Hepatitis A virus (HAV), hepatitis B virus (HBV) and hepatitis C virus (HCV) are responsible for most cases of viral hepatitis. Infection by each type of virus results in a different typical natural disease course and clinical outcome that are determined by virological and immunological factors. HCV tends to establish a chronic persistent infection, whereas HAV does not. HBV is effectively controlled in adults, although it persists for a lifetime after neonatal infection. In this Review, we discuss the similarities and differences in immune responses to and immunopathogenesis of HAV, HBV and HCV infections, which may explain the distinct courses and outcomes of each hepatitis virus infection.

Acute hepatitis A (AHA) involves severe CD8 T cell-mediated liver injury. Here we showed during AHA, CD8 T cells specific to unrelated viruses became activated. Hepatitis A virus (HAV)-infected cells produced IL-15 that induced T cell receptor (TCR)-independent activation of memory CD8 T cells. TCR-independent activation of non-HAV-specific CD8 T cells were detected in patients, as indicated by NKG2D upregulation, a marker of TCR-independent T cell activation by IL-15. CD8 T cells derived from AHA patients exerted innate-like cytotoxicity triggered by activating receptors NKG2D and NKp30 without TCR engagement. We demonstrated that the severity of liver injury in AHA patients correlated with the activation of HAV-unrelated virus-specific CD8 T cells and the innate-like cytolytic activity of CD8 T cells, but not the activation of HAV-specific T cells. Thus, host injury in AHA is associated with innate-like cytotoxicity of bystander-activated CD8 T cells, a result with implications for acute viral diseases.

ObjectiveThe use of tenofovir (TDF) and entecavir (ETV) in patients with chronic hepatitis B (CHB) has led to a decrease in the incidence of hepatocellular carcinoma (HCC) and liver-related events. However, whether there is a difference between the two agents in the extent of improving such outcomes has not been clarified thus far. Therefore, we aimed to compare TDF and ETV on the risk of HCC and mortality.DesignA total of 7015 consecutive patients with CHB who were treated with TDF or ETV between February 2007 and January 2018 at the liver units of the Catholic University of Korea were screened for study eligibility and 3022 patients were finally analysed. Study end points were HCC and all-cause mortality or liver transplantation (LT) within 5 years after the initiation of antiviral therapy. Propensity score matching (PSM) and inverse probability of treatment weighting methods were used.ResultsNo difference was observed between TDF and ETV in the incidence rates of HCC in the entire cohort (HR 1.030; 95% CI 0.703 to 1.509, PSM model, p=0.880) and subgroups of patients with chronic hepatitis and cirrhosis. Also, no difference was observed between TDF and ETV in the incidence rates of all-cause mortality or LT in the entire cohort (HR 1.090; 95% CI 0.622 to 1.911, PSM model, p=0.763), and patients with chronic hepatitis and cirrhosis.ConclusionThis study has demonstrated the clinical outcomes in patients with CHB who received TDF or ETV treatment. There was no difference in the intermediate-term risk of HCC and mortality or LT between the two drugs.