MOLECULAR CHARACTERIZATION ON THE BASIS OF HA, NA AND M GENE REVEALED CHANGES IN CRITICAL AMINO ACID POSITIONS OF INFLUENZA A (H3N2) VIRUS CIRCULATING IN INDIA DURING 2011-2013

Influenza a (H1N1) virus is responsible for acute respiratory infection in human, which occasionally causes epidemic and rarely a pandemic. Full length DNA sequencing of HA, NA and M gene of H3N2 virus from year 2011-2013 was performed for determination of the circulating strains in India along with monitoring status of various mutations associated with drug resistance and virulence. Genetic analysis of HA gene of study samples in comparison to reference strain showed maximum amino acid changes in epitopes of high neutralization efficiencies (antigenic sites A, B and D) along with gain of glycosylation sites at position 45 (except single sample) and loss at position 126 (7 samples). NA gene has four amino acid changes in antibody binding region at position S367N, K369T, S332F and S334I along with gain and loss of glycosylation site at position 367 and 402 respectively whereas no change was observed in its active site. While comparison of deduced amino acid sequences of study samples with Indian strains from earlier years showed six amino acid changes in three antigenic sites on HA protein and three amino acid changes in NA protein epitope sequence. All these changes indicate that the H3N2 virus is undergoing antigenic drift and which may result in the emergence of new antigenic variants. We want to report that our study provided for the first time full length matrix gene sequence of influenza a (H3N2) virus from India.