Foreskin cells may assist HIV transmission

NEW YORK, Jun 09 2000 (Reuters Health) - Over 40 studies have found that males who are circumcised have a lower risk of becoming infected with HIV from an infected sexual partner than uncircumcised men. In a report in the June 10th issue of the British Medical Journal, researchers provide a possible answer to the question of how circumcision may protect against HIV infection.

The authors report that certain cells found in abundance on the inner surface of the foreskin are most likely "the primary point of viral entry into the penis of an uncircumcised man."

Dr. Robert Szabo, of Monash University, Melbourne, Australia, and Dr. Roger V. Short, of the University of Melbourne, note that about 70% of men who are HIV positive have been infected through the penis. Studies show that circumcised men are about two to eight times less likely to contract HIV and other sexually transmitted diseases than uncircumcised men.

Compelling evidence that circumcision directly protects men from HIV infection comes from a study performed in Uganda, the authors report. In that research, scientists studied 50 circumcised men and 137 uncircumcised men. All of the men were HIV negative but had female partners who were HIV positive. Over the 30 months of the study, none of the circumcised men contracted HIV, while 40 of the uncircumcised men contracted the virus. While all the men had free access to condoms, 89% never used them, Szabo and Short note.

Scientists speculate that uncircumcised men are at greater risk for HIV infection because of cells called Langerhans' cells found on the inner surface of the foreskin. During intercourse, the foreskin can be pulled down, exposing the Langerhans' cells to vaginal secretions, which can carry HIV. The virus may bind to receptors on the surface of Langerhans' cells, leading to infection.

Removal of the foreskin also removes the Langerhans' cells, thus reducing the risk of HIV infection from sex with an HIV-positive partner, the researchers conclude.

"Although condoms must remain the first choice for preventing the sexual transmission of HIV, they are often not used consistently or correctly, they may break during use, and there may be strong cultural and aesthetic objections to using them," Szabo and Short write.

Therefore, circumcising males could help reduce rates of HIV transmission, the investigators suggest. But circumcising boys at the time of birth would not affect transmission rates for 15 to 20 years. "Circumcision at puberty, as practised by many Muslim communities, would be the most immediately effective intervention for reducing HIV transmission since it would be done before young men are likely to become sexually active," the team concludes.

Szabo and Short also suggest that the development of agents that can be applied to the penis, a "chemical condom" that blocks HIV from entering cells, may also help to reduce transmission rates, and "might be more effective and acceptable than any mechanical barrier or surgical intervention."

SOURCE: British Medical Journal 2000;320:1592-1594.