Objective To explore the long-term evolutionary characteristics of hepatitis B virus(HBV)genotype Ⅰ.Methods Asymptomatic HBsAg carriers with confirmed genotype Ⅰ infection were selected as study subjects from the Guangxi Long'an cohort.Their HBV serum markers and viral load were detected.HBV DNA was extracted by phenol/chloroform.The whole HBV genome was amplified using nested PCR for cloning sequencing.The data were analyzed by BioEdit,Mega,and other software to conduct bioinformatics analysis of the sequencing results.Results A total of 9 research subjects were included,and 279 full-length gene sequences were obtained.Phylogenetic tree analysis showed that 22.2％(2/9)study subjects had HBV genotype conversion,from genotype Ⅰ1 to genotype C1.In 2004,all HBV strains studied had double mutations(nt1762 A→T/1764 G→A)in the X gene core gene promoter(BCP).88.9％(8/9)of the HBV strains studied had the nt1896(G→A)stop codon mutation in the PreC gene.Most of the study subjects had immune escape mutations and drug resistance mutations,and a total of eighteen immune escape mutations and six multidrug resistance mutations were detected.The immune escape mutation rates of strains in subject GD056,XW511,GA135,XX55,CZ647,TX119,WX058,and YF201 were 69.6％,7.5％,96.7％,94.4％,11.8％,4.7％,100.0％,and 100.0％,respectively.The drug-resistant mutation rates of strains in subjects GA135,XW511,WX058,XX55,YF201,CZ647,and TX119 strains were 6.7％,2.5％,3.8％,50.0％,4.5％,2.9％,and 4.7％,respectively.66.7％,55.6％,and 44.4％of the 2004 and/or 2022 HBV strains were subjected to positive selection pressure on preS/S gene,X gene,and preC/C genes,respectively;the HBV strains carried by all study subjects were dominated by negative selection pressure on the P gene.Conclusions During the natural infection process,HBV genotype may undergo genotype conversion.Genotype Ⅰ has a higher mutation rate in some common clinically relevant hotspot mutations.Immune escape mutations and drug resistance mutations may occur in some strains.Selection pressure on each open reading frame of HBV genome is different.
Hepatitis B virus,HBVGenotype ⅠCloning sequencingevolution
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