Effects of Ser47-Point Mutation on Conformation Structure and Allergenicity of the Allergen of Der p 2, a Major House Dust Mite Allergen.

purposeHypoallergenic recombinant Der p 2 has been produced by various genetic manipulations, but mutation of a naturally polymorphic amino acid residue known to affect IgE binding has not been studied. This study aimed to determine the effect of a point mutation (S47W) of residue 47 of Der p 2 on its structure and immunoglobulin (Ig) E binding. Its ability to induce pro-inflammatory responses and to induce blocking IgG antibody was also determined.

methodsS47 of recombinant Der p 2.0110, one of the predominant variants in Bangkok, was mutated to W (S47W). S47W secreted from

resultsS47W reduced secondary structure and failed to bind the hydrophobic ANS ligand as well as a monoclonal antibody known to be dependent on the nature of the side chain of residue 114 in an adjacent loop. It could also not stimulate IL-8 release from BEAS2B cells. IgE from house dust mite (HDM)-allergic Thais bound S47W with 100-fold weaker avidity, whereas IgE of HDM-allergic Australians did not. S47W still induced basophil degranulation, although requiring higher concentrations for some subjects. Anti-S47W antiserum-immunized mice blocked the binding of human IgE to wild type Der p 2.

conclusionsThe mutant S47W had altered structure and reduced ability to stimulate pro-inflammatory responses and to bind IgE, but retained its ability to induce blocking antibodies. It thus represents a hypoallergen produced by a single mutation of a non-solvent-accessible amino acid.