title: N-linked glycosylation of the hemagglutinin protein influences virulence and antigenicity of the 1918 pandemic and seasonal H1N1 influenza A viruses.
abstract: The hemagglutinin (HA) protein is a major virulence determinant for the 1918 pandemic influenza virus; however, it encodes no known virulence-associated determinants. In comparison to seasonal influenza viruses of lesser virulence, the 1918 H1N1 virus has fewer glycosylation sequons on the HA globular head region. Using site-directed mutagenesis, we found that a 1918 HA recombinant virus, of high virulence, could be significantly attenuated in mice by adding two additional glycosylation sites (asparagine [Asn] 71 and Asn 286) on the side of the HA head. The 1918 HA recombinant virus was further attenuated by introducing two additional glycosylation sites on the top of the HA head at Asn 142 and Asn 172. In a reciprocal experimental approach, deletion of HA glycosylation sites (Asn 142 and Asn 177, but not Asn 71 and Asn 104) from a seasonal influenza H1N1 virus, A/Solomon Islands/2006 (SI/06), led to increased virulence in mice. The addition of glycosylation sites to 1918 HA and removal of glycosylation sites from SI/06 HA imposed constraints on the theoretical structure surrounding the glycan receptor binding sites, which in turn led to distinct glycan receptor binding properties. The modification of glycosylation sites for the 1918 and SI/06 viruses also caused changes in viral antigenicity based on cross-reactive hemagglutinin inhibition antibody titers with antisera from mice infected with wild-type or glycan mutant viruses. These results demonstrate that glycosylation patterns of the 1918 and seasonal H1N1 viruses directly contribute to differences in virulence and are partially responsible for their distinct antigenicity.
authors.affiliation: Immunology and Pathogenesis Branch, Influenza Division, National Center for Immunology and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
authors.forename: Xiangjie
authors.initials: X
authors.lastname: Sun
authors.forename: Akila
authors.initials: A
authors.lastname: Jayaraman
authors.forename: Pavithra
authors.initials: P
authors.lastname: Maniprasad
authors.forename: Rahul
authors.initials: R
authors.lastname: Raman
authors.forename: Katherine V
authors.initials: KV
authors.lastname: Houser
authors.forename: Claudia
authors.initials: C
authors.lastname: Pappas
authors.forename: Hui
authors.initials: H
authors.lastname: Zeng
authors.forename: Ram
authors.initials: R
authors.lastname: Sasisekharan
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: Katz
authors.forename: Terrence M
authors.initials: TM
authors.lastname: Tumpey
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D000956:Antigens, Viral / Q000276:immunology / Q000378:metabolism; D003429:Cross Reactions; D004252:DNA Mutational Analysis; D004195:Disease Models, Animal; D005260:Female; D006031:Glycosylation; D006385:Hemagglutination Inhibition Tests; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000276:immunology* / Q000378:metabolism*; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology* / Q000472:pathogenicity*; D051379:Mice; D008807:Mice, Inbred BALB C; D016297:Mutagenesis, Site-Directed; D009976:Orthomyxoviridae Infections; D037521:Virulence Factors / Q000276:immunology* / Q000378:metabolism*
chemical_list: D000914:Antibodies, Viral; D000956:Antigens, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D037521:Virulence Factors