Characterization of the T-cell epitopes of a major peanut allergen, Ara h 2

Background:  The development of safe and effective immunotherapy for peanut allergy has been complicated by the high anaphylactic potential of native peanut extracts. We sought to map the T-cell epitopes of the major peanut allergen, Ara h 2 in order to develop T-cell targeted vaccines.

Methods:  A panel of eight peanut-specific CD4+ T-cell lines (TCL) was derived from eight peanut-allergic subjects and proliferative and cytokine responses to stimulation with a set of overlapping 20-mer peptides representing the entire sequence of Ara h 2 determined. Proliferation was assessed in 72 h assays via tritiated thymidine incorporation, while interleukin (IL)-5 and interferon (IFN)-γ production were assessed via sandwich enzyme-linked immunosorbent assay (ELISA) of cell culture supernatants.

Results:  Eight of the 17 Ara h 2 peptides were recognized by one or more subjects, with the two peptides showing highest reactivity [Ara h 2 (19–38) and Ara h 2 (73–92)] being recognized by three subjects each. Adjoining peptides Ara h 2 (28–47) and Ara h 2 (100–119) induced proliferative responses in two subjects. Each of these peptides was associated with a Th2-type cytokine response.

Conclusion:  Two highly immunogenic T-cell reactive regions of Ara h 2 have been identified, Ara h 2 (19–47) and Ara h 2 (73–119), providing scope for the development of safe forms of immunotherapy for peanut allergy.