SENSITIZATION TO BLOMIA-TROPICALIS IN PATIENTS WITH ASTHMA AND IDENTIFICATION OF ALLERGEN BLO-T-5

In tropical and subtropical regions of the world, allergens produced b y Blomia tropicalis are an important cause of IgE-mediated sensitizati on among patients with asthma. We compared the relative importance of sensitization to the two mite species among asthma patients from Flori da, Puerto Rico, and Brazil (n = 83), who were concurrently exposed to B. tropicalis and D. pteronyssinus, with patients from the United Sta tes and from the United Kingdom (n = 56) exposed to D. pteronyssinus. In addition, molecular cloning techniques were used to clone and expre ss a major B. tropicalis allergen. There were significant differences between IgE antibody responses to B. tropicalis and D. pteronyssinus t hat were related to exposure: only 22% of patients exposed to both spe cies had a high ratio (> 10) of IgE D. pteronyssinus:B. tropicalis, wh ereas 68% of patients exposed only to D. pteronyssinus had a ratio of > 10 (p < 0.001). A major 14-kD allergen (Blo t 5), cloned from a B. t ropicalis cDNA library, showed 43% sequence homology to D. pteronyssin us Der p 5. Recombinant Blo t 5 produced in 5. coil reacted with 45 to 69% of sera from B. tropicalis-allergic asthmatics and induced positi ve immediate skin tests at 10(-3) to 1 mu g/ml. In vivo and in vitro c omparisons of IgE responses to B. tropicalis, D. pteronyssinus, rBlo t 5, and rDer p 5, showed that B. tropicalis has unique allergens that cause specific IgE responses. The results suggest that B. tropicalis i s an independent cause of sensitization and that use of recombinant Bl o t 5 should lead to a better understanding of the role of B. tropical is in causing asthma in tropical environments.