Exposure to u.v. radiation increases the local level of prostaglandins which may play a role in u.v. radiation-induced herpes simplex virus (HSV) recurrences. We used the guinea-pig model of u.v. radiation-induced recurrent genital HSV-2 disease for examining the effects of indomethacin, a prostaglandin inhibitor, on u.v.-induced recurrences. In the first experiment, performed 100 days after HSV-2 inoculation, treatment with indomethacin for 5 days begun 24 h before u.v.-irradiation decreased the proportion of animals developing HSV disease recurrences from 11/13 (84.6%) to 2/13 (15.4%) (P < 0.001). In the second experiment, performed 135 days after HSV-2 inoculation, treatment with indomethacin for 5 days begun 24 h before u.v.-irradiation decreased the number of animals developing recurrences from 12/21 (57.1%) to 5/21 (23.8%) (P < 0.05). Five days of indomethacin treatment begun 4 h after u.v.-irradiation, however, did not reduce the percentage of animals developing disease recurrences but did decrease the mean number of days with recurrent lesions in animals that developed recurrences. Our data suggest that indomethacin may modify u.v. radiation-induced recurrent lesions by decreasing viral reactivation when given before u.v. radiation exposure or by reducing prostaglandin-induced immunosuppression when given before or after exposure. Future studies are needed for evaluating indomethacin prophylaxis for recurrent HSV disease when prolonged u.v. radiation exposure is anticipated.
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