Herpes simplex virus DNA polymerase, thymidine kinase and deoxyribonuclease activities in cells infected with wild type, ultraviolet-irradiated and defective virus

Effect of incorporation of 5-iodo-2'-deoxyuridine into HSV-1 DNA on virion sensitivity to ultraviolet light

First generation progeny herpes simplex type 1 (HSV-1) virions grown in the presence of 5-iodo-2'-deoxyuridine (IdUrd) were irradiated with either 254 or 302 nm ultraviolet (u.v.) light. The kinetics of virus inactivation revealed decreased sensitivity of IdUrd-substituted virions to irradiation with 302 nm light under all conditions examined, and with 254 nm u.v. light when substituted and control virions were irradiated at equal particle concentrations. Comparison of virus survival after irradiation measured in Vero or Xeroderma Pigmentosum (complementation group A) cells indicated that cellular repair of ultraviolet-induced lesions was not a significant factor in the observed decrease in u.v. sensitivity. IdUrd substitution altered neither the formation of ultraviolet-induced thymidine photoproducts nor the ability of irradiated virions to express delayed early viral enzymes (thymidine kinase, DNA polymerase). It is suggested that nucleocapsid proteins or the highly ordered structure of IdUrd-substituted virions play a key role in u.v. desensitization, either by the formation of non-lethal photoproducts or by the prevention of the formation of DNA-uracilyl free radicals.

Antiviral activity of SK&F 21681 against herpes simplex virus

SK&F 21681 (3,10-dimethyl-10-H-s-triazolo[4',3':2,3]-as-triazino-[ 5,6-b]indole) is an inhibitor of the growth of herpes simplex viruses types 1 and 2 at a concentration of 60 micrograms/ml. It inhibits the synthesis of the viral DNA and the formation of virus particles, although the viral polypeptide synthesis is not significantly affected by this compound. Mutants of herpes simplex viruses types 1 and 2 which are able to grow in the presence of SK&F 21681 were isolated. They induced normal levels of thymidine kinase and DNA polymerase activities in the infected cells and did not show resistance to either 9-[2-hydroxyethoxymethyl] guanine or phosphonoacetic acid.

Characterization of an herpes simplex virus type 2 mutant, which is resistant to acycloguanosine and causes fusion of BSC1 cells

A mutant of herpes simplex virus type 2, which induces low levels of thymidine-kinase activity in infected BSC1 cells and consequently able to grow in the presence of acycloguanosine, was isolated. This mutant has also been shown to cause fusion of BSC1 cells. In BSC1 cells, co-infected with the wild-type strain and the mutant, the yield of each of the two viruses was normal but the rounding and aggregation of cells observed, resembled that found in wild-type infected cultures. When the mixed infection was performed in the presence of acycloguanosine (100 micrometers), the growth of the two virus strains was inhibited, as well as the cytopathic effect in the cultures. It is suggested that under these conditions, the thymidine-kinase which was induced in the infected cells by the wild-type strain, phosphorylated acycloguanosine and the activated drug formed, inhibited the growth of the two viruses by interference in their DNA syntheses.