Molecular, structural, and immunologic relationships between different families of recombinant calcium-binding pollen allergens.
BACKGROUND
Calcium-binding plant allergens can be grouped in different families according to the number of calcium-binding domains (EF hands).


OBJECTIVE
We sought to identify pollens containing crossreactive calcium-binding allergens and to investigate structural and immunologic similarities of members belonging to different families of calcium-binding allergens.


METHODS
By means of multiple sequence alignment and molecular modeling, we searched for structural similarities among pollen allergens with 2 (Phl p 7, timothy grass; Aln g 4, alder), 3 (Bet v 3, birch) and 4 EF hands (Jun o 4, prickly juniper). Purified recombinant Aln g 4 and Jun o 4 were used to determine the prevalence of IgE recognition in 210 patients sensitized to different pollens and to search, by means of ELISA competition, for the presence of cross-reactive epitopes in pollens from 16 unrelated plant species. IgE cross-reactivity among the allergen families was studied with purified rPhl p 7, rAln g 4, rBet v 3, and rJun o 4 and 2 synthetic peptides comprising the N-terminal and C-terminal EF hands of Phl p 7 by means of ELISA competition.


RESULTS
Structural similarities were found by using molecular modeling among the allergens with 2, 3, and 4 EF hands. Pollens from 16 unrelated plants contained Aln g 4- and Jun o 4-related epitopes. Twenty-two percent of the patients with multiple pollen sensitization reacted to at least one of the calcium-binding allergens. A hierarchy of IgE cross-reactivity (rPhl p7 > rAln g 4 > rJun o 4 > rBet v 3) could be established that identified rPhl p 7 as the EF-hand allergen containing most IgE epitopes in the population studied.


CONCLUSIONS
The demonstration that members of different families of calcium-binding plant allergens share similarities suggests that it may be possible to use representative molecules for the diagnosis and therapy of allergies to EF-hand allergens.
Tinghino
Raffaella
R
Department of Immunology, Istituto Superiore di Sanità, Rome.
Twardosz
Anna
A
Barletta
Bianca
B
Puggioni
Eleonora M r
EM
Iacovacci
Patrizia
P
Butteroni
Cinzia
C
Afferni
Claudia
C
Mari
Adriano
A
Hayek
Brigitte
B
Di Felice
Gabriella
G
Focke
Margarete
M
Westritschnig
Kerstin
K
Valenta
Rudolf
R
Pini
Carlo
C
D000485:Allergens / Q000009:adverse effects / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism*; D003429:Cross Reactions; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D006967:Hypersensitivity / Q000209:etiology*; D007073:Immunoglobulin E / Q000097:blood; D008958:Models, Molecular; D008969:Molecular Sequence Data; D006109:Poaceae / Q000009:adverse effects / Q000276:immunology*; D011058:Pollen / Q000009:adverse effects / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D016415:Sequence Alignment; D013329:Structure-Activity Relationship; D014197:Trees / Q000009:adverse effects / Q000276:immunology*
D000485:Allergens; D011994:Recombinant Proteins; D007073:Immunoglobulin E; D002118:Calcium