Immune Response of HLA-DQ Transgenic Mice to House Dust Mite Allergen p2: Identification of HLA-DQ Restricted Minimal Epitopes and Critical Residues

HLA-DQ8 (HLA-DQA1*0301; HLA-DQB1*0302) and HLA-DQ6 (HLA-DQA1*0103; HLA-DQB1*0602) genes were introduced into mouse class II (H-2Aoβ) knockout mice. Transgenic HLA-DQ8 and HLA-DQ6 mice were individually immunized and challenged using synthetic peptides representing HDM (Dermatophagoides pteronyssinus) allergen p2. HLA-DQ8 mice responded to p2 peptides 1–20, 41–60, 51–70, 61–80, 91–110, and 101–120. HLA-DQ6 mice responded to peptides 1–20, 11–30, 21–40, 41–60, and 51–70. Using single amino acid truncated 30-mer peptides, residues necessary for HLA-DQ8 recognition were identified spanning regions 3–12, 50–70, and 91–120. A synthetic peptide comprising residues 3–12 was synthesized and a series of single alanine substitutions was introduced into the minimal peptide. Introduction of alanine residues at positions 3, 11, and 12 resulted in a significant loss of immune recognition. It was concluded that residues 4, 5, 7, 11, and 12 are critical for immune recognition by HLA-DQ8 mice.