Analysis of Antigenic and Genetic Characteristics of Influenza Virus B Circulated in Sichuan Province in 2007

Objective To study the variation of antigenicity and genetic characterization about hemagglutinin of influenza virus subtype B circulated in Sichuan Province.Methods The swallow swabs from the suspected influenza cases in sentinel hospital monitored and suspected epidemic influenza in Sichuan were collected,and virus were isolated by using MDCK cells.The influenza viruses isolated in different time and locations were identified to be influenza virus subtype B by hemagglutination inhibition test,then were performed one-way hemagglutination inhibition test.The viral nucleic acid were extracted to amplify the HAI regions of HA by using RT-PCR,and the amplified products were sequenced to deduct the amino acid sequence.Results The antigenecity of influenza virus subtype B Yamagata series in Sichuan was differrent from that of the stain B/Tianjin//144/2005 but analogic to that of the strain B/Fujianxinluo/54/2006.Compared with influenza virus B/Shenzhen/155/2005,the antigenecity of subtype B victoria sereis in Sichuan has changed.The analytic results of nucleotide and amino acid sequence demonstrated there were 6,4 and 2 amino acids sites replaced respectively in HA1 regions.Conclusion In comparison with the strains B/Tianjin//144/2005 and B/Shenzhen/155/2005,the antigenicity of influenza virus subtype B Yamagata series and Victoria series circulated in Sichuan in 2007 has drifted furtherly.