Abstract:

Objective  To explore the effect of specific immunotherapy with major 3 group recombinant allergen rDer f 3 of Dermatophagoides farinae in murine asthma model.  Methods  Forty BALB/c mice were randomly divided into 4 groups， namely PBS group（negative control）， ovalbumin（OVA） group（positive control）， rDer f 3 allergen sensitization group（asthma group）， and rDer f 3 specific immunotherapy group（SIT group）. The mice in asthma group and SIT group were injected intraperitoneally with purified rDer f 3 protein on days 0， 7 and 14， respectively， and rDer f 3 solution was inhalated from day 21 for 7 days. During the 25th-27th day， mice in SIT group were injected subcutaneously with 100 μg rDer f 3 allergen for 30 min before nasal inhalation. Mice in groups of PBS and OVA were treated with PBS and OVA， respectively. Twenty-four hours after the final challenge， all mice were sacrificed， the bronchoalveolar lavage fluid（BALF） was collected and the total number of white blood cells and the number of eosinophils were recorded. The levels of IL-5 and IFN-γ in BALF and supernatant of cultured splenocytes were detected by ELISA， as well as the serum levels of specific IgE and IgG2a antibodies. Lung tissues were stained with haematoxylin and eosin for histological analysis.  Results  Compared with the asthma group， the rDer f 3-induced lung inflammation was significantly alleviated in SIT group. The total number of white blood cells［（7.03±1.38）×10⁸/ml］ in SIT group was considerably lower than that of OVA group［（22.11±3.70）×10⁸/ml］ and asthma group［（22.75±3.24）×10⁸/ml］（P＜0.01）. The change trend of eosinophil leukocytes was similar with that of white blood cells. IL-5 levels in BALF［（108.20±11.02） pg/ml］ and splenocyte culture supernatant ［（98.34±13.06） pg/ml］ in SIT group were significantly lower than that of OVA group［（182.04±13.94） pg/ml，（208.26±10.63） pg/ml］ and asthma group［（195.33±15.33） pg/ml，（179.54±13.65） pg/ml］（P＜0.01）. Whereas， the level of IFN-γ in BALF［（107.98±12.64） pg/ml］ and supernatant of cultured splenocytes［（105.51±11.62） pg/ml］ in SIT group was significantly higher than those of OVA group and asthma group（P＜0.01）. Compared with OVA group[（26.87±4.30）IU/ml] and asthma group[（35.25±8.84）IU/ml]， a lower level of allergen-specific IgE［（9.12±3.78）IU/ml］ and higher level of allergen-specific IgG2a［（38.52±6.33） μg/ml］ were observed in SIT group（P＜0.01）.  Conclusion  rDer f 3 allergen can reverse allergen-induced airway and lung inflammation in murine asthma model.

Key words: Dermatophagoides farinae, Der f 3, Allergen, Asthma, Specific allergen immunotherapy