Adjuvant pegylated interferon-alpha after nucleos(t)ide analog withdrawal drives a temporally coordinated expansion of regulatory B cells and contraction of HBV-specific T cells

Background and Aims: The NUC-B study showed that a 4-month course of pegylated interferon-alpha (PEG-IFNα) enhanced the outcome and reduced hepatic flares following nucleos(t)ide analog (NUC) withdrawal in HBeAg-negative chronic hepatitis B. Here, we investigated differential T- and regulatory B-cell (B REG ) changes before and during these interventions in a substudy of 41 representative patients. Approach and Results: Antigen-specific T cells were primarily evaluated using quality-controlled IFN-γ ELISpot with 15 pools of genotype-matched HBV core/small-surface peptides, confirmed by multiparameter flow cytometry. B-cell responses were tested with multiparameter flow cytometry and intracellular IL-10 staining. Broader baseline IFN-γ-producing-HBV-specific T cells correlated with higher sustained off-treatment viral control and reduced flares. PEG-IFNα led to a transient reduction in HBV-specific T cells that persisted for over 1 month after treatment. B REG producing the immunosuppressive cytokine IL-10 expanded more than 5-fold during adjuvant PEG-IFNα. The kinetics of B REG induction correlated with flares in both arms and showed a significant inverse temporal correlation with IFN-γ-producing-HBV-specific T-cell frequencies. Conclusions: Baseline breadth and magnitude of HBV-specific T cells should be evaluated as biomarkers to select patients more likely to have favorable outcomes with NUC withdrawal ±PEG-IFNα. The expansion of B REG provides insights into homeostatic mechanisms induced by PEG-IFNα and withdrawal flares, which could constrain HBV-specific T cells while limiting inflammation.