Profilin is a relevant melon allergen susceptible to pepsin digestion in patients with oral allergy syndrome.
BACKGROUND
Melon allergy has been documented by means of double-blind, placebo-controlled food challenges. The most common clinical feature associated with melon allergy is oral allergy syndrome (OAS). However, no relevant allergens of melon have been identified to date.


OBJECTIVE
We sought to identify melon allergens and analyze their digestibility in human saliva and simulated gastric fluid (SGF) to provide a rationale for the OAS.


METHODS
Melon, zucchini, cucumber, and watermelon allergens were identified by means of IgE immunoblotting of sera from 21 patients with OAS after melon ingestion confirmed by means of double-blind, placebo-controlled food challenge. Further characterization was performed with rabbit antisera against sunflower pollen profilin and anticomplex glycans. Lability of allergens was assayed by incubation of melon extract in human saliva and SGF.


RESULTS
Several IgE-binding components between 15 and 60 kd and a main reactive band of 13 kd were detected in melon extract with the pooled sera from patients with melon allergy. As in melon, 13-kd components of zucchini, cucumber, and watermelon extracts were strongly recognized by the IgE antibodies of the patients with melon allergy and were identified as profilins. Putative cross-reacting carbohydrate determinants were also detected. Sera from 71% of patients recognized the melon profilin, and therefore profilin is considered a major allergen. Melon allergens were unaffected by crude human saliva. In contrast, most melon proteins, predominantly the 13-kd component (profilin), were quickly digested in the SGF.


CONCLUSIONS
In patients with OAS, a 13-kd protein identified as a profilin is a major melon allergen highly susceptible to pepsin digestion.
Rodriguez-Perez
Rosa
R
Unidad de Bioquímica, Departamento de Biotecnología, E.T.S. Ingenieros Agrónomos, Madrid; and Servicio de Alergia, Hospital Universitario Doce de Octubre, Madrid, Spain.
Crespo
Jesus F
JF
Rodríguez
Julia
J
Salcedo
Gabriel
G
D000328:Adult; D000485:Allergens / Q000302:isolation & purification; D003285:Contractile Proteins; D003429:Cross Reactions; D028462:Cucumis / Q000009:adverse effects*; D004311:Double-Blind Method; D005512:Food Hypersensitivity / Q000276:immunology* / Q000378:metabolism; D005750:Gastric Juice / Q000378:metabolism; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology; D008840:Microfilament Proteins / Q000276:immunology* / Q000378:metabolism; D010434:Pepsin A / Q000378:metabolism; D010940:Plant Proteins / Q000276:immunology / Q000378:metabolism; D051304:Profilins; D012463:Saliva / Q000378:metabolism
D000485:Allergens; D003285:Contractile Proteins; D008840:Microfilament Proteins; D010940:Plant Proteins; D051304:Profilins; D007073:Immunoglobulin E; D010434:Pepsin A