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Bronchial hyperreactivity induced by tropomyosins from cockroach and shrimp: a mouse model to study in vivo cross-reactivity

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In vivo cross-reactivity among tropomyosins, major pan-allergens among invertebrates, is not established. Our aim was to investigate the effects of purified tropomyosins from cockroach (recombinant Per a 7) and shrimp (natural Lit v 1) on airway inflammation and hyperresponsiveness in a mouse model of asthma.


Balb/c mice, 4 to 6 weeks-old, were sensitized twice with 50μg of rPer a 7 or nLit v 1 intraperitoneally with 1 mg alum, and challenged with 50μg of rPer a 7 or nLit v 1 intranasally for three days. A group was sensitized with rPer a 7 and challenged with nLit v 1 under same conditions. Controls received saline on same days. Twenty-four hours after the last challenge, mice were ventilated with FlexiVent®, and in vivo bronchial hyperresponsiveness was evaluated with increased doses of inhaled methacholine (6.25, 12.5, 25 and 50mg/ml). After ventilation, bronchoalveolar lavage fluid (BALF) was collected and cell counts were performed.


Sensitization and challenge of mice with rPer a 7 or nLit v 1 resulted in increase in bronchial hyperresponsiveness, given by increase in total and tissue resistance and elastance. Total cells in BALF increased in rPer a 7 (1x105 vs 3x105, p<0.01) and nLit v 1 (1x105 vs 1x106, p<0.001) groups, as compared to controls. There was increase in macrophages for rPer a 7 (5x104 vs 1x105, p<0.001) and nLit v 1 (5x104 vs 3x105, p<0.001) and eosinophils for rPer a 7 (2x103 vs 1.4x105, p<0.001) and nLit v 1 (2x103 vs 9.1x105, p<0.001). Mice immunized with rPer a 7 and challenged with nLit v 1 showed no changes in bronchial hyperresponsiveness or eosinophils on BALF as compared to controls (2x103 vs 6x103). However, there was an increase in neutrophils in this group as compared to controls (5x104 vs 1x105, p<0.01).


Experimental asthma induced by purified tropomyosins from cockroach and shrimp mimicked the main characteristics of human asthma. Despite the high degree of sequence identity and IgE immunologic cross-reactivity, our data suggested that in vivo cross-reactivity of these tropomyosins is unlikely.

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Correspondence to Thalita Martins.

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