Evaluating cross-reaction between Formosan termite (Coptotermes formosanus) proteins and cockroach allergens

Authors: Mattison, Chris

Submitted to: American Academy of Allergy Asthma and Immunology
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/2019
Publication Date: N/A
Citation: N/A

Interpretive Summary: The incidence of food and other types of allergies appears to be increasing and this poses substantial health, emotional, and economic burdens for the future. Cockroaches are considered a major class of airborne allergens contributing to allergic disease in urban areas world-wide. Cockroaches and termites are closely related evolutionarily within the same order (Blattodea) and they share some behavioral similarities that have potential for human-termite interactions. Gene sequencing and proteomic analysis indicates several termite proteins likely cross-react with cockroach allergens. To test this idea further, whole termite extracts were analyzed by immunoassay with anti-cockroach allergen IgG and human IgE antibodies from serum samples of cockroach allergic patients. The immunoassay testing with termite extracts revealed cross-reaction between several proteins and the IgG and IgE antibodies to cockroach allergens. To further characterize the reactions and define potential termite allergens, recombinant termite proteins have been purified. To date, termite tropomyosin and arginine kinase proteins have been demonstrated to cross-react with cockroach-allergens. This is the first study to demonstrate directly that recombinant termite proteins cross-react with IgE from cockroach allergic patients. These results suggest that termite tropomyosin may pose a threat to those with cockroach or other allergies due to cross-reactivity, and may contribute as a sensitizing agent in geographic areas infested with termites. This work presents support for the hypothesis that termite proteins may act as allergens and the findings could be applied to development of molecular chimeras with unique and informative epitopes, development of potentially therapeutic hypo-allergens, advances in epitope analysis, and application to clinical studies.

Technical Abstract: Cockroach allergens are a common trigger for allergy and asthma symptoms. Termites are evolutionarily related to cockroaches, cohabitate in human dwellings, and represent an increasing pest problem in the United States. The Formosan subterranean termite (Coptotermes formosanus) is one of the most common species in the southern United States. Sequencing results and mass-spectrometric analysis of peptides from whole termite extract suggested some termite proteins, including tropomyosin (Bla g 7), arginine kinase (Per a 9), and myosin (Bla g 8), would likely cross-react with cockroach allergens. To test this, whole termite extracts were analyzed by immunoassay with anti-cockroach allergen IgG and human IgE from serum samples of cockroach allergic patients. Immunoblot and ELISA testing revealed cross-reaction between several proteins and the IgG and IgE antibodies to cockroach allergens. Recombinant termite proteins, including tropomyosin, arginine kinase, and others, are being tested to confirm cross-reaction with cockroach-allergens and better characterize the proteins. Recombinant C. formosanus tropomyosin and arginine kinase have been expressed in E. coli and purified. Circular dichroism of the purified termite tropomyosin protein demonstrated a characteristic a-helical structure similar to that observed for recombinant shrimp tropomysin (Pen a 1). IgE binding to the recombinant termite tropomyosin from five of 16 cockroach and shrimp allergic donor samples was clearly detected. The recombinant termite tropomyosin caused a dose-dependent increase in degranulation response comparable to that seen with recombinant Pen a 1 when tested with serum IgE from a shrimp allergic donor. Similarly, preliminary immunoblot analysis of recombinant termite arginine kinase indicated IgE cross-reaction with 11 of 12 cockroach or shrimp allergic samples, but not with dust mite allergic or peanut/tree nut allergic samples. This work presents support for the hypothesis that termite proteins may act as allergens and the findings could be applied to development of molecular chimeras with unique and informative epitopes, development of therapeutic hypoallergens, advances in epitope analysis, and application to clinical studies.