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More than 350 million people are chronically infected with hepatitis B virus, and dysfunctional T cell responses contribute to persistent viral infection and immunopathogenesis in chronic hepatitis B (CHB). However, the underlying mechanisms of T cell hyporesponsiveness remain largely undefined. Given the important role of microRNA-146a (miR-146a) in diverse aspects of lymphocyte function, we investigated the potential role and mechanism of miR-146a in regulating T cell immune responses in CHB. We found that miR-146a expression in T cells is significantly upregulated in CHB compared with healthy controls, and miR-146a levels were correlated with serum alanine aminotransaminase levels. Both inflammatory cytokines and viral factors led to miR-146a upregulation in T cells. Stat1 was identified as a miR-146a target that is involved in antiviral cytokine production and the cytotoxicity of CD4+ and CD8+ T cells. In vitro blockage of miR-146a in T cells in CHB greatly enhanced virus-specific T cell activity. Therefore, our work demonstrates that miR-146a upregulation in CHB causes impaired T cell function, which may contribute to immune defects and immunopathogenesis during chronic viral infection. [ABSTRACT FROM AUTHOR]