Sequence conservation predicts T cell reactivity against ragweed allergens

Abstract

Background

Ragweed is a major cause of seasonal allergy, affecting millions of people worldwide. Several allergens have been defined based on IgE reactivity, but their relative immunogenicity in terms of T cell responses has not been studied.

Objective

We comprehensively characterized T cell responses from atopic, ragweed-allergic subjects to Amb a 1, Amb a 3, Amb a 4, Amb a 5, Amb a 6, Amb a 8, Amb a 9, Amb a 10, Amb a 11, and Amb p 5, and examined their correlation with serological reactivity and sequence conservation in other allergens.

Methods

Peripheral blood mononuclear cells (PBMCs) from donors positive for IgE toward ragweed extracts after in vitro expansion for secretion of IL-5 (a representative Th2 cytokine) and IFNγ (Th1) in response to a panel of overlapping peptides spanning the above listed allergens.

Results

Three previously identified dominant T cell epitopes (Amb a 1 176-191, 200-215, and 344-359) were confirmed and three novel dominant epitopes (Amb a 1 280-295, 304-319, and 320-335) were identified. Amb a 1, the dominant IgE allergen, was also the dominant T cell allergen, but dominance patterns for T cell and IgE responses for the other ragweed allergens did not correlate. Dominance for T cell responses correlated with conservation of ragweed epitopes with sequences of other well-known allergens.

Conclusion and clinical relevance

These results provide the first assessment of the hierarchy of T cell reactivity in ragweed allergens, which is distinct from that observed for IgE reactivity and influenced by T cell epitope sequence conservation. The results suggest that ragweed allergens associated with lesser IgE reactivity and significant T cell reactivity may be targeted for T cell immunotherapy, and further support the development of immunotherapies against epitopes conserved across species to generate broad reactivity against many common allergens.

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