The phylogenetic analysis of hepatitis C virus isolates obtained from two Iranian carriers revealed evidence for a new subtype of HCV genotype 3.

Classification of hepatitis C virus is based on phylogenetic analysis of the strains reported world wide. Different strains are classified within 6 major genotypes and several minor groups (subtypes). In addition to epidemiologic value of determining genotype/subtype of this virus, the result may change the therapeutic strategy used for a patient. During a survey on hepatitis C in Iran, we found two cases assigned as 1b genotype by PCR-RFLP on 5' UTR, but three based on core region sequencing. Fragments from 5' UTR, Core and NS5b regions were PCR-amplified and sequenced followed by phylogenetic analysis. Although the 5' UTR of this new strain is very similar to genotypes 1 and 6, analysis of core region classifies it in a separate branch of genotype 3, close to subtypes h and k. Further analysis of NS5b region put this new strain in a separate branch near other subtypes of genotype 3 and 4. These data are suggestive of a new subtype within genotype 3.