- Volume 43, Issue 1, 1979

The effects of mitomycin C and 60Co γ-irradiation, which induce production of SV40 from SV40-transformed hamster cells, on the replication of superinfecting SV40 or virus DNA in cells varying in permissivity for SV40 replication have been examined. These agents enhance replication of SV40 in an uninducible line of SV40-transformed hamster kidney cells and in nonpermissive secondary hamster kidney cells. The same treatments do not affect SV40 replication in semipermissive hamster (BHK21) and human (HEL, HEK) cells and inhibit SV40 replication in permissive monkey (TC-7) cells. We conclude that forms of induction treatment, such as mitomycin C or 60Co γ-irradiation, modify the expression of host cell factors which determine the level of permissivity for SV40 infection.

A type-specific binding antibody to the baboon endogenous virus, M7, reverse transcriptase was developed and characterized using a double antibody immunoprecipitation assay. This assay allows the analysis of non-enzyme neutralizing binding antibody, as well as the detection of early antibody production before high titre enzyme neutralizing antibodies appear. The antibody described is unique among hyperimmune antisera to DNA polymerases in that it recognizes only type-specific determinants on the enzyme molecule. Analysis of the enzymes of several BaEV isolates indicated a grouping of those from Papio cynocephalus, P. anubis and the HL23VBab isolate. The RD-114 enzyme was in a separate class, and the P. papio and P. hamadryas DNA polymerases were distinguished from all the other BaEV enzymes but not from each other.

A clone of Vero cells was isolated and shown to be totally unable to synthesize interferon and insensitive to the toxic effect of poly(rI).poly(rC) treatment. Cells of this clone and mouse L cells were fused by treatment with polyethylene glycol or Sendai virus. Hybrid cell clones were isolated following selection in medium containing hypoxanthine, thymidine and ouabain. The hybrids were sensitive to the antiviral effect of poly(rI).poly(rC) and synthesized mouse, but not primate, interferon. It is proposed that in Vero cells, the gene for interferon synthesis is defective or absent.

Various cells were treated with interferon and then exposed to polyriboino-sinic-polyribocytidylic acid complex [poly(rI).poly(rC)]. With mouse L cells, there was a marked cytotoxic effect from low doses of interferon and poly(rI).poly(rC), whereas chick embryo cells showed an effect only after high doses. When primate cells (LLC.Mk2, BSC.B, Vero and human embryo cells) were treated with human or monkey interferon, poly(rI).poly(rC) was not cytotoxic.

Various strains of influenza C virus grew productively in an established line of monkey kidney cells (LLCMK2) without prior adaptation. When trypsin was added to the medium, higher virus yields were obtained than in other cell cultures. All influenza C virus strains tested formed well defined plaques under the agar overlay medium containing trypsin. Infectivity determined by plaque assay in LLCMK2 cells was higher than that determined by amniotic inoculation of fertile hens’ eggs.