THE PERSISTENT ELEVATED CYTOKINE MESSENGER-RNA LEVELS IN TRIGEMINAL GANGLIA OF MICE LATENTLY INFECTED WITH HSV-1 ARE NOT DUE TO THE PRESENCE OF LATENCY-ASSOCIATED TRANSCRIPT (LAT) RNAS

Trigeminal ganglia (TG) from mice latently infected with wild type HSV -1 contain detectable levels of cytokine transcripts that are not pres ent in TG from uninfected mice. This suggests that during HSV-1 neuron al latency, the immune system is stimulated by the production of one o r more viral proteins. Since the LAT (latency associated transcript) g ene is essential for wild type levels of spontaneous reactivation and is the only highly active viral gene during latency, the stimulation o f cytokines may indicate the presence of a LAT encoded latency protein . We therefore compared the cytokine transcript profiles in the TG of mice latently infected with wild type and LAT negative viruses. Mice w ere latently infected with either: (1) the LAT null mutant dLAT2903; ( 2) its marker rescued virus dLAT2903R; or (3) the parental wild type H SV-1 strain McKrae. As expected, reactivation following explant cultiv ation of TG from latently infected mice was significantly decreased wi th dLAT2903 (P < 0.05)(40 +/- 8%, n = 24) compared with dLAT2903R (85 +/- 7.6%, n = 36) or the parental virus (70 +/- 10.0%, n = 36). The re lative levels of various cytokines was determined by RT-PCR analysis o f TG extracts. None of the cytokine transcripts detected in mice laten tly infected with the wild type or marker rescued viruses were missing or decreased in mice latently infected with the LAT null mutant 30 or 60 days post infection. There were also no differences in the HSV-1 a ntibody titers induced by the LAT negative virus compared to the LAT p ositive viruses. Thus, although LAT facilitated reactivation of HSV-I from explanted mouse TG, expression of LAT during latency did not appe ar to be involved in persistent cytokine expression in TG. This sugges ts that during latency, HSV-1 does not produce a highly antigenic abun dant LAT encoded protein. (C) 1998 Elsevier Science B.V. All rights re served.