Identification of the allergenic components of kiwi fruit and evaluation of their cross-reactivity with timothy and birch pollens.
BACKGROUND
Only a few food allergens have as yet been identified, mainly because of the difficulty of obtaining a sufficient number of patients who are clinically sensitized to a given food. This is more feasible in the case of the oral allergy syndrome (OAS), a common form of food allergy, which is especially prevalent in patients with pollinosis.


OBJECTIVE
We designed a study to identify the allergens of kiwi fruit (Actinidia chinensis) by analyzing the sera of patients with OAS for kiwi and to examine the cross-reactivity of these allergens with timothy and birch pollen allergens.


METHODS
Twenty-seven patients with OAS for kiwi, a positive skin prick test response and serum IgE antibody to kiwi, and a positive open kiwi challenge test result and three patients who had OAS with severe systemic symptoms, which excluded a challenge test, were included in this study. The different polypeptide components of an extract of fresh kiwi were separated by sodium dodecylsulfate-polyacrylamide gel electrophoresis and analyzed by IgE immunoblotting with sera from these patients. Cross-reactivity with the two pollen extracts was assessed by inhibition of the immunoblots with pooled and individual patients' sera.


RESULTS
Twelve IgE-binding components with molecular weights ranging from 12 to 64 kd were identified in the kiwi extract, but only a 30 kd component acted as major allergen, being recognized by sera of 100% of these patients. Inhibition of kiwi immunoblots with timothy and birch pollen extracts demonstrated strong cross-reactivity with some of the kiwi allergens, suggesting complete identity between certain food and pollen allergens; whereas others, particularly the 30 kd allergen, were only partially inhibited, suggesting much weaker cross-reactivity.


CONCLUSIONS
Kiwi fruit contains a large number of allergens widely cross-reacting with allergens in grass and birch pollen extracts. Nevertheless, the major allergen at 30 kd appears to be specific for kiwi.
Pastorello
E A
EA
Third Division of Internal Medicine, University of Milan, Italy.
Pravettoni
V
V
Ispano
M
M
Farioli
L
L
Ansaloni
R
R
Rotondo
F
F
Incorvaia
C
C
Asman
I
I
Bengtsson
A
A
Ortolani
C
C
D000485:Allergens / Q000032:analysis* / Q000737:chemistry / Q000276:immunology*; D001666:Binding Sites, Antibody; D001667:Binding, Competitive / Q000276:immunology; D003429:Cross Reactions; D005638:Fruit / Q000276:immunology*; D006801:Humans; D007073:Immunoglobulin E / Q000737:chemistry; D010936:Plant Extracts / Q000737:chemistry / Q000276:immunology; D006109:Poaceae / Q000737:chemistry / Q000276:immunology; D011058:Pollen / Q000737:chemistry / Q000276:immunology*; D012882:Skin Tests; D014197:Trees / Q000737:chemistry / Q000276:immunology
D000485:Allergens; D010936:Plant Extracts; D007073:Immunoglobulin E