Spatial clustering of the IgE epitopes on the major timothy grass pollen allergen Phl p 1: importance for allergenic activity.
BACKGROUND
The major timothy grass pollen allergen Phl p 1 is one of the most potent and frequently recognized environmental allergens.


OBJECTIVE
We sought to study at a molecular and structural level the IgE recognition of Phl p 1 and its relation to allergenic activity.


METHODS
Monoclonal human IgE antibody fragments specific for Phl p 1 and group 1 allergens from various grasses were isolated from a combinatorial library made of lymphocytes from patients with grass pollen allergy. Recombinant Phl p 1 fragments and the 3-dimensional structure of Phl p 1 were used to localize the major binding site for the IgE antibodies. A rPhl p 1 fragment containing this binding site was expressed in Escherichia coli, purified, and tested for IgE reactivity and allergenic activity with sera and basophils from patients with grass pollen allergy.


RESULTS
Monoclonal antibodies, as well as polyclonal serum IgE, from patients with grass pollen allergy defined a C-terminal fragment of Phl p 1 that represents a sterically oriented portion on the Phl p 1 structure. This Phl p 1 portion bound most of the allergen-specific IgE antibodies and contained the majority of the allergenic activity of Phl p 1.


CONCLUSIONS
IgE recognition of spatially clustered epitopes on allergens might be a general factor determining their allergenic activity.


CONCLUSIONS
Geographic distribution of IgE epitopes on an allergen might influence its allergenic activity and hence explain discrepancies between diagnostic test results based on IgE serology and provocation testing. It might also form a basis for the development of low allergenic vaccines.
Flicker
Sabine
S
Department of Pathophysiology, Center for Physiology and Pathophysiology, Medical University of Vienna, Austria.
Steinberger
Peter
P
Ball
Tanja
T
Krauth
Maria-Theresa
MT
Verdino
Petra
P
Valent
Peter
P
Almo
Steve
S
Valenta
Rudolf
R
D000485:Allergens / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D001665:Binding Sites / Q000276:immunology; D003429:Cross Reactions; D018604:Epitope Mapping; D006801:Humans; D016056:Immunodominant Epitopes / Q000276:immunology* / Q000378:metabolism; D007073:Immunoglobulin E / Q000378:metabolism*; D010446:Peptide Fragments / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D031784:Phleum / Q000276:immunology*; D010865:Pilot Projects; D010940:Plant Proteins / Q000235:genetics / Q000276:immunology*; D011058:Pollen / Q000276:immunology*; D006255:Rhinitis, Allergic, Seasonal / Q000276:immunology / Q000378:metabolism
D000485:Allergens; D016056:Immunodominant Epitopes; D010446:Peptide Fragments; D010940:Plant Proteins; C090396:PHLPI protein, Phleum pratense; D007073:Immunoglobulin E