中国2009年Ⅰ型脊髓灰质炎病毒基因特征分析

Analysis on Genetic Characteristic of Type I Poliovirus in China in 2009

目的研究中国(未包括香港、澳门特别行政区和台湾地区,下同)2009年从急性弛缓性麻痹(Acute FlaccidParalysis,AFP)病例监测系统中,分离到的Ⅰ型脊髓灰质炎(脊灰)病毒(Poliovirus,PV)分子生物学特征,为维持无脊灰状态提供依据。方法采用逆转录-聚合酶链反应(Reverse Transcription-Polymerase Chain Reaction,RT-PCR),对I型PV的VP1编码区进行扩增,并对PCR产物进行核苷酸序列测定和分析;对VP1编码区的核苷酸突变热点和神经毒力位点进行分析,并建立亲缘关系进化树分析毒株间的进化关系。结果中国2009年从AFP病例监测系统中共分离到57株I型PV。对这57株PV进行VP1编码区核苷酸序列测定和分析,未发现PV野毒株或疫苗衍生PV。但发现5株高变异株,其中分离于两例AFP病例的两株高变异株的核苷酸序列同源性100%。同时序列比对结果表明,在VP1编码区的两个核苷酸(nt2747和nt2749)是两个突变热点。结论根据江西省和湖北省两株高变异株的流行病学及实验室检测结果,不能排除它们之间发生了短时间的循环,有待于深入研究。同时,突变热点的存在提示毒株受到选择压力的影响,容易回复突变成野生型,从而带来一系列的神经毒力等表型方面的变化。

Objective To study the molecular characteristics of type 1 poliovirus isolated from the acute flaccid paralysi（sAFP）surveillance system in China in 2009,to provide a scientific basis for maintaining polio-free status for China.Method Polymerase chain reaction（RT-PCR）method was used to amplify the VP1 code region of all the type I poliovirus,and the VP1 coding region of the isolated stains was sequenced and analyzed,the hot-spots and nuerovirulence determinant were analyzed.The phylogenetic tree was constructed based on VP1 region to analyze the evolutionary relationship between the strains.Result The results of VP1 sequencing showed that no wild strains or vaccine-derived poliovirus（VDPVs）were detected.However,five pre-VDPVs were found.And nucleotide sequences of two isolates were in high degree of similarit（y100%）.Sequence alignment showed that two nucleotides in the VP1 region.nt2747 and nt2749 were two mutation hot spots.Conclusion According to the epidemiological and laboratory test results of two high variation strains,the short-term circulation may occur probably,and further research are needed.Meanwhile,the existence of mutation hot spots indicated that strains are easy to reverse into wild-type substitutions,and lead to a series changes of neurological and other virulence when the strains are under selective pressure.