Viral-specific thymidine kinase in sensory ganglia of mice infected with herpes simplex virus.

Dorsal root ganglia (DRG) from herpes simplex virus (HSV)-infected mice were assayed for thymidine kinase (TK) activity at various times after infection. Polyacrylamide-gel electrophoresis revealed two peaks of activity with Rf values ranging from 0.18 to 0.24 (peak I) and 0.40 to 0.46 (peak II). In contrast, DRG from uninfected animals showed only one peak of enzyme activity with an R_f of 0.23. Incubation of infected DRG extracts with anti-HSV γ-globulin eliminated the TK activity in peak II but had no effect on the TK activity in peak I or on the TK activity found in DRG extracts from vaccinia-infected mice. The demonstration that infectious virus could be recovered from cell-free ganglionic homogenates for only 14 days, while HSV-specific TK (peak II) could be detected for up to 60 days, suggests that at least a portion of the viral genome is being continually or intermittently expressed during the chronic phase of the infection.