Circumcision alters penis microbiome, could explain HIV protection

Circumcision drastically alters the microbiome of the penis, changes that could explain why circumcision offers protection against HIV and other viral infections. In a study to be published on April 16 in mBio, the online open-access journal of the American Society for Microbiology, researchers studied the effects of adult male circumcision on the types of bacteria that live under the foreskin before and after circumcision. By one year post-procedure, the total bacterial load in that area had dropped significantly and the prevalence of anaerobic bacteria, which thrive in locations with limited oxygen, declined while the numbers of some aerobic bacteria increased slightly.

"The change in the communities is really characterized by the loss of anaerobes. It's dramatic," says the corresponding author, Lance Price of the Translational Genomics Research Institute (TGen) in Flagstaff, Arizona and George Washington University in Washington, DC. "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," he continues.

show that reduces the risk of in men by 50-60% and reduces the risk of infection with and herpes 2, but the biology behind these benefits is not well understood. It could be that the anatomy of the circumcised penis helps prevent infection, or it could be that changes in the microbiome confer protection, or some combination of the two.

Using swab samples from a large circumcision trial in Uganda, Price and his colleagues at Johns Hopkins and TGen set out to determine whether circumcision significantly alters the penis microbial community. Using a quantitative technique called qPCR along with to identify individual community members, the researchers compared samples from uncircumcised men with samples from circumcised men that were taken both 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 beginning, the microbiota of both groups of men were comparable. One year after their operation the bacterial load in all men had declined somewhat, but in circumcised men the decline was significantly greater than in the uncircumcised controls. And nearly all the bacterial groups that declined were strict anaerobes or facultative anaerobes. Overall, these changes amount to a reduced biodiversity in the microbiota.

"From a public health perspective the findings are really interesting because some of these organisms that are decreasing could cause inflammation," says Price. "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 microbiome] could be a good thing - could have a positive effect," says Price.

Just what role the penile microbiome might play in HIV acquisition is not yet known, but studies suggest that genital bacteria may affect how susceptible the penis is to sexually transmitted viral infections. In uncircumcised men, high bacterial loads may activate cells in the foreskin called Langerhans cells, preventing them from carrying out their normal role in fending off viruses. Instead, these activated Langerhans cells betray the body, binding and delivering HIV particles right to T-cells, where they can initiate an infection. Cutting back on the numbers of bacteria on the penis could, conceivable, prevent these Langerhans cells from becoming turncoats.

To follow up on this work, Price says he and his colleagues plan to address the question of whether the penile microbiome affects HIV transmission by studying possible links between changes in the microbiome and cytokine responses, signaling mechanisms that can activate the immune system.

To Price, this study has implications beyond circumcision. Understanding the changes in the microbiome following surgery could eventually lead to interventions that don't require a surgical procedure. "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, says Price.

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Journal information: mBio

Citation: Circumcision alters penis microbiome, could explain HIV protection (2013, April 16) retrieved 24 August 2019 from
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Apr 16, 2013
So is this result enough to merit a global campaign for circumsision?

Apr 16, 2013
HIV is not a bacteria, it is a virus which is contained in the semen and transmitted via contact with the partner's blood. So this study is totally meaningless. Also, the glans of circumcised men is dry and rough which means that it frequently causes micro lesions and bleeding in vaginas, thus opening the way for the transmission of the virus to women, especially as the lovemaking of circumcised men is much rougher than that of whole men because they have lost from 60% to 80% of their capacity for pleasure - the overwhelming majority of sensitive nerve endings reside in the foreskin.

In Uganda, over 12% of men are Muslim, which means that they abstain from sex before and outside of marriage, thus significantly diminishing the likelihood of their contracting and spreading HIV. This obviously has impacted and falsified this "study".

Apr 17, 2013
mastectomy of both breast reduces the chance of breast cancer, and the removal of the appendix at birth also prevents appendicitis.

Would anyone suggest doing these things as a prophylactic measure??

How about spending some of the money these asinine studies cost on actually finding a cure for AIDS and eradication of other STDs.

Leave my foreskin alone.

I also find the quoted study implausible due to the fact that in Europe, where most (>90%) of children are uncircumcised the HIV infection rate is much lower than in the US where most male children (>90%) are circumcised at birth. i.e. the US, with roughly 4 times the population of Germany, has over 17 times more individuals infected with HIV. These countries have roughly the same level of developmental standing in the world and should be a pretty good comparison as far as safe sex practices and sex ed is concerned. So one should expect a much higher HIV infection rate in Germany due to its large uncircumcised population.

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