Studies on the carbohydrate moiety of Pla l 1 allergen. Identification of a major N-glycan and significance for the immunoglobulin E-binding activity
Article first published online: 6 NOV 2002
Clinical & Experimental Allergy
Volume 32, Issue 11, pages 1628–1634, November 2002
How to Cite
Calabozo, B., Barber, D. and Polo, F. (2002), Studies on the carbohydrate moiety of Pla l 1 allergen. Identification of a major N-glycan and significance for the immunoglobulin E-binding activity. Clinical & Experimental Allergy, 32: 1628–1634. doi: 10.1046/j.1365-2222.2002.01530.x
- Issue published online: 6 NOV 2002
- Article first published online: 6 NOV 2002
- Submitted 13 September 2001; revised 2 March 2002; accepted 18 July 2002
- carbohydrate epitope;
- Pla l 1;
- Plantago lanceolata
Background Pla l 1, the major allergen of Plantago lanceolata pollen, is a glycoprotein that contains an N-glycosylation site. Carbohydrate moieties of many allergenic glycoproteins have been reported to be IgE-binding determinants responsible for cross-reactivity among different species.
Objective To identify the kind of linkages and the type of glycans present in Pla l 1 and to investigate their contribution to the allergic response to this allergen.
Methods Pla l 1 was deglycosylated by N-glycosidase A and the IgE-binding ability of the unglycosylated protein was evaluated by dot-blot. Identification of β1 → 2 xylose and/or α1 → 3 fucose residues in Pla l 1 N-glycan was carried out by incubation with specific antibodies from rabbit antiserum against HRP (anti-HRP). The contribution of this N-glycan to total IgE reactivity was analysed quantitatively by pre-incubation of Pla l 1 with anti-HRP prior to incubation with sera. The role of the carbohydrate moiety of Pla l 1 in cross-reactivity was studied by RAST using unrelated glycoproteins with known sugar composition and structure.
Results The effectiveness of N-glycosidase A to deglycosylate Pla l 1 and the ineffectiveness of the treatment with PNGase F indicate that Pla l 1 carries a complex N-glycan with an α1 → 3 fucose residue in its structure. Furthermore, the presence of β1 → 2 xylose and/or α1 → 3 fucose residues was identified in this N-glycan by means of an ELISA. Pre-incubation of Pla l 1 with an anti-HRP antibody caused a weak but significant reduction in IgE reactivity. Some sera from P. lanceolata-allergic patients reacted positively with four glycoproteins that bear N-glycans of complex type but not with fetuine.
Conclusions Pla l 1 is a glycoprotein that carries at least a complex, major N-linked glycan, with a α1 → 3 fucose residue in its structure and probably also a β1 → 2 xylose. This glycan moiety does not seem to constitute a relevant allergenic epitope of Pla l 1.