title: Effect of Amino Acid Polymorphisms of House Dust Mite Der p 2 Variants on Allergic Sensitization.
abstract: OBJECTIVE
  The sequence variations of the Der p 2 allergen of Dermatophagoides pteronyssinus diverge along 2 pathways with particular amino acid substitutions at positions 40,47,111, and 114. The environmental prevalence and IgE binding to Der p 2 variants differ among regions. To compare IgE binding to Der p 2 variants between sera from Bangkok, Thailand and Perth, Western Australia with different variants and to determine the variant-specificity of antibodies induced by vaccination with recombinant variants.
  
  
  METHODS
  The structures of recombinant variants produced in yeast were compared by circular dichroism and 1-anilinonaphthalene 8-sulfonic acid staining of their lipid-binding cavity. Sera from subjects in Bangkok and Perth where different variants are found were compared by the affinity (IC₅₀) of IgE cross-reactivity to different variants and by direct IgE binding. Mice were immunized with the variants Der p 2.0101 and Der p 2.0110, and their IgG binding to Der p 2.0103, 2.0104, and 2.0109 was measured.
  
  
  RESULTS
  The secondary structures of the recombinant variants resembled the natural allergen but with differences in ANS binding. The IC₅₀ of Der p 2.0101 required 7-fold higher concentrations to inhibit IgE binding to the high-IgE-binding Der p 2.0104 than for homologous inhibition in sera from Bangkok where it is absent, while in sera from Perth that have both variants the IC₅₀ was the same and low. Reciprocal results were obtained for Der p 2.0110 not found in Perth. Direct binding revealed that Der p 2.0104 was best for detecting IgE in both regions, followed by Der p 2.0101 with binding to other variants showing larger differences. Mouse anti-Der p 2.0101 antibodies had a high affinity of cross-reactivity but bound poorly to other variants.
  
  
  CONCLUSIONS
  The affinity of IgE antibody cross-reactivity, the direct IgE binding, and the specificities of antibodies induced by vaccination show that measures of allergic sensitization and therapeutic strategies could be optimized with knowledge of Der p 2 variants.
authors.affiliation: Institute of Molecular Biosciences, Mahidol University, Salaya, Nakorn Pathom Thailand, Thailand.
authors.forename: Sasipa
authors.initials: S
authors.lastname: Tanyaratsrisakul
authors.affiliation: Department of Pediatrics, Faculty of Medicine Siriraj Hospital, Mahidol University, Thailand.
authors.forename: Orathai
authors.initials: O
authors.lastname: Jirapongsananuruk
authors.affiliation: Institute of Molecular Biosciences, Mahidol University, Salaya, Nakorn Pathom Thailand, Thailand.
authors.forename: Bhakkawarat
authors.initials: B
authors.lastname: Kulwanich
authors.affiliation: Telethon Kids Institute, University of Western Australia, Perth, Australia.
authors.forename: Belinda J
authors.initials: BJ
authors.lastname: Hales
authors.affiliation: Telethon Kids Institute, University of Western Australia, Perth, Australia.
authors.forename: Wayne R
authors.initials: WR
authors.lastname: Thomas
authors.affiliation: Institute of Molecular Biosciences, Mahidol University, Salaya, Nakorn Pathom Thailand, Thailand. piboons@gmail.com.
authors.forename: Surapon
authors.initials: S
authors.lastname: Piboonpocanun
keywords: Allergic reaction; Der p 2 Allergen; IgE binding