LAG3⁺ erythroid progenitor cells inhibit HBsAg seroclearance during finite pegylated interferon treatment through LAG3 and TGF-β

HBsAg seroclearance, the ideal aim of anti-hepatitis B virus (HBV) treatment, cannot be achieved easily. Anemia is another common issue for chronic hepatitis B (CHB) patients, which leads to elevation of erythroid progenitor cells (EPCs) and immune suppression in cancer. This study investigated the role of EPCs in HBsAg seroclearance following pegylated interferon-α (PEG-IFN) treatment. CD45⁺EPC accumulation in CHB patients and an AAV/HBV mice model was found in the circulation and liver by flow cytometry and immunofluorescence tests. Wright-Giemsa staining showed that these pathological CD45⁺EPCs presented elevated erythroid cells with relative immature morphologies and atypical cells compared with the control cells. CD45⁺EPCs were associated with immune tolerance and decreased HBsAg seroclearance during finite PEG-IFN treatment. CD45⁺EPCs suppressed antigen non-specific T cell activation and HBV-specific CD8⁺T cells, partially through transforming growth factor β (TGF-β). RNA-seq revealed that CD45⁺EPCs in patients with CHB presented a distinct gene expression profile compared with CD45^-EPCs and CD45⁺EPCs from cord blood. Notably, CD45⁺EPCs from patients with CHB expressed high level of Lymphocyte-activation gene 3 (LAG3), an immune checkpoint molecule, and were then defined as LAG3⁺EPCs. LAG3⁺EPCs diminished the function of antigen presenting cells through LAG3, which was another mechanism by which LAG3⁺EPCs' suppressed HBV-specific CD8⁺T cells. Anti-LAG3 and anti-TGF-β combination treatment decreased serum HBeAg, HBV DNA levels and HBsAg level, as well as HBsAg-expression in hepatocytes during PEG-IFN treatment in the AAV/HBV mice model. Conclusions: LAG3⁺EPCs inhibited the efficacy of PEG-IFN treatment on HBsAg seroclearance induced by LAG3 and TGF-β. Anti-LAG3, anti-TGF-β and PEG-IFN combination treatment might facilitate HBV clearance.