Quantitative analysis of GBV-C RNA in liver and serum by strand-specific reverse transcription-polymerase chain reaction

Quantification of hepatitis C amino acid substitutions 70 and 91 in the core coding region by real-time amplification refractory mutation system reverse transcription-polymerase chain reaction

OBJECTIVE

The effects of hepatitis C virus (HCV) sequence variations on the success of antiviral therapy or the development of hepatocellular carcinoma (HCC) are complex for many reasons. Recently, there have been several reports on the effects of genotype 1b HCV core amino acid substitutions 70 and/or 91 on the outcome of antiviral therapies and the clinical course. The purpose of this study was to establish real-time amplification refractory mutation system (ARMS) reverse transcription (RT)-polymerase chain reaction (PCR) assays for easy detection of these HCV mutations.

MATERIAL AND METHODS

Plasmids p-core-W, including the wild-type HCV core coding region (70R and 91L), and p-core-M, including the mutant-type HCV core (70Q and 91M), were constructed by cloning and PCR-based mutagenesis for control vector of the wild-type core and that of the mutant core, respectively. Using serially diluted forms of these vectors, SyBr Green-based real-time ARMS RT-PCR detection with each of the specific primer pairs was performed.

RESULTS

Each primer could clearly distinguish the difference between p-core-W and p-core-M at the same copy numbers. Concerning substitution 70, the ratios 100:1, 10:1, 1:1, 1:10, and 1:100 of p-core-W versus p-core-M could be distinguished, while for substitution 91, the ratios 100:1, 10:1, 1:1, 1:10, 1:100, and 1:1000 could be distinguished, confirming the sensitivity and specificity of the assay.

CONCLUSIONS

This method could be a useful alternative for the detection of genotype 1b HCV core amino acid substitutions 70 and 91 and be reliably applied for rapid screening.

Weak association between SEN virus viremia and liver disease

Recently, a novel DNA virus designated SEN virus (SEN-V), which is thought to be related to posttransfusion hepatitis, was discovered. The aim of the present study was to clarify the relationship between SEN-V infection and the development of liver disease. We examined SEN-V from the sera of 21 patients with non-B, non-C hepatocellular carcinoma (HCC) and 13 patients with non-B, non-C chronic liver disease (CLD) without HCC who were admitted to our hospital between 1995 and 1997. Thirty-two patients without liver disease served as controls and were also examined for SEN-V. SEN-V DNA was detected by the nested PCR method after extraction of DNA from serum. SEN-V DNA was detected in 74% (25 of 34) of patients with CLD with or without HCC who were negative for both hepatitis B virus surface antigen and anti-hepatitis C virus antibody. SEN-V DNA was detected in 69% (9 of 13) of CLD patients without HCC and in 76% (16 of 21) of HCC patients. The prevalence of SEN-V was no higher in patients with liver disease than in patients without liver disease (24 of 32; 75%). There were no significant differences in age, sex, liver function, history of blood transfusion, or amount of alcohol intake between SEN-V-positive and SEN-V-negative CLD and HCC patients. Genetic analysis suggested that SEN-V is closely related to the TT virus family. SEN-V was detected at almost the same frequency in patients with and without liver disease. SEN-V does not seem to contribute either to the pathogenesis of liver disease or to the development of HCC from chronic liver disease.

Sequence-motif analysis of 5'-untranslated region of GB virus-C in Japanese patients

BACKGROUND

GB Virus C (GBV-C) is considered to belong to the Flaviviridae; however, the structures of the N-terminal end of its putative polyprotein are not well known. The internal ribosomal entry site (IRES) at the 5'-untranslated region of GBV-C and an initiating codon at nucleotides (nt) 552-554 have been proposed. We investigated the validity of this proposal.

METHODS

The 5'-untranslated region of GBV-C was amplified from serum samples of 17 Japanese patients. Polymerase chain reaction-amplified products were directly sequenced and the obtained sequences were analysed by comparing them with the IRES structure of other viruses.

RESULTS

Fifteen of the 17 (88%) GBV-C strains in our patients were classified as being Asian type. The box-A-like sequence (UUUC) and box-B-like sequence (AUCAUGG) observed in the IRES of picornaviruses were highly conserved in all the strains. Based on pair-wise comparisons with the multiple alignment data, overall sequence divergence for the 5'-terminus was 2.9-12%. When compared with the proposed secondary structure of the IRES model, the sequence divergences of the Asian-type GBV-C were higher at the regions of loop structures and lower at the regions of double-stranded RNA. The AUG codons, except for the one located at nt 552-554, produced truncated polyproteins or were not in-frame with the putative protein.

CONCLUSIONS

Our examination of the sequence motif of GBV-C supports the proposal that the GBV-C has common structural motifs for IRES at its 5'-untranslated region and the AUG codon at nt 552-554 may be an initiating codon.

Prevalence of GB virus C (also called hepatitis G virus) markers in Norwegian blood donors

GB virus C (GBV-C), also called hepatitis G virus (HGV), occurs worldwide, but the clinical significance of this virus is still unclear. Plasma samples from 1,001 blood donors were tested by reverse transcription PCR using primers from the NS5 region and by a commercial enzyme-linked immunosorbent assay (ELISA) for the detection of immunoglobulin G antibodies against the putative envelope of HGV (anti-HGV E2). GBV-C/HGV RNA was present in the plasma from 2.5% of the blood donors, and anti-HGV E2 antibodies could be detected in 10.5% of the samples. Only one of the blood donors with viremia had elevated levels of alanine aminotransferase. Among ELISA-positive donors, there was a significantly higher percentage (16.5%) of individuals who had been treated by acupuncture than individuals who had not been given this treatment (9.4%). No other variables showed significant differences. Screening of medical records from 401 recipients of blood from PCR-positive donors revealed no association with liver disease. Four of 12 partners (33%) were HGV RNA positive, and sequence analyses of the strains showed that four of the couples probably were infected with the same strains, while strains from different couples were not identical. Anti-HGV E2 antibodies were detected in serum samples from four other partners. The prevalence of GBV-C/HGV among blood donors in our region is dramatically higher than the prevalence of hepatitis C virus (0.03%).