Cell killing by spleen necrosis virus is correlated with a transient accumulation of spleen necrosis virus DNA.

Spleen necrosis virus productively infects avian and rat cells. The average number of molecules of unintegrated and integrated viral DNA in cells at different times after infection was determined by hybridization and transfection assays. Shortly after infection, there was a transient accumulation of an average of about 150 to 200 molecules of unintegrated linear spleen necrosis virus DNA per chicken, turkey, or pheasant cell. No such accumulation was seen in infected rat cells. Soon after infection there was in chicken cells, but not inturkey, pheasant, or rat cells, also a transient integration of an average of 35 copies of viral DNA per cell. By 10 days after infection, the majority of this integrated viral DNA was lost from the population of infected chicken cells. At the same time, the majority of the unintegrated viral DNA was also lost from infected chicken, turkey, and pheasant cells. The transient cytopathic effect seen in these infected cells also occurred at this time. Late after infection about five copies of apparently nondefective spleen necrosis proviruses were stably integrated at multiple sites in chicken, turkey, pheasant, and rat DNA. These results demonstrate a correlation between the transient accumulation of large numbers of spleen necrosis virus DNA molecules and the transient occurrence of cytopathic effects.