Hepatitis B virus specific immune response: From antigen recognition to liver damage

The hepatitis B virus (HBV) is a noncytopathic virus that can cause acute and chronic liver infections. Chronic evolution of hepatitis is observed in 5-10% of HBV infections occurring in adult life, whereas chronic HBV persistence is much more frequent (90-95%) following perinatal infection. A co-ordinate, rapid and efficient development of humoral and cell mediated HBV specific immune responses is believed to be crucial for successful resolution of infection. This result can likely be achieved only if the immune response is able to avoid spread of the virus beyond critical threshold levels above which the advantage of the virus over the immune system may become irreversible. While the neutralising antibody response against HBV envelope antigens is important before virus invasion of host cells to prevent virus entry into the cells and later to limit cell to cell spread of viral particles, elimination of infected cells is the principal task of the cell mediated immune response. A different strength of the HLA class I and class II restricted T cell responses is observed in patients with acute and chronic HBV infection, suggesting that this difference may influence the final outcome of infection. Thus, potentiation of the weak anti-viral T cell activity expressed by patients with chronic HBV infection to approximate the levels of responses detected in patients who clear the virus spontaneously may represent an objective for future therapeutic strategies aimed at facilitating the eradication of chronic HBV infection.