One hundred forty-two precore/core sequences were obtained from Gambian chr
onic hepatitis B virus (HBV) carriers and the predominant variants defined.
The two point mutations, from A to T and G to A at nt positions 1762 and 1
764 in the basic core promoter region, were found in only 7/99 (7%) of the
samples where this region was sequenced. These mutations were found in both
HBeAg-positive and -negative patients. The precore stop-codon mutation at
nt position 1896 was found in 14/51 (27%) of HBeAg-negative samples, which
is a lower prevalence rate in comparison with other parts of the world with
high carrier rates. In HBeAg-positive patients the core amino acid sequenc
es were conserved, but after seroconversion to anti-HBe significantly more
changes were apparent. Several of the amino acid substitutions found have b
een described previously been in wild-type viruses of other genotypes. (C)
2001 Wiley-Liss, Inc.