Interleukin-33 mediates both immune-related and non-immune-related inhibitory effects against hepatitis B virus

Chronic infection by hepatitis B virus (HBV) is associated with high risks of liver fibrosis, cirrhosis and hepatocellular carcinoma. HBV covalently closed circular DNA (cccDNA) in the nucleus of infected hepatocyte serves as transcription template. Neither natural resolution of acute infection nor current treatment options for chronic infection are believed to cause cccDNA clearance. We previously showed that injection of IL-33-expressing plasmid facilitated clearance of intrahepatic HBV DNA in a mouse model of HBV persistence. In this work, HBV-targeting therapeutic effects of IL-33 were further explored. Murine IL-33 delivered by recombinant adeno-associated virus (AAV-mIL-33) induced clearance of both serum HBV markers and intrahepatic HBV DNA in two mouse models of HBV persistence based on replicon plasmid and recombinant cccDNA (rcccDNA) respectively. Clearance was associated with serum ALT elevations and liver infiltrations by CD4⁺ and CD8⁺ T cells, indicating IL-33-induced cellular immune responses against HBV-harboring cells. Adoptive transfer of splenocytes from AAV-mIL-33-cured mice was indeed sufficient to engender similar clearance in recipient mice. In vitro, intracellular, instead of extracellular, IL-33 was mainly responsible for repressing viral transcription, protein production and genome replication in Huh7 cells transfected with HBV replicon or rcccDNA. IL-33 was shown to be recruited onto rcccDNA minichromosome accompanied by loss of transcriptional activation epigenetic marks. Finally, transfection of IL-33 into HBV-infected HepG2/NTCP cells resulted in reduced transcription, antigen expression and genome replication, suggesting repression of canonical cccDNA. These data demonstrated diverse inhibitory effects on HBV and HBV-infected cells mediated by IL-33, and suggest IL-33 as an interesting therapeutic candidate.