Antigenic surface of the bee venom allergen phospholipase A2. Structural functional analysis of human IgG4 antibodies reveals potential role in protection.
In the human immune response to the main bee venom allergen phospholipase A2 (PLA2), Abs of the IgG4 isotype are associated with protection. The antigenic sites of PLA2 that are recognized by two mAb of this isotype have been analyzed at the molecular level. The interaction of PLA2 with these two Abs has previously been shown to depend on the conformation of the Ag and to be sensitive to lysine modifications. Therefore, genetically engineered Ag displaying single point mutations of lysine residues were generated. Nine out of twelve surface-exposed lysine residues were substituted by glutamate or glutamine, and the effect of individual mutations on mAb binding was analyzed in the context of the folded Ag. Substitution of lysine at position 25 with either glutamate or glutamine completely abrogates binding to both mAb. All other mutants do not show a difference in binding when compared with wild-type Ag. Probing of sera from bee keepers with lysine 25 mutants reveals that a significant proportion of serum Abs of the IgG4 isotype display specificity for this epitope, suggesting that this represents a major B cell-antigenic site in hyperimmune individuals. We further found that both mAbs inhibit the catalytic activity of PLA2, a property that may account for the protective role of IgG4 Abs in hyperimmune individuals.
Dudler
T
T
Swiss Institute of Allergy and Asthma Research (SIAF), Davos.
Schneider
T
T
Annand
R R
RR
Gelb
M H
MH
Suter
M
M
D000485:Allergens / Q000276:immunology*; D000911:Antibodies, Monoclonal / Q000276:immunology; D001483:Base Sequence; D001514:Bee Venoms / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007074:Immunoglobulin G / Q000145:classification / Q000276:immunology*; D008969:Molecular Sequence Data; D009154:Mutation; D010741:Phospholipases A / Q000276:immunology*; D054467:Phospholipases A2; D013329:Structure-Activity Relationship
D000485:Allergens; D000911:Antibodies, Monoclonal; D001514:Bee Venoms; D007074:Immunoglobulin G; D010741:Phospholipases A; D054467:Phospholipases A2