Localisation of a carbohydrate epitope recognised by human IgE in pollen of Cupressaceae

Abstract

The objectives of the present study were: (1) to localise, at the subcellular level, the allergens in pollen of Cupressaceae species, using a monoclonal antibody (mAb 5E6) that is specific for carbohydrate epitopes of allergenic components of Cupressus arizonica pollen extract; (2) to determine whether the glycidic epitope recognised by mAb 5E6 was present in pollen of allergenic species taxonomically unrelated to Cupressaceae; and (3) to determine whether human IgE purified from monosensitive patients recognises the same epitope as mAb 5E6 in Cupressaceae pollen. Immunogold labelling of mAb 5E6 showed a high density of gold particles on the orbicules, supporting the hypothesis that they are important vectors of allergens. A high density was also found on the exine and in the cytoplasm, with the latter finding confirming that fragments of pollen ruptured under humid conditions can represent a vector. The glycidic epitope recognised by mAb 5E6 was detected in all of the species taxonomically unrelated to Cupressaceae, although with varying density. Human IgE recognised the same epitope as mAb 5E6. These findings are consistent with observations of diffuse allergenic cross-reactivity among various allergens. The in situ localisation of a common epitope recognised by both a monoclonal antibody and human IgE could be of importance in immunotherapy.

Cross-reactivity of pollen allergens

“…The amino acid sequences of cloned allergens show high homology among group 1 allergens, but Jun a 1 contains N-glycosylation sites distinct from those of Cry j 1 [5]. A carbohydrate epitope is found in high density in the pollen exine, and is found in unrelated pollens as well [6]. Recent work suggests that the carbohydrate moiety is recognized as an IgE epitope by only a minority of sensitized patients [7].…”

Is the quantity of orbicules released by Dactylis glomerata and Cynosurus echinatus (Poaceae) big enough to play an allergenic role?

“…B. pendula Roth.) (Vinckier et al, 2006), Corylus avellana L. (Vinckier et al, 2005), Cryptomeria japonica (L. f.) D. Don (Miki-Hirosige et al, 1994), and of several species of Cupressus (Suarez-Cervera et al, 2003;Canini et al, 2004). However, they have yet to be found in orbicules of many other clinically important species, including grasses.…”

“…The contrary, however, is found in Cryptomeria japonica and Cupressus spp. where major allergens are present in orbicules (MikiHirosige et al, 1994;Suarez-Cervera et al, 2003;Canini et al, 2004). Also noteworthy is that orbicules are absent from some clinically important species, such as those of Asteraceae and Oleaceae (Vinckier & Smets, 2001a, b).…”

“…Accordingly, orbicules are able to reach the peripheral airways with inhaled air inducing asthma in susceptible individuals if they are loaded with allergens. Recently, the presence of pollen allergens in association with orbicules was verified in some species using immunocytochemical methods (Miki-Hirosige et al, 1994;Suarez-Cervera et al, 2003;Canini et al, 2004;Vinckier et al, 2005Vinckier et al, , 2006. This suggests that orbicules may act as very effective vectors of allergens (Vinckier & Smets, 2001a, b;Vinckier et al, 2005).…”

Sensitization to Airborne Ascospores, Basidiospores, and Fungal Fragments in Allergic Rhinitis and Asthmatic Subjects in San Juan, Puerto Rico

“…There have been numerous studies with different types of allergen sources in which the significance of carbohydrate determinants has been studied [11,50,51,52,53]. Several of these investigations have concluded that these epitopes participate in the cross-reactivity between allergen sources, while in other cases they have been useful in the characterization of certain proteins.…”