Inactivation of Papillomavirus by Low Concentrations of Povidone-Iodine

BACKGROUND AND OBJECTIVES: A recent report by Hermonat et al showed that nonoxynol 9 is completely inactive against bovine papillomavirus, which is very closely related to human papillomavirus. Finding a vaginal microbicide active against human papillomavirus to reduce the risk of sexual transmission of human papillomavirus would be desirable. GOAL OF THIS STUDY: To determine whether povidone-iodine is active in vitro against bovine papillomavirus. METHODS: A bovine papillomavirus-1 stock prepared by extraction of a fibropapilloma was treated with various concentrations of povidone-iodine. The virus/povidone-iodine samples were incubated at 37 degrees C for 15 minutes and then placed on contact-inhibited cells of mouse fibroblast line C127 in 10-cm tissue culture dishes for the transformation assay. At 2 weeks post-infection, oncogenic foci induced by bovine papillomavirus appeared and were counted after the cells were fixed with 4% formaldehyde and stained with methylene blue. RESULTS: Approximately 90% inactivation of papilloma virus was demonstrated with exposure to 0.1% povidone-iodine, and 99.9% inactivation was seen at 0.3%. CONCLUSIONS: The concentrations of povidone-iodine that were effective in this study are lower than concentrations in available over-the-counter preparations of povidone-iodine. Additional research is needed to verify whether papillomavirus is susceptible to other, more acceptable agents. Clinical trials may be warranted to determine whether povidone-iodine or other agents would reduce the rate of sexual transmission of the human papillomavirus strains associated with cervical cancer.