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;42:962-973.)

In contrast to a detailed understanding of antiviral cellular immune responses, the impact of neutralizing antibodies for the resolution of acute hepatitis C is poorly defined. The analysis of neutralizing responses has been hampered by the fact that patient cohorts as well as hepatitis C virus (HCV) strains are usually heterogeneous, and that clinical data from acute-phase and long-term follow-up after infection are not readily available. Using an infectious retroviral HCV pseudoparticle model system, we studied a cohort of women accidentally exposed to the same HCV strain of known sequence. In this single-source outbreak of hepatitis C, viral clearance was associated with a rapid induction of neutralizing antibodies in the early phase of infection. Neutralizing antibodies decreased or disappeared after recovery from HCV infection. In contrast, chronic HCV infection was characterized by absent or low-titer neutralizing antibodies in the early phase of infection and the persistence of infection despite the induction of cross-neutralizing antibodies in the late phase of infection. These data suggest that rapid induction of neutralizing antibodies during the early phase of infection may contribute to control of HCV infection. This finding may have important implications for understanding the pathogenesis of HCV infection and for the development of novel preventive and therapeutic antiviral strategies.vaccines ͉ pathogenesis ͉ host reponses

Virus-specific CD8؉ T cell responses play an important role in the natural course of infection; however, the impact of certain CD8؉ T cell responses in determining clinical outcome has not been fully defined. A well-defined cohort of women inoculated with HCV from a single source showed that HLA-B27 has a strong association with spontaneous clearance. The immunological basis for this association is unknown. However, the finding is especially significant because HLA-B27 has also been shown to have a protective role in HIV infection. We report the identification of an HLA-B27 restricted hepatitis C virus (HCV)-specific CD8؉ T cell epitope that is recognized in the majority of recovered HLA-B27 positive women. In chronically HCV-infected individuals, analysis of the corresponding viral sequence showed a strong association between sequence variations within this epitope and expression of HLA-B27, indicating allele-specific selection pressure at the population level. T he hepatitis C virus (HCV) is a small positivestranded RNA virus within the Flaviviridae family that persists in 70% of infected individuals. Growing evidence suggests that the cellular host immune response against HCV plays an important role in the outcome of infection. Indeed, viral clearance is temporarily associated with sustained HCV-specific CD4ϩ and CD8ϩ T cell responses that accumulate in the infected liver. [1][2][3] In addition, the important antiviral role of virusspecific CD8ϩ T cells has recently been directly demonstrated by CD8ϩ cell depletion studies in chimpanzees. 4 The mechanisms that lead to the failure of the virus-specific T cell response and the persistence of HCV in most patients are still not well understood. 5 Several different pathways, such as a primary failure to induce T cells, functional exhaustion, or the emergence of viral escape mutations, have been discussed. [5][6][7] Indeed, a growing body of evidence suggests that T cell escape mutations develop early during acute HCV infection and that they remain fixed in the circulating quasispecies for several years. [8][9][10][11][12][13][14][15][16][17] However, the development of escape mutations during HCV infection is not universal. For example, viral clearance can occur with minimal epitope variation before From the

RNA of the newly identified human metapneumovirus (HMPV) was detected in nasopharyngeal aspirates of 11 of 63 (17.5%) young children with respiratory tract disease. Markers of infection caused by another member of the Pneumovirinae subfamily of the family Paramyxoviridae, respiratory syncytial virus (RSV), were identified in 15 of these patients (23.8%). Three patients were simultaneously infected with HMPV and RSV. Studies of the clinical characteristics of HMPV-infected children did not reveal any difference between HMPV-infected patients and a control population of RSV-infected patients with regard to disease severity, but the duration of symptoms was significantly shorter for HMPV-infected patients. Phylogenetic analysis of the amplified viral genome fragments confirmed the existence and simultaneous circulation within one epidemic season of HMPV isolates belonging to two genetic lineages.Recently, a new infectious agent, human metapneumovirus (HMPV), was isolated from nasopharyngeal aspirates of young children with respiratory tract illness from The Netherlands (7). HMPV, together with avian pneumovirus serotypes A, B, C, and D, form the Metapneumovirus genus of the Pneumovirinae subfamily of the family Paramyxoviridae (7,8). Information on the biology of HMPV, as well as on the prevalence and clinical significance of HMPV infection, is scarce. Preliminary data, however, demonstrated that HMPV can cause severe respiratory disease in children younger than age 5 years (2, 3, 4, 6, 7). These observations suggest that HMPV can play an important role in the infectious pathology of humans and indicate the necessity of more detailed study of this agent and infections caused by this agent. Here, we report on the prevalence and clinical characteristics of HMPV infection in children with respiratory disease from Germany and on the genetic heterogeneity of the HMPV isolates identified. MATERIALS AND METHODSSpecimens. Nasopharyngeal aspirates were collected from 63 hospitalized patients younger than age 2 years. These patients represented all children in this age group admitted to the Essen University Hospital with upper or lower respiratory tract infection between January and May 2002. Most of these patients presented with wheezing and/or signs of respiratory distress (Table 1). The clinical data for the HMPV-infected patients were compared to those for a control group of children from the same population infected with respiratory syncytial virus (RSV).Reverse transcription (RT)-PCR for HMPV RNA. RNA was extracted from nasopharyngeal aspirates with the RNeasy kit (QIAGEN) and reverse transcribed and amplified with two primer sets. Information on the first set, which included two primers whose sequences were derived from the L gene and which generated a DNA fragment of 171 bp, was kindly provided by van den Hoogen et al. (7). The second set was designed in the present study. It included four primers whose sequences were derived from the nucleocapsid (N) gene. Primer 750as (5Ј-TGCTTTGCTGCCTGTAGATGATGAG) was used to gene...

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The precise mechanisms responsible for the failure of intrahepatic hepatitis C virus (HCV)-specific CD8 ؉ T cells to control the virus during persistent infection have not been fully defined. We therefore studied the CD8 ؉ T-cell response in 27 HLA-A2-positive patients using four previously well-defined HLA-A2-restricted HCV epitopes. The corresponding HCV sequences were determined in several patients and compared with the intrahepatic HCV-specific CD8 T here is emerging consensus that cellular immune responses play an important role in the immunopathogenesis of hepatitis C virus (HCV) infection. 1,2 Indeed, the appearance of functional HCVspecific T-cell responses is kinetically associated with control of viremia in the acute phase of infection. [3][4][5][6][7] Studies in chimpanzees revealed that virus-specific T cells accumulate in the liver and that this coincides with liver disease and viral clearance. 8,9 The central role of virusspecific CD4 ϩ and CD8 ϩ T cells in HCV clearance has further been recently demonstrated by cell depletion studies in chimpanzees. 10,11 HCV-specific T cells are also detectable in chronic hepatitis, although at a lower frequency compared with acute resolving infection. HCV-specific CD8 ϩ T-cell lines have also been generated from the human liver. [12][13][14][15] In two of these studies, cytotoxic CD8 ϩ T-cell lines could be established from approximately half of the chronically infected livers. 12,15 The long-term survival of HCV-specific CD8 ϩ T cells in the liver has also been demonstrated by major histocompatibility complex (MHC) class I tetramer analysis. While no tetramer-positive cells were found in the liver in two studies, 16,17 other studies have detected tetramer-positive CD8 ϩ T cells in livers at frequencies often exceeding 1% to 2% of intraheatic CD8 ϩ T cells, [18][19][20] indicating that these cells accumulate at the primary site of infection.The mechanisms by which HCV is able to evade the virus-specific T-cell response that is present in the infected liver are still only poorly understood. Several dif-

The detection and quantification of hepatitis C virus (HCV) core antigen in serum or plasma by the use of different assay formats have previously been shown to represent useful markers of viral replication. In the present study, the intrinsic performance characteristics and the potential clinical utility of a novel assay for the quantification of total HCV core antigen were comprehensively assessed by using clinical serum samples and specimens contained in various evaluation panels. The Architect HCV Ag assay showed a specificity of 100%. The intra-and interassay coefficients of variation ranged from 3.6 to 8.0% and from 4.7 to 9.5%, respectively. Except for HCV genotype 2 isolates, the analytical sensitivity was always less than 10 fmol core antigen/liter, corresponding to approximately 500 to 3,000 IU of HCV RNA/ml. Linearity was guaranteed throughout the dynamic range (10 to 20,000 fmol/liter). When seroconversion panels were tested, the assay was not inferior to HCV RNA detection and reduced the preseroconversion period by 4 to 16 days. The results obtained by core antigen and HCV RNA quantification for 385 clinical specimens were correlated by regression analysis (r ‫؍‬ 0.857), but the calculated conversion equation differed significantly from the line of identity. Monitoring of viral kinetics by use of either core antigen or RNA concentrations in 38 HCV-infected patients undergoing antiviral combination therapy resulted in very similarly shaped curves in all cases. Finally, the Architect HCV Ag assay was also shown to enable high-throughput screening of in vitro HCV RNA replication. With these results taken together, the Architect HCV Ag assay proved to be a specific, reproducible, highly sensitive, and clinically applicable test format which will find its future place in the context of virological HCV diagnostics.The virological diagnosis of infection with the hepatitis C virus (HCV) is based on the detection of specific anti-HCV antibodies. Since anti-HCV immunoassays, however, cannot distinguish between acute, past, and persistent infections, screening for HCV RNA is currently regarded as the method of choice for the confirmation of an active infection in both immunocompetent patients who are anti-HCV positive and immunocompromised individuals who may not mount an adequate antibody response (9,27,35,41).Assays for the amplification of HCV RNA are expensive and time-consuming and require sophisticated technical equipment and highly trained personnel. These constraints, however, do not apply to the detection of HCV core antigen, which is easy to perform in an immunoassay format, provides results in a comparably short time frame, and, theoretically, is less prone to sample carryover and, hence, contamination than assays based on nucleic acid amplification (17). During the past decade, therefore, several HCV core antigen tests were developed as potential alternatives to HCV RNA testing (1,4,43). The use of these assays in clinical laboratory settings documented that HCV core antigen can be detected in the s...

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