Molecular genetic characteristics of surface protein genes of globe seasonal H3N2 influenza virus in 2010?2011

Abstract:

[Objective] The evolutionary tendency and molecular characteristics of both HA (Hemagglutinin) and NA (Neuraminidase) gene of seasonal H3N2 subtype influenza viruses isolated in 2010-2011 were to be determined, and the molecular information made an important part of control and prevention of influenza worldwide. [Methods] We collected all nucleotide sequences of segment 4 and 6 that contained complete ORF (Open Reading Frames) of HA and NA gene during Jan-2010 and Sep-2011, phylogenetic trees based on ORF sequences of two genes were constructed. Theoretical amino acid (aa) chains of every sequences were deduced to find out the variation sites referring to vaccine strain, and prevalence of changes in functional positions were analyzed. [Results] Among all 267 sequences surveyed, 3 (2 HA and 1 NA) were strains of swine origin, while others could be classified into 2 groups by evolutionary relationships. Compared with vaccine strain, average variation sites on HA and NA antigenic determinant were 5.33 and 2.01, respectively. Sites mutations on RBS (Receptor of Bonding Sites) and HA disulfide as well as NA drug resistant sites were found in 3 different isolates. N-glycosylation sites of HA and NA were increased in most isolates. Besides, variation sites on HA antigenic determinant between isolates from Jiangsu and Guangdong were accounted from 7 to 13. [Conclusion] Two kinds of gene evolutionary characteristic were found in recent seasonal H3N2 subtype viruses. Antigenic difference between epidemical strains and vaccine strain are recommended for development of new vaccines, in spite of they were still unknown, the variations on antigenic positions and N-glycosylation sites between each isolates and vaccine strain would probably alter antigenic characteristics of most isolates surveyed, so further antigen detection work is required to be carried; Health administrative departments in different districts must improve the treatment followed drug resistance situation of local epidemical strains.