[Hemagglutinin gene of influenza A (H3N2) virus from human samples in the 2009 influenza epidemic in Chengdu].

ABSTRACT

OBJECTIVE: To study the antigenic and genetic characteristics of influenza A (H3N2) virus in the 2009 influenza epidemics in Chengdu. METHODS: The influenza virus strains were isolated with MDCK cells from 4869 samples taken from the sentinel surveillance in 2009 in Chengdu. Hemagglutination inhibition (HI) and RT-PCR reaction tests were performed to guide the extraction of viral RNA from the culture fluid of the influenza A (H3N2) virus. The hemagglutinin gene was obtained by RT-PCR and sequenced. RESULTS: The separation rates of swine influenza H1N1, H3N2, H1N1, and B were 25.2%, 7.2%, 4.5%, and 1.5% respectively. The epidemic peaked in summer and autumn. Four amino acids changed in A, B, and D antigenic and receptor binding sites site160N>K, site174K>R/N, site189K>Q, site277R>Q. Glycosylation sites were inserted to sitel60 or absent at site181 in some isolated strains. CONCLUSION: Swine influenza H1N1 viruses dominated the 2009 Chengdu epidemic, with H3N2, H1N1, and B strains coexisting. The influenza A(H3N2) viruses had gene variations due to antigenic drift.