Oligoclonal Analysis of the Atopic T Cell Response to the Group 1 Allergen of Cynodon dactylon (Bermuda Grass) Pollen: Pre- and Post-Allergen-Specific Immunotherapy

Abstract

Background: Bermuda grass pollen (BGP) is an increasingly important seasonal aeroallergen in Australia and other subtropical and temperate regions. BGP shares minimal allergenic cross-reactivity with pollens of rye grass or other Pooideae grasses often used for desensitization regimens in grass pollen allergy. Current allergen immunotherapy is seldom used in asthmatic patients due to IgE-mediated side effects. Since clinically effective immunotherapy is linked with altered allergen-specific T cell response, characterisation of human T cell reactivity to Cyn d 1, the major B cell allergen of BGP, should permit the design of effective and safe immunotherapy for BGP allergy. Methods: Short-term BGP-specific CD4+ T cell lines were established from peripheral blood of 14 BGP-sensitive patients before and after conventional 50% BGP and 50% 7-grass mix subcutaneous specific allergen immunotherapy (SIT). T cell diversity of antigen specificity and function was assessed by proliferation and cytokine production to BGP, Cyn d 1 and Cyn d 1 peptides. Results: Three highly immunogenic regions of Cyn d 1 were identified in 13/14 patients pre-SIT: Cyn d 1 (109–128), (181–209) and (217–241). The SIT regimen was clinically efficacious. Following SIT, decreased proliferation to BGP, Cyn d 1 and Cyn d 1 peptides was observed with a marked decrease in the IL-5:IFN-γ ratio. Conclusions: Cyn d 1 is a major T cell allergen of BGP. Decreased Cyn d 1-specific IL-5 dominant T cell responses were observed in association with clinically effective treatment with the 50% BGP and 50% 7-grass mix. Identified dominant T cell regions of Cyn d 1 should facilitate safer vaccine development for BGP-induced asthma in addition to rhinitis.