Mucosal-Associated Invariant T Cells Are More Activated in Chronic Hepatitis B, but Not Depleted in Blood: Reversal by Antiviral Therapy.

Background: Mucosal-associated invariant T (MAIT) cells might play a role in control of viral replication during chronic hepatitis B (cHBV) infection, but little is known of their number, phenotype, or function in cHBV patients. Methods: We performed flow cytometry on CD3+Vɑ7.2+CD161+ MAIT cells in blood of 55 cHBV patients. Nine patients were sampled before and on entecavir treatment. Six patients on therapy underwent a liver biopsy for flow cytometric analysis. Measurements included MAIT cell frequency, phenotype, and cytokine-producing capacity. Results: The MAIT cells were not deleted in blood or liver of cHBV patients compared with healthy controls, but they had higher percentages of CD38+ MAIT cells in blood, which declined on entecavir treatment. Peripheral MAIT cells of patients in the HBeAg-negative phase were least activated. Cytokine-producing MAIT cells were as frequent, but granzyme B-producing MAIT cells were more frequent upon stimulation with Escherichia coli compared with healthy controls. Conclusions: We demonstrate that, in sharp contrast to hepatitis C virus and human immunodeficiency virus patients, MAIT cells isolated from HBV patients are not deleted but are more activated, which can be normalized by nucleoside analog therapy. These observations may aid in deciphering the role of MAIT cells in immune responses to HBV.