Functional Heterogeneity of Hepatitis B Virus-Specific CD8+ T Cells Mediates the Clinical Outcomes of Infection

Hepatitis B virus (HBV)-specific CD8+ T cells play a crucial role in viral clearance. However, in patients with chronic hepatitis B infections, sustained immune activation leads to functional impairment of these HBV-specific CD8+ T cells. The goal of this study was to clarify whether these virus-specific CD8+ T cells are exhausted or reflect an incomplete response derived from the initial T cell repertoire.

In this study, HBV core 18-27 epitope-specific CD8+ T cells were identified by proliferation through in vitro antigen stimulation. Peptide-specific CD8+ T cells recognizing the cytomegalovirus (CMV) pp65 495-503 epitope were used as a positive control, as they exhibit a robust immune response. Single-cell sequencing was employed to characterize the TCR repertoire of expanded clones. Correlations between T cell subsets and clinical outcomes were analyzed and compared.

Both HBV core 18-27-specific and CMV pp65-specific CD8+ T cells were successfully classified into three functionally distinct subsets: IFNγ+, mTGFβ+, and IFNγ-/mTGFβ-. Those patients with resolved acute HBV infections and HBV core 18-27 specific CD8+ T cells exhibited the highest IFNγ+/mTGFβ+ ratio, reaching levels comparable to those of CMV pp65-specific CD8+ T cells. Inactive HBV carriers exhibited the second-highest IFNγ+/mTGFβ+ ratio, while this ratio was lowest among patients exhibiting viral immune tolerance. HBV core 18-27 tetramer staining and ERGO-Ⅱ Model prediction demonstrated that IFNγ+ subset CD8+ T cells exhibited the highest affinity for this epitope, followed by the mTGFβ+ subset, with IFNγ-/mTGFβ- cells exhibiting the lowest affinity.

These results suggest that individuals with a high IFNγ+/mTGFβ+ ratio exhibit a lower HBV viral load. The IFNγ+/mTGFβ+ CD8+ T cell ratio, in particular, appears to be associated with HBV clearance, and this may be attributable to T cell receptor affinity for HBV epitopes.