Analysis of Hemaggultinin gene of a seasonal influenza A(H1N1) virus isolated in 2011
SHEN Jia-Ren1*; ZHAO Bai-Hui1*; GAO Ye1; YU Xue-Lian1; WANG Jia-Yu1; YUAN Zheng-An1; WU Fan1; XIE Xiao-Hong2; TAO Li-Xin2; ZHANG Xi1
1. Shanghai Municipal Center for Disease Control and Prevention, Shanghai 200336, China; 2. Fengxian District Center for Disease Control and Prevention, Shanghai 201400, China
Abstract：The present paper aims to compare the hemagglutinin antigen (HA)gene of a seasonal influenza A(H1N1) virus isolated in 2011 with the gene from reported seasonal influenza A(H1N1) viruses. The HA fragment and full-genome of A/Shanghai/1167/2011(H1N1) were amplified by reverse transcriptase-polymerase chain reaction (RT-PCR). Molecular biology software was used to analyze the sequencesand draw the phylogenetic tree. The anti-virus antibody level in healthy people was detected by hemagglutination inhibition test. The results showed that the HA gene of A/Shanghai/1167/2011(H1N1) was similar to the HA genes from previous reported seasonal influenza A(H1N1) virus, with homology of 99.2% to the 2008-2009 seasonal A(H1N1) vaccine strain A/Brisbane/59/2007(H1N1), and 72.4% to the A/California/07/2009 vaccine strain respectively. The HA cleavage site was PSIQSR↓QSR, and highly pathogenic molecular characteristics had not appeared yet. HA fragment, encoding 557 amino acids, has nine potential glycosylation sites. Its amino acid sequence was compared with the World Health Organization (WHO) vaccine strains of influenza A/New Caledonia/20/1999(H1N1), A/SolomonIslands/3/2006(H1N1), and A/Brisbane/59/2007(H1N1) respectively. The identified amino acid differences were 15, 12, and 4 respectively , and part of thesedifferences (5/15, 5/12 and 2/5) were located inside the critical epitope clusters (Sa, Sb, Ca1, Ca2 and Cb) Our results indicated that in 2011, 34.33% of healthy people carry antibodies against the isolated strain in their serum, and the geometric mean titer (GMT) was 10.38. A/Shanghai/1167/2011(H1N1) is a seasonal influenza A(H1N1) strain isolated in Shanghai in 2011. Although no significant differences were identified when comparing it to seasonal influenza A(H1N1),, its detection after A(H1N1)pdm09 was identified as the predominant strain should arouse people’s attention. Its antibody level in population is low, and can easily cause a pandemic. The monitoring of such strains in influenza-like population should be improved.
