Identification of mutations at the antigenic and glycosylation sites in hemagglutinin protein of H5N1 strain

摘要

Hemagglutinin (HA) is the principal antigen, present on the viral surface. It is the primary target for neutralizing antibodies. In this paper, wehave carried out studies on human hemagglutinin protein from H5N1 strain with homologous hemagglutinin from non-human sources of H5N1strains. In all strains, part of the antigenic site (128-141) predicted by computer program “Antigenic”, corresponds to immunodominant site Sa ofH1 subtype. In AAF02304 strain, A156→S156 mutation lies at the antigenic subsite of site 2 that corresponds to site B in the H3 subtype. Insome strains of non-human origins, there are mutations at the antigenic sites. Interestingly, in AAY56367 strain mutation L138→H138 lies at thereceptor binding site, which also overlaps the antigenic site. Therefore, this amino acid substitution may influence both the specificity of receptorrecognition and antibody binding. Seven potential glycosylation sites in human HA and in some strains of non-human sources have beenpredicted by computer program, Scan Prosite. In some strains of HA from non-human sources because of mutation, an additional glycosylationsite appeared at the antigenic site. Therefore in these strains the oligosaccharides will mask the surface of HA as well as antigenic site. Hencethese strains will not be recognized by host immune system.