Identification of Two Metallothioneins as Novel Inhalative Coffee Allergens Cof a 2 and Cof a 3

Abstract

BackgroundDust of green coffee beans is known to be a relevant cause for occupational allergic disorders in coffee industry workers. Recently, we described the first coffee allergen (Cof a 1) establishing an allergenic potential of green coffee dust.ObjectiveOur aim was to identify allergenic components of green coffee in order to enhance inhalative coffee allergy diagnosis.MethodsA Coffea arabica pJuFo cDNA phage display library was created and screened for IgE binding with sera from allergic coffee workers. Two further coffee allergens were identified by sequence analysis, expressed in E. coli, and evaluated by Western blots. The prevalence of sensitization to recombinant Cof a 1, Cof a 2, and Cof a 3 and to commercially available extract was investigated by ELISA (enzyme-linked immunosorbent assay) respectively CAP (capacity test) screening in 18 sera of symptomatic coffee workers.ResultsIn addition to the previously described chitinase Cof a 1, two Coffea arabica cysteine-rich metallothioneins of 9 and 7 kDa were identified and included in the IUIS Allergen Nomenclature as Cof a 2 and Cof a 3. Serum IgE antibodies to at least one of the recombinant allergens were found in 8 out of 18 symptomatic coffee workers (44%). Only 2 of the analysed sera (11%) had reacted previously to the commercial allergy test.ConclusionsIn addition to the previously described Cof a 1 we have identified two further coffee proteins to be type I coffee allergens (Cof a 2 and Cof a 3) which may have a relevant potential for the specific diagnosis and/or therapy of coffee allergy.

EAACIMolecular Allergology User's Guide 2.0

“…Cof a 2 and Cof a 3 (9 and 7 kDa, respectively) two cysteine‐rich metallothioneins were identified as further coffee allergens 1694 . Peters et al 1371 showed that the only commercially available diagnostic tests based on native extracts of green coffee beans are not sensitive enough to correctly diagnose a substantial number of affected coffee workers. Their results suggest that the natural allergen extracts do not contain sufficient amounts of the Cof a 1, 2 and 3 1371 .…”

“…Peters et al 1371 showed that the only commercially available diagnostic tests based on native extracts of green coffee beans are not sensitive enough to correctly diagnose a substantial number of affected coffee workers. Their results suggest that the natural allergen extracts do not contain sufficient amounts of the Cof a 1, 2 and 3 1371 . Therefore, the authors suggested the production and application of recombinant coffee allergens for the development of standardized and sensitive diagnostic tools and/or the spiking the natural extract with recombinant coffee allergens to improve the diagnostics of coffee allergy.…”

“…Their results suggest that the natural allergen extracts do not contain sufficient amounts of the Cof a 1, 2 and 3. 1371 Therefore, the authors suggested the production and application of recombinant coffee allergens for the development of standardized and sensitive diagnostic tools and/or the spiking the natural extract with recombinant coffee allergens to improve the diagnostics of coffee allergy.…”

Immunological methods for diagnosis and monitoring of IgE‐mediated allergy caused by industrial sensitizing agents (IMExAllergy)

“…Using commercial ImmunoCAP analysis, sensitization to green coffee beans was found in 2/18 (11%) of workers with symptoms of allergic rhinitis and/or conjunctivitis under coffee dust exposure. ELISA screening showed sIgE reactivity to rCof a 1, rCof a 2, and rCof a 3 in a total of 8 out of 18 (44%) sera of symptomatic coffee workers …”

Addressing Molecular Diagnosis of Occupational Allergies

“…The first coffee bean protein allergen has been isolated, sequenced, and characterized as a class III chitinase with a molecular weight of 32 kDa and listed in the WHO/IUIS database as Cof a 1 [ 44 ]. Two cysteine-rich metallothioneins had been identified as novel coffee allergens (Cof a 2 and Cof a 3; 9 and 7 kDa, respectively) [ 45 ]. Serum IgE antibodies to at least one of the recombinant allergens Cof a 1, 2, and 3 were detected in 44% of 18 symptomatic coffee workers, while only 11% of them showed sIgE binding to the native green coffee extract.…”