Der p 1 and Der p 2 induce less severe late asthmatic responses than native Dermatophagoides pteronyssinus extract after a similar early asthmatic response

Background The models for exposure to house dust in research and clinical p ractice are selected with respect to their role in IgE-mediated immediate h ypersensitivity. The use of isolated major allergens instead of complex all ergen extracts is becoming increasingly popular as it offers some important advantages for quantitative measures in diagnosis and research. Objective To compare house dust mite extract and isolated mite major allerg ens with respect to their ability to induce early and late asthmatic respon ses and bronchial hyperreactivity. Methods Bronchial responses to house dust mite (HDM, Dermatophagoides ptero nyssinus) extract and isolated major allergens from HDM (Der p 1 and Der p 2) were compared in a double-blind, randomized, cross-over study in 20 pati ents with mild to moderate asthma who were allergic to HDM. Allergen was ti trated to a standardized early asthmatic response. Bronchial hyper-responsi veness to histamine (PC(20)histamine) was determined before and after aller gen inhalation to assess allergen-induced bronchial hyperresponsiveness and IL-5 was measured in serum. In addition, the allergens were applied in int racutaneous skin tests and activation of basophil leucocytes and proliferat ion of peripheral blood mononuclear cells was tested in vitro. Results After a similar early asthmatic response (mean Delta forced expirat ory volume in 1 s (FEV1),(max) -29.4 (SD 7.2) vs. -33.1 (8.6) %; mean diffe rence 3.6 (95% CI -0.9 to 8.2) %), the late asthmatic response (mean Delta FEV1,(max) -45.9 (21.9) vs. -32.7 (22.3) %; mean difference 13.2 (3.8-22.3) %), the degree of allergen-induced bronchial hyperresponsiveness (mean Del ta PC(20)histamine, 1.8 (1.0) vs. 1.2 (0.9) doubling dose; mean difference 0.6 (0.2-1.1) doubling dose) and serum IL-5 at 6h were found to be signific antly higher after bronchial challenge with HDM extract than after challeng e with an isolated HDM major allergen. Likewise, there was an increased lat e skin reaction with HDM compared with isolated major allergen after a simi lar early skin reaction. Conclusion Constituents of HDM extract, other than Der p 1 or Der p 2, with no significant influence on the IgE-mediated early asthmatic response cont ribute significantly to the allergen-induced late asthmatic response and br onchial hyper-reactivity.