A Pneumonia Case Associated with Type 2 Polio Vaccine Strains

Li, Mao-Zhong; Zhang, Tie-Gang; Li, Ai-Hua; Luo, Ming; Jiao, Yang; Dong, Mei; Gong, Cheng; Huang, Fang

A nasopharyngeal swab sample was collected at the time of admission. Total nucleic acid (RNA and DNA) was extracted from the clinical specimens using a Thermo The results were positive for the enterovirus RNA, but no other respiratory pathogens were detected. Subsequently, a Type 2 polio vaccine strain was identified with cycle threshold values of 25 using the enterovirus molecular serotyping method and the poliovirus intratypic differentiation method. [4] To further characterize this virus strain, the entire VP1 region was determined directly from the nasopharyngeal swab with the method provided by National Polio Laboratory of China. The VP1 sequences were compared with the sequences available in the GenBank database using the basic local alignment search tool. The results showed that the sequence had 100% nucleotide similarity compared with that of the parental Sabin Type 2 strains. Meanwhile, the poliovirus nucleic acid was identified in the patient's nasopharyngeal swab sample using an Ion Torrent PGM deep sequencing instrument for a viral metagenome analysis. Several other viruses were identified in this sample, including the fowl adenovirus C, the Streptococcus phage, the human endogenous retrovirus, and the choristoneura occidentalis granulovirus, but none were associated with this pneumonia. The virus was also isolated from the patient's nasopharyngeal swab sample using rhabdomyosarcoma (RD) (human RD cell) and L20B (murine cell lines expressing the human poliovirus receptor) cell lines provided by National Laboratory for poliomyelitis in China CDC.