HERPES-SIMPLEX VIRUS GENOME REPLICATION AND TRANSCRIPTION DURING INDUCED REACTIVATION IN THE RABBIT EYE

PCR analysis of herpes simplex virus (HSV) genome replication and prod uctive cycle transcription was used to examine the role of the cornea in the latency-associated transcript (LAT)-mediated reactivation of HS V type 1 (HSV-1) in the rabbit eye model. The reduced relative reactiv ation frequency of 17 Delta Pst (a LAT(-) virus) compared to those of wild-type and LAT(+) rescuants correlated with reduced levels of viral DNA and transcription in the cornea following epinephrine induction. The timing of virus appearance in the cornea was most consistent with tissue peripheral to the cornea itself mediating a LAT-sensitive step in the reactivation process. Specific results include the following. ( i) While viral DNA was found in the corneas of rabbits latently infect ed with either the LAT(+) or LAT(-) virus prior to and during the firs t 16 to 24 h following induction, more was found in animals infected w ith the LAT(+) virus. (ii) A significant increase in levels of viral D NA occurred 20 to 168 h following induction. (iii) The average relativ e amount of viral DNA was lower at all time points following reactivat ion of animals infected with the LAT(-) virus. (iv) Expression of prod uctive cycle transcripts could be detected in corneas of some rabbits latently infected with either the LAT(+) or LAT(-) virus, and the amou nt recovered and the timing of appearance differed during the reactiva tion of rabbits latently infected with the LAT(+) or LAT(-) virus. (v) Despite the reduced recoveries of LAT(-) virus DNA. and productive-cy cle transcripts in reactivating corneas in vivo compared to those of t heir LAT(+) counterparts, such differences were not detected in cultur ed keratinocytes or in experiments in which relatively high titers of virus were superinfected into the eyes of latently infected rabbits. ( vi) A number of LAT(+)-virus-infected rabbits expressed LAT in corneas isolated from uninduced rabbits. When seen, its amount,vas significan tly higher than that of a productive-cycle (VP5) transcript.