Stimulation of human cell DNA synthesis by defective herpes simplex virus type 2

Abstract

To elucidate herpes simplex virus type 2 (HSV-2) stimulation of cellular DNA synthesis, human embryonic fibroblast (HEF) cells were made quiescent in DNA synthesis by treatment with low serum medium before infection at 42°. Results indicated by that HSV-2 stimulated at least two cycles of cellular DNA synthesis. Exposure of HSV-2 to ultraviolet (uv) light for 30 sec inactivated the ability of virus to expand intracellular [ 3H]TdR pools; however, the ability of virus to stimulate cellular DNA synthesis was increased. Longer exposures to uv (120 sec) abolished virus stimulation of cellular DNA synthesis. Stocks enriched for defective virus by serial undiluted passage stimulated a significantly higher amount of [ 3H]TdR incorporation into cellular DNA than standard virus stocks. Data from combined autoradiography and immunofluorescence experiments indicated that during the first cycle of stimulation 30% of the abortively infected cells synthesized viral antigens; about 1% of these cells was simultaneously stimulated in cellular DNA synthesis. Bromodeoxyuridine density-labeling experiments revealed that between 0 and 24 hr HSV-2 stimulated predominantly semiconservative and some repair synthesis of cellular DNA; between 48 and 72 hr virus stimulated only semiconservative cellular DNA synthesis. In conclusion, stimulation of cellular DNA synthesis required viral gene expression and was most likely mediated by defective HSV-2 present in standard virus stocks.