Amino acids 1-20 of the hepatitis C virus (HCV) core protein specifically inhibit HCV IRES-dependent translation in HepG2 cells, and inhibit both HCV IRES- and cap-dependent translation in HuH7 and CV-1 cells

A self-modulating mechanism by the hepatitis C virus (HCV) core protein has been suggested to influence the level of HCV replication, but current data on this subject are contradictory. We examined the effect of wild-type and mutated core protein on HCV IRES- and cap-dependent translation. The wild-type core protein was shown to inhibit both IRES- and cap-dependent translation in an in vitro system. This effect was duplicated in a dose-dependent manner with a synthetic peptide representing amino acids 1-20 of the HCV core protein. This peptide was able to bind to the HCV IRES as shown by a mobility shift assay. In contrast, a peptide derived from the hepatitis B virus (HBV) core protein that contained a similar proportion of basic residues was unable to inhibit translation or bind the HCV IRES. A recombinant vaccinia-HCV core virus was used to examine the effect of the HCV core protein on HCV IRES-dependent translation in cells and this was compared with the effects of an HBV core-recombinant vaccinia virus. In CV-1 and HuH7 cells, the HCV core protein inhibited translation directed by the IRES elements of HCV, encephalomyocarditis virus and classical swine fever virus as well as cap-dependent translation, whereas in HepG2 cells, only HCV IRES-dependent translation was affected. Thus, the ability of the HCV core protein to selectively inhibit HCV IRES-dependent translation is cell-specific. N-terminal truncated (aa 1-20) HCV core protein that was expressed from a novel recombinant vaccinia virus in cells abrogated the inhibitory phenotype of the core protein in vivo, consistent with the above in vitro data.

Specific detection of minus-strand hepatitis C virus RNA by reverse-transcription polymerase chain reaction on PolyA(+)-purified RNA

A full-length complementary DNA (cDNA) clone of the hepatitis C virus (HCV) genome was used to prepare full-length plus- and minus-strand RNA. The minus-strand RNA, which contains a polyA(+) tract complementary to the polyU tract found in the plus strand (genomic) RNA, but not the plus strand RNA, was captured with a commercial polyA(+)-tract isolation system. After elution, the minus strand was amplified by reverse-transcription polymerase chain reaction (RT-PCR). The combination of this procedure and RT-PCR using rTth resulted in an unprecedented level of discrimination of 10 logs(10). HCV minus-strand RNA isolation was unaffected by the addition of an excess of 10(4) of plus strands or by the addition of cellular RNA, and although the polyA(+) isolation step removed 99. 99% of plus strands, there was no loss of minus-strand signal. Minus-strand RNA was detected in RNA extracted from 4/4 liver samples and 4/8 peripheral blood mononuclear cells (PBMC) samples examined. Because the titer of plus-strand HCV RNA in any sample makes a significant contribution to false, random, and self-priming, removal of the plus strand in this manner results in the most accurate method yet devised to confirm the replication of HCV in a population of cells.