青海省1999年脊髓灰质炎Ⅰ型野毒株的分子病毒学分析

Molecular Analysis of the Wild Type Ⅰ Polioviruses Isolated in Qinghai Province, 1999

自中国脊髓灰质炎 (脊灰 )监测网络建立以来 ,有报告的脊灰暴发和流行主要由脊灰Ⅰ型野病毒引起。 1993年在新疆维吾尔自治区分离到 1株Ⅲ型野病毒 ,但未发现Ⅱ型野病毒。此外 ,1995年、1996年在云南省发现 2例Ⅰ型〔1〕、2例Ⅲ型境外输入野毒病例〔2〕。 1994年 10月以来我国本土未发现脊灰野病毒。但是 ,1999年 10月从青海省循化撒拉族自治县分离到 2株脊灰Ⅰ型野病毒 ,1株来自 1位 16月龄的病例 ,另 1株来自该病例的接触者。应用基因测序法对该毒株做了VP1片段序列的测定 ,并与疫苗株SabinⅠ型参考株、国内曾经流行的脊灰Ⅰ型野病毒代表株、我国周边国家部分脊灰Ⅰ型野毒株的序列作了基因同源性比较 ,并由计算机用NeighborJoining和BootstrapTest方法分析处理 ,构建出它们之间的关系树 。

Most poliomyelitis cases and heavy outbreaks in China before Oct. 1994 were caused by wild type Ⅰ poliovirus 〔3-5〕 . No wild type Ⅱ poliovirus but only one wild type Ⅲ poliovirus was reported in China 〔6〕 . In the years of 1995 and 1996, two wild type Ⅰ polioviruses 〔1〕 and two wild type Ⅲ polioviruses 〔2〕 imported from Myanmar were reported in Yunnan Province respectively. It has been five years that no indigenous wild poliovirus was isolated in China since the end of year 1994. However, two wild type Ⅰ polioviruses (PV1/QH3274/CHN99 and C3275c) were isolated recently from Xunhua county, Qinghai Province of China. PV1/QH3274/CHN99 was from an AFP case, a sixteen-month old boy. Another isolate, C3275c, was from his close contact. The sequence of VP1 coding region (300nt) had been identified. No nucleotide difference was found between the two viruses in the 300nt length of VP1 coding region. We compared the homology and analyzed the sequence data of VP1 coding region by computer with the Neighbor Join and Bootstrap methods. The homology with the indigenous wild strains ranges from 77.6% to 82.27%, but it is more than 85% compared with that of the isolates from South Asia. It is acknowledged that the viruses will belong to different subgenetic groups if their homology is less than 85 percent 〔9,10〕 . The result thus shows that PV1/QH3274/CHN99 and C3275c have a farther genetic relationship with type Ⅰ wild polioviruses epidemic during 1989-1994 in China than with those during 1998-1999 in outh Asia, so this indicates that they are very likely the imported viruses. Although the homology with PV1/99031804/MMR99 is up to 93 38%, PV1/QH3274/CHN99 has the closest relations hips with the PV1/99010389/IND98 and PV1/99010408/IND98 in the dendrogram.