Hepatitis B virus X gene impacts on the innate immunity and immune‐tolerant phase in chronic hepatitis B virus infection

The immunologic features involved in the immune-tolerant phase of chronic hepatitis B (CHB) virus (HBV) infection are unclear. The hepatitis B virus X (HBx) protein disrupts IFN-β induction by downregulating MAVS and may destroy subsequent HBV-specific adaptive immunity. We aimed to analyse the impacts of genetic variability of HBx in CHB patients on the immune-tolerant phase during long-term follow-up.Children with CHB in the immune-tolerant phase were recruited and followed longitudinally. HBx gene sequencing of infecting HBV strains was performed, and the effects of HBx mutations on the immune-tolerant phase were assessed. Restoration of the host immune response to end the immune-tolerant phase was investigated by immunoblotting, immunostaining, ELISA and reporter assays of MAVS/IFN-β signalling in liver cell lines, patient liver tissues and the HBV plasmid replication system.A total of 173 children (median age, 6.92 years) were recruited. Patients carrying HBx R87G, I127V and R87G + I127V double mutations exhibited higher cumulative incidences of immune-tolerant phase breakthrough (p = .011, p = .006 and p = .017 respectively). Cells transfected with HBx R87G and I127V mutants and pHBV1.3-B6.3 replicons containing the HBx R87G and I127V mutations exhibited statistically increased levels of IFN-β, especially under poly(I:C) stimulation or Flag-MAVS cotransfection. HA-HBx wild-type interacted with Flag-MAVS and enhanced its ubiquitination, but this ability was diminished in the R87G and I127V mutants.HBx suppresses IFN-β induction. R87G and I127V mutation restored IFN-β production by preventing MAVS degradation, contributing to curtailing the HBV immune-tolerant phase in CHB patients.