Activation of hepatitis C virus following immunosuppressive treatment

Immune-mediated liver damage in chronic hepatitis C

Although the exact mechanisms inducing the hepatic injury in chronic hepatitis C infection are still not completely elucidated, the evidence of a direct cytopathic viral effect is sparse. The overall majority of experimental studies and clinical observations among patients instead favour immune-mediated hepatocellular damage. This does not exclude the possibility of direct cytopathic viral effects partly contributing to the cell injury. The immune reaction is not always harmful, however. Instead, an intact immune system is probably important for virus clearance in acute infection and after interferon treatment. The therapeutic possibilities are still not adequate, and attempts to understand the immunologic events and manipulate them could perhaps in the future give us more effective tools in the management of this disease.

Interferon and cyclosporin A in the treatment of fulminant viral hepatitis

The prognosis of fulminant hepatitis due to non-A, non-B virus infection and acute reactivation of hepatitis B virus in HB carriers is generally poor, and the treatment of choice in Western countries is recognized as liver transplantation. In countries such as Japan where liver transplantation is not readily available, however, these intractable types of fulminant hepatitis have to be treated medically. Based on the assumption that persistent replication of causal viruses and enhanced host immune responses, especially cellular immunity, to eradicate the viruses are the key mechanism in progressive liver cell destruction and the poor prognosis, we attempted a combination treatment with interferon and cyclosporin A for these types of fulminant viral hepatitis. Subjects in the present study consisted of 1 patient with acute severe hepatitis without coma and 13 patients with coma (13 with fulminant hepatic failure) due to non-A, non-B virus and acute reactivation of hepatitis B virus. The patients were given interferon-beta, 300 x 10(4) U daily, and cyclosporin A, at an initial dose of 3 mg/kg, with tapering. Fourteen patients with coma received artificial liver support that we devised. The patient with acute severe hepatitis survived, showing histologically remarkable liver regeneration. Eight of the 14 patients with hepatic coma, all of whom were indications for liver transplantation according to the criteria of the King's College group, survived. Decreased transaminase level, increased liver volume, and histological liver regeneration were observed in all the survivors. The combination of interferon and cyclosporin A is worth attempting in fulminant hepatitis caused by non-A, non-B virus and acute reactivation of hepatitis B virus in HB carriers.

Human immunodeficiency virus infection and hepatitis C pathology

To investigate the possible influence of human immunodeficiency virus (HIV) infection on hepatitis C virus-related liver disease, liver morphology was evaluated in 160 HBsAg-negative patients with chronic hepatitis C, including 68 HIV-positive and 92 HIV-negative cases. No differences were detected in the severity of necro-inflammatory hepatic lesions between HIV-negative and HIV-positive patients when the CD4+ lymphocytes count exceeded 400 cells/mm3. In contrast, HIV-positive patients with CD4+ lymphocytes below 400 cells/mm3 showed a significantly lower grade of portal inflammation and piecemeal necrosis. These results suggest that liver lesions in hepatitis C may largely depend on immunomediated mechanisms.

Importance of the polymerase chain reaction in the study of hepatitis C virus infection

Recently, the principal etiological agent of parenterally transmitted non-A, non-B hepatitis was molecularly cloned from the plasma of an experimentally infected chimpanzee and has been named hepatitis C virus. Determination of the complete nucleotide sequence of the hepatitis C virus genome was a crucial step in preparing the way for future study of this medically important human pathogen. Due to the very low concentration of virus in serum, amplification of viral RNA sequences by reverse transcription and polymerase chain reaction is the only practical method currently available for demonstrating viremia in patients with hepatitis C virus infection. This review examines the pivotal role of the polymerase chain reaction in understanding the biology of hepatitis C virus.