Circumcision reduces HIV infection risk says study

Uncircumcised African men are at higher risk of HIV infection - because the inner surface of the foreskin contains cells that make it highly susceptible to infection.

This new data, believed to be the first of its kind in African men, adds further weight to a South African study that in 2005 revealed that circumcision could protect two-thirds of men from contracting HIV/AIDS.

According to the authors of the new study, published in the American Journal of Clinical Pathology, their research among Kenyan men is the first study of human foreskin tissue that examines why, biologically, uncircumcised African men are more likely to contract HIV than their circumcised counterparts.

There are however existing studies of English, American and Australian men, which found that HIV target cells were found in higher proportions in the foreskin than in other tissues.

In fact, in the US these so-called Langerhans cells were found in the foreskins of adults and children in quantities six times that found in adult cervical tissue.

In the British studies, these Langerhans cells were found in higher densities in the foreskins of children and adults, than in cervical, rectal or vaginal mucosa.

The study authors suggest keratin, or lack thereof in uncircumcised men, may provide the answer.

They explain that in circumcised men the outer surface of the foreskin and the glans penis have thick layers of keratin which acts as a protective layer. However, keratin is all but absent on the inner surface of the foreskin putting this area at higher risk of HIV infection.

Keratin is the substance that forms the basis of nails, horns and claws. They suggest this thick layer of skin cells acts as a barrier to HIV.

The Cape Argus reported last year that circumcision could offer something of an HIV/AIDS "vaccine" after South African research proved that male circumcision was equivalent to a vaccine with 63 percent efficacy.

The study was conducted in Soweto between 2002 and 2005, included more than 3 000 healthy and sexually-active men aged 18 to 24, and its results were hailed as the most exciting HIV prevention information in the previous 10 years.

Now the study of the Kenyan men, aged 18 to 24 who were circumcised in Kisumu, has identified that the density and position of HIV target cells in the foreskins of these men make them "highly susceptible" to HIV infection.

The authors also report that they examined differences in the presence of these HIV target cells in 20 men with no history of sexually-transmitted infections, and 19 with such a history. They reported no statistical difference in the number of HIV target cells in the foreskins of the men in either group.

The other significant factor was that most of these Langerhans cells were found near the surface of the epithelium (the tissue forming the outer layer of mucous membrane), suggesting these were the cells likely to be infected by HIV first.

Most important perhaps, they point out, is that "evidence from studies in diverse settings and populations is consistent: many HIV target cells are present in the human foreskin, and Langerhans cells are present near the mucosal surface of the inner foreskin".

In the light of existing evidence, they suggested, "it is plausible that circumcision reduces the risk of HIV acquisition through the penis by physically removing HIV target cells positioned close to the mucosal surface of the inner foreskin".

In respect of South Africa's foreskin study results last year, Dr Francois Venter, clinical director of Reproductive Health and HIV Research at the University of the Witwatersrand, said that the Soweto study was the first large trial examining male circumcision as an intervention to reduce female to male HIV transmission.

In the Soweto study, about half the more than 3 000 men involved were circumcised by medical professionals, and the rest remained uncircumcised. All received counselling on HIV/AIDS prevention.

But after 21 months, 51 members of the uncircumcised group had contracted HIV, against only 18 members of the circumcised group.

The Kenyan study researchers have called for more studies to identify the exact process by which HIV infiltrates target cells in the penile tissue.

Such research, they said, would increase understanding of how circumcision could protect against HIV infection, but could also be the basis for development of effective penile microbicides.