Detection and preliminary characterization of herpes simplex virus type 1 transcripts in latently infected human trigeminal ganglia.

RNA extracted from human trigeminal ganglia was examined for the presence of herpes simplex virus type 1 (HSV-1) transcripts by Northern hybridization (RNA blot) analysis. By using cloned DNA and single-stranded RNA probes, two abundant colinear HSV-1 transcripts (1.85 and 1.35 kilobases) were detected in ganglia from 9 of 17 individuals. These RNAs overlap the 3' end of the transcript for immediate-early gene ICP0 but are transcribed from the opposite strand; thus, they are antisense relative to the ICP0 mRNA. We also report evidence by in situ hybridization that these latently infected ganglia contain HSV-1 RNA homologous to the BamHI SP region of the genome which is transcribed in the same direction as the other latency transcripts. In Vero cells productively infected with laboratory strain HSV-1 KOS and in cultures infected with different low-passage clinical isolates, only the 1.85-kilobase transcript was detected, and there was variation in the size of this larger latency transcript. These novel transcripts may play a role in maintaining HSV-1 latency in human ganglia.