Cut, cut, cut

A QUANTUM OF SCIENCE

Are HIV rates in the US substantial enough to merit a policy of circumcision?

Following evidence of the protective effect against HIV infection, recent news articles report that the CDC is mulling the idea of endorsing circumcision for all male infants born in the United States. But will it really have that much impact?

First, the science. How does circumcision prevent HIV infection? HIV infections occur when the virus gains entry to cells by binding to a protein called CD4, found on the surface of cells. Cell types rich in CD4 are thus easier targets for a successful HIV infection. One such cell type is the Langerhans cell, a part of the primate epidermal tissue related to defending the body against invading microbes. As it happens, primate foreskin is rich in Langerhans cells, meaning plenty of CD4 protein for the AIDS virus to bind to and invade the body. By removing the foreskin through circumcision, an easy point of entry for the virus is blocked.

(Interestingly, CD4-rich Langerhans cells are found in human foreskin and vaginal tissues, but not in oral or rectal tissues. This suggests that HIV infections use a different biochemical route when introduced into the body through those tissues.)

The idea of reducing the risk of contracting HIV through circumcision is far from new. In 1987 a letter was published in the New England Journal of Medicine suggesting exactly that, and studies done in the last fifteen years bear out that theory. While the methods used and areas studied (largely in Africa) varied, the conclusions were so striking that in at least one case a circumcision/HIV infection study was halted years early so the findings could be considered for public policy discussions. Depending on the area studied and the risk factors of those involved in the study, HIV infection rates were found to be as much as 50% lower among circumcised African men than their intact counterparts. Various attempts have been made to expand the conclusions of individual studies through meta-analysis papers and their conclusions found an even greater protective effect of circumcision when those studied were from high-risk populations.

So why not support a policy of encouraging circumcision in the United States? The same studies being reviewed by the CDC have some counterindications that are well worth considering in any kind of policy discussion.

First, the benefits of circumcision are greatly enhanced among high-risk populations. This means that for the average American man (whose risk is far, far lower than the average African man) the benefits are considerably lessened. This could well have something to do with the fact that an estimated 79% of American men are already circumcised – though as rates of circumcision have fallen to around 65% in the most recent surveys, that number is now trending downward. Secondly, use of barrier protection is far more prevalent in America among all demographics, another factor that reduces the positive impact of circumcision protection. Another risk factor related to the need for additional preventative measures against HIV infection – the rate of STDs causing lesions or ulcers, such as herpes or syphilis, which help HIV enter the body during sexual contact – is lower in America than in most African nations, and treatment for those afflictions is considerably more available. Finally, almost all the research done in this area has been performed in Africa. This means there is a possibility that things could be different among Caucasian populations, simply because they are biochemically distinct from non-Caucasians.

The need for additional research is clear. Until scientists can repeat the highly successful African studies in America, Europe, or ideally both – since circumcision is much less common in European nations than in America – the benefits of circumcision for Western populations will remain a question too open for a substantive policy debate to take place.

For more information:

CDC mulls routine circumcision of infants to reduce spread of HIV (NY Daily News)

Circumcision and heterosexual transmission of HIV infection to men. (Fink, 1987)

Comparative investigation of Langerhans' cells and potential receptors for HIV in oral, genitourinary and rectal epithelia. (Hussain, 1995)

Male circumcision and risk of HIV infection in sub-Saharan Africa: a systematic review and meta-analysis. (Weiss, 2000)

Male circumcision for HIV prevention in young men in Kisumu, Kenya. (Bailey, 2007)

Langerhans cells.

© AQOS / P. Smalley (2009)

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