中国2011年Ⅲ型脊髓灰质炎病毒基因特征分析

Genetic Characteristics of Type 3 Poliovirus in China in 2011

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)2011年急性弛缓性麻痹(Acute Flaccid Paralysis,AFP)病例粪便标本中分离到的Ⅲ型(Type 3)脊髓灰质炎(脊灰)病毒(Poliovirus,PV)(PV_Ⅲ)分子生物学特征,为中国维持无脊灰提供实验室依据。方法采用逆转录-聚合酶链反应(Reverse Transcription-Pogymerase Chain Reaction,RT-PCR)对PV_Ⅲ的衣壳蛋白VP_1编码区基因进行扩增,并对PCR产物进行核苷酸序列测定和分析,对VP_1编码区的核苷酸神经毒力位点和突变热点进行分析,并建立亲缘关系进化树,分析毒株间的进化关系。结果中国2011年从AFP病例粪便标本中,共分离到159株PV_Ⅲ,包括149株疫苗类似株PV和10株免疫缺陷相关的疫苗衍生(Immunodeficiency-associated Vaccine-derived)PV(i_VDPV),未发现Ⅲ型野生型(Wild Type)PV(WPV_Ⅲ)。15株PV_Ⅲ均在VP_1编码区基因已知的神经毒力位点核苷酸2493发生突变。结论突变热点的存在说明PV_Ⅲ的VP_1编码区的核苷酸变异并不是随机分布的,PV_Ⅲ的VP_1编码区基因突变热点可能与PV_Ⅲ的生物学特性有一定的关系。从宁夏回族自治区发现的10株i_VDPVs与以往发现的i_VDPV基因进化上无相关性,证明是新发现的i_VDPV。对VP1编码区的检测为继续维持中国无脊灰状态,为及时发现VDPCs传播和WPV的输入性爆发提供实验室依据。

Objective To evaluate the molecular characteristics of type 3 polioviruses （PVⅢ） isolated from stool samples collected from acute flaccid paralysis （AFP） cases of China（ not including Hong Kong Special Administrative Region,Macao Special Administrative Region and Taiwan sheng）in 2011. Meth- ods The VP I coding regions of the PV HI strains were amplified by Reverse Transcription-Polymerase Chain Reaction （RT-PCR） , and were sequenced and analyzed. Mutation hot-spots and nucleotide deter- minants of neurovirulence were studied. A phylogenetic tree was constructed based on the VP1 coding re-gion to determine the evolutionary relationship between the strains. Results 159 PV nl strains were isolated from the AFP case surveillance sys- tem in China in 2011, including 149 vaccine-re- lated strains and 10 immuno-deficient vaccine-de- rived PV （iVDPV） strains. No wild PVⅢ （WPV m） strains were detected. Among the 159 PVⅢ strains, we found a mutation at nucleotide 2,493, which is a determinant of nuerovirulence. Conclu- sion The existence of mutation hot spots indica- ted that nucleotide acids substitutions in VP1 gene were not randomly distributed. There was some correlation between mutation hot spots in the VP1coding region of PVⅢ and biological characterization. Epidemiological study and laboratory results of the ten iVDPVs from Ningxia Hui Autonomous Region showed that these were newly discovered iVDPVs that had no genetic relation with previously found iVDPVs strains. Analysis of mutations in VP1 code region could provide important lab-based evidence for maintaining polio-free status in China and for timely detec- tion of VDPVs transmission and importation outbreaks.