Mutational epitope analysis and cross-reactivity of two isoforms of Api g 1, the major celery allergen.
For better understanding the cross-reactivity between the major birch pollen and celery allergens, Bet v 1 and Api g 1, respectively, putative epitope areas and structurally important positions for IgE-binding of the isoforms Api g 1.01 and Api g 1.02 were point mutated. The IgE binding capacities were measured in ELISA, the IgE cross-reactivity between the isoforms, mutants and Bet v 1 investigated by ELISA-inhibition experiments with serum pools from patients with confirmed celery allergy (DBPCFC). Api g 1.01 displayed a clearly higher frequency and capacity of IgE binding than Api g 1.02. In Api g 1.01, substitution of lysine against glutamic acid at amino acid position 44, a key residue of the Bet v 1 "P-loop", increased the IgE-binding properties. Structural instability due to proline insertion at position 111/112 resulted in loss of IgE binding of Api g 1.01, but not of Api g 1.02. Between Api g 1.01 and Api g 1.02 only partial cross-reactivity was seen. The data suggest that the IgE epitopes of the two isoforms are distinct and that in contrast to Api g 1.01, the "P-loop" region plays an important role for IgE binding of celery allergic subjects to Api g 1.02. Understanding and investigation of the molecular mechanisms in celery allergy is an important step to generate hypoallergenic proteins for safe and efficacious immunotherapy of food allergy.
Wangorsch
Andrea
A
Division of Allergology, Paul-Ehrlich-Institut, Paul-Ehrlich-Strasse 51-59, D-63225 Langen, Germany.
Ballmer-Weber
Barbara K
BK
Rösch
Paul
P
Holzhauser
Thomas
T
Vieths
Stefan
S
D000485:Allergens / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D019943:Amino Acid Substitution / Q000235:genetics; D052179:Antigens, Plant; D000077102:Apium / Q000276:immunology; D003429:Cross Reactions; D018604:Epitope Mapping; D005512:Food Hypersensitivity / Q000276:immunology; D018698:Glutamic Acid / Q000737:chemistry / Q000235:genetics; D006801:Humans; D016056:Immunodominant Epitopes / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D007073:Immunoglobulin E / Q000276:immunology; D008239:Lysine / Q000737:chemistry / Q000235:genetics; D009154:Mutation; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D011487:Protein Conformation; D017510:Protein Folding; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology
D000485:Allergens; D052179:Antigens, Plant; C096695:Api g 1 protein, Apium graveolens; D016056:Immunodominant Epitopes; D010940:Plant Proteins; D020033:Protein Isoforms; D011994:Recombinant Proteins; C061312:Bet v 1 allergen, Betula; D007073:Immunoglobulin E; D018698:Glutamic Acid; D008239:Lysine