Prevalence and genetic diversity of hepatitis B and delta viruses in pregnant women in Gabon: molecular evidence that hepatitis delta virus clade 8 originates from and is endemic in central Africa

Abstract

Hepatitis B virus (HBV) surface antigen (HBsAg) was found in 9.2% of 1,186 pregnant women from Gabon, of whom 10.1% had the HBe antigen and 89.9% had anti-HBe antibodies. Antibodies to the hepatitis delta virus (HDV) were found in 15.6% of the HBsAg-positive women. The HBV strains were of the A3 and E genotypes. The HDV strains belonged to HDV clades 1 and 8. These results provide clear evidence that HDV clade 8 is indigenous to Africa.

FIG. 1.

Phylogenetic analysis of HBV and HDV strains obtained from pregnant women in Gabon, central Africa. (A) Phylogenetic analysis of a 315-bp fragment of the HBV-S gene from different HBV isolates by the neighbor-joining method with HBV-G (GenBank accession number AF160501) as the outgroup. Fourteen HBV-A3-FE sequences and 2 HBV-E sequences (highlighted in boldface) were compared with 31 HBV sequences from GenBank. *, a complete genome sequence was obtained for the FE-929-MO sample (GenBank accession number EU054331). This HBV subgenotype A3 clustering was confirmed by a separate phylogenetic analysis of the partially overlapping open reading frames coding for the polymerase-reverse transcriptase protein Pol (bootstrap value, 99%); envelope proteins S, M, and L (bootstrap value, 91%); the core protein (bootstrap value, 65%); and the transcriptional trans-activator protein (bootstrap value, 67%). No mutations in cis-acting elements were observed in the FE-929-MO isolate. pFDW294 (GenBank accession number M57663) was used as the reference strain (data not shown). (B) Phylogenetic analysis of a 326-bp fragment of the sHD gene from various HDV isolates by the neighbor-joining method, with HDV-3 used as the outgroup. One HDV-1 sequence (strain FE284-ES) and two HDV-8 sequences (strains FE1072-HO and FE1682-WN) (in boldface) were analyzed with 28 HDV sequences from GenBank.