Hepatitis B surface antigen reduction is associated with hepatitis B core-specific CD8⁺ T cell quality

Despite treatment, hepatitis B surface antigen (HBsAg) persists in patients with chronic hepatitis B (CHB), suggesting the likely presence of the virus in the body. CD8(+) T cell responses are essential for managing viral replication, but their effect on HBsAg levels remains unclear. We studied the traits of activated CD8(+) T cells and HBV-specific CD8(+) T cells in the blood of CHB patients undergoing nucleos(t)ide analog (NUC) therapy. For the transcriptome profiling of activated CD8(+) T cells in peripheral blood mononuclear cells (PBMCs), CD69(+) CD8(+) T cells were sorted from six donors, and single-cell RNA sequencing (scRNA-seq) analysis was performed. To detect HBV-specific CD8(+) T cells, we stimulated PBMCs from 26 donors with overlapping peptides covering the HBs, HBcore, and HBpol regions of genotype A/B/C viruses, cultured for 10 days, and analyzed via multicolor flow cytometry. scRNA-seq data revealed that CD8(+) T cell clusters harboring the transcripts involved in the cytolytic functions were frequently observed in donors with high HBsAg levels. Polyfunctional analysis of HBV-specific CD8(+) T cells utilized by IFN-gamma/TNF alpha/CD107A/CD137 revealed that HBcore-specific cells exhibited greater polyfunctionality, suggesting that the quality of HBV-specific CD8(+) T cells varies among antigens. Moreover, a subset of HBcore-specific CD8(+) T cells with lower cytolytic potential was inversely correlated with HBsAg level. Our results revealed a stimulant-dependent qualitative difference in HBV-specific CD8(+) T cells in patients with CHB undergoing NUC therapy. Hence, the induction of HBcore-specific CD8(+) T cells with lower cytolytic potential could be a new target for reducing HBsAg levels.