HBV S Gene Evolution Analysis Based On NCBI Database

Objective:To understand the HBV S gene evolution characteristics,and provide new theoretical basis for preventing and controlling hepatitis b.Methods:375 HBV S gene sequences were selected in NCBI,and collected from "Shanghai","zhejiang","jiangsu",and divided into B,C two groups.First,S gene amino acid reference sequences were constructed,and then S gene mutation,dynamic changes of genetic diversity,selection pressure and amino acids permutation entropy were analyzed.Results:1.B,C genotype S gene amino acid reference sequences were constructed.2.The maximum amino acid mutant rate site of C genotype was 126,while that of B genotype was 200.5 of 9 vaccine escape sites were found,and 17 of 28 occult infection sites were found.63 amino acid mutant sites of B genotype in whole-S gene were found,and 102 amino acid sites of C genotype(P<0.05),and 43 amino acid mutant sites were coexisted in both;8 amino acid mutant sites of B genotype in "a" determinant were found,and 10 sites of C genotype(P>0.05),and 6 sites were coexisted in both;the proportion of amino acid mutant sites in "a" determinant was no significant different to that in whole-S gene(P>0.05).The proportion of amino acid mutant sequences of C genotype was higher than that of B genotype in both whole-S gene and "a" determinant(P<0.05);The proportion of amino acid mutant sequences of "a" determinant in both B,C genotypes were lower than those of whole-S gene.Amino acid mutation rates of C genotype were higher than those of B genotype in both whole-S gene and "a"determinant.Amino acid mutation rate of C genotype(P<0.05)and B genotype(P?0.05)in "a" determinant were higher than those in whole-S gene respectively.3.Annual average evolutionary rate of C genotype was higher than that of B genotype.The Bayesian skyline plot showed that:genetic diversity of B genotype decreased since 1995,and tended to be stablized in 2012;genetic diversity of C genotype was increasing since 1995,and tended to be stable after 2000,and decreased around 2010.4.? value of B genotype was lower than that of C genotype,and both were lower than one.Zero positive selection site and eight negative selection sites were found in B genotype;eight positive selection sites and seventeen negative selection sites were found in C genotype.5.Only one easy amino acid mutation site was found in B genotype:200;only one easy amino acid mutation site was found in C genotype:126.Conclusions:1.HBV S gene was suffering purifying selection pressure.Amino acid mutant rate in C genotype was higher than that in B genotype,purifying selection pressure and conservatism were lower than those in B genotype.2.Genetic diversity of C genotype had experienced an expansion process from 1995,and genetic diversity of B genotype had decreased.3.C genotype was suffering immune selection pressure and its own purifying pressure,and its own purifying pressure was stronger than immune selection pressure;B genotype was only suffering its own purifying pressure.