Isolation and identification of human influenza virus from a stale respiratory tract specimen with human airway epithelial cells

Abstract

Objective To investigate the possibility of using well-differentiated human airway epithelial cells (HAE) to isolate and identify human influenza A virus from a stale respiratory tract specimen. Methods The stale specimen used in this study was a nasopharyngeal swab specimen collected from a patient with unexplained pneumonia in Qinghai in 2010. It was positive for influenza A virus (H3N2) RNA, but negative for hemagglutination. Equal amount of the specimen was inoculated on HAE and on Madin-Darby canine kidney (MDCK) cells for virus isolation and passage. Cytopathic effects were observed daily after inoculation. Hemagglutination inhibition test was performed at every passage. Electron microscope was used to observe viral morphology. Viral genome was sequenced, followed by molecular evolutionary analysis. Results No progeny virus was isolated in MDCK cells, while a influenza A virus subtype H3N2 strain [A/Qinghai/178/2010(H3N2)] was isolated in HAE with a typical morphology and cytopathic effect of influenza A infection. The hemagglutination inhibition activity was 1∶16. Results of the molecular evolutionary analysis of viral genome showed that the influenza A virus (H3N2) strain was highly homologous to the A/Nanjing/1655/2010(H3N2) strain, which was isolated during the 2010 influenza pandemic in Nanjing. Conclusion HAE can be used for isolation and identification of virus from stale respiratory tract specimens. It is more sensitive than MDCK cells with regard to human influenza virus isolation. Key words: Human airway epithelial cell; Influenza A virus; Virus isolation; Stale specimen