Circumcision Protects against HIV by Altering Bacteria Population: Study

Circumcision changes the kind of bacteria that live on the penis and so offers protections against HIV and other viral infections, according to a new study.

Researchers have found that bacterial composition changes drastically in circumcised penises, going from anaerobic bacteria (which thrive in low oxygen conditions) to mostly aerobic bacteria. The number of bacteria living on the penis drops a year after the procedure.

"The change in the communities is really characterized by the loss of anaerobes. It's dramatic. From an ecological perspective, it's like rolling back a rock and seeing the ecosystem change. You remove the foreskin and you're increasing the amount of oxygen, decreasing the moisture - we're changing the ecosystem," said Lance Price of the Translational Genomics Research Institute (TGen) in Flagstaff, Arizona and George Washington University in Washington, DC. Price is one of the study authors.

Previous studies have shown that circumcised men have nearly 50 percent lower chances of being infected with HIV. Adult circumcision is also known to reduce the risk of other viral infections (viruses that cause genital warts and herpes). However, the mechanism behind the protection offered by the procedure wasn't clear.

For the study, researchers obtained swab samples from circumcised men who were enrolled in a trial conducted in Uganda. Researchers used a quantitative technique called qPCR along with pyrosequencing to identify each bacterial community in the samples. They then compared the bacterial composition in circumcised and uncircumcised men. Also, bacterial commmunties were compared before and after the procedure in circumcised men.

"There was a dramatic and significant change in the penis microbiome as a result of male circumcision," Price said in a news release.

Researchers found that anaerobic bacterial levels reduced significantly, which altered the population of the microbiome on the penis.

The study is published in the journal mBio®

How the microbes on the penis protect men from HIV acquisition isn't yet known. Few studies have suggested that in uncircumcised men, the Langerhans cells (present in the foreskin) are activated due to high bacterial load. These cells become inflamed and instead bind and deliver HIV cells to the T-cells, where the HIV infection begins. Reducing the number of bacteria in the foreskin can thus prevent the Langerhans cells from turning hostile to the body and so prevent an HIV infection.

Price said that understanding how circumcision lowers the chances of acquiring viral infections can help researchers design therapeutics that wouldn't require surgery.

"The work that we're doing, by potentially revealing the underlying biological mechanisms, could reveal alternatives to circumcision that would have the same biological impact. In other words, if we find that it's a group of anaerobes that are increasing the risk for HIV, we can find alternative ways to bring down those anaerobes," he added.