Identification of functional domains in goose interleukin 2

The cytokine interleukin (IL)-2 functions as a growth factor and central regulator in the immune system. Using a recombinant goose IL-2 (goIL-2) monomer expressed in prokaryotic cells as an immunogen, we synthesized 5 goIL-2 neutralizing mAbs to identify the functional domains of goIL-2, and used these mAbs to finely map the functional domains of the goIL-2 protein. The mimotopes of the 5 anti-goIL-2 mAbs, including HHDPWDXLP, ESLSRXXMXXLXP, SHHLPTSXL, HPDPWDAPLSS, and HEPWQLXL, were identified using a phage display library and peptide-competitive enzyme-linked immunosorbent assay (ELISA). These mimotopes constitute 1 conformational functional domain in the goIL-2 molecule—T11I14K15D16E18K19L20G21T22S23M24K25L29E30L31Y32T33P34E36S41W42Q43T44L45Q46 (domain I). The neutralizing mAbs to goIL-2 inhibited the in vitro lymphocyte proliferation stimulated by domain I peptides of goIL-2. A tertiary structural model of goIL-2 showed that domain I is positioned in helix A, long A–B loop, and the N-terminal of helix B. These data provide a clue for defining the interaction between goIL-2 and its receptor.