Hepatitis C: an overview.

Hepatitis C virus (HCV) has been associated with acute and chronic posttransfusion and with sporadic non-A non-B (NANB) hepatitis, cirrhosis, and hepatocellular carcinoma (HCC). Cloning of the sequence encoding an antigenic component of HCV in 1989 led to the development of tests to detect antibody to HCV in serum. Viral HCV RNA can be detected and estimated with polymerase chain reaction (PCR) and branched-chain DNA (bDNA) signal amplification tests. The entire viral genome has been sequenced. The HCV envelope region varies considerably, and infections with mutant HCV have been described. Approximately 0.5-1.5% of healthy blood donors test positive, and HCV infection can be acquired by blood transfusion or i.v. drug abuse. Vertical and sexual transmission of the virus is rare, and the transmission mode remains obscure in a large group of patients. Acute hepatitis C is mild and often asymptomatic. Chronic hepatitis C has an indolent course but may progress to cirrhosis and HCC. Recombinant alpha interferon (IF) is used to treat chronic HCV disease, but no consensus has been reached on patient selection, dose, and duration of treatment. Approximately 50% of treated patients respond, but 50-80% of responders relapse over time. Liver transplantation in patients with end-stage, HCV-related liver disease is often followed by allograft infection. Short-term survival with reinfection is good, but the long-term consequences remain to be defined.

Hepatitis C virus: quantitation and distribution in liver.

The optimal method for viral quantitation and the most appropriate site for determining viral load in patients with chronic hepatitis C virus (HCV) infection are unknown. We developed a method for measuring HCV RNA in the liver with the following features: 1) efficient extraction of RNA from tissue (89% of RNA recovered); 2) accurate amplification using branched DNA with strong concordance between a single sample tested on multiple occasions either in the same or in different runs; 3) good sensitivity (95%) and specificity (100%). HCV RNA was detected in as little as 2 mg of tissue, and viral load determined in a needle biopsy was representative of viral load in other parts of the liver. Within individual livers, 68% of the samples quantitated were within 1.5-fold of the geometric mean, and 95% were within 2.2-fold of the geometric mean. The mean ratio of virus in the liver and serum was 103, range 17.4-286. A delay of 30 minutes before freezing the liver tissue resulted in a reduction in the measured viral load in some, but not all instances. A sensitive, specific and reproducible method for quantitating HCV RNA in the liver has been developed. Measurement of viral load at one site was representative of viral load at other sites. While hepatic HCV RNA levels are consistently greater than serum levels, the ratio of liver of serum viral load varies widely. The clinical use of measurement of viral load in the liver remains to be defined.