Allergenic differences between the domestic mites Blomia tropicalis and Dermatophagoides pteronyssinus

Background House dust mite allergens are the most important indoor allergen s associated with asthma and rhinitis in Singapore and the tropics. Recent data to suggest that besides the Dermatophagoides spp., the domestic mite B lomia tropicalis (Bt) is also an important source of allergens in these reg ions. Objective To evaluate the degree of allergenic cross-reactivity between Bt and D. pteronyssinus (Dp). Methods Cross-reactivity between extracts of Bt and Dp was evaluated by flu orescent allergosorbent (FAST) inhibition studies and cross enzyme immunoel ectrophoresis. Additionally, the major Dp allergens - Der p 1, Der p 2 and Der p 5, were also compared with the Bt extract by dot blot inhibition. Ski n prick and intradermal end-point titration were then carried out to compar e the homologous allergens of the mite species, Blo t 5 and Der p 5. Results FAST inhibition studies showed low to moderate cross-reactivity bet ween the two dust mite extracts (maximum cross-inhibition, 60%). Native all ergens studied by cross enzyme immunoelectrophoresis using mite allergic se ra also showed similar results but with at least four cross-reactive IgE bi nding antigens. Dot blot inhibition studies using allergens of Dp, Der p 1, Der p 2, and Der p 5, showed little cross-reactivity between these allerge ns with components of the crude Bt extracts. Further, evaluation of a recom binant allergen of Bt, Blo t 5, showed low levels of cross-reactivity even with its homologous Dp counterpart, Der p 5. Conclusion These results provide evidence that Bt allergens are distinct an d have relatively low to moderate cross-reactivity with Dermatophagoides sp p, allergens. Bt allergens should therefore be included in the diagnostic p anel for the evaluation of allergic disorders in the tropics, and the devel opment of new diagnostic and therapeutic strategies should include allergen s of Bt.