Molecular biology of the hepatitis C viruses: implications for diagnosis, development and control of viral disease

Characterization of the hepatitis C virus-encoded serine proteinase: determination of proteinase-dependent polyprotein cleavage sites

Processing of the hepatitis C virus (HCV) H strain polyprotein yields at least nine distinct cleavage products: NH2-C-E1-E2-NS2-NS3-NS4A-NS4B-NS5A-NS5B-CO OH. As described in this report, site-directed mutagenesis and transient expression analyses were used to study the role of a putative serine proteinase domain, located in the N-terminal one-third of the NS3 protein, in proteolytic processing of HCV polyproteins. All four cleavages which occur C terminal to the proteinase domain (3/4A, 4A/4B, 4B/5A, and 5A/5B) were abolished by substitution of alanine for either of two predicted residues (His-1083 and Ser-1165) in the proteinase catalytic triad. However, such substitutions have no observable effect on cleavages in the structural region or at the 2/3 site. Deletion analyses suggest that the structural and NS2 regions of the polyprotein are not required for the HCV NS3 proteinase activity. NS3 proteinase-dependent cleavage sites were localized by N-terminal sequence analysis of NS4A, NS4B, NS5A, and NS5B. Sequence comparison of the residues flanking these cleavage sites for all sequenced HCV strains reveals conserved residues which may play a role in determining HCV NS3 proteinase substrate specificity. These features include an acidic residue (Asp or Glu) at the P6 position, a Cys or Thr residue at the P1 position, and a Ser or Ala residue at the P1' position.

Immunoglobulin M reactivity towards the immunologically active region sp75 of the core protein of hepatitis C virus (HCV) in chronic HCV infection

Serum samples from a cohort of patients with chronic hepatitis C virus (HCV) infection were assayed for IgM anti-HCV/core reactivity with a "site-specific" ELISA, in which the solid phase was charged with the synthetic polypeptide analogue corresponding to the first 75 amino acids of the HCV core antigen (sp75). Thirteen of 24 (54%) patients exhibited IgM anti-sp75 reactivity. Both high-titered (1/16,000-1/32,000) and low-titered (1/1,000-1/4,000) IgM anti-sp75 reactive sera were found. IgM anti-sp75 antibodies persisted in the circulation over a long period in patients with fluctuating abnormal ALT levels. There was a striking association between detection of specific IgM anti-sp75 reactivity and the presence of HCV RNA in serum. Thus 11 of 15 (73%) sera containing HCV RNA also contained IgM anti-sp75 antibodies, while none of the HCV RNA-negative sera were IgM anti-sp75 reactive. Five of 11 patients without detectable levels of specific IgM anti-sp75 antibodies had their ALT levels returned to normal within 8 months to 3 years. Furthermore, a significant correlation was noted between the specific IgM anti-sp75 titers and the concentration of total plasma IgM, indicating that the immunological active region sp75 within the capsid of HCV has the capacity to induce an IgM secretion, which constitutes a substantial portion of the total plasma IgM, in patients with chronic HCV infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression and identification of hepatitis C virus polyprotein cleavage products

Hepatitis C virus (HCV) is the major cause of transfusion-acquired non-A, non-B hepatitis. HCV is an enveloped positive-sense RNA virus which has been classified as a new genus in the flavivirus family. Like the other two genera in this family, the flaviviruses and the pestiviruses, HCV polypeptides appear to be produced by translation of a long open reading frame and subsequent proteolytic processing of this polyprotein. In this study, a cDNA clone encompassing the long open reading frame of the HCV H strain (3,011 amino acid residues) has been assembled and sequenced. This clone and various truncated derivatives were used in vaccinia virus transient-expression assays to map HCV-encoded polypeptides and to study HCV polyprotein processing. HCV polyproteins and cleavage products were identified by using convalescent human sera and a panel of region-specific polyclonal rabbit antisera. Similar results were obtained for several mammalian cell lines examined, including the human HepG2 hepatoma line. The data indicate that at least nine polypeptides are produced by cleavage of the HCV H strain polyprotein. Putative structural proteins, located in the N-terminal one-fourth of the polyprotein, include the capsid protein C (21 kDa) followed by two possible virion envelope proteins, E1 (31 kDa) and E2 (70 kDa), which are heavily modified by N-linked glycosylation. The remainder of the polyprotein probably encodes nonstructural proteins including NS2 (23 kDa), NS3 (70 kDa), NS4A (8 kDa), NS4B (27 kDa), NS5A (58 kDa), and NS5B (68 kDa). An 82- to 88-kDa glycoprotein which reacted with both E2 and NS2-specific HCV antisera was also identified (called E2-NS2). Preliminary results suggest that a fraction of E1 is associated with E2 and E2-NS2 via disulfide linkages.

Differences in the hepatitis C virus genotypes in different countries

We recently classified the hepatitis C virus (HCV) into 4 types (HCV-PT, -K1, -K2a and -K2b) according to differences in nucleotide sequences. It was found that HCV-PT, the prototype reported from the U.S.A., was rare in Japan, suggesting that distribution of HCV genotypes may be different in various countries. The prevalence of HCV genotypes was therefore compared in different countries. Genotyping of HCV was performed by slot-blot hybridization analysis using cDNA probes specific to each type of HCV or by restriction fragment length polymorphism analysis. In 121 Japanese non-cancer patients, the prevalence of HCV genotypes was 77.7% for HCV-K1, 16.5% for HCV-K2a and 5.0% for HCV-K2b. HCV-PT was detected in only 1 patient (0.8%). The prevalence in 43 Japanese hepatocellular carcinoma (HCC) patients was 74.4% for HCV-K1, 18.6% for HCV-K2a and 4.7% for HCV-K2b. HCV-PT was found in only 1 sample. In 19 European non-cancer patients, HCV-PT was found in 42.1% and HCV-K1 was found in 52.6%. HCV-K2 was not found. All 7 samples from European HCC patients were HCV-K1, indicating a significantly higher prevalence than in non-cancer patients. In 13 Brazilian non-cancer patients, the distribution pattern was similar to that of the Europeans. In 10 samples from the U.S.A., HCV-PT was found in 70% and HCV-K2 was found in 1 sample. In 18 Chinese non-cancer patients, HCV-K1 was found in 44.4%, HCV-K2a in 50.0% and HCV-K2b in 5.6% HCV-PT was not found. Two samples from Chinese HCC patients were HCV-K1.(ABSTRACT TRUNCATED AT 250 WORDS)

Presence of viral replicative intermediates in the liver and serum of patients infected with hepatitis C virus

Hepatitis C virus (HCV) is a positive-polarity, single-stranded RNA virus, distantly related to the pestivirus and flavivirus genera. These viruses replicate through the formation of a minus-strand RNA intermediate, which encodes the positive-strand genome, which is subsequently encapsidated, enveloped, and released from infected cells. Minus-strand RNA is not found in the mature, circulating virions of flaviviruses. In an attempt to study the relative amounts of viral plus and minus strand in the liver and serum of HCV-infected individuals, we have developed a technique to amplify specifically each of the viral strands using a modified reverse transcriptase/polymerase chain reaction protocol on extracted RNA. Liver tumor and nontumor tissue from a patient with C-100-3 antibody was analyzed using this technique. In both cases, viral plus and minus strands were detected, although the plus-strand signal was several fold stronger than minus-strand signal by Southern hybridization. Sera from 11 C-100-3 antibody-positive patients with abnormal serum AIT levels were similarly analyzed. In all cases viral plus strand was detected, and in 10 of 11 cases viral minus strand was detected. The minus-strand signal was always much weaker than the plus-strand signal and the ratio of plus strand to minus strand varied among patients. No correlation was found between the level of minus strand detected or its ratio to plus strand with the level of serum transaminases or any other clinical parameter.

Detection of hepatitis C virus (HCV) RNA by PCR related to HCV antibodies in serum and liver histology in Swedish blood donors

Serum samples from 103 blood donors or patients with slightly increased serum levels of liver enzymes were tested for antibodies to hepatitis C virus (anti-HCV) using second generation tests and for HCV RNA by the polymerase chain reaction (PCR). PCR was in a nested configuration, using primer pairs from the 5'-nontranslated region. The anti-HCV antibody was found by enzyme linked immunosorbent assay (ELISA) in 93 patients. The anti-HCV confirmatory second generation recombinant immunoblot assay (RIBA) was positive in 44, indeterminate in 34 and negative in 25 subjects. Histopathological examination of the liver was carried out in 51 subjects. HCV RNA was detected in serum of 39/41 (95%) RIBA positive patients, and in 7/34 (21%) RIBA indeterminate subjects, but in none of the RIBA negative subjects. All but one of the PCR positive patients with a RIBA indeterminate pattern exhibited the C22 band. HCV RNA was found in the serum of all but one patients with chronic active or persistent hepatitis, but also in one RIBA positive subject with normal liver tissue. These results imply that most patients with antibodies to two or more HCV antigens by RIBA will have a chronic replicative HCV infection associated with viraemia. HCV viraemia can also be present in some patients, who have antibodies to only one HCV antigen particularly the C22 epitope.

Routine laboratory diagnosis of hepatitis C virus infection

Hepatitis C virus (HCV) is the major cause of parenterally transmitted non-A, non-B hepatitis. The analysis of the genomic sequence of HCV has facilitated the development of a number of diagnostic assays for testing circulating antibodies in serum from patients with HCV infection. Besides the first-generation ELISA and RIBA, which employed the C100-3 non-structural polypeptide, second-generation tests employing both structural and non-structural polypeptides are being rapidly introduced. Several coded panels were employed in a comparative study of HCV-SP ELISA (utilizing a new synthetic peptide whose sequence was derived from the structural region) along with first- and second-generation tests. On the basis of the results, evidently antigens corresponding to the structural components of the virus are more sensitive and specific for the early detection of HCV antibodies than tests using non-structural epitopes. Additionally epitopes of the structural region elicit a very strong antibody response in laboratory animals. An example of one such application is the detection of HCV specific antigens in semen from patients diagnosed with non-A, non-B (NANB) hepatitis. Semen samples from 9 patients clinically diagnosed as having NANB hepatitis were tested by an ELISA using antibodies against HCV-specific structural antigens. The semen from all 9 patients had HCV-specific structural antigens in comparison to semen from 5 healthy donors. Semen from 5 of the 9 patients had significant levels of the HCV-specific antigen. This approach to detecting HCV antigens could, if rigorously tested, evolve into promising new assays for detecting HCV.

Hepatitis C virus infection in liver allograft recipients

The impact of HCV infection after liver transplantation remains a topic of discussion. The aims of this study were to define the prevalence of anti-HCV antibodies in liver donors; the risk of acquired HCV infection and HCV re-infection according to the pre-transplant anti-HCV status; the prevalence of HCV infection in post-transplant chronic hepatitis. Sera from 42 recipients with follow up longer than 6 months and their donors were tested for anti-HCV. By results at pre-transplant time patients were classified as follows: donor (D) negative and recipient (R) negative (D-/R-) 31; D-/R+ 9; D+/R- 1; D+/R+ 1. Twenty-one patients with sustained hepatic dysfunction underwent liver biopsy. In group D-/R-, 5 patients showed anti-HCV positivity and 3 (9.7%) of them had acquired HCV hepatitis. In group D-/R+, 6 patients showed persistent anti-HCV positivity and 4 (44.4%) of them had recurrent HCV hepatitis; of these 2 died due to liver failure. The 2 patients of groups D+/R- and D+/R+ had normal liver function. Anti-HCV negative hepatitis was found in 2 patients. The prevalence of anti-HCV positivity in liver donors appeared low (3.2%). Acquired HCV infection rate was 9.7%. Pre-transplant HCV infection led to a high incidence of recurrence (44.4%). HCV was the major etiological agent in post-transplant chronic hepatitis (77.8%).

Relation of hepatitis C virus to hepatocellular carcinoma

Hepatitis C virus is an enveloped, single-stranded RNA virus with a positive stranded genome of about 9400 nucleotides. It probably belongs to the family of Flaviviridae which replicate via full-length, complementary, negative-stranded RNA. Hepatitis C virus is the predominant etiologic agent of non-A, non-B hepatitis around the world. It frequently leads to chronic hepatitis which may progress to cirrhosis and hepatocellular carcinoma. The currently available antibody assay for hepatitis C virus cannot distinguish between current and past hepatitis C virus infection. We developed a strand-specific reverse double polymerase chain reaction for detection of hepatitis C virus RNA (non-translated and non-structural sequences) in extracts of hepatocellular carcinoma tissues and the surrounding liver. Negative (replicative) and positive (genomic) strands of hepatitis C virus RNA were detected in both liver and tumor tissues in almost equal frequency and relative amounts. These data suggest that hepatitis C virus replicates in hepatocellular carcinoma cells and supports the epidemiologic evidence for an association between chronic hepatitis C virus infection and hepatocarcinogenesis.

Isolate antibody to hepatitis C virus core antigen (C22) by RIBA-2: correlation with HCV-RNA and anti-NS5

The presence of circulating hepatitis C virus genome (HCV-RNA), elevated ALT levels and antibodies to an NS5-derived synthetic peptide have been examined in 13 subjects with isolate positivity for antibodies to the HCV core antigen (C22) on RIBA-2 testing. All subjects were followed up for 8-18 months (mean 12.4 months). In seven subjects (54%), intermittent or persistent viremia was associated with abnormal ALT levels (6 subjects) and with positivity for antibodies to NS5-peptide (6 subjects). On the other hand, in 6 out of 13 subjects (46%) no viral replication, no liver cytonecrosis and no antibodies to NS5 were found. It is concluded that isolate reactivity to C22 by RIBA-2 is a heterogeneous condition that corresponds to two distinct categories of subjects: those with active HCV infection and those without evidence of virus replication. Although HCV-RNA determination is the most reliable means of identifying HCV carriers, antibodies to NS5 can be a useful marker of virus activity. In fact, antibodies to NS5 were detected in 6 out of 7 viremic patients, compared to 0 out of 6 non-viremic patients (P = 0.004). It remains to be elucidated whether the isolate reactivity to core antigen found in non-viremic subjects represents a specific, HCV-induced antibody response, or is an unrelated crossreactivity.

Polymerase chain reaction for the diagnosis of hepatitis B and C viral hepatitis

The detection of HBV, HCV, and HDV genomes through the use of the polymerase chain reaction (PCR) has made possible a new step in viral diagnosis. The main advantages of PCR are its extreme sensitivity and the possibility to develop rapid assays using non-radioactive probes. Several studies have now clearly shown its usefulness for the demonstration of viremias, the identification of seronegative viral carriers, and studies on mother-to-child transmission. Several limitations, however, still hamper the use of PCR and it should not yet be regarded as a routine test. The main developments to be expected in the near future deal with automatisation, prevention of contamination, and quantification.

Persistence of hepatitis B and hepatitis C viral genomes in primary liver cancers from HBsAg-negative patients: a study of a low-endemic area

The role of HBV and HCV in the course of primary liver cancer in patients who are negative for HBsAg has been debated. Using a combination of serological and polymerase chain reaction assays, we investigated the association between HCV and HBV infections and primary liver cancer in 24 HBsAg-negative patients living in France. The presence of HCV RNA and HBV DNA sequences was tested for in serum and in tumorous and nontumorous liver samples. Twelve patients had anti-HCV, and 11 patients had anti-HBs and/or anti-HBc. HCV RNA sequences were found in the serum samples of all anti-HCV-positive patients and none of the patients who were negative. Patients with HCV viremia had HCV RNA genomic sequences and presumed replicative intermediates in both tumorous and nontumorous specimens. Sequence analysis of a hypervariable region in the E2/NS1 gene of HCV showed significant variations between the viral molecules isolated from the nontumorous, tumorous and serum samples. This eliminated the hypothesis of the contamination of the tumor by nontumorous cells and serum particles and assessed that liver tumor cells did contain HCV RNA genomes. Eleven of 22 patients tested had HBV DNA in the serum; 5 patients were anti-HBc positive and anti-HBs positive. Patients with HBV viremia had HBV DNA sequences in both tumorous and nontumorous liver specimens. Selective loss of part of the HBV genome in the tumorous tissue of two of these patients suggested HBV DNA persistence in clonally expanded malignant cells. Only 4 of the 22 patients were negative for both viruses. Our results show that HBsAg-negative hepatocellular cancer in France is associated with chronic HBV or HCV infection and, in some cases, both; these findings are consistent with an etiological role for HBV and HCV in HCC that develops in cirrhotic patients living in areas of low prevalence.

Hepatitis C virus infection and disease. Diagnostic problems

Hepatitis C virus (HCV) is a lipid-enveloped single-stranded RNA virus with an unknown physical structure as only putative HCV particles have been identified by electron microscopy. Although HCV lacks the retroviral properties of being able to integrate into host DNA, it causes chronic infection in a considerable number of infected individuals (40-60%). Chronic infection is associated with a wide spectrum of liver diseases ranging from normal presentation to the different forms of chronic hepatitis, cirrhosis (about 20% of cases) and hepatocellular carcinoma. HCV therefore is not invariably and equally pathogenic, and genetic heterogeneity could be a major cause of such variability. Diagnosis of HCV infection relies on anti-HCV and HCV-RNA detection. Using second-generation assays, diagnostic sensitivity has increased to about 95%, but detection of anti-HCV does distinguish past from present infections. Only rising anti-HCV titres or anti-HCV seroconversion confirm a recent HCV infection. In anti-HCV-negative infections and cases of early acute hepatitis, HCV-RNA detection by RT-PCR represents a valid diagnostic alternative. In patients undergoing interferon therapy, testing for anti-HCV by immunoblotting represents a valid routine tool to monitor response. Anti-C-22 has the highest titre and persists longer while anti-C-100 is the earliest antibody to disappear in responders. The significant association between serum anti-C-100, HCV-RNA and liver disease suggests that anti-C-100 is an indirect marker of hepatitis C, but true markers of HCV-induced liver disease are still lacking.

5' end-dependent translation initiation of hepatitis C viral RNA and the presence of putative positive and negative translational control elements within the 5' untranslated region

Hepatitis C virus (HCV) is a distant relative of pestiviruses and flaviviruses, but it has a 5' untranslated region (UTR) with some features structurally similar to that of picornaviruses. In order to test the role of the 5' UTR in controlling the expression of the HCV polyprotein, we fused full-length or deleted versions of the 5' UTR of HCV-1 RNA to chloramphenicol acetyl transferase (CAT) mRNA to monitor CAT activity in vivo. We found: (1) the full-length 5' UTR of HCV-1 RNA is translationally inactive while 5' deletions which mimic a 5' subgenomic RNA detected in vivo are active, (2) an efficient cis-acting element which represses translation is found at the 5' terminus, (3) a putative element which enhances translation is found near the 3' terminus of the 5' UTR, (4) additional cis-acting elements including small open reading frames (ORFs) upstream from the putative enhancer element downregulate translation. We did not find evidence supporting the existence of an internal ribosome entry site in the 5' UTR of HCV-1 RNA. These data suggest that HCV may employ a distinctive translation control strategy such as the generation of subgenomic viral mRNA in infected cells. Translational control of HCV might be responsible for some of the characteristic pathobiology seen in viral infection.

Storage conditions of blood samples and primer selection affect the yield of cDNA polymerase chain reaction products of hepatitis C virus

We have noticed that suboptimal specimen processing and storage conditions may cause false-negative results in the detection of hepatitis C virus (HCV) RNA in plasma or serum. To establish the influence of specimen handling in a serological laboratory on the rate of detection of HCV RNA by the cDNA polymerase chain reaction (cDNA-PCR), we tested routine serum samples and fresh-frozen plasma samples from the same bleeding from confirmed anti-HCV-positive blood donors. When primers from the NS3/NS4 region were used, HCV RNA was detected in fresh-frozen plasma from 67% of the donors, whereas positive results were obtained with only 50% of the serum samples that had been subjected to routine serological procedures. Analysis of the same samples with primers from the highly conserved 5'-terminal region (5'-TR) revealed an HCV RNA detection rate of 92% for both the routine and the fresh-frozen samples. However, the yield of the amplification product in routine samples was strongly reduced compared with that in fresh-frozen plasma. Comparison of both primer sets for cDNA-PCR showed that the 5'-TR primer set was 10- to 100-fold more effective in detecting HCV RNA. We also analyzed the effect of storage of whole EDTA-blood and serum at room temperature and at 4 degrees C on the yield of the amplification product. A rapid decline in detectable HCV RNA of 3 to 4 log units was observed within 14 days when whole blood and serum were stored at room temperature. By contrast, no perceptible reduction in the cDNA-PCR signal was found in freshly prepared serum stored at 4 degrees C.

A role for hepatitis C virus infection in type II cryoglobulinemia

BACKGROUND

Type II cryoglobulinemia is a vasculitis characterized by cryoglobulins consisting of complexes of polyclonal IgG and monoclonal IgM rheumatoid factors. The cause of these immune complexes is unknown, though both the hepatitis B (HBV) and C (HCV) viruses have been suspected.

METHODS

We studied 19 patients with Type II cryoglobulinemia for markers of HCV and HBV infection. Quantitative HCV antibody and RNA studies were performed on whole serum, cryoprecipitates, and supernatants.

RESULTS

Eight patients (42 percent) had HCV antibodies, and 16 (84 percent) had HCV RNA: Of the 19 patients, 5 (26 percent) had HBV markers, but only 1 had evidence of active HBV infection. Control serum samples from nine patients with Type I cryoglobulinemia were negative for HCV antibody and HCV RNA: There was a close, although not exclusive, association of one type of rheumatoid factor (WA) with HCV RNA: HCV antibody and HCV RNA were concentrated approximately 10-fold and 1000-fold, respectively, in the Type II cryoglobulins examined.

CONCLUSIONS

Type II cryoglobulinemia is strongly associated with concomitant HCV infection and a high rate of false negative serologic tests. HCV virions and HCV antigen-antibody complexes are concentrated in the cryoprecipitates, most commonly in association with the WA type of rheumatoid factor, suggesting a role for HCV in the pathogenesis of mixed cryoglobulinemia.

Improved detection of hepatitis C virus RNA by reverse transcription and polymerase chain reaction

The polymerase chain reaction with prior reverse transcription of RNA into cDNA was applied to hepatitis C virus RNA detection in human serum samples of different origin. In order to eliminate false negative results, the following steps were optimized: RNA extraction, reverse transcription, and oligonucleotide primer selection. We compared different RNA extraction methods using guanidinium salt/detergent and proteinase K digestion/phenol extraction, and tested virus particle enrichment with polyethylene glycol precipitation and ultracentrifugation. RNA extraction with guanidinium salt/detergent was the most efficient method. Ultracentrifugation of single samples did not improve hepatitis C virus RNA detection. Polyethylene glycol precipitation performed poorly. Recombinant thermostable reverse transcriptase produced cDNA from fewer samples than did Moloney murine leukaemia virus reverse transcriptase. Nested oligonucleotide primers from the 5'-terminal non-coding region of the hepatitis C virus genome amplified cDNA from more samples than did primers from the coding regions. Thirty six anti-hepatitis C virus antibody positive samples were tested; nested primers (nucleotides 6 to 327 and 15 to 288) yielded 21 amplificates, whereas primers from the coding region produced 16 amplificates (nucleotides 4684-5276) and 5 amplificates (nucleotides 5166-5270), respectively. The most efficient combination of steps was RNA extraction with guanidinium salt solution, reverse transcription with Moloney murine leukaemia virus reverse transcriptase and nested polymerase chain reaction primed with primers from the 5'-terminal non-coding region of the hepatitis C virus genome. Other combinations produced more false negative results. Three different groups of anti-hepatitis C virus antibody positive individuals had markedly different viraemia patterns: Hepatitis C virus RNA was detected in the sera of only 10% of anti-hepatitis C virus antibody positive blood donors, but in 90% of anti-hepatitis C virus antibody positive patients with clinically manifest hepatitis C, and 90% of anti-hepatitis C virus antibody positive haemophiliacs who had received plasma products in the past which had not been virus-inactivated. No hepatitis C virus RNA could be detected in the sera of 450 anti-hepatitis C virus antibody negative blood donors with elevated serum alanine aminotransferase catalytic concentrations.

Improved diagnosis of chronic hepatitis C virus infection by detection of antibody to multiple epitopes: confirmation by antibody to synthetic oligopeptides

Serum samples from 226 patients covering a wide spectrum of liver disease were tested for antibodies to hepatitis C virus (HCV) using both first and second generation enzyme linked immunosorbent assays. Selected sera were also tested by peptide immunoassays, by the four-antigen recombinant immunoblot assay (RIBA II), and for viral genome by the polymerase chain reaction. Antibody to c100-3 was detected in 61% of patients with chronic non-A, non-B (NANB) hepatitis and/or 46.5% with presumed NANB-related cirrhosis by the first generation test. These figures increased to 77% and 58% when antibodies to recombinant structural and non-structural HCV antigens were sought by the second generation assay. Supplemental testing against peptide Sp75 and Sp65/sp67 confirmed that reactivity of sera by second generation assays was due to antibodies to the additional structural and non-structural antigens. Samples negative by the first generation assay were not confirmed by the supplemental assay using peptides Sp75 and Sp65/Sp67. HCV RNA was detected in 60% of the anti-HCV positive sera tested, most of which were also RIBA II positive. Our findings confirm that the introduction of the structural and non-structural antigens, especially the putative nucleocapsid protein, improves sensitivity of detection of antibodies to HCV, and facilitates diagnosis in patients with "cryptogenic" chronic hepatitis.

Lack of protective immunity against reinfection with hepatitis C virus

Some individuals infected with hepatitis C virus (HCV) experience multiple episodes of acute hepatitis. It is unclear whether these episodes are due to reinfection with HCV or to reactivation of the original virus infection. Markers of viral replication and host immunity were studied in five chimpanzees sequentially inoculated over a period of 3 years with different HCV strains of proven infectivity. Each rechallenge of a convalescent chimpanzee with the same or a different HCV strain resulted in the reappearance of viremia, which was due to infection with the subsequent challenge virus. The evidence indicates that HCV infection does not elicit protective immunity against reinfection with homologous or heterologous strains, which raises concerns for the development of effective vaccines against HCV.

Genetic drift of hepatitis C virus during an 8.2-year infection in a chimpanzee: variability and stability

Extensive variability in genomic sequence, especially at "hypervariable regions" within the NS1/E2 region of the long open reading frame, has been reported for RNA cloned from hepatitis C virus (HCV)-infected humans and chimpanzees. However, genetic changes of HCV occurring during the course of chronic infections in humans and animals have been evaluated only for partial sequences of the HCV genome. We compared two full-length cDNA sequences of HCV obtained from a chimpanzee that was experimentally infected with the HC-J4 strain of HCV: one during the early acute phase and another during a chronic phase 8.2 years afterward. Both isolates had 9412 nucleotides plus the 3' poly(U) tail with varying length organized as follows: 5'UTR (1-341); C (342-914); E (915-1490); NS1/E2 (1491-2528); NS2 (2529-3359); NS3 (3360-5186); NS4 (5187-6380); NS5 (6381-9371); and 3'UTR (9372-9412). We found that 111 (1.18%) of the 9412 nucleotides differed between the two isolates and estimated the mutation rate as approximately 1.44 x 10(-3) base substitutions per site per year. Changes in amino acid coding were associated with 42 mutations, 8 of which were clustered at 5' end of NS1/E2 coding region, so-called "HVR-1." We analyzed the HVR-1 and HVR-2 sequences during the course of infection and found that homologous populations were present at the beginning of infection, and sequence heterogeneity within the region had developed 3.5 years later. Two regions of the HCV genome were characterized by a high degree of conservation of nucleotide sequence: 5'UTR and the 3' half of the NS4 region. The possible secondary structure of the 5'UTR suggests a region for internal ribosomal entry. The 3' half of the NS4 region may also have some specific function which depends upon a strict conservation of nucleotide sequence.

Hepatitis C virus RNA and antibody response in the clinical course of acute hepatitis C virus infection

Hepatitis C virus RNA, anti-hepatitis C virus immune response and biochemical markers of liver injury were investigated in 17 patients with acute non-A, non-B hepatitis. At the first observation, 1 to 3 wk from the clinical onset, all patients had hepatitis C virus RNA in their serum, and most (15 of 17) were positive for second-generation anti-hepatitis C virus enzyme immunoassay. Follow-up serum samples were available for 10 patients. The rate of recombinant immunoblot assay-confirmed anti-hepatitis C virus enzyme immunoassay reactivities increased from 67% in the first 3 wk to 86% after 21 wk. Elevated ALT levels were associated with hepatitis C virus RNA positivity in most of cases, but the viral nucleic acid was also detected in sera with normal or slightly increased enzyme values. None of the single antibodies tested were related to hepatitis C virus RNA positivity or to the clinical phase of the infection. Therefore hepatitis C virus RNA determination might provide important additional information as compared with anti-hepatitis C virus markers, allowing earlier diagnosis, discrimination of active infection and, possibly, prognostic evaluation.

Treatment of children with chronic hepatitis C with recombinant interferon-alpha: a pilot study

Twelve children with chronic non-A, non-B hepatitis were entered in a pilot trial of recombinant interferon-alpha. Although all the children had hepatitis C virus RNA in serum, only five had antibodies against this virus. Children received 3 MU/m2 body surface area interferon-alpha 3 times/wk for 6 mo; they were followed for 24 mo, including the therapy period. One child was dropped from the study, so the results are from the 11 children who completed the study. At the end of the therapy period, 36% of the children had normal ALT levels; this percentage increased to 90% at mo 15 of follow-up. Thereafter, relapse occurred in five children; thus ALT normalization was observed in 5 of 11 children at the 24th month. Moreover, two different ALT patterns were found: HCV antibody-negative children had significant peaks of ALT levels with respect to the basal samples (p less than 0.05) until the third month of the therapy; these levels later decreased. In contrast, HCV antibody-positive children had slight fluctuations of ALT until normal levels were reached. At the end of treatment, three children had HCV RNA; one demonstrated a rebound in ALT levels. Finally, histological activity had decreased significantly in the second liver biopsy specimen in all children. In summary, interferon treatment in children with chronic hepatitis C may be helpful, although these results should be confirmed in controlled trials.

Detection of hepatitis C virus (HCV) RNA sequences in liver tissue by in situ hybridization

In situ hybridization was used to identify the cell types infected by hepatitis C virus (HCV) in the liver. Using an antisense HCV-RNA probe from the 5' non-coding region, HCV-RNAs molecules were detected in liver sections of 4/11 patients with chronic hepatitis C. These 4 positive subjects were also infected by HIV. HCV-RNA-positive strands were detected in scattered hepatocytes as well as in cells identified as mononuclear cells within the inflammatory infiltrates. HCV-RNA negative strands, likely replicative intermediates, were also detected in these cells. This study therefore indicates that replication of HCV may occur in both hepatocytes and mononuclear liver cells.

Detection of hepatitis C virus by polymerase chain reaction and response to interferon-alpha therapy: relationship to genotypes of hepatitis C virus

To investigate the relationship between genotypes of hepatitis C virus and response to interferon-alpha therapy, hepatitis C virus RNA was assayed by polymerase chain reaction with three sets of primers and probes in 70 patients with non-A, non-B chronic hepatitis who received interferon-alpha. Twenty-four patients sustained long-term remissions (complete responders). Polymerase chain reaction for 5'-terminal noncoding region detected hepatitis C virus RNA in 94.3% (66 of 70) of the patients. Polymerase chain reaction for nonstructural region 3, in which primers and a probe were synthesized to be identical to hepatitis C virus-J, detected hepatitis C virus RNA in 40 patients. Polymerase chain reaction for nonstructural region 5-in which sequences of primers and a probe were derived from hepatitis C virus-K2, a genotype different from hepatitis C virus-J--detected hepatitis C virus RNA in 17 patients. Only one patient was positive on both nonstructural region 3 and nonstructural region 5 polymerase chain reaction. Nucleotide sequence of clones obtained from 5' terminal noncoding region polymerase chain reaction products of two patients positive on polymerase chain reaction for nonstructural region 3 and negative on polymerase chain reaction for nonstructural region 5 (group 1) corresponded to that of the hepatitis C virus-J group, and those of clones from two patients negative on polymerase chain reaction for nonstructural region 3 and positive on polymerase chain reaction for nonstructural region 5 (group 2) corresponded to that of hepatitis C virus-K2.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical detection of hepatitis C virus-infected hepatocytes in chronic liver disease with monoclonal antibodies to core, envelope and NS3 regions of the hepatitis C virus genome

The localization of hepatitis C virus-infected hepatocytes in the human liver remains unclear despite the development of a serological assay for the antibody to hepatitis C virus. We studied their localization immunohistochemically with monoclonal antibodies to core, envelope and NS3 antigens of hepatitis C virus. We examined 48 liver biopsy samples from C100-3 antibody-positive patients with chronic liver disease (chronic persistent hepatitis, 5 cases; chronic active hepatitis, 41 cases; cirrhosis, 2 cases) and 12 liver biopsy samples from C100-3 antibody-negative patients with chronic liver disease (type B chronic hepatitis, 8 cases; alcoholic liver disease, 4 cases). In the C100-3 antibody-positive group, positive immunostaining for core antigen, envelope antigen and NS3 antigen was found in 23% (11 of 48), 24% (11 of 45) and 24% (11 of 46), respectively. Negative results were obtained in the C100-3 antibody-negative group. Hepatocytes with positive staining were scattered in the lobules, and they were found in the same regions irrespective of whether the antibody to core antigen, to envelope antigen or to NS3 antigen was used. Each positive cell was strongly stained in the cytoplasm; these decorations disappeared after absorption of the primary antibody with purified antigen. mean ALT levels in the patients with positive immunostaining for core, envelope or NS3 antigen (174.8 +/- 105.7 U/L) tended to be higher than in those with negative immunostaining (142.0 +/- 93.8 U/L). On histological evaluation of liver specimens with a scoring system of the histological activity index, intralobular inflammation and fibrosis had higher scores for samples with positive rather than negative immunostaining (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical evaluation of three anti-HCV ELISAs in patients with various liver diseases

We measured antibodies to hepatitis C virus (HCV) in 380 patients with various liver diseases by three enzyme-linked immunosorbent assays (ELISAs): HCV antibody ELISA test (C100), KCL-163 (KCL) corresponding to the nonstructural protein of HCV, and JCC based on the translation product of the presumptive HCV core gene. Of 233 cases of non-A, non-B (NANB) liver disease, 63.9% were anti-C100 positive, 69.1% were anti-KCL positive, and 79.8% were anti-JCC positive. Detection of serum HCV-RNA in 213 cases of chronic NANB liver disease revealed that the concordance was 80.3% for C100, 86.4% for KCL, 94.8% for JCC, and 95.3% for all three ELISAs. Overall, 85.4% of chronic NANB cases were considered to have type C disease with HCV infection. The most reliable assays for diagnosing chronic NANB liver disease as type C appeared to be the KCL and JCC ELISAs.

[Importance of PCR in the diagnosis of hepatitis C]

The identification of hepatitis C virus, based on DNA amplification, gives a precise estimation of the prevalence of the most frequent agent of NANB hepatitis. The first ELISA allowing the detection of anti-HCV antibodies, had too many false positive results and required the development of more sensitive and specific assays to confirm its results. PCR, allowing the hepatitis C virus diagnosis by showing directly HCV RNA sequences, offers a complementary approach to immunoserological tests. In blood donors with anti-HCV antibodies and with indeterminate or negative confirmatory tests, the finding of HCV RNA sequences reveals serum infectivity. During acute hepatitis, the delay in the appearance of anti HCV hampers acute phase diagnosis. The early detection of HCV RNA in peripheral blood, confirms the diagnosis and opens up therapeutic possibilities. In chronic hepatitis, the diagnosis of seronegative forms may only be resolved by PCR. Moreover, the presence of HCV RNA in peripheral blood represents the only marker of on-going viral replication and coincides with the severity of liver damage. During treatment with interferon, the follow up of HCV RNA sequences makes it possible to monitor its efficacy. The search for HCV RNA sequences directly in liver tissue shows that HCV may replicate in the liver in the absence of viremia. The presence of HCV RNA in the liver and the serum of liver transplanted patients is essential for the etiological diagnosis and management of hepatitis and bone marrow failure occurring after transplantation. Epidemiological study using PCR is a major tool in documenting vertical transmission between mother and child. Finally, PCR is important for the analysis of the HCV genome. Thus, in France there are at least three main strains, one close to the US prototype, the other close to the Japanese strain, possibly responsible for a more severe illness and a third one distinct from the previous two. However, its limits and constraints imply that PCR must not be considered as a routine assay. This emphasizes the need for more simple and rapid diagnostic tests, allowing the detection of HCV antigens and, as in hepatitis B, the progressive unravelling of the life cycle of HCV.

Induction of cytotoxic T cells to a cross-reactive epitope in the hepatitis C virus nonstructural RNA polymerase-like protein

Cytotoxic T lymphocytes (CTL) have been found to mediate protection in vivo against certain virus infections. CTL also may play an important role in control of infection by hepatitis C virus (HCV), but no CTL epitopes have yet been defined in any HCV protein. The nonstructural protein with homology to RNA polymerase should be a relatively conserved target protein for CTL. To investigate the epitope specificity of CTL specific for this protein, we used 28 peptides from this sequence to study murine CTL. Mice were immunized with a recombinant vaccinia virus expressing the HCV nonstructural region corresponding to the flavivirus NS5 gene (RNA polymerase), and the primed spleen cells were restimulated in vitro with peptides. CTL from H-2d mice responded to a single 16-residue synthetic peptide (HCV 2422 to 2437). This relatively conserved epitope was presented by H-2d class I major histocompatibility complex (MHC) molecules to conventional CD4- CD8+ CTL but was not recognized by CTL restricted by H-2b. Moreover, exon shuffle experiments using several transfectants expressing recombinant Dd/Ld and Kd demonstrated that this peptide is seen in association with alpha 1 and alpha 2 domains of the Dd class I MHC molecule. This peptide differs from the homologous segments of this nonstructural region from three other HCV isolates by one residue each. Variant peptides with single amino acid substitutions were made to test the effect of each residue on the ability to sensitize targets. Neither substitution affected recognition. Therefore, these conservative mutations affected peptide interaction neither with the Dd class I MHC molecule nor with the T-cell receptor. Because these CTL cross-react with all four sequenced isolates of HCV in the United States and Japan, if human CTL display similar cross-reactivity, this peptide may be valuable for studies of HCV diagnosis and vaccine development. Our study provides the first evidence that CD8+ CTL can recognize an epitope from the HCV sequence in association with a class I MHC molecule.

[Hepatitis C virus]

Hepatitis C Virus, major causative agent of parenterally transmitted non-A non-B hepatitis was identified by Choo et al. in 1988 using molecular biology technologies. This virus contains a positive stranded RNA genome, it has been shown to have a small diameter. These structure and properties suggest that HCV shares many features in common with Pestiviruses and Flaviviruses. After many years of research, two major objectives were reached: -the identification of viral genome and the main purified viral polypeptide derived from recombinant yeast. Major information were recently appearing about the nucleotide sequences of different isolates coming from US, Europe and Japan; -the preparation of specific tool (ELISA anti-HCV) for detection of circulating HCV antibodies.

[Analytical study of the Abbott and Ortho tests for screening and confirmation of anti-HCV antibodies. Le groupe de Travail "Hépatites virales" de la Société Française de Transfusion Sanguine]

Anti-HCV systematic screening on blood donation was mandatory in France since first of March 1991. Two laboratories (Ortho-Chiron and Abbott) have introduced in Europe successively two kinds of hepatitis C positive diagnosis with 1st and 2nd generation ELISA screening and confirmatory assays. The aim of this multicentric study was to evaluated the sensibility and specificity of these tests. For that, they used 10,090 blood sera. As a result we have seen that the new "second generation" screening assays have a higher sensitivity without less of specificity for the confirmatory tests.

Characterization of the hepatitis C virus E2/NS1 gene product expressed in mammalian cells

Truncated and full-length versions of the hepatitis C virus protein domain encoding a presumptive envelope glycoprotein designated E2/NS1 were stably expressed in CHO cell lines. Characterization of the processing events involved in the maturation of E2/NS1 revealed that a high-mannose form resident in the endoplasmic reticulum was the most abundant form detected intracellularly. The ionophore carboxyl cyanide m-chlorophenyl-hydrazone was used to show that the E2/NS1 glycoprotein resided in the endoplasmic reticulum. The full-length form of E2/NS1 appeared to be cell-associated and could not be detected as a secreted product. C-terminal truncated molecules could be detected in the extracellular media as fully processed glycoproteins containing terminal sialic acid additions. These truncated glycoproteins are predicted to be biologically relevant targets of the host immune response and are therefore potential subunit vaccine candidates.

Recent developments in the molecular cloning and characterization of hepatitis C and E viruses

The molecular properties of the genomes of both hepatitis C virus (HCV) and hepatitis E virus (HEV), the major etiologic agents of non-A, non-B hepatitis, are briefly described. The organization of the genome of each of these viruses is discussed and compared to those of other related or distantly related viruses that contain single-stranded, positive-sense RNA genomes. In the case of HEV, the reactivity of expressed proteins and genetic divergence of geographically distinct isolates are also described within the context of sequence variation, type-common epitopes and type-specific epitopes.

Genomic typing of hepatitis C viruses present in China

Hepatitis C virus (HCV) genomic clones were obtained from the serum of Chinese HCV carriers using a polymerase chain reaction-based approach. Consensus sequences were derived from (1) the structural region (nt 1-1543) for one carrier, (2) the hypervariable region V (nt 1156-1233) from four carriers and (3) region V3 from four carriers. Region V3, located in the nonstructural domain NS5 (nt 7066-7137), has been previously shown to be a particularly good marker for the genomic typing of HCV isolates [Inchauspe et al., Proc. Natl. Acad. Sci. USA 88 (1991) 10292-10296]. Comparison of these sequences with sequences from geographically distinct HCV isolates indicates that Chinese HCV strains are closely related to, though distinguishable from, Japanese prototype strains. One amino acid motif, GGAA, located in region V, was found to be conserved only among Chinese isolates. This may define a new subgroup among HCV isolates.

Hepatitis C virus (HCV) circulates as a population of different but closely related genomes: quasispecies nature of HCV genome distribution

Sequencing of multiple recombinant clones generated from polymerase chain reaction-amplified products demonstrated that the degree of heterogeneity of two well-conserved regions of the hepatitis C virus (HCV) genome within individual plasma samples from a single patient was consistent with a quasispecies structure of HCV genomic RNA. About half of circulating RNA molecules were identical, while the remaining consisted of a spectrum of mutants differing from each other in one to four nucleotides. Mutant sequence diversity ranged from silent mutations to appearance of in-frame stop codons and included both conservative and nonconservative amino acid substitutions. From the relative proportion of essentially defective sequences, we estimated that most circulating particles should contain defective genomes. These observations might have important implications in the physiopathology of HCV infection and underline the need for a population-based approach when one is analyzing HCV genomes.

Long-term follow-up of anti-hepatitis C virus antibodies in patients with acute nonA nonB hepatitis and different outcome of liver disease

We screened 74 patients with nonA nonB acute hepatitis (37 of post-transfusion PTH, and 37 of non-post-transfusion, NPTH, origin) for the presence of anti-HCV by tests detecting either C100-3 antibodies alone (ELISA I) or C100-3 plus C33c plus C22-3 antibodies (ELISA II). Samples were taken at the onset of disease and then serially for a period of time ranging from 12 to 60 months. An increased number of anti-HCV positive cases (86% vs 69%) and an earlier seroconversion were observed with the second compared to the first generation ELISA. Positive samples were confirmed by recombinant immunoblot assay (RIBA), which was also used to study the kinetics of the antibody response to individual HCV antigens. Anti-C33c and anti-C22-3 antibodies were the first detectable markers of HCV infection in 80% and 20% of the patients, respectively. Thirty-two percent of the patients studied showed complete and persistent biochemical recovery, whereas 68% maintained a chronic elevation of the transaminase values. Among the 20 patients who showed early and persistent normalization of the transaminase values, complete disappearance of all antibody reactivities was limited to five of them, whereas in four cases only anti-C100-3 and anti-5-1-1 became negative.

Expression of MBP-HCV NS1/E2 fusion protein in E. coli and detection of anti-NS1/E2 antibody in type C chronic liver disease

To characterize the putative NS1/E2 (non-structural protein 1/envelope 2) domain of HCV (hepatitis C virus), we expressed the hydrophilic three-quarters of this domain in a form of MBP (maltose binding protein) fusions in Escherichia coli. When we checked the positive frequency of antibody to this fusion protein, 17% of patients with type C chronic liver disease had this antibody. However, they were all positive for HCV-RNA in sera. These results suggest that the appearance of anti-NS1/E2 antibody does not serve as evidence of viral clearance.

Serological markers of posttransfusion hepatitis C viral infection

Serological markers for hepatitis C virus (HCV) infection were measured in serial samples from 14 posttransfusion chronic non-A, non-B hepatitis patients by a semiquantitative dot blot immunoassay. The assay detected antibodies to HCV by use of recombinant proteins that represent putative HCV capsid (core), nonstructural protein 3 (NS3) (33c), and NS4 (c100) epitopes. Seroconversion to anti-HCV antibodies (anti-HCV) was detected in all patients. The average time to active antibody production detected by any of the recombinant proteins was 13.8 (range, 3.6 to 22.0) weeks posttransfusion or 4.6 (range, -4.5 to 13.4) weeks after the first biochemical marker of illness. Anti-HCV were detected earliest by the core antigen in most cases; however, the patterns of anti-HCV responses varied significantly among individuals. Overall, the addition of the core and NS3 antigens to the assay enabled the detection of the antibody response 4 to 5 weeks earlier than did the addition of the c100 antigen, the sole antigen used in current screening tests in the United States. Passively transferred antibodies were detected by at least one antigen in early posttransfusion samples from 12 patients and decayed below detectable levels for all antigens in only 2 patients. Antibodies to all three gene products were evident in the last sample from all five patients monitored for greater than 3 years from transfusion indicating the persistence of antibodies in patients with chronic illness. Our data show that the period following the onset of hepatitis during which anti-HCV are not detected by current screening assays can be greatly shortened by the detection of anti-HCV responses by a combination of core, NS3, and c100 antigens.

A new type of hepatitis C virus in patients in Thailand

Partial nucleotide sequences in the tentative NS5 region of the hepatitis C viral genome obtained from patients with chronic hepatitis in Thailand were analyzed by reverse transcription followed by the polymerase chain reaction. Of ten samples studied, four showed low homologies to any known type of HCV: the homologies of the nucleotide sequences of these clones with HCV-J, -US, -K2a and -K2b were 66.5-69.1%, 66.5-68.2%, 61.2-64.1% and 64.4-66.2%, respectively, and the homologies of their deduced amino acids sequences were 71.7-75.2%, 71.7-75.2%, 69.0-72.6% and 69.9-73.5%, respectively. These four clones were classified a new distinct type of HCV, named HCV-T. Moreover, the nucleotide and amino acid sequence homologies of the four HCV-T clones showed that the HCV-T type could be classified into two genotypes, HCV-Ta and HCV-Tb.

Hepatitis C virus (HCV)-RNA in non-A, non-B chronic hepatitis in France. Nucleotide sequence of a French HCV isolate

The sera of 36 French patients with post-transfusional and sporadic non-A, non-B (NANB) chronic hepatitis were investigated, with a combination of serological and polymerase chain reaction (PCR) assays, for HBV and HCV infections. Eighty-nine percent of the patients were found positive with serological and/or molecular tests. Among the positive patients, 68% (22/32) were found positive for both anti-HCV and HCV-RNA, 16% (5/32) and 16% (5/32) were found positive only for anti-HCV or HCV-RNA, respectively. HBV-DNA sequences were detected in two patients associated to the HCV viraemia. This study confirms the extremely high prevalence of HCV infection in NANB chronic hepatitis in France. It also shows the possible co-infection by HCV and HBV in NANB hepatitis. We have also determined the nucleotide sequence of the 5' non-coding, E1, E2/NS1 and NS3/NS4 regions of a French isolate using the polymerase chain reaction. Comparison of these nucleotide sequences with those available from American and Japanese isolates showed a significant genetic variability. The genetic variability is higher in the E2/NS1 (13 to 33% and 12 to 30% at the nucleic acid and amino acid level, respectively) than in the E1 (10 to 28% and 7 to 21%) and NS3/NS4 (5 to 21% and 2 to 7%) regions. The sequence of the French isolate is more closely related to that of the American HCV prototype than to the Japanese HCV isolates. This study confirms the extent of HCV genetic variability.