Circumcision Can Prevent HIV Infection by Altering Penis Microbiome

The Argument for Male Circumcision: Preventing HIV Infection by Altering Penis Microbiome
Circumcision leads to less bacteria in the penis, which in turn can prevent against HIV and other STDs. Langerhans cells, shown here, are defense cells found in the penis and other skin areas.

While circumcision is ultimately a personal decision, one recent study argues that more parents may want to consider it. A study performed by researchers of the Translational Genomics Research Institute (TGRI) reports that circumcision leads to a change in the bacterial community - aka, the "microbiome" - that could lead to better protection from HIV infection.

Circumcision is one of those hot-button medical issues that, over the years, has moved from side to side in the eyes of the general public. The prevalence of circumcision varies wildly by country and between ethnic groups, and changes drastically over the years.  In the U.S., for example, 91 percent of boys born in the 80s and 83 percent of boys born in the 80s were circumcised; across the Atlantic in the United Kingdom, only 15.8 percent of men ages 16-44 are circumcised.

One reason that circumcision, once a religious tradition, has become so widespread in some parts of the world, is the belief that it offers some medical benefits. In particular, many medical professionals believe the procedure may offer extra protection against sexually transmitted diseases and other infections.

In fact, past studies have shown that circumcision can reduce the risk of HIV infection in men by 50 to 60 percent. It can also reduce the risk of human papillomavirus (HPV) and herpes infection. Exactly why, though, is not understood.

The TGRI researchers, led by Dr. Lance Price, hypothesized that it may have something to do with the microbiome of the penis.

The study, which will be published in April 16 in mBio, the open-access, online-only journal of the American Society for Microbiology, looked at how circumcision affected the amount and types of bacteria living under the foreskin and on and around the penis.

Researchers used numbers based on a circumcision trial involving 156 Ugandan men, all of whom were circumcised as adults.

Just one year after the procedure, the total bacterial load had dropped by 33.3 percent. In addition, the population of anaerobic bacteria (which thrive in oxygen-poor environments) decreased dramatically while some specific types of aerobic bacteria (which need oxygen to live) increased.

In the study, the researchers put forth the idea that in uncircumcised men, high bacteria counts may activate Langerhans cells in the foreskin. These cells are found throughout the skin in the outermost parts of the human body and normally act as our body's first line of defense, fighting off infectious agents. When activated, however, the Langerhans cells can actually facilitate transmission of HIV by recruiting the specific cells that HIV attempts to target - called the CD4+ T-cells - and allowing HIV to bind to them.

More research still needs to be done, but this, Price and his fellow researchers believe, is a positive step forward.

"Understanding the changes in the microbiome following surgery could eventually lead to interventions that don't require a surgical procedure," Price wrote. "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 and prevent HIV infection in all sexually active men."

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