Journal of Virology, September 2001, p. 8166-8172, Vol. 75, No. 17
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.17.8166-8172.2001
Medical Virology Section, Laboratory of Clinical Investigation, National Institute of Allergy and Infectious Diseases,1 and Division of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration,2 Bethesda, Maryland 20892
Received 17 January 2001/Accepted 18 May 2001
To better understand the mechanisms responsible for the observed
effects of deletions in the promoter region of the latency-associated transcript (LAT) gene in impairing herpes simplex virus (HSV) reactivation, we generated mice transgenic for a 5.5-kb HSV type 2 (HSV-2) genomic fragment spanning the major LAT, along with the
LAT promoter and flanking regions, in the C57BL/6 background. The mice
expressed abundant 2.2-kb major LATs in trigeminal ganglia (TG) and
other tissues. The effects of the transgene on HSV-2 infection,
latency, and reactivation were assessed. When infected with wild-type
(WT) HSV-2 or its LAT promoter deletion (LAT
) mutant,
primary lung fibroblast lines established from normal C57BL/6 and
transgenic mice supported virus growth equally well. The replication of
these viruses in the mouse eye and their spread to TG and brains were
similar. The quantities of latent viral DNA in TG of transgenic and
normal mice, as determined by real-time PCR, were comparable. UV
light-induced reactivation of the LAT
mutant from
transgenic mice (0 to 7%) was no more frequent than that from normal
mice (0 to 14%), while WT virus was reactivated from 13 to 54% of
normal mice and 22 to 54% of transgenic mice. The cumulative data
indicate that, when expressed transgenically, the HSV-2 major LAT
cannot influence HSV-2 infection or latency and cannot complement the
defect in reactivation of the LAT
mutant. These results
imply that the phenotype of reduced reactivation associated with the
LAT
mutant is related to a function encoded in the LAT
promoter but not to the major LAT itself.
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