Two distinct subtypes of hepatitis C virus defined by antibodies directed to the putative core protein

Clustering of rare peptide segments in the HCV immunome

Our previous research and a comprehensive meta-analysis of data from the literature on epitope mapping has revealed that the B cell epitope repertoire is allocated to rare peptide motifs, i.e., antigenic peptide sequences endowed with a low level of similarity to the host proteome. From a clinical point of view, low-similarity peptides able to evoke an immune response appear to be of special interest for the rational design of vaccines for poorly treatable diseases such as hepatitis-C virus (HCV) infection. Indeed, low similarity peptides would guarantee the highest specificity and lowest cross-reactivity, i.e., effectiveness without adverse side-effects. In this study, aimed at gaining further information for the development of effective anti-HCV peptide-based vaccines, the HCV epitopes recognized by human antibodies and currently catalogued in the Immune Epitope Data Base (IEDB) were examined for pentamer sequence similarities to the human proteome. We report that the analyzed HCV determinants are characterized by the presence of fragment absent from (or scarcely represented in) human proteins. These data confirm the low-similarity hypothesis, according to which a low-similarity to the host proteome defines the nonself character of microbial antigens and modulates peptide immunogenicity. Moreover, this study indicates a concrete and safe immunotherapeutic approach which might be used in a universal anti-HCV vaccine.

Genetic variations in a well conserved 5'-untranslated region of hepatitis C virus genome isolated in Pakistan

The diversity and extent of sequence variations between hepatitis C virus (HCV) isolates from Pakistan were studied and the probable effects of these variations were assessed on secondary viral structures. Sequencing and phylogenetic analysis was performed on 33 samples, of which 25 were typed as genotype 3 by RFLP (restriction fragment length polymorphism) and 8 remained unresolved. Rooted neighbour-joining (NJ) tree revealed that 28 isolates were HCV type 3a and 5 isolates were typed as 3b. The majority of unresolved samples clustered in a different branch of genotype 3, supported by a bootstrap value of 71%. Another, cluster, cluster I, was found to have a bootstrap value of 81%. Genetic distance values showed significant diversity of isolates in these two clusters compared to the reference sequences. Pair-wise comparison showed the presence of additional restriction sites of HaeIII and RsaI in unresolved isolates. In conclusion, unique sequence variability was observed in the 5'-UTR of HCV type 3 isolates from Pakistan. One of the reasons for this sequence variability is the presence of mutations, which are additional restriction sites in the 5'-UTR. These mutations were also responsible for failure of conventional RFLP to type some of the HCV isolates.

Changes in hepatitis C virus (HCV) antibody status in patients with chronic hepatitis C after eradication of HCV infection by interferon therapy

BACKGROUND

Changes in hepatitis C virus (HCV) antibody status were followed for 10 years after the eradication of HCV by interferon (IFN) therapy in 30 patients with chronic hepatitis C who showed a sustained virological response.

METHODS

HCV core antibody titer, third-generation HCV recombinant immunoblot assay (RIBA) grade (measuring the presence of antibodies for core, NS3, NS4, and NS5 antigens), and genotype-specific antibodies to the HCV NS4 region were measured annually with commercially available kits for these antibodies.

RESULTS

For grade of HCV antibody determined by RIBA, the most significant decrease was observed with anti-NS5 antibody, followed by anti-NS4, anti-NS3, and anti-core antibodies, in that order. Tests for anti-NS5 and anti-NS4 antibodies had negative results in almost 50% of patients 10 years after eradication of HCV. In contrast, the results of tests for anti-core antibody were still markedly positive in most patients. However, anti-core antibody titer decreased continuously during the 10-year follow-up period. Antibodies to the NS4 region specific for HCV genotypes 1 and 2 also decreased during the follow-up period. Differences in the rate at which antibody titers decreased were observed between antibodies for genotypes 1 and 2; as a consequence, the serological type of HCV changed during the follow-up period in some patients.

CONCLUSIONS

HCV antibody titer appears to continue to decrease during the 10 years after eradication of HCV by IFN therapy.

Synthetic peptide-based immunoassay as a supplemental test for HCV infection

INTRODUCTION

Hepatitis C virus (HCV) is a single strand RNA hepatotrophic virus infecting 170 millions around the world and 20% of Egyptian blood donors. Although there has been significant improvement in the enzyme immunoassays (EIAs) in population screening of HCV infection, the development of a low variability, easy to automate and inexpensive supplemental test to support the current immunoassays was of a major concern to several laboratories.

OBJECTIVES

In the current study, we embarked on a systematic study to analyze by DNA sequencing several HCV isolates to identify conserved core protein sequences and perform explorative analysis of five synthetic peptides from the core/E1 region in anti-HCV antibody assays.

METHODS

We designed four synthetic-core specific peptides and an E1-specific peptide. These peptides were used to screen HCV antibodies in sera of 100 HCV positive patients and 100 HCV negative subjects and compared the results with those obtained by the commercial systems based on second and third generation enzyme-linked immunosorbent assays.

RESULTS

Our results showed that all peptides detect HCV antibodies in infected sera to varying degrees. The synthetic peptide (a.a. 21-40) of the core protein had 99% sensitivity, 100% specificity and was highly reproducible.

CONCLUSION

The above findings make this core peptide a candidate product for developing a supplemental test for chronic HCV infection in the Egyptian population.

Advances in the molecular diagnosis of hepatitis C and their clinical implications

Serologic assays for diagnosis of hepatitis C infection may yield indeterminate results despite improvements in sensitivity and specificity through second- and third-generation assays. Direct detection of hepatitis C virus (HCV) RNA based on qualitative reverse transcription-polymerase chain reaction or transcription-mediated amplification allows diagnosis in the early stages of acute infection and in patients unable to mount an antibody response. Quantitative HCV RNA assays are useful for selecting appropriate antiviral therapies, but until recently they have lacked comparability between tests. More sensitive qualitative assays should be used for determining duration of treatment or recognizing a sustained virologic response to therapy. Hepatitis C virus genotyping can be performed from a limited sequence analysis of the viral genome by using various techniques. Although newer genotyping methods are relatively practicable and are satisfactory for the discrimination of the majority of genotypes, discrimination between subtypes can be challenging. Serologic typing of HCV lacks sensitivity and specificity compared with molecular-based techniques. Recent advances in serologic assays and nucleic acid detection techniques allow physicians to make accurate diagnoses, and these assays serve as important tools in treatment planning.

Advances in the molecular diagnosis of hepatitis C and their clinical implications

Serologic assays for diagnosis of hepatitis C infection may yield indeterminate results despite improvements in sensitivity and specificity through second- and third-generation assays. Direct detection of hepatitis C virus (HCV) RNA based on qualitative reverse transcription-polymerase chain reaction or transcription-mediated amplification allows diagnosis in the early stages of acute infection and in patients unable to mount an antibody response. Quantitative HCV RNA assays are useful for selecting appropriate antiviral therapies, but until recently they have lacked comparability between tests. More sensitive qualitative assays should be used for determining duration of treatment or recognizing a sustained virologic response to therapy. Hepatitis C virus genotyping can be performed from a limited sequence analysis of the viral genome by using various techniques. Although newer genotyping methods are relatively practicable and are satisfactory for the discrimination of the majority of genotypes, discrimination between subtypes can be challenging. Serologic typing of HCV lacks sensitivity and specificity compared with molecular-based techniques. Recent advances in serologic assays and nucleic acid detection techniques allow physicians to make accurate diagnoses, and these assays serve as important tools in treatment planning.

Hepatitis C virus clearance is prominent in women in an endemic area

BACKGROUND

The clinical and virological backgrounds of cases with previous hepatitis C virus (HCV) infection (positive for HCV antibody (anti-HCV) and HCV-RNA negative) in an HCV endemic area were examined to identify factors related to the clearance of HCV.

METHODS

The study population comprised 3117 inhabitants, 1037 male and 2080 female, from an HCV endemic area. Hepatitis C virus antibody was detected by a passive haemagglutination test. The HCV-RNA and the HCV genotype were detected by using the polymerase chain reaction method. The HCV serotype was determined by enzyme immunoassay by using the peptides of the core region.

RESULTS

Twenty-two per cent of the inhabitants were positive for anti-HCV, with males and the elderly having a significantly higher antibody titre (P < 0.01) than youths and females. Hepatitis C virus-RNA was detected in 78% of the HCV antibody-positive cases. The rate of HCV-RNA positivity was significantly higher in males than in females (P < 0.01). No relationship was found between HCV-RNA positivity and age. The HCV genotype 1b was the predominant genotype among the HCV-RNA-positive cases. Mixed genotypes (1b + 2a) were observed in 12% of cases, primarily in elderly males and females. In cases with previous HCV infection, serotype 1 was the most common serotype, and there appeared to be no relationship between the distribution of HCV serotypes and age and gender. There was a female predominance with regard to previous HCV infection, but not to being HCV carriers (P < 0.01).

CONCLUSIONS

Gender, not HCV genotype, is the primary factor influencing HCV clearance.

Clinical significance of hepatitis C virus genotypes

On the basis of phylogenetic analysis of nucleotide sequences, multiple genotypes and subtypes of hepatitis C virus (HCV) have been identified. Characterization of these genetic groups is likely to facilitate and contribute to the development of an effective vaccine against infection with HCV. Differences among HCV genotypes in geographic distributions have provided investigators with an epidemiologic marker that can be used to trace the source of HCV infection in a given population. HCV genotype 1 may represent a more aggressive strain and one that is less likely to respond to interferon treatment than HCV genotype 2 or 3. However, these observations require confirmation before HCV genotyping can be used in clinical settings.

Clinical significance of hepatitis C virus genotypes

On the basis of phylogenetic analysis of nucleotide sequences, multiple genotypes and subtypes of hepatitis C virus (HCV) have been identified. Characterization of these genetic groups is likely to facilitate and contribute to the development of an effective vaccine against infection with HCV. Differences among HCV genotypes in geographic distributions have provided investigators with an epidemiologic marker that can be used to trace the source of HCV infection in a given population. HCV genotype 1 may represent a more aggressive strain and one that is less likely to respond to interferon treatment than HCV genotype 2 or 3. However, these observations require confirmation before HCV genotyping can be used in clinical settings.

Viral heterogeneity of the hepatitis C virus

This review summarises the classification of hepatitis C virus as a flavivirus, the identification and detection of HCV genotypes, and reviews the current information concerning the geographical and risk group associations of the common genotypes in Europe.

Clinical significance of hepatitis C virus genotypes

The advent of genotyping assays has stimulated investigators around the world to study the molecular epidemiology of hepatitis C virus (HCV) infection in specific patient categories, as well as possible correlations with the clinical and histological features of chronic liver disease and response to antiviral treatment. While a general consensus has been reached on the worldwide epidemiology and distribution of HCV types in certain risk categories (i.e. intravenous drug users), the association between genotype 1b and severe liver disease is still controversial. Although generalized use of genotyping is not presently recommended for clinical or epidemiological monitoring, several studies emphasize to the importance of HCV genotyping as part of a therapeutic algorithm. This recommendation is based on overwhelming evidence in support of a correlation between genotype 1 and a poor response to interferon-a alone or in combination with ribavirin.

Presence of multiple genotype-specific antibodies in patients with persistent infection with hepatitis C virus (HCV) of a single genotype: evidence for transient or occult superinfection with HCV of different genotypes

OBJECTIVE

We investigated the significance of multiple genotype-specific antibodies in patients with persistent infection with hepatitis C virus (HCV) of a single genotype.

METHODS

Titers of genotype-specific antibodies to group 1 and 2 HCV polypeptides in the NS4 region of HCV were measured in 53 hemophiliacs and 58 nonhemophiliacs who were persistently infected with HCV of a single genotype. In addition, sequence variability in hypervariable region 1 (HVR1) of HCV was evaluated in these patients.

RESULTS

The presence of antibodies to both group 1 and 2 polypeptides, reflecting a mixture of serotypes, was more frequent in hemophiliacs (11 of 53 patients, 20.8%) than in nonhemophiliacs (two of 58 patients, 3.4%; p = 0.01). HVR1 sequence variability in 13 patients with mixed serotypes was higher than in 87 patients with a single serotype (21.1 +/- 4.3% vs 8.5 +/- 6.3%; p < 0.01).

CONCLUSIONS

A mixture of HCV serotypes was more common in hemophiliacs with persistent HCV infection of a single genotype who were at high risk of exposure to HCV than in nonhemophiliacs, and the sequence variability of the infecting strains was high in these patients. These data are suggestive of the effects of superinfection with HCV of different genotypes. The presence of multiple genotype-specific antibodies to HCV may be evidence of transient or occult superinfection with HCV of different genotypes in patients with persistent infection by HCV of a single genotype.

Antigenic heterogeneity of the hepatitis C virus NS4 protein as modeled with synthetic peptides

The effect of sequence heterogeneity on the immunologic properties of two strong antigenic regions of the hepatitis C virus (HCV) NS4 protein was studied by using a set of 443 overlapping 20-mer synthetic peptides. One antigenic region comprising the cleavage site between NS4a and NS4b (region 5-1-1) was modeled with peptides derived from 73 different known sequences, representing HCV genotypes 1-6. The other antigenic region, designated region 59 and located at the C-terminus of the NS4b protein, was modeled with peptides from 7 known sequences representing genotypes 1-3. All peptides were tested for antigenic reactivity by enzyme immunoassay with a panel of anti-HCV-positive serum specimens representing genotypes 1-5. The data demonstrated that immunoreactive peptides fell into two groups. One group, represented by N-terminal peptides, demonstrated genotype-independent immunoreactivity; the other group, from the central part of region 5-1-1, showed strict genotype specificity. Nineteen peptides from the genotype-independent group strongly immunoreacted with a wide range of serum samples containing antibodies to all 5 HCV genotypes. Twenty-five peptides from the genotype-specific group were found to strongly react with serum containing antibodies only to the genotype from which the peptides were derived. Similar to the N-terminal part of region 5-1-1, peptides derived from region 59 did not show genotype-specific immunoreactivity. Some peptides derived from the central part of region 59 showed very strong and broad antigenic reactivity. Thus, after examining two antigenic regions of the NS4 protein, we identified short sequences that can be used for the efficient detection of either genotype-independent or genotype-specific HCV antibodies.

Quantitative antibody responses to structural (Core) and nonstructural (NS3, NS4, and NS5) hepatitis C virus proteins among seroconverting injecting drug users: impact of epitope variation and relationship to detection of HCV RNA in blood

To gain insight into the natural history of hepatitis C virus (HCV), 13 human immunodeficiency virus (HIV)-seronegative injecting drug users were studied who seroconverted for HCV as determined by third-generation enzyme-linked immunosorbent assay, showed an ensuing antibody response to HCV, and were not treated with any antiviral drugs during follow-up. Subjects included 13 untreated HIV-negative individuals, of whom 5 (38.5%) apparently cleared HCV and were polymerase chain reaction (PCR)-negative in at least 3 consecutive samples, 3 (23.1%) showed transient viremia and were PCR-negative in 1 sample during the study period, and the other 5 (38.5%) showed persistent viremia. Viremia was determined longitudinally by reverse-transcription PCR (RT-PCR) and quantified by branched DNA (bDNA). HCV genotypes were determined on serial samples during follow-up. Quantitative antibody levels to core, NS3, NS4, and NS5 were determined using the Chiron RIBA HCV-titering Strip Immunoblot Assay, which is based on HCV genotype 1. The antibody responses to core, NS3, NS4, and NS5 were erratic. In individuals infected with HCV genotype 1, significantly higher median antibody responses to core (P =.02) and to NS4 (P =.04) were found as compared with those infected with other genotypes, showing a significant impact of HCV genotype specificity of the assay. In groups infected with HCV genotype 1, significantly higher median NS3 antibody titers (2.61 relative intensity [RI] vs. 0.38 RI; P =.003) were found in the individuals with persistent viremia than in those with apparent resolution of HCV RNA in blood. In groups infected with genotypes other than genotype 1, significantly higher median NS3 antibody titers (0.89 RI vs. 0.03 RI; P =.0004) and NS5 antibody titers (1.86 RI vs. 0.01 RI; P =.006) were found in the individuals with persistent viremia than in those with apparent resolution of HCV RNA in blood. Individuals with viral persistence had higher HCV-RNA loads with higher antibody responses as compared with individuals with apparent viral clearance from blood. Apparent viral clearance from blood was observed in an unexpectedly high percentage (38.5%), associated with a significant decrease of antibodies to NS3, independent of HCV genotype, as compared with individuals with persistent viremia (P <.005). Apparent viral clearance from blood with gradual loss of antibodies to various HCV proteins, independent of HCV genotype, was observed in 4 of the 5 individuals within approximately 1 year after HCV seroconversion, whereas 1 of these individuals apparently cleared the virus from blood, with complete seroreversion.

HCV core immunodominant region analysis using mouse monoclonal antibodies and human sera: characterization of major epitopes useful for antigen detection

Monoclonal antibodies (MAbs) were generated by immunizing mice with a truncated recombinant protein corresponding to the immunodominant region (residues 1-120) of hepatitis C virus (HCV) nucleocapsid protein. The specific recognition by either human sera or mouse monoclonal antibodies of overlapping peptides spanning the core region 1-120 as well as the comparison with epitopes described earlier allowed the fine mapping of HCV core. Within the region 1-120, the major antigenic domain could be restricted to the first 45 amino acids. Indeed, the peptide S42G (residues 2-45) allowed the detection of an anti-HCV core response by all anticore-positive human sera examined. According to their epitope localization, three groups of mouse MABs could be evidenced that were directed against different regions of core. Group II MAbs recognized a strictly linear epitope (QDVKF, residues 20-24), whereas group I MABs were directed against a conformational epitope mainly located at the amino acid residues (QIVGG, 29-33). The epitope of group III MABs was also conformational (PRGRRQPI, residues 58-65). These three epitopes appeared close but different from the three major human epitopes RKTKRNTN, VYLLPR, and GRTWAQPGYPWPLY (residues 7-17, 34-39, and 73-86, respectively). Group II MAB 7G12A8 and group I MAB 19D9D6 were used in a sandwich ELISA for the capture and the detection, respectively, of viral core antigen in sera of patients with chronic HCV infection. After treatment of sera with triton x 100 in acidic conditions, amounts of viral antigen as low as 20 pg/ml of sera could be detected.

Hepatitis C virus infection: Review and implications for the dentist

OBJECTIVE

The purpose of this report was to review the current literature on hepatitis C virus infection, with particular attention to the aspects of interest for dental health care staff.

MATERIAL AND METHODS

The authors searched original research and review articles on specific aspects of hepatitis C virus infection, including articles on virology, epidemiology, transmission, diagnosis, natural history, extrahepatic manifestations, therapy and oral aspects of hepatitis C virus infection. The relevant material was evaluated and reviewed.

RESULTS

Hepatitis C virus is an RNA virus that is present throughout the world and has major geographic variations. The virus, transmitted mainly by means of blood contact, causes chronic hepatitis in up to 80% of cases and may give rise to hepatic cirrhosis and hepatocellular carcinoma in a significant proportion of patients. Although it is of limited efficacy, interferon alpha is currently the drug of choice in the treatment of the infection. Hepatitis C virus infection is associated with a number of extrahepatic manifestations that may include oral diseases such as lichen planus or sialadenitis. Although there are documented cases of nosocomial transmission to health care workers after percutaneous exposure, the prevalence of hepatitis C virus among dental staff members is probably similar to that in the general population.

CONCLUSION

Hepatitis C virus infection is a relatively common infection worldwide (1.4% in the US general population) that causes significant chronic hepatic disease. The dentist is thus likely to face a growing number of patients with a diagnosis of hepatitis C virus infection. For this reason it is essential for dental health care workers to be aware of the principal features of the disease and of its oral and dental implications.

Cryoglobulinaemia among maintenance haemodialysis patients and its relation to hepatitis C infection

It has been shown that hepatitis C virus (HCV) infection is closely associated with mixed type cryoglobulinaemia. It is also known that HCV infection is rampant among chronic haemodialysis patients. We studied 531 renal failure patients on maintenance dialysis including 170 with positive HCV antibodies for cryoglobulinaemia, and its incidence was compared with controls which consisted of 242 chronic hepatitis C patients without renal failure and 183 healthy adults. Cryoglobulinaemia was present in 30.6% of dialysis patients with HCV infection, 10.8% of dialysis patients without HCV infection, 29.8% of patients with chronic hepatitis C without renal failure, and 0% of healthy adults. Among the 30 new renal failure patients who were started on dialysis within 6 months, four were positive for HCV antibodies, and one of them had cryoglobulinaemia; of the 26 HCV-negative patients, four (15%) were cryoglobulinaemic. The cryocrit values among dialysis patients were much lower than those of the control cases and other reports on non-dialysis cases. Patients with cryoglobulinaemia were generally younger compared with patients negative for this condition. There was no correlation between cryoglobulinaemia and past blood transfusion, underlying disease or length of dialysis. Cryoglobulinaemic patients seem to develop renal failure at relatively young ages and a considerable proportion of cryoglobulinaemic dialysis patients may have already had cryoglobulinaemia at the time of the start of haemodialysis. There was no indication that the presence of cryoglobulin in serum adversely affects the liver disease nor increases serum virus load in HCV-infected dialysis patients. Thus, it was concluded that although HCV infection has a certain role in the development of cryoglobulinaemia in dialysis patients, they develop cryoglobulinaemia less frequently and produce cryoglobulin to a lesser degree in the presence of HCV infection as compared with non-dialysis patients.

Antigenic variation of core, NS3, and NS5 proteins among genotypes of hepatitis C virus

Assays that detect antibody to hepatitis C virus (HCV) are used to screen blood donors and patients with hepatitis. Current enzyme-linked immunosorbent assay (ELISA)-based methods are invariably based upon antigens from expressed recombinant proteins or oligopeptides from HCV type 1. Some HCV antigens used in screening assays are coded by regions of the HCV genome that show extensive variability; therefore, HCV type 1-based assays may be less effective for the detection of antibody elicited by infection with other genotypes. In this study, we have measured antibody reactivity of sera from 110 hepatitis C patients infected with type 1b, 3a, or 4a to genotype-specific and cross-reactive epitopes present in recombinant proteins from HCV genotypes 1b (core, NS3, and NS5), 3a (NS3, NS5), and 4a (core, NS3), corresponding to those used in current third-generation screening ELISAs. By comparing the serological reactivities of sera to type-homologous and type-heterologous antigens, we detected a significant type-specific component to the reactivity to NS3 (61 to 77% of the total reactivity) and NS5 (60% of the total reactivity). Furthermore, despite the similarities in the amino acid sequences of the core antigens of type 1b and type 4a, we also found significantly greater reactivity to type-homologous antigens, with approximately 25% of reactivity being type specific. These findings are consistent with previous findings of fivefold weaker reactivity of sera from HCV type 2- and HCV type 3-infected blood donors in the currently used third-generation ELISAs and suggest that these assays are suboptimal for screening populations in which the predominant genotype is not type 1.

Virology of hepatitis C virus

Advances in molecular biology techniques have allowed the cloning of HCV and the characterization of this virus. This article provides a short summary of our current knowledge on the genomic organization of HCV, the implications of its genetic heterogeneous nature, and the probable replication strategy of this virus.

Effective detection of active HCV infection: HCV RNA carrier state in a context free of hepatitis symptoms

HCV immunological assays have limited specificity due to considerable variability of genomic coding sequences. Accordingly, PCR RNA detection also shows variable incidence of HCV in a non-A, non-B (NANB) hepatitis context. We used in-house designed nested PCR applying primers from the 5' untranslated region in 150 thalassemic patients classified in four groups according to anti-HCV screening and glutamic-pyruvate transaminase (GPT) levels. Group A: anti-HCV+/high GPT levels; group B: anti-HCV+/normal GPT levels; group C: anti-HCV(-)+high GPT levels; group D: anti-HCV(-)+normal GPT levels. Viral incidence and concentration, both high in group A, decreased towards group D. Group C RNA incidence was unexpectedly high and, moreover, one control case proved HCV-RNA+. Compared with the Amplicor kit or primers were considerably more sensitive.

Comparative study of three methods for genotyping hepatitis C virus strains in samples from Spanish patients

Hepatitis C virus (HCV) genotypes may be investigated by a variety of laboratory methods that target different parts of the HCV genome and have various degrees of technical difficulty. Since the choice of a particular method is difficult, we compared the performance of (i) a type-specific PCR with type-specific primers from the core region, (ii) molecular hybridization of the PCR-amplified 5' noncoding region to type-specific probes, and (iii) identification of type-specific antibodies against epitopes of nonstructural region 4 by enzyme-linked immunosorbent assay (ELISA). One hundred fifty-one patients with biopsy-proved chronic hepatitis and HCV RNA in serum were investigated. The HCV genotype was identified in 99%, 100%, and 85% of the cases by type-specific PCR, probe hybridization, and ELISA, respectively. The type-specific PCR disclosed infection with type 1a in 3%, type 1b in 74%, and type 3a in 4% of the cases and suggested infection with two or more HCV types, including 2a/2c and 2b, in the remaining 18%. Apparently mixed infections were more prevalent in patients with past intravenous drug use (P < 0.001), but cloning and sequencing of PCR products did not confirm a mixed infection in any of the four cases investigated. Concordant results were obtained by the three procedures with virtually all of the samples in which the type-specific PCR revealed a single HCV genotype. Type-specific hybridization and ELISA usually recognized the genotype producing the strongest DNA band in samples in which type-specific PCR suggested a mixed infection. In conclusion, the three procedures evaluated in this study are reliable for investigation of HCV genotype. Type-specific PCR provides information about HCV subtypes, but a mixed infection detected with this method should be interpreted with caution.

Detection and clinical features of hepatitis C virus type 6 infections in blood donors from Hong Kong

The genotype distribution of hepatitis C virus (HCV) was investigated in 212 viraemic blood donors from Hong Kong. A subset of the samples was investigated using three different genotyping assays to establish the accuracy of each in this population. These assays were restriction fragment length polymorphism (RFLP) of amplified 5' noncoding region (5'NCR) sequences, RFLP of the core region, and a serotyping assay using peptides from two antigenic regions of NS4. Genotypes detected in Hong Kong blood donors were 1a (6.2%), 1b (58.8%), 2a (1.4%), 2b (1.4%), 3a (1.9%), and 6a (27.0%). All genotyping assays produced concordant results. No evidence was obtained for the presence of type 6 group variants recently identified in Southeast Asia, other than type 6a. A serotyping assay based upon the detection of type-specific antibody to epitopes in NS4 produced similar results to the genotyping assays (98% concordance), but a reduced sensitivity (75%) compared with genotyping methods. Sequence variation in NS4 was not the cause of the reduced rate of detection of type 6 antibody in this population. Eighty-four percent donors infected with type 6a were male, compared to 75% donors infected with type 1b. The median alanine transaminase (ALT) level in type 6 infected donors was lower than in type 1b, (43.8 and 51.1 U/l, respectively) although these values were not statistically significant (P = 0.094). There was no significant difference between the ages of donors infected with types 1b and 6a. Risk factors for HCV infection in the blood donors included blood transfusion, intravenous drug abuse, and tattooing. A significantly greater number of donors infected with HCV-6a reported a history of drug abuse (66%) than donors infected with HCV-1b (7%).

Hepatitis C virus genotypes in the liver and serum of patients with chronic hepatitis C

OBJECTIVE: To evaluate the prevalence of hepatitis C virus (HCV) genotypes in a central area of Italy (Umbria); to analyze the correspondence of the genotypes detected in serum and liver samples; to study the relationship between HCV genotypes and severity of liver disease; to test whether co-infection with more than one HCV subtype could be influenced by the source of infection. METHODS: Genotyping by polymerase chain reaction with core-specific primers (Okamoto method) was performed in the serum and liver from 48 consecutive patients with histologically confirmed chronic C hepatitis. RESULTS: HCV genotype 1b was the prevalent strain and was not associated with more severe histologic damage. Data show a very good correspondence between genotypes identified in serum and liver specimens (91%). Mixed infections (with subtypes 1b and 2a) correlated significantly with intravenous drug abuse (p=0.001). CONCLUSION: We confirmed that subtype 1b is prevalent in central Italy. Co-infection with more than one subtype is not rare in intravenous drug abusers.

Heterogeneity of hepatitis C virus

A great deal of information on the molecular heterogeneity of hepatitis C virus (HCV) has been achieved since its discovery in 1989. However, little is known about the clinical significance of these variations. Based on the degree of sequence variation, HCV has been classified into six major groups or types, differing by 31-34% at the nucleotide level over the entire virus genome. Each type is divided into several subtypes that differ by 20-23% in nucleotide sequence. Viruses within the same subtype are up to 10% divergent and, within infected individuals, vary by up to 1.5%. Genotype distributions are not homogeneous around the world and may reflect both historical and recent parenteral routes of transmission. The clinical implication of these genomic variations are not yet fully elucidated: genotype 1b has been associated with end-stage liver disease, including liver cirrhosis and hepatocellular carcinoma, but this finding might rather reflect its earlier introduction to the populations studied. Consistent evidence exists that types 2 and 3 have a higher response rate to interferon treatment than type 1, although the interplay between genotype and viral load in determining the response is still unclear. Immunohistochemical studies indicate a stronger activation of the endogenous interferon system in the liver of patients infected with type 1 compared to those infected with types 2 and 3, explaining, at least in part, its low responsiveness to exogenous interferon treatment. Biological, sequence-dependent variations of genotypes have been poorly investigated to date, but differential efficiency of translation activity of the 5' non-coding region has been reported. The availability of "in vitro" systems for evaluating pathogenetic aspects and neutralization mechanisms will improve the present knowledge on this world-wide infectious disease and on the clinical usefulness of distinguishing between genotypes.

Serotyping of hepatitis C virus in chronic type C hepatitis in Taiwan: correlation with genotypes

To evaluate the usefulness of a new serologic assay to group hepatitis C virus (HCV), genotypes identified by this serotyping method were compared to those identified by a polymerase chain reaction (PCR) assay with type-specific primers in 71 Taiwanese patients with chronic type C hepatitis. The group-specific antibodies against different HCV genotypes were detected by using an enzyme-linked immunosorbent assay (ELISA) based on group-specific recombinant peptides (C14-1 and C14-2) within the NS4 region. Among 71 patients positive for current second-generation HCV antibodies, HCV RNA was detected in 55 patients by PCR with primers from the 5' untranslating region, and in 52 by genotype-specific PCR. In 49 (89%) of 55 viremic patients, the results of serotyping by ELISA showed complete agreement with those determined by PCR genotyping, and none of the patients showed a group opposite to that of HCV genotype. The positive rate of group-specific antibodies (69/71;97%) was even better than that of the PCR (55/71;78%). We conclude that this new serotyping assay is highly sensitive and specific for the determination of HCV genotypes, and will be useful in future epidemiologic studies, as well for clinical application.

Response to interferon in chronic hepatitis C due to mixed genotype infection

We examined the response to interferon (IFN) in patients with chronic hepatitis C (CHC) due to two different genotypes of hepatitis C virus (HCV) infection. Among 64 CHC patients studied, one (2%) had HCV-RNA genotype I, 36 (56%) had genotype II, 19 (30%) had genotype III, 2 (3%) had genotype IV and 6 (9%) had both genotypes II and III. There was no significant difference in age, sex, history of blood transfusion and liver histology among patients with genotypes II, III and II + III. The HCV-RNA titre of genotype II patients was significantly higher than that of genotype III patients (P < 0.05). However, there was no significant difference in the HCV-RNA titre between genotype II + III and the other groups. The complete response rate achieved with IFN therapy was significantly higher in genotype III patients (74%) than in genotype II patients (17%; P < 0.01). Of the six patients with genotype II + III, a complete response to IFN was only achieved by two patients (33%), both of whom had a low HCV-RNA titre ( < or = 10(4.5) copies/mL) and HCV serotype 2. The remaining four patients had HCV serotype 1 and three of the patients had a high HCV-RNA titre ( > or = 10(5) copies/mL). The HCV genotype III was lost in two patients after IFN therapy. These data suggest that HCV-RNA titre and HCV serotype are important factors for predicting the efficacy of IFN therapy in patients with mixed genotype infection and show direct evidence of higher susceptibility towards CHC of patients with genotype III than genotype II.

Detection of hepatitis C virus specific core protein in serum of patients by a sensitive fluorescence enzyme immunoassay (FEIA)

A protein-capture fluorescence enzyme immunoassay (FEIA) was developed using monoclonal antibodies (mAbs) against recombinant hepatitis C virus (HCV) core protein. Four hybridoma cell lines (5E3, 5F11, 515S, 1080S) were established and characterized. These monoclonal antibodies (mAbs) each had IgG1 and OgG2 isotypes, and recognized major B cell epitopes within the immunodominant nucleoprotein amino terminal subregion. Using mAb 5F11 as the first antibody to the solid phase and beta-D-galactosidase-conjugated mAb 5E3 as the second antibody to the protein, we established a specific HCV core protein capturing FEIA capable of detecting as little as 20 pg/ml of recombinant HCV core protein. HCV core protein in serum was detectable after treatment with 4.0% polyethyleneglycol, 0.5 NaOH, and 5% Triton X-100. The results of a peptide inhibition assay indicated that this FEIA is specific for HCV RNA positive sera. The quantity of HCV core protein detected in serum was significantly correlated to the level of HCV RNA. The detection limit for HCV core proteins was an HCV RNA per titer of approximately 10(4)/ml. Using this FEIA system, the detection ratio of HCV core protein in patients with chronic HCV infection was 92.3% (70/76).

Identification of immunodominant, group-specific and subcomplex-specific, continuous epitopes in the core regions of Japanese encephalitis virus using synthetic peptides

Two flaviviruses, Japanese encephalitis (JE) virus and Dengue (DEN) virus which have high pathogenicity for humans, continue to pose a serious public health problem in tropical and subtropical countries of the world. In order to identify the immunodominant B-cell epitopes for diagnostic application, we have prepared a series of 15-mer synthetic peptides from JE virus core protein based on computer analysis. Four linear, immunodominant epitopes corresponding to amino acids 91-105 (P78), 1-15 (P73), 8-22 (P74), and 34-48 (P75) of JE virus core proteins were identified by employing an enzyme-linked immunosorbent assay (ELISA), using high-titered immune sera from JE-vaccinated children. P78 was found to be the most immunodominant. The sero-specificity of these peptides was tested by binding to seroconverted samples from JE and DEN-1 patients. P78 and P74 belonged to group-specific epitopes which reacted with both JE and DEN-1 patient sera. P73 and P75 belonged to subcomplex-specific epitopes which reacted only with JE but not with DEN-1 patient sera. The study suggests that these peptides corresponding to the immunodominant epitopes of JE virus core protein might have the potential to be used as peptide-based diagnostic reagents for the detection and differentiation of JE and DEN antibody responses.

Comparative evaluation of two serologic typing methods for hepatitis C virus

Serologic methods of typing for hepatitis C virus offer advantages over PCR-based typing methods in terms of speed and simplicity of sample preparation and in the use of standard laboratory equipment. We examined the sensitivities and specificities of two hepatitis C virus serotyping assays which use sets of type-specific antigenic peptides derived from the core or the nonstructural 4 (NS4) regions and compared the results with those of molecular typing with type-specific primers from the core region. Although there was a good concordance between serotyping by either assay and genotyping, we found that the sensitivities of both serologic assays were less than optimal compared with that of molecular typing, with only about 50% of samples being unequivocally typed. Moreover, amino acid sequence similarities within the regions of the genome used for serotyping preclude differentiation into subtypes, which may have important clinical and therapeutic implications.

Survey of type 6 group variants of hepatitis C virus in Southeast Asia by using a core-based genotyping assay

Previous surveys of the prevalences of genotypes of hepatitis C virus (HCV) in different populations have often used genotyping assays based upon analysis of amplified sequences from the 5' noncoding region (5'NCR), such as restriction fragment length polymorphism (RFLP) or hybridization with type-specific probes (e.g., InnoLipa). Although highly conserved, this region contains several type-specific nucleotide polymorphisms that allow major genotypes 1 to 6 to be reliably identified. Recently, however, novel HCV variants found in Vietnam and Thailand that are distantly related to the type 6a genotype (type 6 group) by phylogenetic analysis of coding regions of the genome often have sequences in the 5'NCR that are similar or identical to those of type 1 and could therefore not be identified by an assay of sequences in this region. We developed a new genotyping assay based upon RFLP of sequences amplified from the more variable core region to investigate their distribution elsewhere in southeast (SE) Asia. Among 108 samples from blood donors in seven areas that were identified as type 1 by RFLP in the 5'NCR, type 6 group variants were found in Thailand (7 from 28 samples originally identified as type 1) and Burma (Myanmar) (1 of 3) but were not found in Hong Kong (n = 43), Macau (n = 8), Taiwan (n = 6), Singapore (n = 2), or Malaysia (n = 18). Although this small survey suggests a relatively limited distribution for type 6 group variants in SE Asia, larger studies will be required to explore their distribution in other geographical regions and the extent to which their presence would limit the practical usefulness of 5'NCR-based genotyping assays for clinical or epidemiological purposes.

Influence of viraemia and genotype upon serological reactivity in screening assays for antibody to hepatitis C virus

Detection of antibody to recombinant proteins derived from hepatitis C virus (HCV) genotype 1 represents the principal method for diagnosis of HCV infection. A method was developed for quantifying antibody reactivity in two third-generation enzyme immunoassays (Ortho EIA 3.0 and Murex VK48), and the influence of viraemia, HCV genotype, and host factors such as age, gender, and risk group upon antibody levels were investigated in a consecutive series of 117 anti-HCV-positive volunteer blood donors. Viraemic donors (as assessed by the polymerase chain reaction; PCR) showed significantly higher levels of anti-HCV by the Ortho EIA than those who were nonviraemic (adjusted mean difference of 10.1 fold after multiple regression analysis). The only other factor to influence significantly antibody level was genotype, where it was found that donors infected with type 1 showed 4 to 4.5 times greater serological reactivity by the Ortho assay than those infected with type 2 or 3. Antibody levels by the Ortho assay correlated closely to those detected by the Murex VK48 assay, and similar differences between PCR-positive and negative donors and between those infected with different genotypes were found. Differences in serological reactivity between genotypes indicate that a large proportion of epitopes of the type 1a or 1b recombinant proteins used in current assays are genotype specific. Variation in sensitivity of screening assays for different genotypes is of potential concern when used in countries where non-type 1 genotypes predominate in the blood donor or patient population.

Comparison of genotyping and serotyping methods for the identification of hepatitis C virus types

The usefulness of identification of hepatitis C virus (HCV) genotype has recently been investigated for the clinical management of patients infected by HCV. In the present study, the HCV genotype infecting 127 patients was determined by two different methods: HCV genotyping using a dot-blot assay with type-specific probes derived from the 5'-UTR of HCV genome and HCV serotyping using an ELISA system in which type-specific antibodies against the NS4 region were detected. Overall, a good correlation of the two methods was observed, the main discrepancy being 4 patients with sequence-confirmed HCV-2 (2 cases) and HCV-3 (2 cases) genotypes recognized as HCV-1 by serotyping. Mixed infections were not detected by either method. In 19 PCR negative sera, in which the HCV genotype could not be evaluated, no particular serotype profile was observed. In conclusion, the molecular and serological techniques are almost equivalent in determining the viral type, although in individual cases, especially in PCR negative patients, the clinical meaning of the serotyping result remains to be determined.

Hepatocyte regeneration in chronic hepatitis C and interferon treatment: analysis of immunohistological identification of proliferating cell nuclear antigen (PCNA)

To evaluate the usefulness of proliferating cell nuclear antigen (PCNA) immunostaining in the assessment of the efficacy of interferon (IFN) therapy in chronic hepatitis C, we investigated the proliferative activity of hepatocytes in 67 patients with chronic hepatitis C, using this immunostaining method. The percentage of PCNA-positive hepatocytes was 2.4% in patients with chronic persistent hepatitis, 2.5% in those with chronic aggressive hepatitis 2A, and 3.9% in those with chronic aggressive hepatitis 2B. The PCNA count increased with the progression of the liver disease. Patients were classified as complete, partial, and non-responders to IFN; the percentage of PCNA-positive hepatocytes before IFN therapy was 1.6% in the complete responders, 3.9% in the partial responders, and 4.9% in the non-responders. There was a significant negative correlation between the percentage of PCNA-positive hepatocytes and the response to IFN treatment. Thirty-two of 53 cases (60.4%) in which the PCNA labeling index (LI) was less than 5.0 were complete responders compared with 13 of 14 cases (92.9%) in which the PCNA LI was higher than 5.0, representing partial responders or non-responders (P < 0.001). Most complete responders had a low PCNA LI, irrespective of HCV genotype. Our findings indicate that PCNA immunostaining is a simple and reliable index of cell proliferation in liver regeneration, and may be a useful predictor of the response to IFN treatment in chronic hepatitis C.

Genotypes and virus load in patients with hepatitis C infection

Virus load was tested by means of PCR calibrated with standards and HCV genotypes were determined by the LIPA-technique using sera from 123 HCV patients. Of these 39 were on renal hemodialysis treatment, 19 suffered from hemophilia, 13 were i.v. drug users and the remaining 52 had none of these risk factors (chronic hepatitis group). The most prevalent subtype in Austria was 1b followed by 3a and 1a. However, genotype 1b infections were found relatively less often in hemophilia patients and drug users than in the other groups, indicating that hemophiliacs probably had been infected by an antihemophilic plasma coming from South American or Asian donors. The highest amounts of virus were found in patients infected with genotype 3a. Determination of the patient's virus load and of the infecting subtype of HCV may be helpful in planning interferon alpha therapy.

Linear B-cell epitopes of the NS3-NS4-NS5 proteins of the hepatitis C virus as modeled with synthetic peptides

A set of 150 synthetic peptides spanning the proteins NS3-NS4-NS5 of the hepatitis C virus (HCV) was synthesized and tested with a panel of 20 sera obtained from HCV-infected patients. Of 62 peptides prepared from the NS3 region, none exhibited strong antigenic reactivity. Rather, five peptides from this region demonstrated specific reactivity with only 5-10% of anti-HVC-positive sera. Nonetheless, it is well known that the NS3 region contains strong antigenic epitopes. These epitopes appear to be modeled in a functionally active manner with recombinant proteins and cannot be mimicked properly with short synthetic peptides. This finding suggests that the major NS3 antigenic epitopes are conformationally dependent. Seven of 20 peptides prepared from the NS4 region were immunoreactive. Five peptides from this region demonstrated very strong HCV-specific antigenic reactivity. Four of the five peptides belong to the recognized immunoreactive 5-1-1 region located inside the C100-3 antigen. One peptide demonstrating immunoreactivity with approximately 90% of anti-HCV-positive sera was found outside the C100-3 region at the C-terminal part of the NS4 protein. Of 68 peptides synthesized from the NS5 protein, 30 were immunoreactive. Six of the 30 demonstrated immunoreactivity with 35-50% of anti-HCV-positive sera. Thus, the NS4 and NS5 regions of the HCV polyprotein contain a large number of specific, broadly reactive, linear antigenic epitopes. The highly antigenic reactivity of the NS5 region suggests that this protein may have significant diagnostic potential.

Current status of the molecular genetics of hepatitis C virus and its utilization in the diagnosis of infection

BACKGROUND

Since the discovery of hepatitis C virus (HCV) as a major cause of non-A non-B hepatitis, advances have been made in our understanding of the molecular biology of HCV and its relatedness to the flaviviruses and pestiviruses. The use of molecular techniques to construct an antibody assay has enabled the accumulation of information concerning the natural history and pathogenesis of HCV infection.

OBJECTIVES

The objective was to review the literature to March 1994 on the structure, function and genetics of HCV and to correlate these findings with approaches to diagnosis that have contributed to our understanding of HCV infections.

STUDY DESIGN

We reviewed the virological and medical literature from 1988 to March of 1994 with a focus on the stated objectives.

RESULTS

Although the structure of HCV has been well-defined, our knowledge of the function of all the genes of HCV is incomplete. Structural core and envelope proteins as well as enzymes have been described. The 5' end of the polypeptide is most conserved. Genotyping of isolates varies according to the part of the gene examined. Several genotypes exist and tend to predominate in global populations. Antibodies to the various proteins can be measured by EIA assays and positive specimens often require confirmatory testing. Uniquely sensitive nucleic acid detection systems for RNA amplified by PCR have enabled a better understanding of the natural history, epidemiology and responses to treatment.

CONCLUSIONS

Well-designed studies for the detection of nucleic acid, antibodies and antigens using a variety of viral gene products will provide even more information about HCV infections and help lead to treatment and prevention.

Evaluation of a multiple peptide assay for typing of antibodies to the hepatitis C virus: relation to genomic typing by the polymerase chain reaction

A panel of 16 type-specific synthetic peptides corresponding to variable antigenic regions within the hepatitis C virus (HCV) core, nonstructural 4 (NS4), and NS5 proteins was synthesised. The peptide panel was used to develop an enzyme immunoassay (EIA) for the detection of antibodies directed to HCV type 1 (genotypes I/1a and II/1b), type 2 (genotypes III/2a and IV/2b), and type 3 (genotype V/3). The peptides corresponded to residues 68-81 of the HCV core (types 1, 2, and 3), residues 1692-1705 and 1710-1728 of HCV NS4 (types 1a, 1b, 2a, 2b, and 3), and residues 2303-2319 of HCV NS5 (types 1a, 1b, 2a, and 2b). The 16-peptide panel was evaluated using human sera from 46 carriers of HCV, which were genotyped in parallel by the polymerase chain reaction (PCR) using primers specific for types I, II, III, IV, and V of HCV core. Of the 46 carriers, 14 (30%) were infected by HCV genotype I, 7 (15%) by genotype II, 16 (35%) by HCV genotype IV, and 6 (13%) by HCV of genotype V. Two carriers had double infections of types I and II, and the HCV strain of one carrier could not be genotyped. Using the serotyping system, 40 (89%) out of the 45 genotyped carriers were found to contain type-specific antibodies corresponding to the genotypes identified by PCR. In 5 of the 23 carriers infected by genotypes I and/or II, antibodies specific for HCV type 1 could not be detected, whereas all 16 carriers infected by genotype IV were serologically typed as type 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Classification of hepatitis C viruses based on phylogenetic analysis of the envelope 1 and nonstructural 5B regions and identification of five additional subtypes

Genotyping of hepatitis C virus-positive sera by means of a line probe assay indicated that < 3% of European samples, but up to 30% of Gabonese sera, could not be classified as either 1a, 1b, 2a, 2b, 3a, 3b, 4c, 5a, or 6a. Such samples were analyzed in the 5' untranslated region and in the nonstructural 5 (NS5) region. Classification based on phylogenetic analysis of the commonly used 222-bp-long NS5B region was possible for most but not all of the selected sera. Therefore, the core/envelope 1 region (579 bp) and a larger NS5B (340 bp) region were also analyzed. Only the phylogenetic analysis of the 340-bp NS5B region of these newly identified and published isolates provided unambiguous classification into types and subtypes. Furthermore, unequivocal evidence for four subtypes in type 2 and eight subtypes in type 4 was provided. A specific recognition sequence in the 5' untranslated region was observed for every newly identified subtype. Based on 1830 pair-wise comparisons in NS5B, isolates belonging to the same subtype showed evolutionary distances of < 0.127 and isolates of the same type exhibited evolutionary distances of < 0.328. These phylogenetic border distances can be conveniently used for classification of hepatitis C virus isolates into types and subtypes.

Hepatitis C: progress and problems

The hepatitis C virus (HCV), a single-stranded RNA virus, is the major cause of posttransfusion hepatitis. HCV isolates differ in nucleotide and amino acid sequences. Nucleotide changes are concentrated in hypervariable regions and may be related to immune selection. In most immunocompetent persons, HCV infection is diagnosed serologically, using antigens from conserved regions. Amplification of RNA may be necessary to detect infection in immunosuppressed patients. Transmission by known parenteral routes is frequent; other means of spread are less common and may represent inapparent, percutaneous dissemination. Infection can lead to classical acute hepatitis, but most infected persons have no history of acute disease. Once infected, most individuals apparently remain carriers of the virus, with varying degrees of hepatocyte damage and fibrosis ensuing. Chronic hepatitis may lead to cirrhosis and hepatocellular carcinoma. However, disease progression varies widely, from less than 2 years to cirrhosis in some patients to more than 30 years with only chronic hepatitis in others. Determinants important in deciding outcome are unknown. Alpha interferon, which results in sustained remission in selected patients, is the only available therapy. Long-term benefits from such therapy have not been demonstrated. Prevention of HCV infection by vaccination is likely to be challenging if ongoing viral mutation results in escape from neutralization and clearance.

Hepatitis C virus (HCV) core serotypes in chronic HCV infection

Recently, two distinct hepatitis C virus (HCV) serologic types have been identified on the basis of amino acid variations in the core region. The two serologic types can readily discriminate between genotypes I-II-V (serotype 1) and III-IV (serotype 2), according to the Okamoto classification. We compared HCV core serotyping with genotyping with sera from 363 anti-HCV-positive patients (309 HCV RNA positive by PCR) using a synthetic core peptide-based enzyme immunoassay and PCR amplification of core region sequences with type-specific primers, respectively. Serologic responses to HCV serotypes were successfully identified in 164 (45%) patients, of whom 153 were viremic. Eighty-nine patients had evidence of exposure to serotype 1: 8 of these were infected with genotype I, 50 were infected with genotype II, 2 were infected with genotype III, 7 were infected with genotype V, 13 had infections with mixed genotypes, 3 were infected with an indeterminate genotype, and 6 were nonviremic. Seventy-four patients had been exposed to serotype 2: 64 were infected with genotype III, 3 were infected with mixed genotypes, 2 were infected with an indeterminate genotype, and 5 were nonviremic. The serum of one patient, infected with genotype III, showed reactivity to both serotypes. Comparative evaluation of HCV core region serotyping and genotyping with sera from 294 viremic patients infected with a known HCV genotype showed a remarkable concordance between HCV core region genotyping and serotyping, with only 2 apparently discordant serum samples (both from patients with genotype III infection) of 148 (1.4%) successfully serotyped samples. Serotype 1 infection was more frequently observed in patients with overt chronic liver disease and accounted for all successfully serotyped samples from intravenous drug abusers. In contrast, serotype 2 was more prevalent in subjects with biochemically silent HCV infection (alanine aminotransferase, < 45 U/liter), in agreement with previous findings at the molecular level. HCV core serologic typing is a simple, inexpensive, and highly reproducible assay that can be applied to more than 50% of viremic HCV antibody carriers prior to the use of more sophisticated molecular typing techniques. Moreover, it may be helpful in tracking transmissions routes, particularly for incorrectly stored samples in which the RNA has degraded or for subjects who have cleared the virus and therefore have only antibodies remaining to testify to a remote infection. The lack of recognition of the core sequence from residues 67 to 81, which contains a minor B-cell epitope used to detect type-specific immunoreactivity, may explain the negative serologic findings for half of the patients.