Extrathymic CD8 and CD4 Double Positive T Cells Presenting Vigorous HBV-Specific Responses Accelerate HBV Clearance

Hepatitis B virus (HBV) infection is a worldwide health problem. Both CD4+ and CD8 + T cells play crucial roles in HBV clearance from acute patients. Nevertheless, an extrathymic CD4 and CD8 double positive T (DPT) cell subset have been reported earlier, the function of these cells in HBV infection is still poorly understood. Herein, peripheral blood mononuclear cells were collected from hepatitis B patients. HBV model mice were established via hydrodynamic injection (HDI) of pAAV-HBV1.2 plasmid. T cells subsets were analyzed with flow cytometry. We found that in acute HBV infection extrathymic DPT cells were significantly increased in acute patients and HDI-based HBV model mice. Unlike thymic DPT cells, these extrathymic DPT cells activated with a CD44 + CD62L+ central memory phenotype. Furthermore, in vitro cultured DPT cells showed the capability to rapidly proliferate and produce multi cytokines after stimulation with HBV peptides. The performance of adoptive transfer depicted that DPT cells were able to migrate into the liver. Immunohistochemistry data from liver biopsies of patients showed that DPT cells were more prone to detection in acute tissue. Purified DPT cells could efficiently kill HBV peptide-loaded hepatocytes in a cytotoxicity assay, and the frequency of DPT cells were reversely correlated with HBV clearance in model mice. Importantly, the transferred DPT cells accelerated the clearance of HBV in mice. Collectively, our study revealed that extrathymic DPT cells are an important immune subset, contributing to viral clearance during HBV infection, which may benefit cure of chronic hepatitis B.