Marla Husnik, a biostatistician in the Vaccine and Infectious Disease Institute, co-authored a study that associated infection with anal human papillomavirus (HPV)—a virus that can cause anal and cervical cancers—with a higher risk of new HIV infection in previously HIV-negative men who have sex with men (MSM). Led by Dr. Peter Chin-Hong of the University of California, San Francisco, the study now appears on online ahead of print in the journal AIDS.
In previous studies, other sexually transmitted infections have been associated with higher risk of HIV infection and HPV is the most common sexually transmitted infection.
“We analyzed data from a subset of participants within the EXPLORE study—a large proof-of-concept clinical trial conducted in six cities in the U.S. from 1999-2003—among 4,295 MSM who were at high risk for HIV infection,” Husnik said. “Our analysis included 1,409 of these men who were also tested for HPV infection. Results indicated a strong independent association for increased risk of HIV acquisition among the men infected with multiple anal HPV types.”
The study was conducted at clinical sites in Boston, Denver, New York and San Francisco. Behavioral risk factors associated with HIV-infection, blood testing and HPV cytology were assessed every six months for up to four years during the study.
"We think that HPV enhances susceptibility to HIV infection through two mechanisms. Anatomically, the virus causes anal lesions. These lesions bring blood vessels closer to the surface and also the lesions' skin layer is thinner and more easily shredded, which frequently causes bleeding. These disruptions of the mucosal barrier could allow easier entry for HIV," Chin-Hong said.
In addition, HPV activates the immune system. The inflammatory cells recruited to the HPV lesions—dendritic cells, macrophages and CD4 T cells—are the immune cells most susceptible to HIV infection.
HPV vaccine effectively prevents acquisition of the virus by women. Clinical trials testing the effectiveness of the vaccine in MSM are currently under way.
Co-authors of the study include researchers from the University of Pittsburg, San Francisco Department of Public Health, Centers for Disease Control, Denver Department of Public Health, New York Blood Center and Fenway Community Health Center in Boston.
[Adapted from a news release from the University of California, San Francisco.]