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

This paper presents a summary of the recommendations that were formulated f or the purposes of unifying the nomenclature for hepatitis C virus (HCV), b ased upon guidelines of the International Committee on Virus Taxonomy (ICTV ), and provides guidelines for the incorporation of sequence data into an H CV database that will be available to researchers through the internet, Bas ed upon the available data, the genus Hepacivirus should be regarded as com prising a single species with HCV-1 as the prototype. All currently known i solates of HCV can be divided into six phylogenetically distinct groups, an d 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,g enus requires additional clinical, virological, and immunological informati on. 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 ge notypes 6, 7, 8, 9, and II. We propose that existing subtype designations a re reassigned within these clades based upon publication priority, the exis tence of a complete genome sequence and prevalence. The assignment of isola tes to new clades and subtypes should be confined to isolates characterized from epidemiologically unlinked individuals. Comparisons should be based o n nucleotide sequences of at least two coding regions and preferably of com plete genome sequences, and should be based on phylogenetic analysis rather than percent identity. A forum for discussion and contributions to these r ecommendations will be made available at the international HCV database at http://s2as02.genes.nig.ac.jp.