Membrane proteins specified by herpes simplex viruses. IV. Conformation of the virion glycoprotein designated VP7(B2)

Genome structure and virion polypeptides of the primate herpesviruses Herpesvirus aotus types 1 and 3: comparison with human cytomegalovirus

Two serologically distinguishable primate herpesviruses, Herpesvirus aotus type 1 and type 3, were examined with regard to their genomes and structural polypeptides. The duplex DNA genomes of these two viruses were found to be essentially identical in molecular weight (Mr approximately equal to 145 X 10(6)) and guanine plus cytosine composition (55%). Both contained unique and inverted repeat nucleotide sequences of the same size and arrangement, which, as judged by DNA-DNA hybridization and restriction enzyme analyses, were at least 95% homologous. In addition, no differences were observed in electrophoretic profiles of virion polypeptides. Because of their great similarity with respect to these criteria, the two viruses ought to be considered independent isolates (or strains) of a single virus, which should be designated H. aotus type 1. The elevated molecular weight and presence of two sets of inverted repeat sequences closely resemble the structure of the human cytomegalovirus genome. However, no sequence homology (less than 5%) nor similarity in virion polypeptides was detected between H. aotus type 1 and human cytomegalovirus.

Multimeric forms of herpes simplex virus type 2 glycoproteins

Herpes simplex virus type 2-specific glycoproteins present in detergent extracts of infected cells were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under conditions designed to permit detection of multimeric forms of these glycoproteins. Two high-molecular-weight glycosylated species were detected when samples were disrupted at lower temperatures or in the absence of any reducing agents. One multimer having an apparent molecular weight of 275,000 was identified as a multimer of the gA or gB glycoprotein or both. The second glycoprotein, having a molecular weight of approximately 230,000, was identified as a multimeric form of the gC glycoprotein. These data indicate that the gC as well as the gA and gB glycoproteins of herpes simplex virus type 2 may exist in a multimeric form.

Antibody responses in humans to individual proteins of herpes simplex viruses

Sera from 231 women were used to examine their frequency of precipitation of various herpes simplex virus type 1 and 2 (HSV-1 and HSV-2) proteins and to determine if there was a rank order of immune responsiveness of humans to these HSV antigens. Radiolabeled viral proteins were reacted with serum and immune complexes isolated with staphylococcal protein A. Individual antigens were resolved by polyacrylamide gel electrophoresis and visualized by fluorography. As a group, these sera precipitated 31 HSV-1 and 27 HSV-2 proteins. HSV-1 polypeptides with molecular weights of 133,000, 99,000, and 82,000, as well as HSV-2 polypeptides with molecular weights of 131,000 and 101,000, were precipitated by essentially all sera that contained antibodies to HSV-1 and HSV-2. When attempts were made to order the viral proteins by constructing precipitation profiles ranking the antigens in patterns according to their frequency of precipitation, it was observed that the antigens were generally not ordered. Demographic analysis of the sera suggested that the differences in the number of proteins precipitated were associated with differences in age, education, age at first marriage, and income, which collectively may reflect the frequency of exposure to the virus.

gA and gB glycoproteins of herpes simplex virus type 1: two forms of a single polypeptide

Utilizing a combination of preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis and sodium dodecyl sulfate-hydroxylapatite column chromatography, we have separated and purified the gA and gB glycoproteins of the major virus-specific glycoprotein region from herpes simplex virus type 1-infected cells. By using purified antigen preparations, antisera specific to each of these glycoproteins were produced. Immunoprecipitation from detergent extracts of infected cells and radioimmune precipitation of the purified antigens have shown that the anti-gA and anti-gB sera each recognize both the gA and the gB glycoproteins. The anti-gA serum was also shown to neutralize virus despite the presence of only minute quantities of the gA glycoprotein in virions. Pulse-chase studies have indicated that the gA and gB glycoproteins are synthesized from a common precursor polypeptide. Together, these data demonstrate that the gA and gB glycoproteins of herpes simplex virus type 1 are antigenically similar but not identical and probably represent two different forms of the same polypeptide which differ in their degree of glycosylation.

Alterations in glycoprotein gB specified by mutants and their partial revertants in herpes simplex virus type 1 and relationship to other mutant phenotypes

The tsB5 mutant of herpes simplex virus type 1 (HSV-1) strain HFEM was shown previously to be temperature sensitive for accumulation of the mature form of glycoprotein gB, for production or activity of a factor required in virus-induced cell fusion, and for production of virions with normal levels of infectivity. In addition, a previous study showed that virions produced by tsB5 at permissive temperature were more thermolabile than HFEM virions and contained altered gB that did not assume the dimeric conformation characteristic of HFEM. Results presented here demonstrate that, at permissive temperature, tsB5 differs from HFEM in another respect: plaques formed by tsB5 are syncytial on Vero cells (but not on HEp-2 cells), whereas plaques formed by HFEM are nonsyncytial on both cell types. In addition, our results indicate that tsB5 produces an oligomeric form of gB, but that it differs in electrophoretic mobility and stability from the gB dimers of HFEM. The major purpose of this study was to investigate the dependence of the various tsB5 mutant phenotypes on the temperature sensitivity of gB accumulation and on the alterations in oligomeric conformation of gB produced at permissive temperature. For this work the following HSV-1 strains related to tsB5 or HFEM were analyzed: (i) phenotypic revertants selected from tsB5 stocks for nonsyncytial plaque morphology on Vero cells or for ability to form plaques at restrictive temperature (38.5 degrees C); (ii) a plaque morphology variant of HFEM selected for its syncytial phenotype on Vero cells; (iii) temperature-sensitive recombinants previously isolated from a cross between tsB5 and the non-temperature-sensitive syncytial strain HSV-1(MP); and (iv) a phenotypic revertant selected from one of the recombinant stocks for its ability to form plaques at 39 degrees C. These strains were all compared with tsB5 and HFEM at three different temperatures in two different cell lines with respect to plaque formation, yield of infectious progeny, virus-induced cell fusion, and accumulation of gB. The results of our analyses on all the strains tested revealed the following correlations between mutant phenotypes and the accumulation and oligomeric conformation of gB. (i) There was a direct and quantitative relationship between the accumulation in infected cells of infectious progeny and of the mature form of gB, providing strong support for the hypothesis that this form of gB is necessary to the production of infectious virions. The oligomeric conformation of gB characteristic of HFEM is apparently not required for virion infectivity; nor was virion thermostability necessarily related to the presence of the HFEM-like oligomeric form of gB. (ii) The previously reported correlation between temperature sensitivity of gB accumulation and virus-induced cell fusion was confirmed for tsB5 and extended to other virus strains, and coordinate reversion of these traits was also demonstrated, providing support for the hypothesis that gB has a role in virus-induced cell fusion. At 37 degrees C, intermediate between permissive and restrictive temperatures, some of the mutants and partial revertants induced cell fusion despite reduced accumulations of the mature form of gB, suggesting that the amount of mature gB present did not determine the extent of fusion and that other forms of gB as well as other factors should be investigated with regard to the process of cell fusion. (iii) Some of the mutants and partial revertants could form plaques at 38.5 degrees C despite reduced accumulations of gB and infectious progeny, indicating that the cell-to-cell transmission of viral infection may be at least in part independent of these factors.

Membrane proteins specified by herpes simplex viruses. V. Identification of an Fc-binding glycoprotein

A glycoprotein with affinity for the Fc region of immunoglobulin was isolated from extracts of cultured cells infected with herpes simplex virus type 1, and experiments were done to characterize its properties and to investigate whether it could account for the Fc-binding activity previously demonstrated on the surfaces of intact herpes simplex virus-infected cells. The technique of affinity chromatography was used to identify and isolate the Fc-binding glycoprotein and to demonstrate the specificity of its interaction with immunoglobulin G-Fc. Although three electrophoretically distinguishable Fc-binding polypeptides were identified by affinity chromatography, these three species appear to be different forms of the same translation product, based on comparisons of proteolytic digestion products and on the kinetics of appearance of each form after a brief pulse with radioactive amino acids. The results suggest that one polypeptide, designated pE, is processed to yield gE1, which is in turn processed to yield gE2. Both gE1 and gE2 are glycosylated membrane proteins and both can be labeled by the lactoperoxidase-catalyzed radioiodination of intact infected cells, indicating the presence of these proteins in surface membranes of the cells. Increases in the amounts of gE1 and gE2 at the cell surface were found to parallel the increase in Fc-binding activity of intact infected cells.

Membrane proteins specified by herpes simplex viruses. III. Role of glycoprotein VP7(B2) in virion infectivity

Experiments done with a temperature"sensitive mutant of herpes simplex virus type 1 (HSV-1) have revealed that one of the virisn glycoproteins, designated VP7(B2), is apparently not required for the production of enveloped virus particles, whereas it does play a critical role in virion infectivity. The mutant, designated HSV-1[HFEM]tsB5, fails to accumulate VP7(B2) at nonpermissive temperature and produces virions that lack detectable quantities of this glycoprotein and that have very low specific infectivity. The poor infectivity of the virions is most readily explained by failure of penetration into the host cell rather than by failure of adsorption to cells because it was shown that the VP7(B2)-deficient virions can bind to cells and that polyethylene glycol, an agent known to promote membrane fusion, can significantly enhance infectivity of the adsorbed virions.