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目的研究中国首例疫苗相关麻痹型脊髓灰质炎(VAPP)的免疫缺陷患者持续排出的免疫缺陷疫苗衍生脊髓灰质炎(脊灰)病毒(iVDPV)的分子生物学特征,并分析持续排毒对中国维持无脊灰状态的影响。方法对分离于该患儿12份粪便标本的12株Ⅱ型iVDPV和5株Ⅲ型iVDPV毒株使用逆转录-聚合酶链反应(RT-PCR)扩增VP1区基因片段,然后对扩增产物进行核苷酸序列测定与分析,并使用生物信息学的方法分析了毒株核苷酸序列之间的同源关系以及相关性。结果在间隔145d的时间里采集了6次双份粪便标本,除了第1次采集的双份粪便标本中未分离到Ⅲ型脊灰病毒外,Ⅱ型和Ⅲ型iVDPVs连续在粪便标本中分离到。12株Ⅱ型脊灰病毒主序列中的变异位点基本是随机分布在VP1基因上的,与SabinⅡ型相比,变异率为0.86%~2.55%;诸多核苷酸位点的变异大多是同义突变,主序列编码的氨基酸与SabinⅡ型相比共引起8个氨基酸位点突变,其中第103位和143位是12条主序列的共同变异位点,显示它们的主序列是相关的,并且都是来源于SabinⅡ型疫苗株的。尤其是nt 2 909位点(U→C)变异,导致Ile143突变为Thr143,是一个已知的与神经毒力回复野生型相关的位点。与标准SabinⅢ型相比,5株Ⅲ型脊灰病毒序列同源性非常高,并且核苷酸突变几乎是均匀地分布在整个VP1基因上的,变异率为2.56%~2.78%,毒株序列都是来源于SabinⅢ型疫苗株,氨基酸共出现10个突变位点,其中9个为它们所共享,显示了非常高的相关性。结论Ⅱ型iVDPV以居群的形式存在,主序列之间有相关性,Ⅲ型iVDPV序列有高度的相关性,但与Ⅱ型的居群形式不一样,可以看出Ⅲ型疫苗株病毒适应人体肠道进行复制并获得较高传播性的能力比Ⅱ型要差。中国首例iVDPV在分子病毒学上与已知循环的疫苗衍生脊灰病毒(cVDPVs)无本质上的差别,存在着iVDPVs与cVDPVs相互转变的潜在可能性。维持较高的口服脊灰减毒活疫苗(OPV)免疫覆盖率,是阻止脊灰野病毒输入和防止VDPVs发生人际间传播的关键。另外,保持急性弛缓性麻痹病例监测系统和脊灰实验室网络具有较高的敏感性,重新评估现在的OPV免疫策略,在全球证实消灭脊灰野病毒后适时制订停止OPV免疫的策略,都是降低这种潜在危险的重要手段。
Objective To investigate the molecular biology of the immunodeficiency-associated vaccine-derived poliovirus (iVDPV) sustained by the first vaccine-associated paralytic poliomyelitis (VAPP) immunodeficiency in China and to analyze the effects of sustained detoxification on China’s maintenance Polio-free status effects. Methods VP1 gene fragments were amplified by reverse transcription polymerase chain reaction (RT-PCR) from 12 strains of iVDPV and 5 strains of type 3 iVDPV isolated from 12 stool specimens of the infants. The amplified products The nucleotide sequences were determined and analyzed. The homology and correlation between the nucleotide sequences of the strains were analyzed by bioinformatics methods. Results Six double stool specimens were collected at intervals of 145d. Type Ⅱ and Ⅲ iVDPVs were continuously isolated from stool specimens except that no poliovirus type Ⅲ was detected in the first two stool specimens . The variation of the 12 major poliovirus type Ⅱ sequences was basically randomly distributed in the VP1 gene, with the variation rate of 0.86% -2.55% compared with that of the Sabin Ⅱ type. Most of the nucleotide variations were the same In the sense mutation, the amino acid encoded by the main sequence caused a total of eight amino acid mutations compared with the Sabin type II, of which the 103 and 143 positions were the common mutation sites of the 12 main sequences and showed that their main sequences were related and Are derived from Sabin type II vaccine strains. In particular, the mutation at nt 2 909 (U → C) resulted in the mutation of Ile143 to Thr143, which is a known site associated with the neurotoxicity response in the wild type. Compared with the standard Sabin Ⅲ type, the five strains of type Ⅲ poliovirus have very high sequence homology, and the nucleotide mutations are almost uniformly distributed in the whole VP1 gene with the mutation rate of 2.56% -2.78%. The sequence of the strains All originated from the Sabin type III vaccine strain. A total of 10 amino acid mutations were found, of which 9 were shared by them and showed a very high correlation. Conclusion The type II iVDPV exists in the form of population, and there is a correlation between the main sequences. The type III iVDPV sequences have a high degree of correlation, but not the same as the type II population. It can be seen that the type III iVDPV strains adapt to the human body The ability of the gut to replicate and gain higher transmission is worse than type II. The first case of iVDPV in China is essentially identical in molecular virology to the known circulating vaccine-derived poliovirus (cVDPVs), with the potential for a mutual transformation between iVDPVs and cVDPVs. Maintaining a high oral coverage of live attenuated poliovaccine (OPV) vaccine is the key to preventing the entry of poliovirus and preventing interpersonal transmission of VDPVs. In addition, maintaining acute flaccid paralysis case monitoring system and polio laboratory network with high sensitivity, re-evaluation of the current OPV immunization strategy, the global confirmation of eradication of poliovirus timely development of strategies to stop OPV immunization, are reduced An important means of this potentially dangerous.