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A Mallakin, ME Myles, S Higaki, K Maruyama, NM Sawtell, RL Thompson, JM Hill; Title: HSV-1 LAT Null Mutant has Low In Vivo Reactivation Frequency with an Increased Corneal Virulence in the Rabbit Eye Model . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4322.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To determine if a LAT null mutant (17AH) with a large deletion (1.9 kb that includes the entire LAT promoter and 827 bp of the 5’ end of the primary LAT transcript) shows altered corneal virulence and/or reactivation phenotype compared with the parental (17 Syn+) and rescued (17AHR1) virus. Methods:Rabbit corneas were scarified and inoculated with 25 ml (2 x 105 PFU/eye) of the three viruses: 1) parental (17 Syn+), 2) LAT null mutant (17AH) and 3) LAT+ rescue (17AHR1). Infection was assessed by slit lamp examination (SLE) every other day from day 3 to day 21. All eyes that recovered (intact corneal epithelium and no stromal lesions) received transcorneal iontophoresis of epinephrine for three consecutive days. Ocular swabs to detect infectious HSV-1 were done for seven consecutive days. Results:Significant stromal involvement was seen in 20% of the LAT null mutant (17 AH) eyes after infection; eyes infected with the parental and rescued viruses showed essentially no stromal lesions. All eyes used in reactivation experiment were judged normal by SLE before epinephrine iontophoresis. After iontophoresis, positive eyes for infectious virus were obtained from 1 of 8 eyes (13%) in the LAT null mutant (17AH) group, 13 of 18 eyes (72%) in the parental (17 Syn+) group, and 11 of 17 eyes (65%) in the rescued virus (17AHR1) group. The percentage of swabs positive for infectious virus was low (3/56: 5%) in the LAT null mutant group, compared with the parental group (62/126: 49%) and the rescued virus group (38/119: 32%). To determine the correlation between reactivation and genome copy number in this study, TG from rabbits were collected and will be examined by quantitative PCR assay for the genome copy number. Conclusion:The parental (17 Syn+) and rescued (17AHR1) virus had high reactivation frequency following epinephrine iontophoresis. Rabbits latently infected with the LAT null mutant (17AH) showed significantly decreased reactivation (5%), compared to the reactivation frequency in rabbits infected with the parental and rescued viruses. A unique feature of the 17AH LAT null mutant is an increase in stromal disease during the acute phase of the infection.
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