Molecular characteristics of hemagglutinin gene of influenza A (H3N2) virus strains circulating in Jiangsu province, China, 2013-2014

Abstract

Objective To analyze the genetic characteristics and the evolution of the influenza A (H3N2) virus strains circulating in Jiangsu province between 2013 and 2014. Methods This study analyzed thirty-one representative strains of influenza A (H3N2) virus, which were isolated in different regions of Jiangsu province and during different time periods from 2013 to 2014. Results Genetic distances in nucleic acid and amino acid between a strain used for vaccine production (A/Texas/50/2012) and the 31 strains were 0.010 5 and 0.012 4. Similarities between them in nucleic acid and amino acid sequences were 97.9%-99.6% and 97.2%-99.3%. Phylogenetic analysis showed that the hemagglutinin (HA) genes of the 31 strains were divided into three different groups. Three strains isolated in 2013 and three strains isolated in 2014 belonged to Group 1 and Group 2, respectively, while the others belonged to Group 3. Three positive selection sites (237, 366 and 367) in HA protein were observed by REL model. Compared with the strain used for vaccine production, the 31 strains were characterized by amino acid substitutions (N128A/T and P198S/A) in HA protein and all of the mutations located in B-cell epitopes. The total number of mutation sites reached 24. Compared with the A/Texas/50/2012 strain, seven strains presented the glycosylation site 126NWT, and three strains showed disappeared glycosylation sites of 45NSS and 144NNS. Evaluation of vaccine efficacy for A(H3N2) virus strains showed that the vaccine efficacy was not very well. Conclusion The HA gene of A(H3N2) virus had undergone a greater variation and the vaccine efficacy was not very well in Jiangsu province during 2013 to 2014, which made the influenza A(H3N2) virus become the circulating strain. Key words: Influenza A virus; H3N2 subtype; Hemagglutinin; Molecular characteristics