Insufficient immunity led to virologic breakthrough in NAs-treated chronic hepatitis B patients switching to Peg–IFN–ɑ

Virologic breakthrough (VBT) may occur in chronic hepatitis B (CHB) patients after switching from nucleos(t)ide analogues (NAs) to pegylated interferon alpha (Peg-IFN-ɑ). This study aimed to characterize the clinical and immunological features of VBT.In NAs-treated patients switching to Peg-IFN-ɑ, innate and adaptive immune cell proportions were examined in peripheral blood and liver biopsy specimens. In vitro effect of IFN-ɑ on the expressions of toll-like receptors 2 (TLR2) and programmed cell death ligand 1 (PDL1) on monocytes, programmed cell death 1 (PD1) on CD8+T cells was examined. Peripheral blood mononuclear cells (PBMCs) were treated with TLR2 agonist and/or PDL1 blockade to evaluate their effect on HBV replication.33 of 166 patients switching to Peg-IFN-ɑ experienced VBT after NA cessation, with majority being hepatitis B e antigen (HBeAg) positive or having higher hepatitis B core-related antigen (HBcrAg) levels. Patients with VBT exhibited lower proportions of TLR2+monocyte and increased PD1+HBV-specific CD8+T cell during the early phase of Peg-IFN-ɑ therapy after NA cessation in peripheral blood, as well as fewer TLR2+CD68+macrophages but more PDL1+CD68+macrophages and PD1+CD8+T cells in liver tissues. Simultaneous use of TLR2 agonist and PDL1 blockage ex vivo suppressed HBV replication by promoting cytokines production and CD8+T cells cytotoxicity. Upon in vitro IFN-ɑ stimulation, PDL1+monocytes and PD1+CD8+T cells were upregulated, whereas TLR2+monocytes were not increased in PBMC isolated from HBeAg-positive patients, or those with high HBcrAg titers.In NAs-treated patients, lower TLR2+monocyte and increased PD1+HBV-specific CD8+T cell proportions potentially contribute to VBT after switching to Peg-IFN-ɑ therapy. This insufficient immunity may be associated with the HBeAg status and HBcrAg levels.