title: Operational and topological analyses of antigenic sites on influenza C virus glycoprotein and their dependence on glycosylation.
abstract: In our previous study, seven monoclonal antibodies specific for influenza C virus glycoprotein (gp88) were prepared and tentatively classified into two groups: group A (J14, J9, Q5, K16) has neutralization activity whereas group B (S16, J6, J15) does not. These antibodies were used to analyse the antigenic structure of gp88 and to examine the effect of glycosylation on the antigenicity of the glycoprotein. Operational analysis with a panel of antigenic variants selected with each of the group A antibodies identified two non-overlapping antigenic sites on the gp88 molecules, site A-1 recognized by J14, J9 and Q5 and site A-2 by K16. Sites A-1 and A-2 were shown, however, to be topographically overlapping by competitive binding assays. Competitive binding analysis with group B antibodies identified two additional non-over-lapping antigenic sites, site B-1 recognized by S16 and site B-2 by J6 and J15. It was found in radioimmunoprecipitation experiments that antibodies to sites B-1 and B-2 were reactive not only with gp88 but with its non-glycosylated form (T76) synthesized in the presence of tunicamycin. Antibodies to sites A-1 and A-2, in contrast, immunoprecipitated the T76 polypeptide in only trace amounts or not at all. Additionally, Western blot analysis showed that denatured gp88 blotted on nitrocellulose was reactive with antibodies to sites B-1 and B-2 but not with those to sites A-1 and A-2. These observations suggest that glycosylation of gp88 selectively influences the integrity of antigenic sites A-1 and A-2 which are composed of conformation-dependent epitopes.
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D000914:Antibodies, Viral / Q000276:immunology; D000956:Antigens, Viral / Q000276:immunology*; D000939:Epitopes / Q000276:immunology; D006023:Glycoproteins / Q000276:immunology*; D006031:Glycosylation; D009982:Gammainfluenzavirus / Q000276:immunology*; D009975:Orthomyxoviridae / Q000276:immunology*; D014764:Viral Proteins / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D000956:Antigens, Viral; D000939:Epitopes; D006023:Glycoproteins; D014764:Viral Proteins