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Recombinant tropomyosin from Ascaris lumbricoides: a model to investigate IgE cross-reactivity among invertebrates and the role of parasite infections in the development of allergy and asthma


Tropomyosin has been associated to IgE cross-reactivity among different invertebrates. It has been demonstrated a high degree of amino acid sequence identity among tropomyosins from these organisms. Our group has reported for the first time the identification of Periplaneta americana tropomyosin as a major cockroach allergen (Per a 7 allergen). We have also shown that the cDNA sequence encoding Ascaris lumbricoides tropomyosin presents a high degree of homology to tropomyosins from different invertebrates, including other parasites, cockroach, mites and shrimp. The aim of the present study is to express recombinant Ascaris lumbricoides tropomyosin using the Pichia pastoris system. Using the recombinant protein, we will measure levels of specific IgE antibodies to A. lumbricoides tropomyosin by ELISA, in patients with asthma and/or rhinitis, allergic to cockroach, and in a group of children living in Natal, in an area of high prevalence of A. lumbricoides infection. Inhibition assays, using tropomyosins from different invertebrates, will be carried out to evaluate IgE cross-reactivity. Immunofluorescence experiments will be conducted to investigate the presence of tropomyosin in the L3 A. lumbricoides larvae (evolutionary stage during pulmonary passage) and quantitative expression of mRNA coding for tropomyosin will be performed in Ascaris and cockroach tissue. The results of the present study, which include analysis of the molecular structure of tropomyosins and identification of IgE epitopes, may help to understand the role of parasite infections in the development of allergic response. (AU)

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