Dominating IgE-binding epitope of Bet v 1, the major allergen of birch pollen, characterized by X-ray crystallography and site-directed mutagenesis.

Abstract

Specific allergy vaccination is an efficient treatment for allergic disease; however, the development of safer vaccines would enable a more general use of the treatment. Determination of molecular structures of allergens and allergen-Ab complexes facilitates epitope mapping and enables a rational approach to the engineering of allergen molecules with reduced IgE binding. In this study, we describe the identification and modification of a human IgE-binding epitope based on the crystal structure of Bet v 1 in complex with the BV16 Fab' fragment. The epitope occupies approximately 10% of the molecular surface area of Bet v 1 and is clearly conformational. A synthetic peptide representing a sequential motif in the epitope (11 of 16 residues) did not inhibit the binding of mAb BV16 to Bet v 1, illustrating limitations in the use of peptides for B cell epitope characterization. The single amino acid substitution, Glu(45)-Ser, was introduced in the epitope and completely abolished the binding of mAb BV16 to the Bet v 1 mutant within a concentration range 1000-fold higher than wild type. The mutant also showed up to 50% reduction in the binding of human polyclonal IgE, demonstrating that glutamic acid 45 is a critical amino acid also in a major human IgE-binding epitope. By solving the three-dimensional crystal structure of the Bet v 1 Glu(45)-Ser mutant, it was shown that the change in immunochemical activity is directly related to the Glu(45)-Ser substitution and not to long-range structural alterations or collapse of the Bet v 1 mutant tertiary structure.

• Authors: Michael D Spangfort, Osman Mirza, Henrik Ipsen, R J Joost Van Neerven, Michael Gajhede, Jørgen N Larsen
• Journal: Journal of immunology (Baltimore, Md. : 1950) (J Immunol) Vol. 171 Issue 6 Pg. 3084-90 (Sep 15 2003) ISSN: 0022-1767 [Print] United States
• PMID: 12960334 (Publication Type: Journal Article)

Chemical References

• Allergens
• Antigens, Plant
• Immunodominant Epitopes
• Peptide Fragments
• Plant Proteins
• Bet v 1 allergen, Betula
• Immunoglobulin E
• Glutamic Acid
• Serine

Topics

• Allergens (chemistry, genetics, immunology, metabolism)
• Amino Acid Sequence
• Animals
• Antigens, Plant
• Betula (immunology)
• Binding Sites, Antibody (genetics)
• Binding, Competitive (genetics, immunology)
• Crystallography, X-Ray (methods)
• Glutamic Acid (genetics)
• Immunodominant Epitopes (chemistry, genetics, immunology, metabolism)
• Immunoglobulin E (blood, metabolism)
• Mice
• Models, Molecular
• Molecular Sequence Data
• Mutagenesis, Site-Directed
• Peptide Fragments (chemistry, genetics, immunology, metabolism)
• Plant Proteins (chemistry, genetics, immunology, metabolism)
• Pollen (chemistry, genetics, immunology)
• Serine (genetics)
• Surface Properties