Evolutionary analysis of the antigenic determinant, glycosylation, and sialidase sites of neuraminidase from the human influenza A virus isolated in China from 1995 to 2012

Background: Improve the understanding of evaluative characteristics of the NA gene, NA protease active sites, and NA glycosylation sites in H1N1 virus isolated from China during 1995-2012. Method: A total of 200 NA gene sequences were downloaded from the National Center for Biotechnology Information’s GenBank. Phylogenetic analyses, multiple sequence alignment, glyco-sylation sites analyses, and protein structure prediction were conducted with Mega5.05, ClustalW, NetNGlyc1.0 program, and SWISS-MODEL server, respectively. Results: The NA genes of the Chinese pandemic H1N1 2009 virus were different from those of 1995-2008 seasonal sequences (low similarity of 75.5%-77.1%), but were similar to strains from other countries (high similarity of 99.1%-99.9%). The Chinese resistant strains were close to the wild-type strains but had low similarity from other countries. Six glycosylation sites (44 (NHT), 50 (NQS), 58 (NST), 63 (NHT), 70 (NNT), 434 (NTT), and 455 (NWS)) significantly changed, and four other sites remained stable. A total of 8 and 11 NA sialidase activity and auxiliary sites were conserved, respectively, except for the H275Y substitutions in 11 strains. The most common mutations were R222Q, V234M, D344N, and K254R. H275Y, despite its missing glycosylation sites, can change its 3D structure. Conclusions: Except for sialidase, some of the antigenic determinants and glycosylation sites from Chinese H1N1 influenza NA genes have changed in the past 20 y, which is related to the periodic