Identification of hepatitis B virus vertical transmission from father to fetus by direct sequencing.

To identify the possibility of hepatitis B virus (HBV) vertical transmission from father to fetus, eight male HBV carriers whose wives were negative for any HBV marker and their eight aborted fetuses who had been infected with HBV in utero, were studied. S gene 451 approximately 660 nucleotide sequence of HBV in 6 cases of father/fetus pairs and C gene 2022 approximately 2321 nucleotide sequence in the other 2 cases of father/fetus pairs were amplified by nested polymerase chain reaction (NPCR), and sequenced. HBV DNA was detected in the semen and spermatid of male HBV carriers. The homologies of HBV sequences between father and fetus were very high. Six father/fetus pairs had the same subtype adw. The sequences of the fragment were identical between father and fetus in 4 cases. Especially in case 3, both father and fetus had the same point mutation, which caused an amino acid substitution at codon 126. The other two cases had point mutations in the fetus at nucleotide positions 491, 494, 546, 581 resulting in amino acid substitution at codons 113, 114, 131, 143. The C gene 2022 approximately 2321 nucleotide sequences in two cases were identical. There were eleven common point mutations between father and fetus, but those mutations did not cause phenotypic changes. Our finding suggested that HBV vertical transmission from father to fetus was present. A HBV carrier father may transmit the virus to his fetus by spermatid.