The effect of gramicidin, a topical contraceptive and antimicrobial agent with anti-HIV activity, against herpes simplex viruses type 1 and 2 in vitro

The effect of an anti-HIV compound, gramicidin, previously used as a topical antibiotic and vaginal contraceptive, on the replication of herpes simplex viruses (HSV) type 1 and 2 has been examined. Human WI-38 fibroblasts were inoculated with either HSV type in the presence of serial dilutions of gramicidin and reduction in viral yield was measured by ELISA. The 50% inhibitory dose (IC50) of gramicidin against 3 HSV-1 and 4 HSV-2 isolates was equal to 0.3 microgram/ml and was comparable to the efficacy of the anti-HSV agent acyclovir (ACV). The IC50 of gramicidin required to protect WI-38 from cytolytic effect of HSV was 10 micrograms/ml at day 5 postinfection, indicating that at this time point the activity of gramicidin was inferior than that of ACV. Nevertheless, gramicidin suppressed the replication of ACV-resistant thymidine kinase and DNA polymerase HSV mutants at doses effective against ACV-sensitive strains. The results suggest that the antimicrobial and spermostatic agent, gramicidin, has potential against sexually transmitted diseases (STDs) and for prophylaxis of sex-borne HIV and HSV infections.