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AIDS 2012: Human Papillomavirus Doubles Risk of HIV infection

Pre-existing human papillomavirus (HPV) infection is associated with a 2-fold increase in the risk of HIV acquisition in women, and risk also rose for both heterosexual and gay/bisexual men, according to an 8-study review presented at the recent XIX International AIDS Conference (AIDS 2012) in Washington, DC, and published in the August 7, 2012, advance online edition of AIDS.

HPV is a common sexually transmitted infection that many people acquire soon after they become sexually active. High-risk, or oncogenic, types including HPV-16 and HPV-18 cause cervical and anal cancer; other types cause warts. Vaccines can protect against the most common cancer-causing types, and vaccination is now recommended for young women and men ages 9-26 years.

It has long been recognized that HIV positive people are more likely to have HPV, carry more different HPV types on average, and are less likely to spontaneously clear that virus. Some evidence suggests the reverse is also true, with HPV increasing the likelihood of HIV infection.

Catherine Houlihan from the London School of Hygiene and Tropical Medicine and an international team of colleagues performed a systematic review and meta-analysis to look for evidence that prevalent or pre-existing HPV increases the risk of acquiring HIV.

The researchers identified studies meeting inclusion criteria in the Pubmed and Embase medical literature databases and conference abstracts through the end of July 2011. Eligible studies were longitudinal or case-control, identified HPV DNA by standard sensitive tests, and determined HPV status both before and after HIV acquisition. They evaluated publication bias and statistical heterogeneity, and calculated "population-attributable fractions," or proportion of HIV infections attributable to pre-existing HPV.

Results

• 8 published studies were included in the review, along with further previously unpublished data from 5 of the authors.
• All but 1 were conducted in the U.S., the other in South Africa.
• 6 studies looked at women, 1 at heterosexual men, and 1 at men who have sex with men.
• 7 of these studies found an association between prevalent HPV and risk of HIV acquisition.
• HIV risk doubled among women with pre-existing infection with any HPV type (hazard ratio [HR]  2.06).
• However, the researchers noted that some studies did not adequately adjust for confounding factors, and comparison groups varied across studies.
• The association was similar for both high-risk and low-risk HPV types (HR 1.99 and 2.01, respectively), with weak evidence of publication bias.
• The 2 studies of men also showed associations between HPV and HIV acquisition(meta-analysis was not possible due to limited data).

o   HPV infection of the penis among heterosexual men nearly doubled the risk of contracting HIV (adjusted HR 1.8);

o   Anal HPV infection among gay/bisexual men more than tripled the risk of contracting HIV (adjusted HR 3.5).

• Unpublished data from 1 study of women showed an association between the HPV types targeted by available vaccines (16, 18, 11, and 6) and HIV acquisition.
• Calculated population-attributable fractions of HIV cases due to infection with any HPV type ranged from 21% to 37%.

"Meta-analysis of studies in women showed an association between prevalent HPV infection and HIV acquisition, although included studies were at risk of bias and residual confounding," the researchers concluded in their AIDS 2012 poster. "A similar association was seen in MSM and heterosexual men."

"If further studies validate the association between HPV infection and HIV acquisition, HPV vaccines may reduce HIV incidence in high HPV prevalence populations, in addition to preventing cervical cancer," they wrote in their AIDS report.

"As HPV vaccine programs are introduced, surveillance studies will be important to monitor the impact of HPV vaccination on HIV acquisition," they recommended.

8/10/12

References

CF Houlihan, NL Larke, D Watson-Jones, et al. HPV infection and increased risk of HIV acquisition: a systematic review and meta-analysis. XIX International AIDS Conference (AIDS 2012). Washington, DC, July 22-27, 2012. Poster WEPE258.

CF Houlihan, NL Larke, D Watson-Jones, et al. HPV infection and increased risk of HIV acquisition. A systematic review and meta-analysis. AIDS. August 7, 2012 (Epub ahead of print).