Jerusalem, 18 March, 2026 (TPS-IL) — A new study from Israel and Ethiopia suggests that gut bacteria—the microbes living in the intestines—may help people living with HIV repair damage caused by the virus. The discovery could lead to future treatments that use gut bacteria to protect against infections.
The research, led by Prof. Eran Elinav of the Weizmann Institute of Science and Prof. Hila Elinav of Hadassah University Medical Center, was conducted under extraordinary circumstances. Prof. Eran Elinav’s lab was destroyed in a missile strike in June 2025, and Dr. Jamal Ali Mahdi, one of the study’s lead researchers from Ethiopia’s Tigray region, had to flee his home during a civil war. Despite these obstacles, the team spent nearly a decade collecting and analyzing samples.
The study analyzed stool samples from about 70 HIV carriers in Israel and a similar number in Ethiopia, alongside control groups of people without the virus. Gut bacteria can help people living with HIV by partially repairing the immune damage the virus causes in the intestines. Scientists focused on CD4 T-helper cells, which are a main target of HIV and play a crucial role in the immune system. All participants were receiving HIV treatment, although newer therapies were not widely available in Ethiopia.
“Even when the immune system recovers throughout the body as a result of effective HIV drug treatment, the T cells in the intestinal mucosa do not recover completely due to the presence of the virus in the intestine,” said Prof. Hila Elinav. “Therefore, it was particularly relevant to examine the interrelationships between intestinal bacteria and immune system cells in people living with HIV.”
The researchers found that HIV infection changes the composition of gut bacteria. Some strains disappear while others multiply. Certain changes were seen in both Israeli and Ethiopian participants, suggesting a universal biological response, while others reflected differences in diet and lifestyle.
Prof. Eran Elinav explained: “Immune system cells normally shape gut bacteria by releasing antimicrobial molecules. When HIV attacks the immune system, this balance shifts, letting some bacteria thrive. We wanted to see if gut bacteria, in turn, affect the immune system.”
To test this, scientists transferred gut bacteria from HIV carriers and uninfected donors into mice with depleted microbiomes. The results were striking: mice receiving bacteria from HIV carriers developed higher levels of CD4 cells in the intestines than those given bacteria from healthy donors. The gut bacteria were actively helping repair the immune system, compensating for some of the damage caused by the virus.
However, the effect has limits. When bacteria came from participants with advanced HIV or AIDS, they could no longer support CD4 cells. Additional experiments showed that mice with microbiomes from HIV carriers were better at fighting infections common in people with weakened immunity—but only if the disease had not progressed too far.
“At the basic science level, this study provides clear evidence that gut bacteria and the immune system influence each other,” Prof. Eran Elinav said. “Gut bacteria act almost like an immune organ—they respond to immune damage and help the body recover.”
The findings could also lead to new treatments. Unlike genetics, the microbiome can be modified through diet, probiotics, bacterial molecules, or targeted viruses that attack specific bacteria. Prof. Hila Elinav said: “Much research is still needed, but this study shows it may one day be possible to support the immune system of people with HIV using gut bacteria, reducing the risk of dangerous infections.”
Diet can play an important role in supporting gut bacteria that help the immune system. Tailored nutritional programs could become a simple, non-invasive way to strengthen the population of CD4 cells in the intestines and improve overall immune function.
In addition to diet, researchers are exploring more targeted ways to harness gut bacteria for immune support. Specific probiotic strains could be given to boost the population of helpful microbes, while molecules secreted by these bacteria might be used as therapies to stimulate immune cells. Bacteriophages—viruses that selectively attack harmful bacteria—could also be employed to shape the microbiome and favor strains that protect against immune damage.
The study was recently published in the peer-reviewed Nature Microbiology.