Sequence Polymorphisms of Major German Cockroach Allergens Bla g 1, Bla g 2, Bla g 4, and Bla g 5

Abstract

Background: The allergenicity of allergens could be influenced by amino acid substitutions in B- or T-cell epitope regions. The German cockroach is known to produce potent allergens inducing strong IgE-mediated allergic reactions. This study was performed to investigate sequence variations in major allergens of the German cockroach. Methods: Reverse transcriptase PCR was used to amplify the cDNA sequences encoding major allergens of the German cockroach (Bla g 1, Bla g 2, Bla g 4, and Bla g 5). Results: The deduced amino acid sequences revealed 38 Bla g 1 variants with 1–7 amino acid substitutions (98.6–99.8% identity), 28 Bla g 2 variants with 1–3 substitutions (99.1–99.7%), 27 Bla g 4 variants with 0–32 substitutions (82.4–100%), and 8 Bla g 5 variants with 1–2 substitutions (99.0–99.5%), respectively. Bla g 1 and Bla g 2 showed sporadic amino acid substitutions despite the divergence in their sequences. Bla g 4 exhibited frequent variations, with clusters of substitutions in residues 29–38, 52–80, and 132–155. Sequence variations in Bla g 4 imply the presence of multiple isoforms and isoallergens, which may in turn have various effects on the IgE-binding capacity and T-cell responsiveness. Only 8 variants were found in Bla g 5, with infrequent amino acid changes of one or two residues. Conclusions: Analyses of T-cell and IgE-binding epitope regions would clarify the effect of sequence polymorphisms on allergenicity, which in turn will aid in the design of allergen formulations for diagnosis and immunotherapy for cockroach allergies.