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Objective To understand the genetic and antigenic variations of influenza A (H1N1) isolates in Shanghai area in winter of 2010.Methods A total of 137 throat swabs were collected from patients with influenza-like illness in the sentinel hospital in Shanghai area from December 2010 to January 2011,then inoculated into Madin-Darby canine kidney (MDCK) cells.The types of influenza were identified by direct immunofluorescence assay (DIF) and influenza A (H1N1) subtype was determined by reverse transcriptase-polymerase chain reaction (RT-PCR).The mutations of gene and amino acid locus were analyzed through the whole genome sequencing of hemagglutinin (HA),neuraminidase (NA) and polymerase (PB2) segments from some influenza A (H1N1) isolates.Results Total of 53 human influenza virus strains were isolated including 48 influenza A (H1N1) virus strains.Nineteen strains were selected for sequencing by simple random sampling.The phylogenetic tree of HA gene revealed that the latest isolates and most of influenza A (H1N1) viruses isolated before June 2010 were not in the same stem.Analysis of amino acid residues in HA protein showed that mutations were found in antigenic determinant region in some strains.Residues at the enzyme active sites of NA protein were strictly conservative,no change was observed in amino acid residues which were related to drug resistance against oseltamivir and zanamivir.The 627 and 701 residues in PB2 protein were glutamic acid and aspartic acid,respectively,which was still the feature of avian influenza virus,but E677G mutation was detected.Conclusion Compared to influenza A (H1N1) strains isolated in spring and summer,some variations have been detected in the strains isolated in Shanghai area in winter of 2010,some antigen drift and adaptive evolution in mammalian hosts have appeared.
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Objective To establish a clinical test assay for detecting common respiratory viruses and enteroviruses (EV) by using mixed cultured Madin-Darby canine kidney cells (MDCK), human epidermoid cancer cells (Hep-2) and African green monkey kidney cells (Vero) to isolate common respiratory viruses and enteroviruses. Methods Throat swabs with influenza A and B viruses,adenovirus and EV71 were incubated with mixed cultured MDCK, Hep-2 and Vero in a single vial to observe the presence of cytopathic effects. Polymerase chain reaction (PCR), reverse transcription (RT)-PCR and monoclonal antibody-based immunofluorescene assay were also used for confirmatory test. Results The sensitive cell lines developed obvious cytopathic effects to the corresponding viruses, which were confirmed by the specific green particles observed by immunofluorescence assay and specific target PCR segments. Conclusions The shell-vial of mixed cells can simultaneously isolate different common respiratory viruses and EV. The isolated pathogens can be further confirmed by antigen test and PCR. This assay may improve the diagnosis of clinical viral diseases.
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Objective To understand epidemic characteristics of human influenza A and the genetic and antigenic variations of H1N1 influenza A isolates in Shanghai area in 2009. Methods Throat swabs were collected from patients with influenza-like illness in the sentinel surveillance clinic in Shanghai area in 2009, then inoculated in Madin-Darby canine kidney (MDCK) cell lines. The types of influenza were identified by direct immunofluorescence assay (DIF) and the subtypes were determined by reverse transcriptase-polymerase chain reaction (RT-PCR). Segments of hemagglutinin (HA) and neuraminidase (NA) genes of some 2009 H1N1 influenza A isolates were amplified and sequenced. HA and NA gene mutations of 2009 H1N1 influenza A isolates were analyzed. Results Seasonal H1N1 and H3N2 influenza A viruses co-circulated during the spring of 2009 in Shanghai area. Seasonal H3N2 began to co-circulate with 2009 H1N1 in August (the 32nd week) and finally2009 H1N1 became dominate since the 40th week. The phylogenetic tree of 2009 H1N1 HA segment revealed that the isolates from different regions and months were interspersed with each other, but all were clustered into one branch which closed to strains in Spain, Russia, Denmark and other European countries. Mutations were found in some HA amino acid sites, but none of them was in the antigenic determinant region. No change was observed in the 274 NA amino acid residues which were related to the drug resistance to oseltamivir. PB2 protein analysis showed that the 627 and 701 amino acid residues were glutamic acid and aspartic acid respectively, which were the same encoded amino acid with avian flu PB2 protein. Conclusions Seasonal H1N1 and H3N2 co-circulated in the spring of 2009, then both 2009 H1N1 and seasonal H3N2 were prevalent in Summer and Autumn, and 2009 H1N1 finally became dominate in Autumn. Compared to early 2009 H1N1 strains, variations are detected in H1N1 influenza A viruses, but none of them has epidemiological influence, and viruses still show high affinity with human and low-pathogenic characteristics.
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Objective To understand the sensitivity of cytopathogenic effect (CPE) in MadinDarby canine kidney cells(MDCK) that cultured influenza A pharyngeal swab specimens of patients for one,two and three passages. Methods Influenza A pharyngeal swab specimens of patients were inoculated in MDCK for three blind passages. The presence of CPE of every passage was observed by inverted microscope. Results Of the 279 influenza A pharyngeal swab specimens of patients tested by colloidal gold, the presence of CPE in MDCK for one,two and three passages was 65.9%(184/279),91.4%(255/279) and 96.4%(269/279), respectively. Two hundred and seventy-one of 279specimens were identified as influenza A by multiplex reverse transcription-polymerase chain reaction (RT-PCR). Conclusion The positive separation rate can reach more than 95% by inoculating influenza A pharyngeal swab specimens of patients in MDCK for three blind passages.