Induction of innate inflammatory responses is the major cause of liver toxicity associated with AAV-mediated RNA interference (P4007)

Abstract

Abstract Adeno-associated virus (AAV)-mediated RNA interference shows promise as a therapy for chronic hepatitis B virus (HBV) infection, but its low efficacy and hepatotoxicity pose major challenges. We have generated AAV vectors containing different promoters and a panel of HBV-specific short hairpin RNAs (shRNAs) to investigate factors that contribute to the efficacy and pathogenesis of AAV-mediated RNA interference. HBV transgenic mice injected with AAV vectors containing the U6 promoter produced abundant shRNAs, resulting in significant, but transient, HBV suppression and severe liver injury. AAVs containing the weaker H1 promoter did not cause liver injury, but their therapeutic efficacy was highly dependent on the sequence of the shRNA. Mice treated with the toxic U6 promoter-driven shRNA showed little change in hepatic microRNA levels, but a dramatic increase in hepatic leukocytes and inflammatory cytokines and chemokines. Hepatotoxicity was completely absent in immunodeficient mice and significantly alleviated in wild-type mice depleted of macrophages and granulocytes, suggesting that host inflammatory responses are the major cause of liver injury induced by U6 promoter-driven shRNA. Our results demonstrate that a combination of the H1 promoter and a highly potent shRNA can achieve sustained HBV suppression without inducing inflammatory side-effects.