Amy J. Weiner

Consensus proposals for a unified system of nomenclature of hepatitis C virus genotypes

International standardization and coordination of the nomenclature of variants of hepatitis C virus (HCV) is increasingly needed as more is discovered about the scale of HCV‐related liver disease and important biological and antigenic differences that exist between variants. A group of scientists expert in the field of HCV genetic variability, and those involved in development of HCV sequence databases, the Hepatitis Virus Database (Japan), euHCVdb (France), and Los Alamos (United States), met to re‐examine the status of HCV genotype nomenclature, resolve conflicting genotype or subtype names among described variants of HCV, and draw up revised criteria for the assignment of new genotypes as they are discovered in the future. A comprehensive listing of all currently classified variants of HCV incorporates a number of agreed genotype and subtype name reassignments to create consistency in nomenclature. The paper also contains consensus proposals for the classification of new variants into genotypes and subtypes, which recognizes and incorporates new knowledge of HCV genetic diversity and epidemiology. A proposal was made that HCV variants be classified into 6 genotypes (representing the 6 genetic groups defined by phylogenetic analysis). Subtype name assignment will be either confirmed or provisional, depending on the availability of complete or partial nucleotide sequence data, or remain unassigned where fewer than 3 examples of a new subtype have been described. In conclusion, these proposals provide the framework by which the HCV databases store and provide access to data on HCV, which will internationally coordinate the assignment of new genotypes and subtypes in the future. (HEPATOLOGY 2005.)

Analysis of a Successful Immune Response against Hepatitis C Virus

To investigate the type of immunity responsible for resolution of hepatitis C virus (HCV) infection, we monitored antibody and intrahepatic cytotoxic T lymphocyte (CTL) responses during acute (<20 weeks) infection in chimpanzees. Two animals who terminated infection made strong CTL but poor antibody responses. In both resolvers, CTL targeted at least six viral regions. In contrast, animals developing chronic hepatitis generated weaker acute CTL responses. Extensive analysis of the fine specificity of the CTL in one resolver revealed nine peptide epitopes and restriction by all six MHC class I allotypes. Every specificity shown during acute hepatitis persisted in normal liver tissue more than 1 yr after resolution. These results suggest that CD8+CTL are better correlated with protection against HCV infection than antibodies.

Detection of hepatitis C viral sequences in non-A, non-B hepatitis

The role of hepatitis C virus (HCV) in post-transfusion non-A, non-B hepatitis (NANBH) was investigated by analysing clinical samples for both HCV RNA by cDNA/polymerase chain reaction and antibodies against C100-3 by radioimmunoassay. Of fifteen chronic NANBH patients and one patient with chronic cryptogenic liver disease, ten were positive for anti-C100-3 and seven of the ten had viral sequences in their livers. However, two patients negative for anti-C100-3 also had substantial levels of HCV RNA in their livers. In acute post-transfusion NANBH (one surgical patient and two experimentally infected chimpanzees), HCV RNA was detected in the absence of anti-C100-3. In addition, infectious plasma from a seronegative patient with acute post-transfusion NANBH and a seronegative pool of plasma from a chimpanzee with chronic post-transfusion NANBH had high levels of HCV. These findings show that anti-C100-3-positive patients with chronic post-transfusion NANBH are likely to be viraemic; confirm that antibodies to C100-3 are a marker for infectivity; and suggest that the prevalence of HCV infections may be underestimated from the frequency of antibodies to C100-3 alone.

Variable and hypervariable domains are found in the regions of HCV corresponding to the flavivirus envelope and NS1 proteins and the pestivirus envelope glycoproteins

Based on the flavi- and pestivirus model of genome organization for the hepatitis C virus (HCV) (1-5), the nucleotide and deduced amino acid sequences of the putative envelope (E1) and the junction between the E1 and NS1/envelope 2 (E2) region from six different human isolates of HCV were compared with the nucleotide and predicted amino acid sequences of the prototype hepatitis C virus (HCV-1) (5). The overall percentage of nucleotide and amino acid changes among all six isolates, including HCV-1, from nucleotide 713 to 1630 (amino acid 129 to 437) was between 3 and 7%, which is comparable to that seen in some flaviviruses (6-8). An analysis of the number of nucleotide and deduced amino acid sequence changes among all six isolates and HCV-1 revealed a moderately variable domain of approximately 40 amino acids in the E1 region and a hypervariable domain (Region V) of approximately 28 amino acids, which is directly downstream from a putative signal peptide sequence, in the junction between E1 and NS1/E2. A similar hypervariable domain is not found in the C-terminus of the envelope polypeptide or in the N-terminus of the NS1 polypeptide domain of the flaviviruses. These findings suggest that the mature NS1/E2 polypeptide starts about amino acid 380 and that the NS1/E2 domain may correspond to a second envelope glycoprotein as in the case of the pestivirus. The observed heterogeneity in the putative structural proteins of HCV may have important ramifications for future vaccine development.

Classification, nomenclature, and database development for hepatitis C virus (HCV) and related viruses: proposals for standardization

SummaryThis paper presents a summary of the recommendations that were formulated for the purposes of unifying the nomenclature for hepatitis C virus (HCV), based upon guidelines of the International Committee on Virus Taxonomy (ICTV), and provides guidelines of the incorporation of sequence data into an HCV database that will be available to researchers through the internet. Based upon the available data, the genus Hepacivirus should be regarded as comprising as comprising a single species with HCV-1 as the prototype. All currently known isolates of HCV can be divided into six phylogenetically distinct groups, and we recommend that these groups are described as clades 1 to 6. Whether or not these should be regarded as different species within the Hepacivirus genus requires additional clinical, virological, and immunological information. Clades 1, 2, 4, and 5 would correspond to genotype 1, 2, 4, and 5 while clade 3 would comprise genotype 3 and genotype 10, and clade 6 comprise genotypes 6, 7, 8, 9, and 11. We propose that existing subtype designations are reassigned within these clades based upon publication priority, the existence of a complete genome sequence and prevalence. The assignment of isolates to new clades and subtypes should be confined to isolates characterized from epidemiologically unlinked individuals. Comparisons should be based on nucleotide sequence of at least two coding regions and preferably of complete genome sequences, and should be based on phylogenetic analysis rather than percent identity. A forum for discussion and contributions to these recommendations will be made available at the international HCV database at http://s2as02.genes.nig.ac.jp.

Structure, sequence and expression of the hepatitis delta (|[delta]|) viral genome

Biochemical and electron microscopic data indicate that the human hepatitis δ viral agent contains a covalently closed circular and single-stranded RNA genome that has certain similarities with viroid-like agents from plants. The sequence of the viral genome (1,678 nucleotides) has been determined and an open reading frame within the complementary strand has been shown to encode an antigen that binds specifically to antisera from patients with chronic hepatitis δ viral infections.

Confirmation of hepatitis C virus infection by new four-antigen recombinant immunoblot assay

A new four-antigen recombinant immunoblot assay (4-RIBA) for confirmation of hepatitis C virus (HCV) C-100 enzyme-linked immunosorbent assay (ELISA) reactivity was tested in stored serum samples (1984-86) of blood donors and recipients and compared with results from polymerase chain reaction (PCR) analysis of fresh (1990) plasma samples in donors and recipients from the original study. Of 37 HCV C-100 ELISA-positive blood products, 8 were 4-RIBA positive, of which 7 were implicated in post-transfusion non-A, non-B hepatitis (PT-NANBH) and/or PCR confirmed recipient HCV infection. Of 9 recipients with PT-NANBH, 8 were reactive in 4-RIBA (6 positive and 2 indeterminate). With fresh plasma samples, 3 donors and 6 recipients who were 4-RIBA positive were also PCR positive. 4 4-RIBA indeterminate and 78 4-RIBA negative samples of donors and recipients were PCR negative. Of 6 4-RIBA positive recipients, 5 were PCR positive four to six years later. 1.6% of the 383 recipients became chronically infected with HCV. The new 4-RIBA represents a candidate confirmation test to discriminate between infective and non-infective HCV C-100 ELISA-positive blood donors.

T-lymphocyte response to hepatitis C virus in different clinical courses of infection.

BACKGROUND To assess the role played by the immune response in the outcome of hepatitis C virus infection, the CD4+ T-lymphocyte response to viral antigens was studied in infected individuals with different clinical courses. METHODS Using six recombinant proteins of hepatitis C virus, the study assessed the proliferative responses of peripheral blood mononuclear cells from 41 patients with chronic hepatitis C, 11 patients whose chronic hepatitis was successfully treated with interferon alfa and 11 healthy HCV seropositive individuals. RESULTS (1) Sixty-five percent of hepatitis C virus-seropositive individuals had CD4+ T-cell responses to viral proteins. (2) All viral proteins were immunogenic for T cells, although NS4 was the most immunogenic. (3) There was a significant correlation between the presence of CD4+ T cell responses to Core and a benign course of infection in healthy seropositives, most of whom were viremic. CONCLUSIONS CD4+ T-cell responses to Core, although they do not coincide with virus clearance, are associated with a benign course of infection and may be required to maintain humoral and cellular responses protective against the disease.

Classification, nomenclature, and database development for hepatitis C virus (HCV) and related viruses

SummaryThis paper presents a summary of the recommendations that were formulated for the purposes of unifying the nomenclature for hepatitis C virus (HCV), based upon guidelines of the International Committee on Virus Taxonomy (ICTV), and provides guidelines of the incorporation of sequence data into an HCV database that will be available to researchers through the internet. Based upon the available data, the genus Hepacivirus should be regarded as comprising as comprising a single species with HCV-1 as the prototype. All currently known isolates of HCV can be divided into six phylogenetically distinct groups, and we recommend that these groups are described as clades 1 to 6. Whether or not these should be regarded as different species within the Hepacivirus genus requires additional clinical, virological, and immunological information. Clades 1, 2, 4, and 5 would correspond to genotype 1, 2, 4, and 5 while clade 3 would comprise genotype 3 and genotype 10, and clade 6 comprise genotypes 6, 7, 8, 9, and 11. We propose that existing subtype designations are reassigned within these clades based upon publication priority, the existence of a complete genome sequence and prevalence. The assignment of isolates to new clades and subtypes should be confined to isolates characterized from epidemiologically unlinked individuals. Comparisons should be based on nucleotide sequence of at least two coding regions and preferably of complete genome sequences, and should be based on phylogenetic analysis rather than percent identity. A forum for discussion and contributions to these recommendations will be made available at the international HCV database at http://s2as02.genes.nig.ac.jp.

CD81 is a central regulator of cellular events required for hepatitis C virus infection of human hepatocytes.

ABSTRACT Infection with hepatitis C virus (HCV) is still a major public health problem, and the events leading to hepatocyte infection are not yet fully understood. Combining confocal microscopy with biochemical analysis and studies of infection requirements using pharmacological inhibitors and small interfering RNAs, we show here that engagement of CD81 activates the Rho GTPase family members Rac, Rho, and Cdc42 and that the block of these signaling pathways drastically reduces HCV infectivity. Activation of Rho GTPases mediates actin-dependent relocalization of the HCV E2/CD81 complex to cell-cell contact areas where CD81 comes into contact with the tight-junction proteins occludin, ZO-1, and claudin-1, which was recently described as an HCV coreceptor. Finally, we show that CD81 engagement activates the Raf/MEK/ERK signaling cascade and that this pathway affects postentry events of the virus life cycle. In conclusion, we describe a range of cellular events that are manipulated by HCV to coordinate interactions with its multiple coreceptors and to establish productive infections and find that CD81 is a central regulator of these events.