NEURONS CONTAINING LATENCY-ASSOCIATED TRANSCRIPTS ARE NUMEROUS AND WIDESPREAD IN DORSAL-ROOT GANGLIA FOLLOWING FOOTPAD INOCULATION OF MICE WITH HERPES-SIMPLEX VIRUS TYPE-1 MUTANT IN 1814

The herpes simplex virus type 1 (HSV-1) mutant in1814 lacks the abilit y to trans-activate immediate early gene transcription and enter lytic replication but it can establish and reactivate from latency. We ther efore investigated the number of neurons that expressed latency-associ ated transcripts (LATs) in animals latently infected with in 1814, the rescued revertant (1814R), or wild-type (wt) HSV-1. The percentage of LAT+ neurons increased with increasing doses of each of the viruses. After inoculation of equal amounts of infectious virus many more LAT- neurons were observed in animals infected with in1814 than with 1814R or wt HSV-1. Whereas the LAT+ neurons in animals infected with 1814R o r wt HSV-1 were largely confined to lumbar dorsal root ganglia (DRG) L 4/L5/L6 (those which innervate the lower leg), in animals infected wit h in 1814 they were also present in DRG not directly involved with suc h innervation (thoracic 12 and 13, L1, L2 and L3). We concluded that t he large number of LAT+ neurons observed with in1814 was related to th e high particle numbers in the inoculum and that spread of virus was r elated to limited replication as well as to the low neurovirulence of in1814. This spread was not unique to in1814 but when it occurred with more virulent viruses such as 1814R or wt HSV-1, it resulted in the d eath of the host.