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Journal of Virology, February 1999, p. 920-929, Vol. 73, No. 2
Ophthalmology Research Laboratories,
Cedars-Sinai Medical Center Burns & Allen Research Institute, Los
Angeles, California 90048,1 and
Department of Ophthalmology, UCLA School of Medicine, Los
Angeles, California 900242
Received 18 September 1998/Accepted 22 October 1998
The herpes simplex virus type 1 (HSV-1) latency-associated
transcript (LAT) gene is essential for efficient spontaneous
reactivation of HSV-1 from latency. We previously reported that
insertion of the LAT promoter and just the first 1.5 kb of the 8.3-kb
LAT gene into an ectopic location in the virus restored wild-type
spontaneous reactivation to a LAT null mutant. This mutant, LAT3.3A
(previously designated LAT1.5a), thus showed that the expression of
just the first 1.5 kb of LAT is sufficient for wild-type spontaneous
reactivation. We also showed that in the context of the entire LAT
gene, deletion of LAT nucleotides 76 to 447 (LAT mutant
dLAT371) had no effect on spontaneous reactivation or
virulence. We report here on a LAT mutant designated LAT2.9A. This
mutant is similar to LAT3.3A, except that the ectopic LAT insert
contains the same 371-nucleotide deletion found in dLAT371.
We found that LAT2.9A had a significantly reduced rate of spontaneous
reactivation compared to marker-rescued and wild-type viruses. This was
unexpected, since the combined results of dLAT371 and
LAT3.3A predicted that spontaneous reactivation of LAT2.9A would be
wild type. We also found that LAT2.9A was more virulent than wild-type
or marker-rescued viruses after ocular infection of rabbits. This was
unexpected, since LAT null mutants and LAT3.3A have wild-type
virulence. These results suggest for the first time (i) that regions
past the first 1.5 kb of LAT can compensate for deletions in the first
1.5kb of LAT and may therefore play a role in LAT dependent spontaneous
reactivation and (ii) that regions of LAT affect viral virulence.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
A Herpes Simplex Virus Type 1 Latency-Associated
Transcript Mutant with Increased Virulence and Reduced
Spontaneous Reactivation
*
Corresponding author. Mailing address: Ophthalmology
Research Laboratories, Cedars-Sinai Medical Center Burns & Allen
Research Institute, Davis Bldg., Rm. 5072, 8700 Beverly Blvd., Los
Angeles, CA 90048. Phone: (310) 855-6457. Fax: (310) 652-8411. E-mail: Wechsler{at}CSMC.edu.
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