| Summary: | Background: The current desirable endpoint of treatment against chronic hepatitis B virus infection (cHBV) is to achieve a functional cure, which is defined as HBsAg loss (sAg-L) with or without anti-HBs seroconversion. However, the immunological features that are associated with functional cure have not been studied in detail. Methods: 172 cHBV patients (67 HBeAg+ and 105 HBeAg-), including 141 HBsAg retained (sAg-R) patients (115 chronic hepatitis and 26 asymptomatic carriers), 31 sAg-L patients, and 24 healthy individuals (vaccinated but not infected with HBV) were examined for their T cell phenotypic profile and HBV-specific T cell responses by flow cytometry. 18 cHBV patients with low serum HBsAg levels were also longitudinally followed for their T cell phenotypic profile and HBV-specific T cell responses up to 60 weeks. Findings: sAg-L patients showed distinct CD4+ and CD8+ T cell phenotype fingerprints compared to those of sAg-R patients, as mainly indicated by the upregulation of HLA-DR on both CD4+ and CD8+ T cells, and a potent HBcAg-specific CD8+ T cell response. The changes in the T cell phenotype in cHBV patients were even more profound during rapid HBsAg decrease and was associated with interferon α treatment. The expression of HLA-DR (r = 0·3269, p = 0·0037), CD95 (r = 0·2796, p = 0·0151), CD40L (r = 0·2747, p = 0·0156), CTLA-4 (r = 0·2786, p = 0·0148), TIM-3 (r = 0·3082, p = 0·0068), CD107a (r = 0·3597, p = 0·0013) on CD4+ T cells, and HLA-DR (r = 0·3542, p = 0·0016), CD69 (r = 0·2507, p = 0·0279), CD107a (r = 0·2875, p = 0·0112) on CD8+ T cells were positively correlated with the rate of HBsAg decrease. The expression of HLA-DR (r = 0·2846, p = 0·0009) and CD95 (r = 0·2442, p = 0·0049) on CD8+ T cells were positively correlated with the magnitude of the HBcAg-specific T cell responses in cHBV patients. Importantly, CTLA-4, CD95 and CD107a expression on CD4+ T cells, as well as HLA-DR and TIM-3 expression on CD8+ T cells in combination with HBsAg quantification were identified as potential predictive factors for sAg-L within 48 weeks in cHBV patients. Interpretation: The onset of HBsAg decrease and subsequent loss in cHBV patients on treatment is associated with significant alterations of both CD4+ and CD8+ T cell phenotypes. Characterization of the T cell phenotype in cHBV patients may present predicative value for sAg-L. Funding: National Natural Science Foundation of China, National Scientific and Technological Major Project of China, Integrated Innovative Team for Major Human Diseases Program of Tongji Medical College, “Double-First Class” Project for the International Cooperation Center on Infection and Immunity, HUST.
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