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Figure 1. Summary of hepatitis B virus (HBV) and host interactions. When humans are exposed to HBV, either acute hepatitis with subsequent virus clearance or persistent infection may develop. Those who are infected in the early stages of life, and via vertical transmission, are prone to progress to persistent infection. HLA-DP and -DQ loci are associated with persistent HBV infection in East Asians. Chronic persistent HBV infection starts with the presence of hepatitis B e-antigen (HBeAg), known as the immune tolerance stage. In this phase, Africans tend to clear HBeAg before puberty while East Asians tend to clear HBeAg between the second and fourth decades of life. About 5% of HBeAg-negative patients still present with active viral replication. Many immune-related genes participate in HBV clearance. Inability to effectively clear HBV may result in liver cirrhosis and increased HBV mutations and integrations into the human genome. All of these events and some genetic polymorphisms in the host may promote hepatocarcinogenesis. HCC: hepatocellular carcinoma