Phylogenetic analysis of new hepatitis B virus isolates from Nigeria supports endemicity of genotype e in west Africa

Isolates of hepatitis B viruses were collected from 20 acute and chronic he patitis patients in a highly endemic region of Nigeria. Sequencing classifi ed the isolates to the ayw4, as they all contained the amino acid variation s characteristic for that serotype. In the pre-S2 region of five isolates, three to seven amino acids were deleted, suggesting that immune escape muta tions previously associated only with chronic HBV infection may be observed also in acute disease. Phylogenetic, analysis of the complete pre-S2/S (la rge S) genes (831 nt) demonstrated that all the viruses belonged to the sam e genotype E. So far, no isolates of genotype E have been found in any othe r region of the world, including the Americas. This may suggest a relativel y recent introduction of this genotype into humans and would explain the re latively low genetic diversity of viruses belonging to this genotype. One g enotype E virus had been found previously in a chimpanzee, and viruses belo nging to the CHIMP genotype are related to other genotype E viruses. These findings are compatible with a transmission of genotype E viruses from chim panzees to humans. (C) 2001 Wiley-Liss, Inc.