Gb. Devirao et al., HERPES-SIMPLEX VIRUS TYPE-1 DNA-REPLICATION AND GENE-EXPRESSION DURING EXPLANT-INDUCED REACTIVATION OF LATENTLY INFECTED MURINE SENSORY GANGLIA, Journal of virology, 68(3), 1994, pp. 1271-1282
Infectious virus assays and PCR amplification of DNA and RNA were used
to investigate herpes simplex virus DNA replication and gene expressi
on in two murine in vitro models for virus reactivation. We examined l
atent infections with wild-type (wt), precisely defined latency-associ
ated transcript-negative (LAT(-)) mutants, and LAT(+) rescuants of the
se mutants of the 17syn(+) strain of virus in both murine trigeminal a
nd lumbosacral ganglia and of the KOS(M) strain in the latter. In expl
ants of ganglia latently infected with the LAT(-) mutant of strain 17s
yn(+) virus, a reduction in number of cultures exhibiting cytopathic e
ffects due to virus reactivation and measurable delays in virus recove
ry were observed compared with wt or the LAT(+) rescuant. This LAT-spe
cific effect was not seen in explants of lumbosacral ganglia latently
infected with mutants derived from the KOS(M) strain of virus. Althoug
h there was appreciable variation between individual animals, no signi
ficant difference between LAT(+) and LAT(-) virus in time of onset of
viral DNA replication in explanted ganglia was seen with use of either
virus strain. There was a slight decrease in the relative amount of v
iral DNA recovered compared with internal cellular controls in latentl
y infected ganglia harboring the LAT(-) mutant of 17syn(+) compared wi
th the wt virus or the LAT(+) rescuant. This reduced relative amount r
anged from 0 to as much as 50% but averaged 20%. Such differences were
not seen in infections with KOS(M)-derived mutants. In contrast, alth
ough expression of productive-cycle transcripts could be detected with
in 4 h following explant cultivation of latently infected ganglia, no
differences between LAT(+) and LAT(-) viruses could be seen. As discus
sed, these data place specific constraints on possible models for the
role of LAT expression in in vitro reactivation systems.