To investigate the adaptation of poliovirus Sabin 2 in human embryonic lung diploid fibroblast（KMB17） and its relation to nucleotide mutations of 5′ noncoding region（5′NCR）,the Sabin 2 vaccine virus was passaged serially in KMB17 for seventeen passages.The infectious titers of Sabin 2 virus increased along with the passages,the highest titer reached 8.0 LgCCID50/ml at passage 13（P13）.During passage,there were three nucleotide mutations appeared in 5′NCR,G changed to C at position 20,C to U at position 189 and G to A at position 481.The results showed that Sabin 2 poliovirus adapted well in KMB17 after 17 passages.The nucleotide mutation at position 481 that appeared from passage 3 on indicated the possibility of virulent reversion.
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