Effect of smoked tobacco tar on the growth, cytolytic action, DNA synthesis, and gene expression of herpes simplex virus.

Previous experiments have shown that topical application of smoked tobacco tar condensate to HSV-infected oral mucosae of mice promotes neoplastic changes. Although HSV is an oncogenic virus, the virus must be inactivated and lose its cytolytic activity to be oncogenic in vitro and in vivo. Therefore, we investigated the effect of the water-extractable components of smoked tobacco tar condensate (smoked tobacco tar extract) on the growth, cytolytic activity, DNA synthesis, and gene expression of type 1 herpes simplex virus (HSV-1). Diluted tar extracts in tissue culture medium markedly inhibited the replication and cytolytic activity of HSV-1 in vitro. The smoked tobacco tar extract also notably inhibited the synthesis of viral DNA and late gene expression in a dose-dependent manner. The synthesis of alpha- and beta-classes of viral proteins was not affected by the extract. Therefore, it is probable that the smoked tobacco tar extract inhibits the synthesis of viral DNA directly rather than indirectly by depressing early gene expression.