HERPES-SIMPLEX VIRUS TYPE-1 GENE-EXPRESSION AND REACTIVATION OF LATENT INFECTION IN THE CENTRAL-NERVOUS-SYSTEM

Restricted gene expression takes place during latent infection of herp es simplex virus type 1 (HSV-1) in the human peripheral nervous system and has been linked with viral reactivation. The state of HSV-1 gene expression in the central nervous system (CNS) during latency is uncle ar and we, therefore, examined gene expression in the brainstem of exp erimental mice and normal humans. Only part of the transcription patte rn present during latent infection in peripheral sensory ganglia (PSG) was identified in the human brainstem by in situ hybridization and No rthern blot analysis for HSV-1-specific transcripts. Instead of three HSV-1 latency-associated transcripts (LATs) present in PSG and demonst rated by Northern blot analysis, only one was identified in mouse brai nstem and none was detected in human brainstem. These findings might b e attributed to the relatively low amounts of HSV-l-specific latency-a ssociated RNAs in brainstem tissue. Combined with our inability to rea ctivate HSV-1 from explanted mouse brainstem, these findings suggest t hat tissue levels of latency-associated gene expression play a role in HSV-1 reactivation and have relevance to the very low incidence of HS V-l-induced CNS disease compared with peripheral mucocutaneous disease .