been determined. Contained within this sequence is a major open reading frame of 479 amino acids. The carboxyterminal three-fourths of the derived HSV-2 protein sequence showed a high degree of sequence homology to the HSV-1 gC amino acid sequence reported by Frink et al. (J. Virol. 45:634-647, 1983). The amino-terminal region of the HSV-2 sequence, however, showed very little sequence homology to HSV-1 gC. In addition, the HSV-1 gC sequence contained 27 amino acids in the amino-terminal region which were missing from the HSV-2 protein. Computer-assisted analysis of the hydrophilic and hydrophobic properties of the derived HSV-2 sequence demonstrated that the protein contained structures characteristic of membrane-bound glycoproteins, including an amino-terminal signal sequence and carboxy-terminal hydrophobic transmembrane domain and charged cytoplasmic anchor. The HSV-2 protein sequence also contained seven putative N-linked glycosylation sites. These data, in conjunction with mapping studies of Para et al. (J. Virol. 45:1223-1227, 1983) and Zezulak and Spear (J. Virol. 49:741-747, 1984), suggest that the protein sequence derived from the HSV-2 genome corresponds to gF, the HSV-2 homolog of HSV-1 gC.     

Varicella-zoster virus complements herpes simplex virus type 1 temperature-sensitive mutants.

Varicella-zoster virus (VZV) can complement temperature-sensitive mutants of herpes simplex virus. Of seven mutants tested, two, carrying mutations in the immediate-early ICP4 and ICP27 proteins, were complemented. This complementation was not seen in coinfections with adenovirus type 5 or cytomegalovirus. Following transfection into CV-1 cells, a DNA fragment containing the VZV short repeat sequence complemented the ICP4 mutant. These data demonstrate a functional relationship between VZV and herpes simplex virus and have allowed localization of a putative VZV immediate-early gene.     

Properties of herpes simplex virus type 1 and type 2 DNA polymerase

Herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) DNA polymerases were highly purified from infected HeLa BU cells by DEAE cellulose, phosphocellulose and DNA cellulose column chromatography. DNA exonuclease activity but not endonuclease activity was found associated with both types of DNA polymerase. Both DNA polymerase activities could be activated by salt in a similar fashion with the optimal activity in the range of ionic strength between 0.22 and 0.29 alpha. At an ionic strength of 0.14, spermidine and putrescine in the concentration range (0--5 mM) studied could mimic the action of KCI in stimulating DNA polymerase activity. Spermine, in the same concentration range, had a biphasic effect. At an ionic strength of 0.29 all three polyamines were inhibitory. HSV-1 and HSV-2 DNA polymerase are similar in their column chromatographic behavior, sedimentation rate in sucrose gradient centrifugation, and activation energy, but they differ in their heat stability at 45 degrees C with the HSV-2 enzyme more stable than the HSV-1 enzyme. Kinetic behavior of both enzymes is similar, with Km values for deoxyribonucleoside triphosphates in the range of 5 . 10(-7) to 1.8 . 10(-8) M. IdUTP and dUTP served as apparent competitive inhibitors with respect to dTTP, and AraATP acted as an apparent competitive inhibitor with respect to dATP. AraATP could not replace dATP in the DNA polymerization reaction; in contrast, IdUTP could replace TTP. Phosphonoformic acid behaved as an uncompetitive inhibitor with respect to DNA. The ID(50) value estimated was foind to be dependent on the purity of the DNA polymerase used and the ionic strength of the assay condition. Each DNA-polymerase associated DNA exonuclease had the same stability at 45 degrees C as its DNA polymerase. The associated DNAase activity was inhibited by phosphonoformic acid and high ionic strength of the assay condition.     

Multimeric forms of herpes simplex virus type 2 glycoproteins.

Molecular clones of closed circular DNA molecules of a mink cell focus-inducing murine leukemia virus (MCF-13 MuLV) were generated. Closed circular DNA molecules isolated from a Hirt extraction of recently infected NIH/3T3 cells were inserted at their unique EcoRI site into lambda gtWES.lambda B. Restriction endonuclease analysis of inserts of two clones indicated that they represented intact MCF-13 MuLV genomes. One viral insert contained two large terminal repeat sequences, and the other contained only one. A 300-base-pair DNA fragment located in the envelope region of the MCF-13 MuLV genome was determined to be related to xenotropic MuLV sequences.     

Hand-to-hand transmission of herpes simplex virus type 1

Droplets of tissue culture fluid containing herpes simplex virus type 1 were placed on the palm of the hand. Each 0.01 ml droplet was taken from a stock virus suspension with a titre of 10(7.5) TCID50/0.1 ml. At 0, 15, 30, 60 and 120 min a droplet was firmly touched with the middle finger of the right hand, after which, attempts were made to recover virus from the finger. At 0 min, when the virus-containing droplet was in a liquid state, there was a 100% rate of virus recovery. By 15 min the droplets had dried out, and after touching dried out droplets there was a 40% virus recovery rate, even though experimental procedures demonstrated that infectious virus was present in the dried out droplets at all test times. If the finger was moistened with tap water or saliva, there was a 100% recovery rate of virus after touching dried out droplets, as well as after touching droplets in a liquid state.     

Cloning of a ribonucleotide reductase gene of the herpes simplex virus type 2 strain G

The ribonucleotide reductase (RR) 2 gene of the HSV-2 strain G was cloned, sequenced, and expressed in an E. coli cell. The RR2 gene was located on the PstI 2.4 kb fragment, which was cloned and sequenced. The ORF of the gene was 1,011 bp and its termination codon was TAG; also, the CATATAA sequence was present in the promoter of the RR2 gene. A Poly A signal sequence (AATAAA) was found in the 3'-noncoding region. The RR2 proteins that were produced in the E. coli and Vero cells were confirmed using a Western blot analysis. SDS-PAGE revealed that the molecular weights of the fusion-RR2 that was produced in the E. coli cells were approximately 24 kDa and 38 kDa in the Vero cells. The RR2 proteins were soluble. The differences in the molecular weights might be due to modifications in the Vero cells.     

Sequences of herpes simplex virus type 1 that inhibit formation of stable TK+ transformants.

We have identified two regions of the herpes simplex virus type 1 (HSV-1) genome that inhibit DNA-mediated transformation of thymidine kinase-less L (Ltk-) cells by the cloned HSV-1 tk gene. When plasmids containing the EcoRI fragments EK or JK were mixed at 30 fmol/ml with the tk gene and transfected into Ltk- cells, the frequency of transformation was inhibited 80 to more than 90% relative to the control. Of the remaining 10 EcoRI fragments of the HSV-1 genome, 8 were inactive and 2 were weakly active. A 6.1-kilobase PstI subclone between 0.743 and 0.782 map units was isolated from pEK. This clone, pEK-P3P4, exhibited antitransformation activity toward HSV-1 tk and also the bacterial genes gpt and neo. pEK-P3P4 contains the alpha 27 gene, and restriction endonuclease inactivation and subcloning studies established that alpha 27 alone did not inhibit transformation. However, alpha 27 plus sequences both upstream and downstream of alpha 27 did inhibit transformation. In addition, alpha 0 or alpha 4 could substitute for alpha 27 in effecting antitransformation with these sequences. Therefore, an alpha gene and two additional loci in pEK-P3P4 are required for antitransformation. A second antitransforming locus in the reiterated sequences common to EK and JK and distinct from those in pEK-P3P4 was also identified but not characterized in detail. How antitransformation may be an expression of regulation of viral and host cell gene expression is discussed.     

Evidence that neomycin inhibits binding of herpes simplex virus type 1 to the cellular receptor.

The effect of neomycin, a phosphoinositide-binding aminoglycoside, on herpes simplex virus type 1 (HSV-1) infection of BHK cells was studied. We showed earlier that it specifically inhibits HSV-1 production but not HSV-2 production (Langeland et al., Biochem Biophys. Res. Commun. 141:198-203, 1986). We now show that neomycin had no effect on cellular protein synthesis, as judged by the appearance of 35S-labeled polypeptides separated by polyacrylamide gel electrophoresis. Virus-induced polypeptides, however, were strongly inhibited at neomycin concentrations above 2 mM. Comparison among different aminoglycosides showed a variation in inhibition of HSV-1 production that paralleled the cationic charge of the aminoglycosides. HSV-1 receptor binding at 4 degrees C was completely inhibited by neomycin. At 37 degrees C both receptor binding and internalization, as measured by an indirect assay, appeared to be inhibited by more than 90%. The effect of neomycin on the infection was almost immediate upon the addition of the drug and preceded virus internalization. Possible mechanisms of the neomycin effect are discussed.     

Oligomeric structure of glycoproteins in herpes simplex virus type 1.

A number of herpes simplex virus (HSV) glycoproteins are found in oligomeric states: glycoprotein E (gE)-gI and gH-gL form heterodimers, and both gB and gC have been detected as homodimers. We have further explored the organization of glycoproteins in the virion envelope by using both purified virions to quantitate glycoprotein amounts and proportions and chemical cross-linkers to detect oligomers. We purified gB, gC, gD, and gH from cells infected with HSV type 1 and used these as immunological standards. Glycoproteins present in sucrose gradient-purified preparations of two strains of HSV type 1, KOS and NS, were detected with antibodies to each of the purified proteins. From these data, glycoprotein molar ratios of 1:2:11:16 and 1:1:14:9 were calculated for gB/gC/gD/gH in KOS and NS, respectively. gL was also detected in virions, although we lacked a purified gL standard for quantitation. We then asked whether complexes of these glycoproteins could be identified, and if they existed as homo- or hetero-oligomers. Purified KOS was incubated at 4 degrees C with bis (sulfosuccinimidyl) suberate (BS3), an 11.4 A (1A = 0.1 mm) noncleavable, water-soluble cross-linker. Virus extracts were examined by Western blotting (immunoblotting), or immunoprecipitation followed by Western blotting, to assay for homo- and hetero-oligomers. Homodimers of gB, gC, and gD were detected, and hetero-oligomers containing gB cross-linked to gC, gC to gD, and gD to gB were also identified. gH and gL were detected as a hetero-oligomeric pair and could be cross-linked to gD or gC but not to gB. We conclude that these glycoproteins are capable of forming associations with one another. These studies suggest that glycoproteins are closely associated in virions and have the potential to function as oligomeric complexes.     

Characterization of baculovirus-expressed herpes simplex virus type 1 glycoprotein K.

The DNA region encoding the complete herpes simplex virus type 1 (HSV-1) glycoprotein K (gK) was inserted into a baculovirus transfer vector, and recombinant viruses expressing gK were isolated. Four gK-related recombinant baculovirus-expressed peptides of 29, 35, 38, and 40 kDa were detected with polyclonal antibody to gK. The 35-, 38-, and 40-kDa species were susceptible to tunicamycin treatment, suggesting that they were glycosylated. The 38- and 40-kDa species corresponded to partially glycosylated precursor gK (pgK) and mature gK, respectively. The 29-kDa peptide probably represented a cleaved, unglycosylated peptide. The 35-kDa peptide probably represented a cleaved, glycosylated peptide that may be a precursor to pgK. Indirect immunofluorescence with polyclonal antibody to gK peptides indicated that the recombinant baculovirus-expressed gK was abundant on the surface of the insect cells in which it was expressed. Mice vaccinated with the baculovirus-expressed gK produced very low levels (< 1:10) of HSV-1 neutralizing antibody. Nonetheless, these mice were partially protected from lethal challenge with HSV-1 (75% survival). This protection was significant (P = 0.02). Despite some protection against death, gK-vaccinated mice showed no protection against the establishment of latency. Surprisingly, gK-vaccinated mice that were challenged ocularly with a stromal disease-producing strain of HSV-1 had significantly higher levels of ocular disease (herpes stromal keratitis) than did mock-vaccinated mice. In summary, this is the first report to show that vaccination with HSV-1 gK can provide protection against lethal HSV-1 challenge and that vaccination with an HSV-1 glycoprotein can significantly increase the severity of HSV-1-induced ocular disease.     

Virion component of herpes simplex virus type 1 KOS interferes with early shutoff of host protein synthesis induced by herpes simplex virus type 2 186.

Herpes simplex virus (HSV) strains HSV type 1 (HSV-1) KOS and HSV-2 186 are representative of delayed and early shutoff strains, respectively, with regard to their ability to inhibit protein synthesis in Friend erythroleukemia cells. When these cells were simultaneously infected with HSV-1 KOS and HSV-2 186, HSV-1 KOS interfered with the rapid suppression of globin synthesis induced by HSV-2 186. The observed interference was competitive and not due to exclusion of HSV-2 by HSV-1 at the level of adsorption. Furthermore, UV-irradiated HSV-1 KOS was also effective at interfering with the early shutoff function of HSV-2 186, indicating that a virion component is responsible for the observed interference.     

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.     

Host range temperature-sensitive mutants of herpes simplex virus type 2.

Two small-plaque mutants of herpes simplex virus type 2 (HSV-2) (strain 333), whose growth at 39 C was blocked in certain cell types (cell-dependent temperature sensitivity), were compared compared with parental virus in a number of biological assays. One mutant (no. 69) was found to produce a large number of morphologically normal, but noninfectious, particles; under nonpermissive conditions, these mutant particles were able to interfere with the replication of wild-type HSV-2. The other mutant (no. 74), which is known to belong to a different complementation group, appeared to direct little virus DNA synthesis, even at the permissive temperature. Progeny production and virus DNA synthesis in cells infected by mutant 74 were delayed in comparison with wild-type virus-infected cells. Both mutants were found to be more sensitive to UV irradiation than the parental virus; this was especially marked in the case of mutant 74. Moreover, this mutant was found to have a high transforming efficiency at much lower doses of irradiation than those needed to abolish the cytopathic effect of wildtype HSV-2.     

Temperature-sensitive host range mutants of herpes simplex virus type 2.

Herpesviruses are capable of several types of infection of a host cell. To investigate the early events which ultimately determine the nature of the virus-host cell interaction, a system was established utilizing temperature-sensitive mutants of herpes simplex virus type 2. Four mutants have been isolated which fail to induce cytopathic effects and do not replicate at 39 C in hamster embryo fibroblast cells. At least one mutant is virus DNA negative. Since intracellular complementation is detectable between pairs of mutants, a virus function is known to be temperature sensitive. However, all four mutants induce cytopathic effects and replicate to parental virus levels in rabbit kidney cells at 39 C. This suggests that a host cell function, lacking or nonfunctional in HEF cells but present in rabbit kidney cells at 39 C, is required for the replication of these mutants in hamster embryo fibroblasts cells at 39 C. Therefore, we conclude that these mutants are both temperature sensitive and exhibit host range properties.     

Disulfide bonds of herpes simplex virus type 2 glycoprotein gB.

Glycoprotein B (gB) is the most highly conserved envelope glycoprotein of herpesviruses. The gB protein is required for virus infectivity and cell penetration. Recombinant forms of gB being used for the development of subunit vaccines are able to induce virus-neutralizing antibodies and protective efficacy in animal models. To gain structural information about the protein, we have determined the location of the disulfide bonds of a 696-amino-acid residue truncated, recombinant form of herpes simplex virus type 2 glycoprotein gB (HSV gB2t) produced by expression in Chinese hamster ovary cells. The purified protein, which contains virtually the entire extracellular domain of herpes simplex virus type 2 gB, was digested with trypsin under nonreducing conditions, and peptides were isolated by reversed-phase high-performance liquid chromatography (HPLC). The peptides were characterized by using mass spectrometry and amino acid sequence analysis. The conditions of cleavage (4 M urea, pH 7) induced partial carbamylation of the N termini of the peptides, and each disulfide peptide was found with two or three different HPLC retention times (peptides with and without carbamylation of either one or both N termini). The 10 cysteines of the molecule were found to be involved in disulfide bridges. These bonds were located between Cys-89 (C1) and Cys-548 (C8), Cys-106 (C2) and Cys-504 (C7), Cys-180 (C3) and Cys-244 (C4), Cys-337 (C5) and Cys-385 (C6), and Cys-571 (C9) and Cys-608 (C10). These disulfide bonds are anticipated to be similar in the corresponding gBs from other herpesviruses because the 10 cysteines listed above are always conserved in the corresponding protein sequences.