Analysis of the nonviral antigens immunoprecipitable by SV40 T antibody from SV40-transformed human/mouse hybrid cell lines

A temperature-sensitive (ts) mutant of herpes simplex virus type 1 (HSV-1), tsJ12, is able to undergo one cycle of replication at the nonpermissive temperature (39°) yielding wild-type quantities of enveloped virus particles. These particles contain viral DNA which is as infectious as wild-type viral DNA; however, they are not infectious. Analysis of [¹⁴C]glucosamine-labeled mutant-infected cell extracts by one- and two-dimensional polyacrylamide gel electrophoresis demonstrated that at 39° tsJ12 fails to induce the synthesis of both the mature gB glycoprotein and its dimeric form which are normal constituents of the virion envelope. Polyethylene glycol, an agent which promotes membrane fusion, enhances the infectivity of tsJ12 virions by greater than 1000-fold following adsorption of virus to susceptible cells demonstrating that mutant virions are able to attach to cells but not penetrate. Consistent with a defect in the virion envelope, tsJ12 is able to interfere with the production of infectious wild-type virus, presumably by the formation of pseudotypic virions composed of wild-type viral genomes in gB-deficient envelopes. Physical mapping of the is defect in this mutant demonstrates that it lies within the limits of the DNA sequence which specifies gB on the physical map of the genome. A ts⁺ revertant of tsJ12 is as infectious as wild-type virus and synthesizes a gB glycoprotein which is indistinguishable from that of wild-type virus. Thus, biological and biochemical studies of tsJ12 and of a ts+ revertant of this mutant (1) demonstrate that glycoprotein gB is essential for infectivity at the level of penetration and (2) further define the physical map location of the gene for this glycoprotein.