Parvalbumin, a cross-reactive fish allergen, contains IgE-binding epitopes sensitive to periodate treatment and Ca2+ depletion.
BACKGROUND
Type I allergy to fish is a severe health problem in countries in which a large percentage of the population derive income from fishing.


OBJECTIVE
The aim of the study was to characterize cross-reactive IgE-binding components in six different fish species (cod, tuna, salmon, perch, carp, and eel). The effect of reducing extraction conditions, periodate treatment, and depletion of Ca2+ on binding of IgE to the allergens was investigated.


METHODS
Extracts were prepared under nonreducing and reducing conditions. IgE-binding components were characterized by IgE immunoblotting, and cross-reactive epitopes were studied by IgE-immunoblot inhibition experiments. To reveal calcium-sensitive or carbohydrate-containing epitopes, nitrocellulose-blotted extracts were exposed to ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) and periodate.


RESULTS
Sera from all patients allergic to fish (n = 30) displayed IgE reactivity to parvalbumin, a 12 kd protein present in fish extracts from six different species. Reducing extraction conditions had no effect on IgE binding to parvalbumins, whereas periodate treatment and depletion of protein-bound calcium led to a substantial reduction of IgE binding. Parvalbumins from six different species contained cross-reactive IgE epitopes.


CONCLUSIONS
Parvalbumin represents a cross-reactive fish allergen. It contains IgE epitopes that are sensitive to periodate treatment and Ca2+-depletion.
Bugajska-Schretter
A
A
Institute of Medical and Chemical Laboratory Diagnostics, AKH, University of Vienna, Austria.
Elfman
L
L
Fuchs
T
T
Kapiotis
S
S
Rumpold
H
H
Valenta
R
R
Spitzauer
S
S
D000485:Allergens / Q000737:chemistry* / Q000302:isolation & purification; D000818:Animals; D002118:Calcium; D003429:Cross Reactions; D000939:Epitopes / Q000737:chemistry / Q000302:isolation & purification; D005399:Fishes / Q000276:immunology*; D005512:Food Hypersensitivity / Q000209:etiology / Q000276:immunology; D006801:Humans; D007120:Immunochemistry; D007073:Immunoglobulin E / Q000097:blood; D010320:Parvalbumins / Q000737:chemistry / Q000276:immunology* / Q000302:isolation & purification; D010504:Periodic Acid; D013045:Species Specificity
D000485:Allergens; D000939:Epitopes; D010320:Parvalbumins; D010504:Periodic Acid; D007073:Immunoglobulin E; C009288:metaperiodate; D002118:Calcium