Genetic analysis of wild polioviruses and its ecology

痘病毒是一种典型的肠道病毒，通过粪口途径在人与人之间传播，人类是唯一敏感的动物。只要保持良好的卫生条件，就能防止脊髓灰质炎的大规模爆发。然而，为了根除脊髓灰质炎，通过口服疫苗和真实的时间临床和病毒学监测的社区一级广泛免疫是必不可少的。世界卫生组织于1988年启动了全球消灭脊髓灰质炎计划。本研究对中南半岛地区已被口服疫苗病毒取代的脊髓灰质炎野病毒进行了基因分析。1997年，从越南的1例急性弛缓性麻痹（AFP）患者和柬埔寨的8例患者中分离到野生型脊髓灰质炎病毒。它们都是I型脊髓灰质炎病毒。他们都在当地被诊断为AFP病例，他们的粪便样本被送往日本。分离病毒，鉴定，并进行细胞内分化。测定了它们的VP1区核苷酸序列，并与本地区以前分离的脊灰野毒株进行了比较。而1997年分离的9株菌株属于同一菌株群。从越南北部分离的脊髓灰质炎病毒均为疫苗衍生病毒，其数量在这三年中有所减少。这些结果在日本得到了证实。相反，在南越和日本得到的结果有些出入。利用表达脊灰受体基因的小鼠La细胞，高效、选择性地分离出脊灰病毒，迄今为止，本地区最后一例脊灰野病毒引起的脊髓灰质炎病例被认为是1997年3月19日发现的病例。此后，未分离到野生脊髓灰质炎病毒。需要进行更广泛的监测，以证明无脊髓灰质炎。

Po1iovirus is a typical enterovirus and transmits from humans to humans by fecal oral routes Human being is the only sensitive animal. If good sanitary condition is once archived and maintained big outbreak of poliomyelitis wl11 be protected. However, in order to eradicate the disease poliomyelitis, community level-extensive immunity by oral vaccination and real time clinical-and viorological surveillance are essential. World Health 0rganization launched the global eradication program in 1988.In this study, we performed the genetic analysis of the wild polioviruses which has been replaced by oral vaccine viruses in Indochina area. In l997, wild type polioviruses were isolated from one patient with acute flaccid paralysis (AFP) from Vietnam and 8 from Cambodia. They were all type I poliovirus. They were all diagnosed locally as AFP cases and their stool samples were sent to Japan. We isolated viruses, identified add performed intratypic differentation. The nucleotide sequences of their VP1 region were determined and compared with those of wild viruses previously isolated in this area.In previous years, there were several different strains of wi1d polioviruses were isolated in this region. However, the 9 strains isolated in 1997 belonged to the same group of strain. From the North Vietnam, isolated polioviruses were all vaccine derived viruses, and their number has been decreased in these three years. Those results were confirmed in Japan. In contrast, there were some discrepancy in the results obtained in South Vietnam and Japan. By the use of mouse La cells expressing polio receptor gene, polioviruses were efficiently and selectively isolated.The last case of poliomyelitis by wild poliovirus in the region is so far considered to be the one found on March l9,1997. Since then, no wild polioviruses were isolated. More extensive surveillance is necessary to certify as polio-free.