Evidence for multiple processes affecting virus survival in irradiated mammalian cells

The survival curves of uv-irradiated herpes simplex virus assayed in uv- or x-irradiated rat cells were analyzed with regard to radiation-enhanced reactivation (RER) and other processes produced by cell irradiation. Results in rat mammary tumor cells (which express RER) and in rat embryo cells (which do not express RER) were compared. Irradiation of the cells caused a change in virus survival in both cell types, which was partially expressed as a decrease in the extrapolation of the second component of the virus survival curve. RER was expressed as a change in the D0(1/slope) of the survival curves and reached a plateau level by 6 J/m2 or 10 Gy of cell irradiation. These two types of changes in the virus survival curves are apparently independent. An additional process occurred in heavily uv-irradiated tumor cells which cannot be easily interpreted. A brief analysis of methods to quantitate RER indicates that the D0 of the virus survival curve is more useful than the commonly used reactivation factor