HIV and The Gut Microbiome: Prebiotics and Probiotics
In the previous article, I introduced the microbiome. To review, recall that our bodies are essentially a reservoir of billions, even trillions of bacteria and other microorganisms (viruses, fungi, parasites). They are essential to helping us stay healthy. Disease occurs when harmful organisms invade our bodies (e.g. influenza, malaria, hepatitis C, Staphylococcus). The microbiome refers to the diversity of microorganisms associated with a specific organ at a specific time.
When we are healthy, the microbiome contains a delicate balance of bacteria and other organisms that actually help us. But disease can also occur when the microbiome is disrupted by harmful bacteria and the balance is thrown off from normal. In the previous article, we discussed how disrupting the normal balance of bacteria in the vaginal microbiome can increase the risk of acquiring HIV. The largest volume and diversity of bacteria is found in the gut (intestinal) microbiome. HIV infection has a profound effect on the gut microbiome and this may provide opportunities to improve control of the disease.
Very soon after the HIV viral infection reaches the blood, the viruses launch an aggressive attack on the largest immune system complex in the body. This complex of specialized tissue surrounds the gut (intestines) and the HIV virus kills off many of the important immune cells that protect our bodies; cells known as CD4+ lymphocytes or T lymphocytes. This damage is irreversible. Even with very effective therapy for decades, these cells from the gut that are killed off during the early infection are never replaced. HIV’s attack of the immune system around the intestines produces two major effects that have long-term importance in the disease. First, the virus causes subtle damage to the intestinal wall which allows small amounts of bacteria to leak out from the intestine into the bloodstream.
The immune system begins to attack these bacteria slowly streaming into the blood from the gut. This results in a mild form of inflammation. When I say inflammation, this means that the body is reacting similarly to what we see in patients with diseases like arthritis and inflammatory bowel disease. Some of the same chemicals produced in these diseases can be found in the blood of HIV patients.
The good news: HIV medications reduce the amount of inflammation as they control the virus. The bad news is the amount of inflammation is still higher than normal, even with effective HIV treatment. This inflammation in HIV is a problem because it can cause damage in the blood vessels and increase the risk of cardiovascular disease.