Genetic Polymorphisms and Allergenicity of Blo t 5 in a House Dust Mite Allergic Filipino Population

Abstract Background: Blo t 5, a   major  allergen   from   the   house   dust   mite Blomia  tropicalis  had been   identified  as   an important trigger of allergic diseases. Effects of sequence variations to the IgE binding activity of Blo t 5 remain unclear. Objectives: The study determined gene polymorphisms of Blo t 5, expressed the recombinant Blo t 5 allergen in E. coli system and determined its IgE reactivity in house dust mite allergic Filipino patients. Methods: Gene polymorphism was determined using Polymerase Chain Reaction and DNA sequencing.  Recombinant Blo t 5 was expressed as a GST-fusion protein in E. coli and purified by affinity chromatography. IgE-binding activity of 230 age- and sex-matched allergic and non-allergic subjects was subjected to Enzyme-linked Immunosorbent Assay and Western blot analysis. Results: Five polymorphic variants of Blo t 5 were identified with 26 DNA base and 12 amino acid substitutions thus implying a high degree of sequence diversity. Of the 115 cases, 73.91% and 66.09% showed reactivity to Blo t extract and rBlo t 5 respectively. Total and specific IgE levels of allergic and non-allergic subjects differ significantly (p<0.0001). Conclusion : Blo t 5 gene exhibits polymorphic variants with predicted amino acid sequences resulting to changes in its IgE epitopes. These polymorphisms may suggest variability of allergenic properties of Blo t 5. The incorporation of the Blo t 5 variants in the panel of diagnostic allergens and immunotherapy is highly recommended. Keywords: Allergenicity, Blomia tropicalis, House Dust Mite, Immunoglobulin, Polymorphism, recombinant Blo t 5