中国部分甲型肝炎病毒流行株结构蛋白区基因特征分析

Capsid Protein Gene Characteristics of Hepatitis A Virus Strains Prevalent in China

目的分析中国部分甲型肝炎（甲肝）病毒（Hepatitis A Virus,HAV）流行株结构蛋白VP3-VP1编码区核苷酸及氨基酸序列特点,并比较与甲肝减毒活疫苗（Hepatitis A Attenuated Live Vaccine,Hep A-L）标本序列差别。方法收集39份甲肝病例急性期血清样本及2份市售Hep A-L标本,经核酸提取、逆转录及巢式聚合酶链反应,测得结构-非结构蛋白VP3-VP1-2A编码区序列,进行基因亲缘关系、氨基酸序列同源性等分析。结果检测到的部分HAV流行株序列均为IA亚型,其在结构-非结构蛋白VP3-VP1-2A编码区核苷酸和氨基酸序列同源性分别为94.8%-100%和99.3%-100%,与检测的2份Hep A-L标本的核苷酸和氨基酸序列同源性为90.6%-91.9%和99.1%-99.4%。其中的1条序列在VP3-56位,发生丝氨酸（Serine,Ser）→脯氨酸（Proline,Pro）替代;3条序列在VP1-112位,发生苏氨酸（Threonine,Thr）→异亮氨酸（Isoleucine,Ile）替代,靠近中和抗原位点VP1-114位;所有序列在已发表的中和抗原位点处氨基酸无变化。选择压力分析表明,检测到的部分HAV流行株序列在VP3-VP1编码区处于负向选择。检测的2份Hep A-L标本序列均为IB亚型,在已发表的中和抗原位点处氨基酸无变化。结论HAV的结构蛋白编码区核苷酸序列存在一定差异,但其氨基酸序列相对保守。检测到的3条HAV流行株序列在中和抗原位点附近发生氨基酸替代,值得进一步研究。

Objective To analyze VP3-VP1 region of the capsid protein gene of hepatitis A viruses（ HAV） prevalent in China and compare with this region in hepatitis A attenuated live vaccine（ Hep A-L）virus strains. Methods The nucleotide sequences of VP3-VP1-2A regions of HAV strains were isolated from serum from 39 patients with hepatitis A infection and compared phylogenetically and homologically with the region isolated from 2 Hep A-L strains. Results All 39 HAV strains were subgenotype IA,with94. 8%- 100% homology of nucleotide sequence and 99. 3%- 100% homology of amino acid sequence.The 2 Hep A-L strains belonged to subgenotype IB with 90. 6%- 91. 9% homology of nucleotide sequence and 99. 1%- 99. 4% of amino acid compared with the prevalent strains. Substitutions were found at VP3-56（ Serine →Proline） in 1 strain,and at VP1-112（ Threonine →Isoleucine） in other 3 strains,which were close to the neutralizing epitope site VP1-114. Negative selection was found in the VP3-VP1 region.No amino acid changes at published neutralizing epitope sites of VP3-VP1 region were seen. Conclusion There are gene differences in HAV protein-coding regions,but amino acid sequences were relatively conserved. Amino acid substitution at VP1-112（ Threonine → Isoleucine）,near the neutralizing epitope site VP1-114 was found in 3 strains; further study is warranted.