Hepatitis C virus.

HepCV is the major cause of NANB PT hepatitis and is also implicated as the cause in a large proportion of sporadic cases of NANBH. Chronic infection with HepCV has also been linked to the development of hepatocellular carcinoma. Chimpanzees and marmosets are the only animals found to be experimentally infectable and the virus has not been propagated in any cell culture system. HepCV is an enveloped virus with a diameter of 30-60 nm and a 10-kb positive-stranded RNA genome. Its genome organization resembles that of the flaviviruses and pestiviruses. A 5'-untranslated segment of 341 nucleotides precedes a continuous ORF of 9030/9033 nucleotides which is followed by a 54 nucleotides long 3'-non-coding segment. Further work is required to resolve the question of whether the genomic RNA possesses a 3'-poly(U) or poly(A) tail. The genome also carries an internal poly(A) segment towards the 5'-end of its ORF. Genomic RNA is probably translated into a single polyprotein of 3010/3011 amino acids which is processed into functional proteins. The viral proteins have not been identified, but on the basis of the predicted amino acid sequences, hydrophobicity plots, location of potential glycosylation sites and similarities of these properties to those of pesti- and flaviviruses, the following genome organization has been predicted. The predicted viral structural proteins, a nucleocapsid protein and two envelope glycoproteins are located at the amino-terminal end of the polyprotein. They are followed by a highly hydrophobic protein and proteins that exhibit proteinase, helicase and replicase domains and thus are probably involved in RNA replication and protein processing. The replicase domain is located close to the carboxy terminus of the polyprotein. Although the overall nucleotide and amino acid homologies between HepCV and pestiviruses are low, a number of similarities exist that point to a closer ancestral relationship to the latter than the flaviviruses. First, the 5'-untranslated segment of the HepCV genome resembles that of the pestivirus genomes in size and presence of several short ORFs and it contains several segments with high nucleotide homology. Second, the two putative envelope glycoproteins of HepCV resemble two of the three putative envelope glycoproteins of the pestiviruses. Because its genome organization and predicted virion structure closely resemble those of the flaviviruses and pestiviruses, HepCV has been proposed to be placed in the family Flaviviridae.(ABSTRACT TRUNCATED AT 400 WORDS)