title: Delineation of four antigenic sites on a paramyxovirus glycoprotein via which monoclonal antibodies mediate distinct antiviral activities.
abstract: Six hybridoma antibodies specific for the hemagglutinin-neuraminidase (HN) molecule of the parainfluenza type 1 virus strain 6/94 were used to demonstrate the existence of four distinct antigenic sites on the HN molecule. Three of the sites (A, B-C, D) are topologically nonoverlapping, because antibodies to these sites bind noncompetitively to the HN molecule. Two sites (B, C) are operationally nonoverlapping, because mutations in site B do not detectably modify the antigenic site C. Although antibodies to each site had similar potencies (activity per microgram of antibody) in hemagglutination inhibition tests, antibodies to sites A and C or D differed approximately 100-fold in their potency to neutralize virus. Also, the antibody to site A strongly inhibited viral neuraminidase activity, whereas antibodies to sites C and D (and to a lesser extent to site B) enhanced the neuraminidase activity. Lastly, only antibodies to sites C and D formed precipitates in Ouchterlony double diffusion against detergent-disrupted virus. Because all six anti-HN antibodies are of IgG isotype and exhibited similar avidity for HN, these findings suggest that the ability of anti-HN antibodies to interact with the viral protein and to alter viral functions is largely dependent on their fine specificity.
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000032:analysis / Q000276:immunology*; D000915:Antibody Affinity; D000918:Antibody Specificity; D000937:Antigen-Antibody Reactions; D000956:Antigens, Viral / Q000235:genetics / Q000276:immunology*; D001667:Binding, Competitive; D006385:Hemagglutination Inhibition Tests; D006825:Hybridomas / Q000276:immunology; D005779:Immunodiffusion; D051379:Mice; D008807:Mice, Inbred BALB C; D009439:Neuraminidase / Q000378:metabolism; D009500:Neutralization Tests; D010222:Parainfluenza Virus 1, Human / Q000235:genetics / Q000276:immunology; D018184:Paramyxoviridae Infections / Q000276:immunology*; D011863:Radioimmunoassay
chemical_list: D000914:Antibodies, Viral; D000956:Antigens, Viral; D009439:Neuraminidase