Genetic polymorphisms and allergenicity of Blo t 5 in a house dust mite allergic Filipino population.

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.

OBJECTIVE: 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.

METHOD: 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, 68.70% and 59.13% 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).

CONCLUSIONS: 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.