By Liz Highleyman 27/11//07
A group of researchers reported on the identification of a new HCV genotype originating in Central Africa.
HCV genotypes 1, 2, and 3 are most common in North America and Western Europe. Genotype 4 is most common in Africa, including Egypt, and the Middle East, but is increasingly seen in some parts of Europe such as Spain. Genotype 5 also has been reported most often in Africa and the Middle East. Genotype 6 predominates in Southeast Asia.
As background, they noted HCV genotypes 1, 2, and 4 display significant genetic diversity in Africa, while genotypes 3 and 6 show high genetic diversity in southern Asia. On the other hand, genotype 5 is comprised of only 1 subtype, and its origin has not yet been established.
The investigators identified 3 HCV variants (QC69, CS101285, and CS101300) that clustered together, but did not fall within the classification of the 6 known genotypes. QC69 was isolated from a patient residing in Canada, while CS101285 and CS101300 were obtained from patients in Belgium. However, all 3 patients came from the Democratic Republic of Congo, where they were presumably infected.
In order to better characterize these variants and study their evolutionary relationships with the other genotypes, the researchers determined the entire coding region sequence of QC69 and partial coding region sequences of CS101285 and CS101300.
QC69 contained an open reading frame of 3013 amino acids. It showed 33.4% to 35.5% nucleotide and 28.1% to 31.0% amino acid divergence compared with genotypes 1a-H77, 2a-HCJ6, 3a-NZL1, 4a-ED43, 5a-EUH1480, and 6a-EUHK2.
Phylogenetic analysis showed that QC69 forms a branch distinct from other HCV genotypes, confirming that it constitutes a novel genotype. Additional analysis indicated a closer relationship between QC69 and genotype 2 variants, analogous to the relationship between genotype 1 and 4 variants. The analysis also showed that QC69 was not a result of recombination between known genotypes.
“The finding of a new genotype in Central Africa will contribute in elucidating the origin of the worldwide HCV epidemic,” the researchers concluded. “We propose that these 3 isolates be classified as genotype 7 of HCV.”
Reference
D Murphy, J Chamberland, R Dandavino, and others. A New Genotype of Hepatitis C Virus Originating from Central Africa, AASLD 2007. Abstract
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