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 def ined 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 c hains of Fel d 1 were tested in proliferation assays on polyclonal T-c ell lines and far the ability to bind Fel d 1-specific IgE in ELISA an d histamine release assays. Results: Assay of T-cell lines derived fro m 53 subjects allergic to cats demonstrated that the majority of T-cel l reactivity is found in chain 1 of Fel d 1. Two peptides (Fel-1 and F el-2) containing major epitopes, alone or as a mixture, efficiently ac tivated T cells and exhibited minimal detectable reactivity with IgE b y 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 th e ability to decrease T-cell responses in patients with cat allergy as a new form of immunotherapy.