[Relationship between C genotype HBV mutation and intrauterine transmission]

Objective: To analyze the virus genome mutation of mothers with C genotype HBV and explore its relationship with HBV intrauterine transmission. Methods: A total of 399 mothers carrying HBV and their newborns hospitalized in the obstetrics department of the Third People's Hospital of Taiyuan from 2011 to 2013 were selected. Necessary information about mothers and children was obtained through a questionnaire survey and medical records. HBV DNA and HBV serological markers were detected by quantitative fluorescence PCR and electrochemiluminescence. Within 24 hours after birth and before active/passive immunization, those with positive HBsAg and/or HBV DNA in femoral venous blood were determined as HBV intrauterine transmission. According to the requirements of cloning and sequencing, mothers' HBV DNA load should be ≥10⁶ IU/ml. Among 54 cases of HBV intrauterine transmission, 22 pairs of mothers and their newborns meeting the requirements of cloning and sequencing were used as the intrauterine transmission group. The same number of mothers and their newborns without intrauterine transmission was selected as the random seed method's control group. After PCR amplification of HBV DNA, gene cloning, and sequencing, the gene mutation analysis of mothers with C genotype HBV was performed. Results: Among the 44 samples, 39 (88.63%, 39/44) were genotype C, 2 were genotype B, and 3 were mixed genotype B, and C. A total of 406 clone beads from 42 mothers with C genotype HBV were analyzed for gene mutation, including 204 in the intrauterine transmission group and 202 in the control group. The base substitution mutation rate of PreS1, S, C, and P regions in the HBV intrauterine transmission group were significantly lower than those in the control group (χ ranged from 8.67 to 40.73, P<0.05). The mutation rate of base deletion in PreC and X regions in the HBV intrauterine transmission group was lower than that in the control group (χ values were 17.82 and 34.78, P<0.001). Two clones in the X region had 31 bp insertion mutations between nt1644 and nt1645, and two clones had 27 bp insertion mutations between nt1649 and nt1650, all of which took place in the control group. Conclusions: The base substitution mutations in the PreS1, S, C, and P segments of the HBV genome in mothers with C genotype HBV were associated with the occurrence of intrauterine transmission of HBV. Deletion mutations in the PreC region, insertion and deletion mutations in the X region may reduce intrauterine transmission risk.