Study suggests why circumcised men are less likely to become infected with HIV

By | January 6, 2010, which substantially lowers HIV risk in men, also dramatically changes the bacterial communities of the penis, according to a study led by scientists at the Translational Genomics Research Institute (TGen) and Johns Hopkins University and published Jan. 6 in the scientific journal PLoS ONE.

And these bacterial changes may also be associated with earlier observations that women whose male partners are circumcised are less likely to develop bacterial vaginosis, an imbalance between good and harmful bacteria.

The study — The Effects of Circumcision on the Penis Microbiome — could lead to new non-surgical HIV preventative strategies for the estimated 70 percent of men worldwide (more than 2 billion) who, because of religious or cultural beliefs, or logistic or financial barriers, are not likely to become circumcised.

“It has important public-health ramifications,” said Dr. Lance B. Price, Director of TGen’s Center for Metagenomics and Human Health and co-lead author of the scientific paper, which describes the world’s first molecular assessment of the bacterial diversity of the male reproductive organ.

This new study is part of a larger effort by the U.S. National Institutes of Health to study and describe the “human microbiome” — the microbes that exist collectively on and in the human body. Other projects are focused on microbiomes involving the skin, nose, mouth, digestive and female genitourinary tract. Jointly, the goal of these projects is to define the various roles of microbes in human health and disease.

In investigating the impact of male circumcision on the penis microbiome, a collaborative team from TGen and the Johns Hopkins Bloomberg School of Public Health found for the first time that circumcision significantly changes the bacterial community of the penis.

Other epidemiological studies have shown that male circumcision is associated with significant reductions in HIV acquisition in men.

The strongest evidence for a cause-and-effect relationship between circumcision and HIV risk reduction came from three randomized-control trials in sub-Saharan Africa, where the circumcision rate is relatively low and the HIV infection rate is relatively high. All three demonstrated a more than 40 percent reduction in HIV acquisition among circumcised men.

The largest of these three studies — in Rakai, Uganda — was led by Dr. Ronald H. Gray, a renowned epidemiologist at Johns Hopkins and the scientific paper’s senior author. Dr. Gray’s group collected penile swabs from all of the circumcision trial study participants, which provided the data for the new TGen-Johns Hopkins study.

The new study found that circumcision — the removal of the foreskin, or prepuce, from the penis — eliminates an area of mucous membrane and dramatically changes the penile bacterial ecosystem. Significantly, TGen’s analysis of more than 40 types of bacteria, using a 16S rRNA gene-based pyrosequencing approach, suggests that the introduction of more oxygen following circumcision decreases the presence of anaerobic (non-oxygen) bacteria and increases the amount of aerobic (oxygen-required) bacteria.

“This study clearly shows that male circumcision markedly reduces genital colonization with anaerobic bacteria in men,” said Dr. Gray, the William G. Robertson Jr. Professor in Population and Family Planning at the Johns Hopkins Bloomberg School of Public Health.

“These bacteria, which cannot grow in the presence of oxygen, have been implicated in inflammation and a number of infections affecting both men and women. Our randomized trials have shown that male circumcision prevents HIV infection in men and protects their female partners from vaginal infections, especially bacterial vaginosis. It is possible that the virtual elimination of anaerobic bacteria by circumcision contributes to these benefits of the procedure,” Dr. Gray said.

Several mechanisms have been proposed for how circumcision reduces HIV acquisition in men:

  • Circumcision reduces the amount of mucosal tissue exposed to vaginal secretions during heterosexual intercourse and thus may reduce the potential interactions between the virus and its target immune cells.
  • Circumcision results in a process called keratinization, whereby the top layer of the inner foreskin becomes thicker, which may provide additional protection for the underlying target immune cells.
  • Circumcision-associated physiological changes of the penis — including lower moisture and oxygen availability around the head of the penis — may reduce the number of pro-inflammatory anaerobic bacteria that could make the target immune cells more vulnerable to HIV infection.

“These potential explanations are not mutually exclusive and may work in concert to reduce HIV risk,” said Dr. Price, an Associate Investigator in TGen’s Pathogen Genomics Division. …

via Study suggests why circumcised men are less likely to become infected with HIV.

4 thoughts on “Study suggests why circumcised men are less likely to become infected with HIV

  1. PJ

    It becomes increasingly clear, as more and more studies are done, that the same group of U.S. researchers keep looking for newer ways, and more and more excuses, to promote
    circumcision. If it weren’t so serious, it would almost be comical.

    These individuals seem to have a fixation with promoting and performing circumcisions. Perhaps the next study should be of these researchers’ brains, to discover why they have
    such an unhealthy fascination with cutting off healthy foreskins from others. It almost borders on pathological! (Or, could it be just their way to get more research dollars?) Perhaps the next study should be a mental health assessment of these researchers, conducted by unbiased psychiatrists and psychologists. Hopefully there’s a treatment for their disorder.

    My advice to men- Skip the circumcision! Men and women, if you’re concerned about bacteria, consume more probiotics, including lactobacillus acidophilus taken orally and
    applied topically. This will increase the number of good bacteria inside the body and upon the skin, and help counteract the harmful bacteria. Most stores sell probiotics today, and they’re not hard to find. This dietary approach is far less invasive than putting knives to the genitals, but perhaps less satisfying to these researchers.

  2. Hugh7

    In the real world, circumcision makes no difference to the transmission of HIV. In at least six African countries, more of the circumcised men have HIV than the non-circumcised, according to the National Health and Demographic Surveys.

    PJ is right. Whenever you see circumcision advocacy, check who’s behind it. Almost without exception, you’ll find the same few, very busy people: Daniel Halperin, Robert Bailey, Stefan Bailis, Stephen Moses, Malcolm Potts, Ronald Gray, Thomas Quinn, Helen Weiss, Brian Morris, Edgar Schoen, Thomas Wiswell and a handful of others. (Sure enough, this one is by Grey.) Their interest in circumcision – like any man’s involvement in things penile – is not necessarily utterly dispassionate. Halperin, for example, is on record as thinking his descent from a ritual circumciser means “maybe in some small way I’m ‘destined’ to help pass along [circumcision] to people in [other] parts of the world ….” Some of these people have reached high places and are now moulding policy. This is NOT a concensus among physicians, it is a planned campaign.

  3. Bacterial Vaginosis

    Stop eating sweets and start eating a well balanced diet with lots of water and no soda. this should clear it up.

  4. gina

    Einen schoenen Artikel hast du hier geschrieben. Dieser Artikel hat mich irgendwie animiert auch wieder mehr zu bloggen, werde mich jetzt gleich mal hinsetzen und einen neuen Artikel schreiben.

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