Israeli-Ethiopian study shows gut microbes help shore up immunity in early HIV

Researchers at the Weizmann Institute of Science and Hadassah Medical Center reported on 12 February 2026 that bacteria living in the human gut actively help the immune system cope with HIV, at least in the early stages of infection. The study, published in Nature Microbiology, was led by Prof. Eran Elinav of Weizmann together with Prof. Hila Elinav, an infectious-disease specialist who heads the Hadassah AIDS Center in Jerusalem.

The team analysed stool samples from about 70 people living with HIV in Israel and a similar number in Ethiopia, collected at several points during their infection, and compared them with samples from uninfected people in the same regions. Samples in Ethiopia were gathered with doctors from Mekelle University and local clinics in Tigray, building on long-standing ties between the Hadassah AIDS Center and Ethiopian clinicians. As the disease progressed, the mix of gut bacteria shifted in step with falling counts of CD4 T cells, the immune cells HIV attacks. Some changes appeared in both countries, while others seemed to reflect local diet and lifestyle.

To test whether the microbes were a cause rather than just a sign of these changes, the researchers transferred gut bacteria from participants into mice that had no microbes of their own. Since mice cannot catch HIV, any effect had to come from the bacteria. Microbes from people in early HIV raised the number of CD4 T cells in the mice's intestines, even above the level produced by microbes from healthy donors, and helped the animals clear an intestinal parasite. Microbes from people with advanced disease, or AIDS, had lost that protective effect.

The authors describe the result as human-based evidence that the microbiome works partly as an immune organ. Because gut bacteria can be changed through diet, probiotics or bacterial products, they suggest such approaches could one day help protect people with HIV from opportunistic infections, especially in places where full antiretroviral care is hard to reach. They stress that this would complement, not replace, antiviral drugs, and that the specific helpful microbes still need to be identified.