[Genetic characteristics of influenza A/H3N2 virus neuraminidase gene: a survey from 2010 to 2012 in Qinghai Province, China].

This study aims to perform a survey of genetic variation in neuraminidase (NA) gene of influenza A/H3N2 virus, as well as related resistance to NA inhibitors, in Qinghai Province of China, 2010 to 2012. Strains of influenza A/H3N2 isolated during an influenza survey from 2010 to 2012 in Qinghai were enrolled by random sampling. Viral RNA was extracted and amplified by RT-PCR. Purified PCR products were sequenced thereafter. Genetic analysis of nucleic acid and the derived amino acid sequences was performed by MEGA 4.0. Phylogenetic trees were also constructed. Strains isolated during 2010-2011 in this study clustered closely with World Health Organization (WHO) 2010-2012 reference vaccine strain A/Perth/16/2009 and 2008-2010 reference vaccine strain A/Brisbane/10/2007 on the phylogenetic tree, while the 2012 isolates were located on another branch. In analysis of derived amino acid sequences, the 2010 isolates mutated at K81T, the 2011 isolates mutated at I26V and D127N, while the 2012 isolates mutated at E41K, P46A, I58V, T71N, L81P, D93G, D127N, D151N, and I307M. The D151N mutation added a glycosylation site to the activity center of NA. No significant variation was discovered in H3N2 NA gene of 2010-2011 isolates in Qinghai, China. Isolates of 2012 were found with significant mutation, which has the potential of inducing minor resistance to NA inhibitors like zanamivir and oseltamivir.