Hepatitis B Transmission: Is Vertical Transmission the Major Route in Intermediate Endemic Areas? A Proof-of-Concept Study Based on Mother–Child Genotypes

Abstract

The route of hepatitis B transmission is believed to be horizontal in India, though pediatric studies showed mother as source in the majority of chronic HBV (CHB) cases. We aimed at establishing the fact that mother-child transmission is the main route of acquisition by documenting genotypically identical viruses in mother-child pairs. Blood samples of consecutive children (≤ 18 years) with CHB and high DNA (< 10,000 IU/mL) and their positive mothers were collected from January 2013 to December 2015. Polymerase chain reaction (PCR) products of HBV-DNA were amplified and sequenced by using BigDye Terminator Cycle Sequencing Kit v3.1 and aligned with previously described sequences in the region of interest for genotypes A to G by using BioEdit software. Phylogenetic tree was generated using p-distance algorithm in MEGA software version 6. Genotyping of 59 (33 children and 26 mothers) subjects include genotype A in 24 (40.7%) and genotype D in 35 (59.3%). Both mother-child pair genotyping was possible in 25. The median age of 25 children (20 males) was 9 (interquartile range, IQR: 4-11) years. The distribution of genotypes among mother-child pairs was similar. The concordance between children and their mothers was 24 of 25 (96%). Evolutionary analysis showed significant similarities between mother and child sequences for both genotype A and D, suggesting thereby the same virus. In conclusion, mother-baby transmission seems to be the major route of acquisition of HBV in children in India and near-complete homology in genetic sequences between mother-child pairs is definite proof for that. However, a larger epidemiological study is required to substantiate our findings.