【Objective】 To provide an experimental basis for exploring the reason of HBV maternal vertical transmission immune blocking failure

we studied the mutation profiles and genotypes of hepatitis B virus ( HBV) in the Pre S and S regions of pregnant women with high level serum HBV-DNA before delivery. 【Methods】 HBV DNA were extracted from the serum of 41 pregnant women with HBsAg positive and HBV-DNA≥105 IU/mL. Based on the sequence alignment of all HBV genotypes

specific primers targeting all HBV genotypes were designed to amplify the Pre S and S regions of HBV followed by sequence analysis on the sequencing data available. 【Results】 1. Among the 41 cases

29 cases (70.73%) showed mutations in the Pre S and S regions

substitution was the main mutation model. Among all cases

PreS1

pre S2 and S regions mutations frequency were 8.96%

9.88%

and 3.24%

respectively

mutation frequency in pre S1 and pre S2 regions were significantly higher than that in S region (P < 0.05). 2. Genotypes based on the mutation in S region and homology tree model were analyzed. In the 41 cases

22 cases were genotype B

and 19 cases were genotype C. The mutation frequency in the Pre S and S regions between genotype B and genotype C were not statistically significant (P > 0.05). Genotype B and genotype C had their own clusters

homology rate was less than 90% between cluster B and cluster C

but in the cluster B and cluster C the homology rate were 96% and 95%

respectively. 【Conclusion】 1. Mutations of HBV Pre S and S regions were common in pregnant women with high level serum HBV-DNA before delivery. The most common mutation in the Pre S and S regions of HBV was substitution

mutation frequency in pre S1 and pre S2 regions were higher than that in S region. 2. The homology rate between different genotypes was low

and study on the mutation pattern of HBV Pre S and S regions should be analyzed independently in each genotype.