11 genotypes!

[Guest guest]

HCV genotypes

HCV is classified into eleven major genotypes (designated 1-11), many subtypes (designated a, b, c, etc.), and about 100 different strains (numbered 1,2,3, etc.) based on the genomic sequence heterogeneity.89

The variability is distributed throughout the genome. However, the non-coding regions at either end of the genome (5'-UTR and 3'-UTR; UTR-untranslated region) are more conserved and suitable for virus detection by PCR.89

The genes coding for the envelope E1 and E2 glycoproteins are the most variable. Amino acid changes may alter the antigenic properties of the proteins, thus allowing the virus to escape neutralizing antibodies.89

Genotypes 1-3 have a worldwide distribution. Types 1a and 1b are the most common, accounting for about 60% of global infections. They predominate in Northern Europe and North America, and in Southern and Eastern Europe and Japan, respectively. Type 2 is less frequently represented than type 1. Type 3 is endemic in south-east Asia and is variably distributed in different countries. Genotype 4 is principally found in the Middle East, Egypt, and central Africa. Type 5 is almost exclusively found in South Africa, and genotypes 6-11 are distributed in Asia.39, 58, 94, 103

The influence of viral genotype in the pathogenesis of liver disease is still controversial. Environmental, genetic, and immunological factors may contribute to the differences in disease progression, so characteristic of HCV infection, observed among patients.58

The determination of the infecting genotype is however important for the prediction of response to antiviral treatment: genotype 1 is generally associated with a poor response to interferon alone, whereas genotypes 2 and 3 are associated with more favourable responses.58 The current gold standard of therapy - pegylated interferon-a in combination with ribavirin – significantly improves response for all genotypes. 65

http://www.who.int/csr/disease/hepatitis/whocdscsrlyo2003/en/index2.html