In our gut live millions of microorganisms of different species, which play an essential role in various processes of the body. It is known that an imbalance in these microbial populations, known as intestinal dysbiosis, is associated with different pathologies. Now, a study conducted by the Institute for AIDS Research IrsiCaixa, in collaboration with the Fight AIDS Foundation, shows that this dysbiosis is associated with a deterioration of the immune system, and that the more serious this deterioration is, the more evident is the imbalance. This confirms that not all patients with HIV have dysbiosis, but that it is very important to diagnose the infection as soon as possible to avoid the destruction of immune cells. In addition, it evidences the need to develop specific tests to know if a patient with HIV has this imbalance. The work has been published in the journal Mucosal Immunology.
HIV, the virus that causes AIDS, damages the intestinal mucosal barrier, allowing the passage of bacteria into the bloodstream and lymph nodes, which causes chronic inflammation and a deterioration of the immune system. Up until now, it was known that the virus also caused intestinal dysbiosis and which patients were more likely to suffer it. However, the current study shows that dysbiosis occurs more frequently when the immune system is deteriorated, so if a person becomes infected with HIV but begins the treatment soon, this will prevent the deterioration of the immune system and will be less likely to suffer this imbalance intestinal. "For this reason it is essential to diagnose the infection as soon as possible, since people with a more damaged immune system are more likely to develop clinical complications. In addition, once an imbalance has occurred in the microbiome, a full recovery can not be ensured," says Yolanda Guillén, a post-doctoral researcher at the Microbial Genomics group at IrsiCaixa.
Diversity of microbial populations
In order to perform the study, researchers have worked with 156 people, 127 of whom were infected with HIV and 27 were not. Patients were categorized into different groups based on the deterioration of their immune system. Using fecal samples, the intestinal microbiome of each individual was characterized with a massive sequencing method, which allows to sequence all the DNA of the sample, and not only of a specific bacterial marker genes, as had been done up to now. Then, the species contained in the samples were classified and the different microbial genes were quantified, also classifying the metabolic functions of each microbial population.
The work points out remarkable differences between the composition of the microbiomes with more and less gene richness. Researchers have detected, for example, that people with less diversity of bacteria have a lack of methanogens, microorganisms specialized in the production of methane that are essential for the maintenance of intestinal balance.
The description of the microbiome may have future utility in the treatment of people with HIV. "The results suggest that the analysis of the microbiome could be used as a tool to identify which patients are more likely to suffer clinical complications, which would be those with less microbial richness," says Roger Paredes, the group's lead investigator. "Results also show that in order to know which patients have intestinal dysbiosis we have to make direct measurements using microbial markers. We are working on simplifying the microbiota analysis tests so that, one day, they can reach clinical practice," he adds.
Scientific paper: Low nadir CD4+ T-cell counts predict gut dysbiosis in HIV-1 infection. Guillén Y, Noguera-Julian M, Rivera J, Casadellà M, Zevin AS, Rocafort M, Parera M, Rodríguez C, Arumí M, Carrillo J, Mothe B, Estany C, Coll J, Bravo I, Herrero C, Saz J, Sirera G, Torrella A, Navarro J, Crespo M, Negredo E, Brander C, Blanco J, Calle ML, Klatt NR, Clotet B, Paredes R. Mucosal Immunol. 2018 Aug 31. doi: 10.1038/s41385-018-0083-7. [Epub ahead of print]
Image: Steve Gschemeissner