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Wellness experts agree that circumcision lowers rates of HIV infection, but until now, researchers didn’t fully understand why getting snipped was so beneficial to sexual health. However, a new study published in the journal mBio has found that changes in the population of bacteria living on and around the penis may be partly responsible.
Led by Lance Price of the Translational Genomics Research institute (TGen), the researchers conducted a detailed genetic analysis of the microbial inhabitants of the penis among a group of Ugandan men, using the latest technology that make sequencing the genes of organisms faster and more accessible. The study participants provided samples before circumcision and again a year later.
The results revealed that the circumcised men harboured dramatically fewer bacteria that survive in low oxygen conditions, a year after the operation. Compared with uncircumcised men, those who had been snipped had 81% less bacteria overall, and Price said this could have a dramatic effect on the men’s ability to guard their wellbeing against infections like HIV. So why does this bacterial change mean that circumcised men lower their risk of transmitting HIV by as much as 50%?
Specialised immune cells, known as Langerhans cells, are responsible for activating your immune defences, but a high burden of bacteria could disrupt this ability. Your Langerhans are usually responsible for grabbing invading microbes like bacteria or viruses, and presenting them to immune cells. This primes your body to recognize and react against the pathogens, but if your bacterial load increases, so do your inflammatory reactions and, as a result, your Langerhans start to infect healthy cells with the offending microbe, instead of just presenting them.
According to Price, who is also professor of occupational and environmental health at George Washington University, the Langerhans cells could be feeding HIV directly to healthy cells. His research team plans to look into how the signalling molecules that immune cells use to communicate with each other might be influenced by bacterial populations. He commented, ‘There is a real revolution going on in our understanding of the microbiome. The microbiome is almost like another organ system, and we are just scratching the surface of understanding the interplay between the microbiome and the immune system.’