Circumcision significantly changes the micro-biome of the penis, possibly explaining why it offers protection against HIV and other viral infections.

The research findings were published in the journal mBio, from the American Society for Microbiology, and analyzed the effects of adult male circumcision on the kinds of bacteria that exist under the foreskin before and following circumcision.

One year after circumcision, the amount of bacteria in the foreskin area decreased greatly and the incidence of anaerobic bacteria – which live in areas without oxygen – were reduced, while the number of some aerobic bacteria increased moderately.

Corresponding author Lance Price, of the Translational Genomics Research Institute (TGen) in Flagstaff, Arizona and George Washington University in Washington, DC, explained:

“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.”

Previous randomized trials revealed that circumcision decreases the risk of HIV infection in males by 50-60% and reduces the risk of infection with herpes simplex virus type 2 and human papillomavirus.

However, the biology associated with these advantages is not yet well defined. Experts believe that the anatomy of the circumcised penis aids in the prevention of infection – or it could be the alterations in the micro-biome consult protection, or a combination of the two.

Price and his team of investigators at Johns Hopkins and TGen used swab samples from a large circumcision trial in Uganda. They aimed to examine whether circumcision greatly changes the penis microbial community.

By using a quantitative method called qPCR with pyrosequencing to pinpoint individual community members, the authors were able to compare samples from circumcised men with samples from uncircumcised men that were taken before the procedure and one year later.

“There was a dramatic and significant change in the penis microbiome as a result of male circumcision,” says Price.

At the start, the microbiota of both groups of men were comparable. One year following the procedure, the total bacteria in all the males had decreased slightly, but in circumcised men the reduction was significantly larger than in the uncircumcised men. Close to all of the bacterial categories that fell were strict anaerobes or facultative anaerobes. In total, these alterations contributed to a decreased biodiversity in the microbiota.

Prices says:

“From a public health perspective the findings are really interesting because some of these organisms that are decreasing could cause inflammation. We’re used to thinking about how disrupting the gut microbiome can make someone more susceptible to an infection. Now we think maybe this disturbance [in the penile micro-biome] could be a good thing – could have a positive effect.”

The exact contribution that the penile micro-biome makes in HIV acquisition is still a mystery, but studies point out that genital bacteria can impact on how vulnerable the penis is to sexually transmitted viral infections.

In uncircumcised men, large bacterial loads can encourage movement in cells in the foreskin called Langerhans cells, stopping them from doing their normal activities in warding off viruses.

These activated Langerhans cells end up attacking the body – binding and sending HIV particles directly to T-cells – where they can start an infection. Eliminating the number of bacteria on the penis could prevent these Langerhans cells from becoming traitors to the body.

The authors plan to address the question of whether penile micro-biome affect HIV transmission in future research. They plan to study potential associations between changes in the micro-biome and cytokine responses – signaling mechanisms that cause the immune system to react.

Price believes the changes in the micro-biome after the procedure could eventually result in interventions that don’t require surgery.

He concludes, “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.”

In July of 2012, AVAC (Global Advocacy for HIV Prevention) released a report calling for voluntary medical male circumcision in order to prevent the spread of HIV.

In 2001, the government of Rwanda began non-surgical circumcision to prevent HIV. The device used in this procedure is called PrePex – is surgery-free and blood-loss free.

Written by Kelly Fitzgerald