Continued expression of a poly(A)+ transcript of herpes simplex virus type 1 in trigeminal ganglia of latently infected mice.

Radioactively labeled cDNAs were prepared by using as the template poly(A)+ mRNA from trigeminal ganglia of mice latently infected with herpes simplex virus type 1. These cDNAs were used as hybridization probes for Southern blots of cloned herpes simplex virus type 1 DNA fragments. Specific hybridization to fragments from the terminal repetition of the L segment was detected with probes derived from mRNAs obtained as early as 3 weeks and as late as 17 months postinoculation. Fine mapping of the region of hybridization showed that the viral transcripts originated from DNA sequences coding for the immediate-early gene IE-1 (alpha-0). These results indicate that IE-1, or an as yet unidentified gene colinear with it, is continuously expressed during latency.