Latency of herpes simplex virus type-1 in human geniculate and vestibular ganglia is associated with infiltration of CD8+ T cells

Herpes simplex virus type-1 latency and CD8+ T-cell occurrence were investigated in the trigeminal, geniculate, and vestibular ganglia from seven deceased humans. The HSV-1 "latency-associated transcript" was assessed by in situ hybridization and quantitative RT-PCR. Infiltration of CD8+ T cell was detected by immunohistochemistry and quantitative RT-PCR. The data show that HSV-1 latency and CD8+ T-cell infiltration are not solely confined to the trigeminal ganglia but can also occur in other cranial ganglia along the neuroaxis. However, the HSV-1 latency transcripts in the geniculate and vestibular ganglia were expressed at a very low level. The difference in CD8 transcript levels among HSV-1 latently infected trigeminal ganglia, geniculate, and vestibular ganglia was less conspicuous. Colocalization of latent HSV-1 and CD8+ T cells in geniculate and vestibular ganglia supports further the hypothesis that HSV-1 reactivation is possible in these ganglia and is the cause of Bell's palsy and vestibular neuritis.