March 18, 2009

HPV Infection Rates High in HIV-Positive MSM

Nearly 100 percent of HIV-positive men who have sex with men (MSM) are infected anally with the human papillomavirus (HPV), and once infected, few are able to clear the virus, according to a study published in the April 1 issue of The Journal of Infectious Diseases and reported by aidsmap.

HPV is a known cause of genital warts and both anal and cervical cancer. Some strains are more likely to cause the warts, while others are likely to lead to cancer. Researchers have previously found high rates of HPV infection among MSM, and even higher rates among HIV-positive men. No large studies, however, have documented changes in infection rates—either acquiring new HPV strains or clearing the virus—over a period of time.

Alexandra de Pokomandy, MD, from the University of Montreal in Canada, set out to do just that, and she and her colleagues enrolled 247 HIV-positive MSM, conducting regular questionnaires, anal swabs and anal biopsies on the participants during an average of three years. The average age of the study participants at study entry was 43, and 38 percent were smokers, which is a known risk factor for cervical cancer in women with HPV infection. On average, the men had been living with HIV for about a decade, and 93 percent were receiving antiretroviral therapy.

Pokomandy and her colleagues found that 98 percent were infected with HPV. Most were infected with multiple strains of HPV, and the majority had at least one strain of the virus associated with anal cancer. The study also found that men continued to become infected with new strains over time. These numbers represent infection rates that are three times higher than in HIV-negative MSM in other studies. Moreover, the authors found that fewer than 13 percent were able to clear HPV infection.

Pokomandy’s team hopes to explore the actual risk of precancerous (dysplasia) and cancerous lesions in this population as the study continues. In the meantime, aidsmap comments that the results reported so far indicate that the new HPV vaccine may have limited benefit in HIV-positive men —it may only be effective for men who have not yet become sexually active with other men.

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