Clearance of the hepatitis B virus (HBV), a noncytopathic double-stranded DNA virus, requires the coordinated response of innate and adaptive, humoral and cellular immune systems. In more than 90% of immunocompetent adults who become infected, this immune response is quite vigorous, resulting in acute, self-limited hepatitis with rapid reduction of viral load and long-lasting, protective humoral and cellular immunity. However, in 5% of HBV-infected immunocompetent adults, and most cases of vertical transmission of HBV, persistent infection and chronic necroinflammatory liver disease evolve which may eventually lead to liver cirrhosis and hepatocellular carcinoma.
In HBV infection, the cellular immune response is thought to contribute to both viral clearance and liver cell injury. These two opposing functions have even been attributed to the same cell: upon cognate recognition of viral peptides on MHC class I molecules of HBV-infected cells, CD8+...
