April 17, 2013
Researchers from the Translational Genomics Research Institute in Flagstaff, Ariz., report that a study conducted in Uganda indicates that removal of the foreskin deprives anaerobic bacteria of a place to thrive and gives the immune system a better opportunity to fight off the human immunodeficiency virus (HIV). The study may explain why circumcision cuts HIV risk by 50 to 60 percent. Previous theories attributed increased HIV risk for uncircumcised men to the potential for tears of the foreskin or the increased amount of surface area.
Study leader Dr. Cindy Liu compared removal of the foreskin to clear-cutting a forest, which changes the community of animals living there. Similarly, circumcision deprives anaerobic bacteria of the opportunity to thrive in the coronal sulcus, the groove behind the head of the penis. Liu stated that bacteria -- especially anaerobic bacteria -- cause inflammation that triggers the immune system to respond with T4 cells, which are necessary for HIV to survive and replicate. Populations of bacteria in an uncircumcised man attract T4 cells that give HIV an entry point. Without bacteria to mobilize HIV-susceptible T4 cells, other immune cells can destroy the virus.
The study engaged 156 Ugandan men aged 15 to 49 in a year-long randomized study where half of the men received circumcision and half did not. Because one in six people in Uganda are HIV-infected, 5,000 Ugandan men volunteered to participate in the study. After one year, bacteria -- especially anaerobic bacteria -- had dropped by 81 percent for the circumcised men. Bacteria on the coronal sulcus had dropped by 33 percent. Further studies will look at ways to alter bacterial populations without circumcision.
The full report, "Male Circumcision Significantly Reduces Prevalence and Load of Genital Anaerobic Bacteria," was published online in the journal mBio (2013; doi: 10.1128/mBio.00076-13).