Latency-associated transcript but not reactivatable virus is present in sensory ganglion neurons after inoculation of thymidine kinase-negative mutants of herpes simplex virus type 1

The presence of herpes simplex virus (HSV) latency-associated transcript (LAT) was investigated in sensory ganglion neurons of mice after inoculation with thymidine kinase (TK) mutants of HSV. Ganglion serial sections were examined in order to quantitate numbers of LAT-positive neurons. After inoculation with TK-positive HSV, virus was isolated during latency from explants of most ganglia, and LAT was detected by in situ hybridization in 96% of ganglia. After inoculation with HSV TK mutants, virus was isolated from 0% of ganglia, but LAT was detected in 95 to 100% of ganglia. After inoculation of TK mutants of HSV, therefore, although latent infection as indicated by the isolation of virus from ganglion explants was not detected, the presence of LAT was common. These results suggest that the lack of reactivatable virus after inoculation of HSV TK mutants may be related to a role for HSV TK expression in the reactivation process.