Volume 4 Supplement 2

5th International Symposium on Molecular Allergology (ISMA 2013)

Open Access

A Phl p 7-specific IgG4 antibody inhibits allergic patients IgE cross-reactivity to allergens from the EF-hand family: importance of affinity and degree of cross-reactivity

  • Elisabeth Gadermaier1,
  • Louise K James2,
  • Mohamed H Shamji3,
  • Katrina Blatt4,
  • Tetiana Garmatiuk1,
  • Rebecca Beavil2,
  • Sabine Flicker1,
  • Peter Valent4,
  • Stephen R Durham3,
  • Hannah J Gould2 and
  • Rudolf Valenta1
Clinical and Translational Allergy20144(Suppl 2):O8

DOI: 10.1186/2045-7022-4-S2-O8

Published: 17 March 2014

Background

The calcium-binding 2EF-hand protein Phl p 7 from timothy grass pollen is a cross-reactive pollen panallergen that can induce severe clinical symptoms in allergic patients. Recently, a human Phl p 7-specific IgG4 antibody which inhibited IgE binding to Phl p 7 was isolated and characterized.

Objective

To study epitope-specificity and cross-reactivity of the Phl p 7-specific IgG4 with homologous pollen allergens as well as the extent of cross-protection.

Methods and results

Sequence comparison showed a comparable sequence identity of approximately 70% between the 2EF-hand pollen allergens (Timothy grass: Phl p 7; Alder: Aln g 4; Birch: Bet v 4; Turnip rape: Bra r 1; Lamb´s quarter: Che a 3; Olive: Ole e 3) and a lower sequence identity of 44% with the 4EF-hand allergen from olive pollen (Ole e 8). While patients´ IgE showed extensive cross-reactivity with the EF-hand allergens, the Phl p 7-specific IgG4 showed limited cross-reactivity. Best cross-reactivity was observed with Ole e 3 whereas the other EF-hand allergens were less recognized by the Phl p 7-specific IgG4 in dot blot experiments. Calcium-depletion experiments showed that the binding of the Phl p 7-specific IgG4 depended on the presence of calcium. Using peptide-specific antisera the binding site of the IgG4 was located in the C-terminal portion of the allergen which contains the second calcium-binding EF-hand motif. Biacore experiments revealed interesting differences regarding the affinity of the Phl p 7-specific IgG4. Phl p 7 and Ole e 3 were recognized with the highest affinity (KD´s: Phl p 7: 2,11x10-9M; Ole e 3: 6,18x10-9M) whereas the affinities to the other cross-reactive allergens was much lower (Bet v 4: 6,26x10-6M; Bra r 1: 6,57x10-6M; Aln g 4: 7,93x10-6M). The cross-inhibition of patients´ IgE reactivity to the EF-hand allergens and the inhibition of allergen-induced basophil activation obtained with the Phl p 7-specific IgG4 followed its intensity of cross-reactivity and affinity with the homologous allergens.

Conclusion

Our results demonstrate that the Phl p 7-specific IgG4 antibody shows cross-inhibition of allergic patients IgE reactivity and basophil activation induced by homologous allergens according to cross-reactivity and affinity. Funded by grants P23318-B11 and in parts by grants F4607 and F4605 of the Austrian Science Fund (FWF).

Authors’ Affiliations

(1)
Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna
(2)
Randall Division of Cell and Molecular Biophysics, King’s College London
(3)
National Heart/Lung Inst, Imperial College London Allergy and Clin Immunol
(4)
Department of Internal Medicine I, Medical University of Vienna, Vienna General Hospital

Copyright

© Gadermaier et al; licensee BioMed Central Ltd. 2014

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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