Absence of extensive genetic heterogeneity of hepatitis C virus in antibody-negative chronic hepatitis C

DNA immunization efficiently targets conserved functional domains of protease and ATPase/helicase of nonstructural 3 protein (NS3) of human hepatitis C virus

Nonstructural protein 3 (NS3) of human hepatitis C virus (HCV) is a conserved multi-functional protein essential for replication and translation of viral RNA and polyprotein processing. Early T-cell response against NS3 is capable of restricting viremia. We aimed at characterizing the immunogenicity in gene immunization of the conserved regions of NS3 critical for protein folding and activity. C57BL/6 mice were injected with NS3 gene of Russian HCV 1b isolate 274933RU. Immunization did not exert any overt histological changes and had no long-term effects on the immune status of NS3 gene-recipients. The immune response in NS3 gene-recipients was screened by antibody ELISA, T-cell proliferation test and immune assays for specific cytokine production. T-lymphocytes of NS3 gene-recipients proliferated in response to peptides representing conserved regions of protease and ATPase/helicase. Stimulated T-lymphocytes produced IL-2, and in response to protease-derived peptides, also IFN-gamma. Potent and long-lasting antibody response was raised against conserved NS3 regions including "Greek-key" motif of protease, motifs II, V and polynucleotide-binding domains of ATPase/helicase. Thus, gene immunization effectively targeted conserved regions critical for NS3 protease and helicase function. In type and specificity, immune response of NS3 gene-immunized mice mimicked immunity achieved in the acute self-limiting HCV infection of human and primates and in virus-exposed healthy individuals, indicating promiscuity of NS3 as immunogen.

Amino acid substitutions in codons 9-11 of hepatitis C virus core protein lead to the synthesis of a short core protein product

BACKGROUND

Previous in vitro experiments have indicated that if the ninth codon of the hepatitis C virus (HCV) core gene is mutated from arginine to lysine, a short 16-kDa (P16) instead of a 21-kDa (P21) core protein will be produced. In this study, we aimed to investigate whether similar mutations existed in patients with chronic HCV infection and whether such mutations led to the expression of P16.

METHODS

The core gene was isolated from patients' sera by reverse transcription-polymerase chain reaction and sequenced.

RESULTS

Three of 10 patients with hepatocellular carcinoma were found to have mutant viruses with missense mutations at codons 9-11: arginine-to-glycine mutation at codon 9 (case 1); lysine-to-glutamine mutation at codon 10 (case 5); and lysine-to-asparagine/threonine-to-alanine double mutations at codons 10 and 11 (case 8). Site-directed mutagenesis and in vitro translation experiments revealed that P16 was expressed by all three mutants. Using gel-purified P21 and P16 proteins obtained from transformed Escherichia coli, the serum titres of anti-P21 and anti-P16 were assayed. Unequal titres of anti-P16 and anti-P21 were found in only cases 1, 5 and 8. A rabbit antibody directed against P16 but not P21 was thus generated for immunohistochemical analysis. P16 was detected in the nuclei of hepatocytes in the peri-hepatoma tissue of a single case (case 1).

CONCLUSIONS

These data indicate that missense mutations at codons 9-11 can occur during chronic HCV infection, which results in the expression of P16 core protein.

Anti-HCV RIBA/LiaTek reactivity and HCV genotype in EIA-negative patients with viremia

Individuals infected with hepatitis C virus (HCV) usually produce anti-HCV antibodies detectable by enzyme immunoassay (EIA); however, in certain viremic cases this antibody does not appear. To investigate whether anti-HCV in these cases is detectable by Western blot (WB), 38 HCV RNA positive/anti-HCV EIA-negative sera were tested by RIBA 3.0 or LiaTek III. The HCV genotypes (INNO-LiPA) were analyzed to determine whether the variance in these genotypes can be the reason for the late, weak antibody production or its absence. As the control group, 282 EIA-positive/HCV RNA-positive patients were examined. A single band reactivity of various intensities by RIBA or LiaTek was observed in 16/38 EIA negative sera. Positive results with NS3 were detected in 4 sera and weak positive (+/-) with core, NS3, and NS5 in 5, 6, and 1 sera, respectively. In 3 cases with anti-NS3, the seroreversion was observed in follow-up. The distribution of genotypes in anti-HCV-negative versus anti-HCV-positive groups was: 1b alone, 50.0% vs. 78.0%; 3a alone, 13.2% vs. 15.6%; and mixed (1b+3a), 36.8% vs. 5.0%, respectively. The follow-up studies showed that viremia was lost spontaneously in 12/35 patients. In some patients infected with two genotypes, the spontaneous loss of the 3a genotype was observed. The study showed that WB tests are useful for serological confirmation of HCV infection in some EIA negative/HCV RNA-positive patients but, because seroreversion may occur, sequential sera samples should be tested. No unusual HCV genotype was detected in anti-HCV-negative/HCV RNA-positive cases, but the frequency of mixed infection with the 1b+3a genotypes in this group was found to be higher than that in anti-HCV-positive hepatitis patients.

HCV seroreactivity and detection of HCV RNA in cirrhotics

This study was carried out to determine the presence of HCV infection in cirrhotic patients and to compare their serologic profiles with detection of HCV RNA by RT-PCR. Liver function profiles were assessed and correlated with infection. Coinfection of HCV with HBV was studied in the Indian context Sera from 62 patients of biopsy confirmed cirrhosis and an equal number of asymptomatic controls were tested for HCV by two ELISA (third generation) kits and nested reverse transcription PCR using primers from the 5'NCR. Other tests included HBV serology (ELISA for HBsAg and anti-HBc) and liver function tests. Twenty-four (38.7%) cases were HCV infected, of which 17 (70.8%) had past exposure to HBV or were coinfected with HBV (either being chronically infected or carriers of HBV). There was no significant difference in the clinical and liver function profiles of HCV infected and uninfected cirrhotics. Similarly, no difference was observed in cases coinfected with both HCV and HBV compared with those infected with HCV alone. Although the difference between positivity of HCV RNA and of anti-HCV was not significant, HCV RNA and anti HCV were present together in only 7/62 (11.3%) cases. Thus testing for both antibody and HCV RNA would be more appropriate than either test alone. HBV infection was seen in about one-fourth of HCV infected cirrhotics. About one-fourth (25.8%) patients had non-B, non-C cirrhosis in whom testing for HCV variants and other recently characterized hepatitis viruses could be performed.

The use of polymerase chain reaction in plasma pools for the concomitant detection of hepatitis C virus and HIV type 1 RNA

BACKGROUND

Detection of viral nucleic acids might increase blood transfusion safety through the detection of recently infected blood donors during the preseroconversion window period. Individual screening is difficult to apply, because of technical and financial constraints.

STUDY DESIGN AND METHODS

A polymerase chain reaction (PCR)-based assay including a polyethylene glycol precipitation step was developed for the concomitant detection of hepatitis C virus (HCV) and HIV type 1 (HIV-1) RNA in plasma pools corresponding to 50 blood donations by the use of commercial assays.

RESULTS

The assay had a sensitivity of less than 33 copies per mL for HCV RNA and 1000 copies per mL for HIV-1 RNA for each individual sample included in the pool. The eight preseroconversion samples with HCV RNA between 1,250 and 762,000 copies per mL were all detected when 100-microL aliquots from the samples were introduced into 5-mL pools of 50 blood donations.

CONCLUSIONS

A PCR-based pooling assay associating a prepurification step with polyethylene glycol allows for the screening of blood donations for HCV and HIV-1 RNA without marked loss of sensitivity from that seen with commercially available assays. This procedure might increase blood safety through systematic screening of blood donations at relatively low cost.

Case report: Clinical and virological analyses of a patient positive for hepatitis C virus-RNA by branched DNA assay but negative for anti-hepatitis C virus antibodies

Infection with hepatitis C virus (HCV) is usually diagnosed by the presence of antibodies against fusion proteins or peptides derived from different regions of the HCV genome. However, a subgroup of patients with HCV viraemia are seronegative for antibody against hepatitis C virus (anti-HCV) by conventional antibody assays. We analysed serum samples from a patient with liver cirrhosis who tested negative for anti-HCV by a second-generation assay, but positive for HCV-RNA by reverse transcription polymerase chain reaction (RT-PCR) and branched DNA signal amplification. To identify possible mutations that could explain the failure of detection of anti-HCV by second-generation assay, PCR-amplified DNA fragments of the core region derived from the serum were cloned and sequenced. Nucleotide (nt) and amino acid (aa) sequence analyses (nt 1-486, aa 1-162) showed no mutations revealing stop codons, frame-shifts, deletions or insertions, but the presence of two amino acid substitutions (aa 75 and 91) when compared with HCV-J, a prototype strain of genotype 1b isolated from a Japanese patient. One of these two mutations (aa 75) was situated in the second hydrophilic domain of the core peptide, but analysis of the hydropathy profile showed only a little change. The two mutations were identical to those identified in other Japanese HCV isolates. The serum immunoglobulin level and T and B cell counts were normal in our patient. Our data suggest that the absence of anti-HCV in this patient was not due to mutations of major epitopes of HCV. Low-dose prednisolone administration just after transfusion may have induced immunological tolerance against HCV in this patient.

Reduced antibody reactivity to hepatitis C virus antigens in hemodialysis patients coinfected with hepatitis B virus

Antibody reactivities to hepatitis C virus (HCV) antigens and to synthetic peptides derived from different parts of the HCV genome (core, NS4, and NS5) were evaluated in HCV-infected hemodialysis patients. In the RIBA 3 assay, NS5 was significantly less recognizable by sera of hemodialysis patients compared to other HCV-infected subjects. Among hemodialysis patients, those coinfected with hepatitis B virus (HBV) (positive for hepatitis B surface antigen [HBsAg+]) showed a reduction in reactivity to C33 and C100. Sera of only 23% of the hemodialysis patients (37 of 161) reacted with more than three of eight peptides tested, significantly fewer than the 60% (12 of 20) of the sera of other HCV-infected patients tested (P = 0.001). This immunosuppression was also manifested by a reduced frequency of recognition of additional peptides on follow-up. An even more reduced reactivity was observed among the HBV-coinfected patients (HBsAg+). The low-responder hemodialysis patients were not infected with any particular genotype of HCV, and the same HCV genotypes observed in the whole group of hemodialysis patients (1a, 1b, 2a, and 3a) were found circulating in the low-responder group. Even in this low-responder population, the good performance of two peptides (peptide 716, corresponding to a portion of the core, and peptide 59, corresponding to a portion of NS4) corroborates the immunodominance of the conserved epitopes within these peptides.