01 Set Association Between Mucosal-Associated Invariant T (MAIT) Cells and Gut Microbiome: Friend or Foe in Chronic Viral Infections?

Esther Merlini

MAITs are a subset of unconventional T cells involved in antimicrobial responses, that have been reported severely impaired in chronic viral infections. We hypothesized that altered microbiome, described in HIV and HCV infections, might affect MAITs frequency and function, weakening their antimicrobial activity and favoring MT, thus supporting immune activation and disease progression.
In 12 HIV+, 12 HCV+, 30 HIV+/HCV+ and 15 healthy controls (HC) we measured circulating MAIT frequency/function (flow cytometry) and plasma/stool microbiome/MT (Illumina Technology).
Irrespective of viral infection, infected pts showed lower circulating MAITs, with exhausted and activated phenotypes and higher proportion of functionally-defective CD161-TCRVa7.2+ vs HC.
We observed similar plasma 16s levels, but higher % of Chitinophagaceae and Sphingomonadaceae and lower Oxalobacteraceae in all the infected pts. MAIT frequency inversely correlated with plasma Chitinophagaceae and Streptococcaceae, positively with plasma Enterobacteriaceae and stool Pseudomonadaceae and Actinomycetaceae
The impaired frequency/functions in HIV, HCV and HIV/HCV pts confirm the weak antibacterial ability of MAITs in the setting of chronic infection, supporting their role in disease progression. Besides, the different association between MAITs and some bacteria families suggest their potential for aggravating or suppressing inflammation, opening novel therapeutic perspectives, such as bacteria supplementation to antiHIV or HCV treatment.