[Sequence analysis of the HA1 regions of hemagglutinin gene from influenza viruses (H3N2) isolated from children in Beijing in 2004 indicated antigenic variation].
OBJECTIVE
To identify variations in hemagglutinin genes from influenza viruses (H3N2) isolated from infants and young children with acute respiratory infection (ARI) between March, 2004 and April 2005.


METHODS
RNAs from influenza A virus strains (subtype H3) isolated from specimens collected from ARI children were extracted followed by amplification for HA1 fragments from hemagglutinin (HA) genes by RT-PCR. The sequences of the fragments were defined by direct sequencing for the PCR products or the target inserts after the PCR fragments were cloned into the TA-cloning vector pBS-T and analyzed by bioinformatic software.


RESULTS
Fragments of 987 bps of HA1 (encoding 329 amino acids) from a total of 32 strains of influenza A virus (subtype H3) isolated from the 2004 season and 1 from the 2003 season were amplified and the sequences were compared with vaccine reference strains recommended by WHO which were used in recent years. There were several consistent amino acid variations which involved in both antigenic epitopes A and B and receptor binding site (RBS) for isolated strains in the 2004 influenza season compared with the vaccine strains used during the recent years and the virus strains isolated in March 2004, indicated the antigenic drift of the viruses isolated in 2004 influenza season may lead to variant viruses.


CONCLUSIONS
The variations of the HA genes from influenza virus (subtype H3) strains in the 2004-2005 influenza season were confirmed by sequence analysis for the HA1 regions of the hemagglutinin genes, which indicate that the antigenic drift would have been caused by the diversification of the genes and the efficacy of the recently used vaccines should be kept under close watch.
Zhu
Ru-nan
RN
Laboratory of Virology, Beijing Municipal Laboratory of Infection and Immunity, Capital Institute of Pediatrics, Beijing 100020, China.
Xu
Hong
H
Qian
Yuan
Y
Wang
Fang
F
Deng
Jie
J
Zhao
Lin-qing
LQ
Liao
Bin
B
Huang
Rong-yan
RY
D000940:Antigenic Variation; D002648:Child; D002681:China / Q000453:epidemiology; D019143:Evolution, Molecular; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics*; D006801:Humans; D053122:Influenza A Virus, H3N2 Subtype / Q000235:genetics* / Q000276:immunology / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology / Q000276:immunology / Q000821:virology*; D012367:RNA, Viral / Q000235:genetics; D017423:Sequence Analysis, RNA
D019267:Hemagglutinin Glycoproteins, Influenza Virus; D012367:RNA, Viral