Definition of the human T-cell epitopes of Fel d 1, the major allergen of the domestic cat

Background: A heterodimeric acidic glycoprotein (Fel d 1) has been defined as the major allergen of the domestic cat. Because T-cell help is required for the initiation and maintenance of allergic responses, it is of importance to determine the T-cell–reactive regions of the Fel d 1 molecule. Methods: Overlapping peptides corresponding to the two chains of Fel d 1 were tested in proliferation assays on polyclonal T-cell lines and for the ability to bind Fel d 1–specific IgE in ELISA and histamine release assays. Results: Assay of T-cell lines derived from 53 subjects allergic to cats demonstrated that the majority of T-cell reactivity is found in chain 1 of Fel d 1. Two peptides (Fel-1 and Fel-2) containing major epitopes, alone or as a mixture, efficiently activated T cells and exhibited minimal detectable reactivity with IgE by ELISA or histamine release assay. Conclusions: Two Fel d 1 peptides containing major T-cell epitopes have been identified, have been shown to bind minimal Fel d 1–specific IgE, and are now being tested for the ability to decrease T-cell responses in patients with cat allergy as a new form of immunotherapy. (J A LLERGY C LIN I MMUNOL 1996;98:884-94.)