Anal infection with human papillomavirus (HPV) was almost universal amongst HIV-positive gay men in a Canadian study published in the April 1st edition of the Journal of Infectious Diseases. The study also found that there was a high prevalence of infection with cancer-associated strains of human papilloma virus and that few men cleared such infections during the course of the study.
Furthermore, during the three years of the study a significant proportion of men became infected with strains of HPV associated with a high risk of pre-cancerous and cancerous cell changes in the anus.
The findings of the study are likely to inform the emerging debate about the value of providing HIV-positive individuals with the recently approved vaccines for HPV. Although the use of these vaccines is only approved for girls in their early teens, some HIV physicians are privately speculating that it may be worthwhile screening their patients for infection with strains of human papilloma virus associated with a high risk of anal and cervical cancer and administering the vaccine to patients who are not infected.
HIV-positive gay men are significantly more likely to develop pre-cancerous and cancerous cell changes in their anus than HIV-negative gay men. HIV treatment does not appear to offer direct protection against the development of anal cancer.
Development of pre-cancerous and cancerous cell changes in the anus is strongly associated with certain strains of human papilloma virus.
Previous research has found a high prevalence of anal infection with HPV in HIV-positive gay men, but there is little information on the natural history of such infections in this population.
Canadian researchers from the HIPVIRG (Human Immunodeficiency and Papilloma Virus Research Group) therefore designed a three-year prospective study involving 247 HIV-positive gay men to answer this and a number of other questions.
Men recruited to the study were assessed for infection with human papilloma virus at baseline and followed up every six months for three years for further evaluation. Blood tests were performed to determine which strains of HPV patients were infected with. Demographic information was also obtained, as was information on the use of HIV treatment, CD4 cell count and viral load.
The mean age of men participating in the study was 43 years. The average (median) duration of HIV infection was eleven years, and 36% of men had been diagnosed with AIDS. On entry to the study, the median CD4 cell count was 380 cells/mm3 and 56% of individuals had an undetectable viral load. A total of 93% of patients were taking HIV treatment. The mean duration of follow up was 31 months. After 24 months of follow-up, median CD4 cell count had increased from baseline to 480 cells/mm3.
Testing conducted on entry to the study showed that almost all (98%) of the men had anal infection with human papilloma virus. Of the five men not infected at baseline, three acquired anal HPV infection during the course of the study.
Most of the men (91%) were infected with multiple strains of human papilloma virus (median, five strains).
The most prevalent type of human papilloma virus was the cancer-associated HPV-16 (38%), HPV-6 infection was present in 35% of men, HPV-42 in 29%, and HPV-18, another type strongly associated with a high risk of anal cancer, was present in 25%.
Few of the men cleared the infection. The strain of human papilloma virus with the lowest clearance rate was HPV-16 (twelve episodes cleared per 1000 person-months). The clearance rate of HPV-18 was 20 per 1000 person-months.
There was also a high rate of new human papilloma virus infections in the study. Over a third of patients uninfected with HPV-16 acquired the infection during the course of the study, with 13% becoming infected with HPV-18. No information was provided by the investigators about the role or otherwise of immune reconstitution in the clearance of HPV infection.
"HIV infection not only increases HPV persistence but also increases the risk of acquisition of new HPV infections and reactivation of latent infections," write the investigators.
De Pokomandy A et al. Prevalence, clearance, and incidence of anal human papillomavirus infection in HIV-infected men: the HIPVIRG study. J Infect Dis 199: 965-73, 2009.