Interleukin-1 and tumor necrosis factor-α trigger restriction of hepatitis B virus infection via a cytidine deaminase AID

Virus infection is restricted by intracellular immune responses in host cells and this is typically modulated by stimulation of cytokines. The cytokines and host factors which determine the host cell restriction against hepatitis B virus (HBV) infection are not well understood. We screened 36 cytokines and chemokines to determine which were able to reduce the susceptibility of HepaRG cells to HBV infection. Here, we found that pretreatment with IL-1β and TNFα remarkably reduced the host cell susceptibility to HBV infection. This effect was mediated by activation of the NF-κB signaling pathway. A cytidine deaminase, activation-induced cytidine deaminase (AID), was upregulated by both IL-1β and TNFα in a variety of hepatocyte cell lines and primary human hepatocytes. Another deaminase APOBEC3G was not induced by these proinflammatory cytokines. Knocking down of AID expression impaired the anti-HBV effect of IL-1β, and overexpression of AID antagonized HBV infection, suggesting that AID was one of the responsible factors for the anti-HBV activity of IL-1/TNFα. Although AID induced hypermutation of HBV DNA, this activity was dispensable for the anti-HBV activity. The antiviral effect of IL-1/TNFα was also observed on different HBV genotypes, but not on hepatitis C virus. These results demonstrate that proinflammatory cytokines IL-1/TNFα trigger a novel antiviral mechanism involving AID to regulate host cell permissiveness to HBV infection. Introduction The intracellular immune response can eliminate pathogens from a host and host cells possess different mechanisms to counteract viral infection depending on the virus type. Human immunodeficiency virus (HIV) infection is restricted by cellular proteins designated as restriction factors including APOBEC3G (A3G), TRIM5α, tetherin/BST-2 and SAMHD1 (1,2). All of these factors can be induced by stimulation with interferon (IFN). Hepatitis C virus (HCV) is eliminated by type I and III IFNs derived from dendritic cells or infected-hepatocytes (3-6). In hepatocytes this process involves a series of antiviral factors that are downstream genes of IFN, IFN stimulated genes (ISGs). Influenza virus spread and virulence is inhibited by cytokines such as IFNs and TNFα. Responsive genes for these mechanisms include IFN-induced cellular Mx proteins which are dynamin-like GTPases (7,8). However, these cytokine-induced antiviral immune responses are poorly understood in hepatitis B virus (HBV) infection. HBV infection is a worldwide health problem affecting more than 350 million people and is a major cause of the development of liver cirrhosis and hepatocellular carcinoma (9-11). During the course of infection, a number of cytokines and chemokines are upregulated in HBV-infected patients including IFNα/γ/λ, TNFα, IL-1, IL-6, IL-10, IL-12, IL-15 and IL-8 (12-15). Some of these cytokines are reported to suppress HBV replication (3,16-21). In particular, type I, II and III IFNs suppress the replication of HBV in vitro and in vivo (19,20,22-26). Although one of the downstream genes of IFN, A3G, has the potential to reduce HBV replication (27-34), it is still under argument whether this protein is responsible for the anti-HBV activity of type I IFN because it has been previously reported by Dr. Trono’s group that the induction of A3G does not explain the IFN-induced inhibition of HBV replication (28,35). Moreover, these studies were carried out using an HBV transgene which only reproduces a portion of the whole HBV life cycle, mainly focusing on intracellular HBV replication. Here, we screened for cytokines and chemokines that affected HBV infection in HepaRG cells, a human hepatocyte cell line susceptible to HBV by gest on Sptem er 1, 2017 hp://w w w . jb.org/ D ow nladed from