Characterization of in-vitro responses to immune modulation of HBV core ₁₈ -specific vs HBV pol₄₅₅-specific CD8⁺ T cells

Introduction and aim Currently several new therapeutic strategies including direct antiviral treatments and immunomodulatory options are being developed aiming at functional cure (HBsAg loss) of chronic HBV infection (CHB). One option to modulate immune responses to achieve higher rates of HBsAg loss is to restore the exhausted T cell response. Recently, it has been reported that T cells targeting different HBV epitopes can be phenotypically and functionally different. However, the restoration capacity of these T cells has not been investigated. Thus, we studied the phenotype, function and the restoration capacity of HBV core₁₈- and pol₄₅₅-specific CD8⁺ T cells from patients with CHB.

Methods Peripheral blood mononuclear cells (PBMCs) from 27 HLA-A2 positive CHB patients were isolated. Core₁₈- and pol₄₅₅-specific T cells were phenotypically characterized in 24 patients using peptide-loaded MHC I dextramer based enrichment. Furthermore, the function and the restoration capacity of epitope-specific T cells from 12 patients were measured after in vitro culture of PBMCs with core₁₈ and pol₄₅₅ peptides with or without α-PD-L1 antibody, IL-12 and mitochondria-targeted antioxidant Mito-Tempo. Intracellular cytokine assay was used as functional readout.

Results Core₁₈- and pol₄₅₅-specific CD8⁺ T cells showed diverse phenotypes with higher functionality and higher rate of memory-like phenotype in core₁₈-specific CD8⁺ T cells. The expression of IFNγ in core₁₈-specific CD8⁺ T cells significantly increased after using αPD-L1 antibody (IFNg median = 0.49 vs 0.98; p = 0.021). However, the expression of IFNγ in pol455-specific CD8⁺ T cells did not significantly changed after using αPD-L1 antibody. In contrast, IL-12 significantly enhanced the IFNγ expression of pol₄₅₅-specific CD8⁺ T cells (pol₄₅₅ vs pol₄₅₅+IL-12 median = 0.04 vs 0.91; p = 0.0015) and not of core₁₈-specific CD8⁺ T cells. The ability of Mito-Tempo in enhancement of core₁₈- and pol₄₅₅-specific CD8⁺ T cells function was only observed in few patients in our cohort and there were no differences between the epitopes.

Conclusion Our data confirmed the previous studies that core₁₈- and pol₄₅₅-specific CD8⁺ T cells are phenotypically and functionally different. Furthermore, we showed that the response of HBV-specific T cells to different immune modulations varies depending on the targeted antigens. These results have potential implications for developing immunotherapeutic approaches to achieve functional HBV cure.

Publication History

Article published online:
04 January 2021