Enhancing HBV-specific T cell responses through a combination of epigenetic modulation and immune checkpoint inhibition

Abstract Objective Chronic hepatitis B virus (HBV) infection results in the exhaustion of HBV-specific T cells and the development of epigenetic imprints that impair immune responses and limit the effectiveness of immune checkpoint inhibitor (ICI) monotherapy, such as αPD-L1. This study aimed to determine whether the DNA methyltransferase inhibitor decitabine (DAC) can reverse these epigenetic imprints and enhance the efficacy of ICI in restoring HBV-specific T cell responses. Methods We investigated HBV-specific CD4 + and CD8 + T cell responses by 10-day in vitro stimulation of peripheral blood mononuclear cells (PBMCs) from patients with chronic HBV infection. PBMCs were stimulated with HBV core-specific overlapping peptide pools and HLA-A*02-restricted peptides, including core 18 and pol 455 . The immunomodulatory effect of the combination of DAC/αPD-L1 was assessed via flow cytometry. Responder stratification was investigated by comparison of clinical characteristics, ex vivo DNA methylation analysis of PBMCs, and determination of IFNγ plasma levels. Results Treatment with DAC and αPD-L1 enhanced HBV-specific CD4 + T cell responses in a significant proportion of 53 patients, albeit with variability. The effect was independent of the HBcrAg level. Ex vivo DNA methylation revealed hypermethylation of key genes like IFNG among DAC-responders versus non-responders, supported by altered ex vivo IFNγ plasma levels. Further analysis of HBV-specific CD8 + T cell responses in 22 HLA-A*02-positive patients indicated distinct response patterns between HBV-core 18 - and HBV-pol 455 -specific T cells, with pol 455 -specific CD8 + T cells showing increased susceptibility to DAC/αPD-L1, surpassing αPD-L1 monotherapy response. Conclusions The combination of DAC and αPD-L1 shows promising effects in improving HBV-specific T cell responses in vitro . Our study highlights the potential of remodeling exhaustion-associated epigenetic signatures to enhance HBV-specific T cell restoration, suggesting a novel immunotherapeutic avenue for chronic HBV infections. Graphic Abstract Highlights Remodeling epigenetic signatures with a DNA methyltransferase inhibitor enhances the effectiveness of immune checkpoint inhibition in restoring HBV-specific T cell responses. Responsiveness is associated with specific IFNγ DNA methylation patterns and plasma levels. Epigenetic remodeling had distinct effects on two CD8 T cell epitopes, with more pronounced effects on HBV-pol 455 -specific CD8 + T cell responses.