The ability of HCV to remain cell associated and prevent host cell death is the main determinant of viral pathogenicity, which causes persistent infection in the liver. Presence of closely related but heterogeneous population of virus genome is one of the important factors responsible for persistence of HCV infection in the liver.
Hepatocytes and possibly B lymphocytes are the natural targets of HCV. Results of recent studies show that at least 50% of hepatocytes may be infected with HCV in patients with chronic hepatitis. In most infected people, viremia persists and is asso-ciated with a variable degree of hepatic inflammation and fibrosis.
Chronics hepatitis is characterized by lymphocyte infiltration either within the portal tract or in the liver lobule and portal and periportal fibrosis. Portal inflammation, interphase hepatitis, and lobular necrosis are the main histopathological features of chronic hepatitis caused by HCV.
Immunity to HCV may not be lifelong, and serum antibodies to HCV are usually protective. Cell-mediated immunity, mainly cytotoxic T lymphocytes, contributes primarily to liver inflam-mation and ultimately to tissue necrosis.