IL-21-based therapies induce clearance of hepatitis B virus persistence in mouse models.

Chronic hepatitis B virus (HBV) infection causes hepatitis, liver cirrhosis and hepatocellular carcinoma. Covalently closed circular DNA (cccDNA) is the sole viral transcription template and not affected by current treatment options, constituting a key determinant of HBV persistence. Novel therapeutics with demonstrable effectiveness against cccDNA are required. : Previously, we established an HBV persistence mouse model using replicon plasmid derived from a clinical isolate (termed BPS) and identified IL-21 as a potent clearance-inducer. We also described another persistence mouse model based on cccDNA mimics produced termed recombinant cccDNA (rcccDNA). In this work, effectiveness of IL-21-based gene and cellular therapies was tested using these models. : In both models of HBV persistence, single injections with adeno-associated virus (AAV) expressing murine IL-21 highly efficiently induced clearance of both HBV markers from serum, and more importantly, BPS DNA and rcccDNA from mouse liver. Mechanistically, IL-21-induced clearance was associated with activation and liver infiltration of CD8 T cells, and CD8 antibody injections negatively affected AAV-IL-21 effectiveness. More notably, adoptive transfer of CD8 T cells from AAV-IL-21-cured mice engendered clearance in acceptor HBV persistence mice. Furthermore, cured mice were protected against re-challenge with long-lived memory. Most significantly, infusion of splenocytes from treatment-naïve mice stimulated with IL-21 protein and HBV antigen could also induce clearance in treatment-naïve mice. : These data demonstrate IL-21-based gene and cellular therapies as valid candidates for treating chronic HBV infections, with potential in removing cccDNA-harboring hepatocytes via activated CD8 T cells accompanied by long-term protective memory.