Molecular Analysis of Hepatitis B Virus in Mothers-Children Pairs

ackground: Vertical transmission of Hepatitis B Virus (HBV) is the primary infection source for infants, but little is known on the proportion of children that have acquired HBV from their mothers. Objective: We investigated the relationship of HBV sequencing in HBVpositive children and their mothers and explored the HBV phylogenetic tree. Methods: Serum-extracted HBV-DNA from 38 individuals (13 children paired to nine mothers, 16 unpaired infected children) was amplified by polymerase chain reaction and the target region HBV surface glycoprotein (amino acids 40-171) was directly sequenced. Following editing and alignment of these sequences, phylogenetic tree analysis was performed using the neighbourjoining and maximum-likelihood methods. Results: Analysis was successfully performed in 29 subjects (23 children and six mothers), including six mother-child pairs. All individuals were infected by genotype D. Subgenotype adw3 prevailed (21, 72.4%), followed by ayw2 (4, 13.8%) and ayw3 (4, 13.8%). Among six mother-child pairs, three had identical and three had different subgenotypes. Phylogenetic analysis revealed that HBV sequences from three children did not cluster with their siblings suggesting a different source of infection. Conclusion: Our findings suggest that HBV subgenotypes in infected children may not be identical to their mothers’ and point to non-vertical HBV transmission in childhood.