Site-specific glycosylation of the Newcastle disease virus haemagglutinin-neuraminidase.

Members of the Avulavirus, Respirovirus and Rubulavirus genera of the Paramyxoviridae family of viruses utilise haemagglutinin-neuraminidase glycoproteins as their attachment proteins. These glycoproteins are oligomeric type II integral membrane proteins, which possess haemagglutination and sialidase activity. Previous studies have shown that the N-linked glycans present on these proteins can modulate the ability of the virus to infect host cells and stimulate the host immune system. However, site-specific heterogeneity of these glycans has not been defined. This study concerns characterisation of the glycan compositions attached to haemagglutinin-neuraminidase of the Avulavirus Newcastle disease virus, which causes Newcastle disease in a range of avian species. Haemagglutinin-neuraminidase was derived from egg propagated virions of V4-VAR, an isolate of the avirulent strain QLD/66. Reverse-phase liquid chromatography tandem mass spectrometry strategies including collision induced dissociation, higher-energy collision dissociation and electron-transfer dissociation were implemented to characterise glycopeptides from the haemagglutinin-neuraminidase protein. Overall 63, 58, and 37 glycan compositions were identified at asparagine residues 341, 433 and 481, respectively. N-linked sites 433 and 481 were observed to contain high mannose glycans with paucimannose glycans also observed at site 481. Asparagine residues 341, 433 and 481 contained complex or hybrid glycans with many of the compositions containing variations of fucose and sulfate or phosphate. Sialyation of complex or hybrid N-linked glycans was additionally observed at sites 341 and 433. In addition, a previously undocumented O-linked glycopeptide was identified from the stalk domain of the haemagglutinin-neuraminidase protein. These finding will form the basis for future quantitative glycomic studies of the distribution of glycan structures across N-linked glycosylation sites of Newcastle disease virus haemagglutinin-neuraminidase and assessment of the functional significance of the O-linked glycan in the stalk domain of this protein.