Identification of autoreactive CD8+T cell epitopes from tetraspanin-7 in humanized mice and type 1 diabetes patients

Objective: T-cell-mediated destruction of pancreatic β cells leads to Type 1 diabetes Mellitus (TIDM). Tetraspanin-7(TSPAN7) has recently been identified as an autoantigen in T1DM patients. Autoreactive CD8+T cell recognize β-cell-derived epitopes in the context of major histocompatibility complex class I molecules. However, little is known about the TSPAN7-derived immunogenic epitopes that are presented in the context of human HLA molecules. Methods: Here predicted candidate HLA-A*0201-restricted peptides derived from TSPAN7 were selected using four computer-assisted algorithms. HLA-A*0201-transgenic mice were immunized with TSPAN7 DNA vaccination to induce the CD8+T cell activity in vivo. The immunogenicity of the predicted candidate peptides was detected using IFN-γ ELISpot assay and T cell proliferation assay in vitro. Furthermore, we tested peripheral blood mononuclear cells (PBMCs) from 24 recent-onset T1DM patients and 14 healthy controls for reactivity to predicted candidate TSPAN7 peptides directly ex vivo. Results: Twenty-four candidate HLA-A*0201-restricted peptides derived from TSPAN7 were selected. The results demonstrated TSPAN7(13-21), TSPAN7(17-25), TSPAN7(66-74), TSPAN7(96-104), TSPAN7(227-235) were HLA-A*0201-restricted CD8+T cell epitopes in humanized mice. They were recognized by PBMCs from HLA-A*0201 T1DM patients while not recognized in HLA-A*0201 healthy controls. Furthermore, immunized mice showed a significant proliferative response to these five peptides in vitro. In addition, TSPAN7(41-50), TSPAN7(87-95), TSPAN7(208-216) induced IFN-γ releasing by CD8+ T cells were also frequently detected in recent-onset T1DM patients, although these epitopes were not detected in humanized mice. Conclusion: This experiment identified immunogenic HLA-A*0201-restricted CD8+T cells epitopes derived from TSPAN7 in transgenic mice and diabetic patients, illustrating the possible role of TSAPN7-specific CD8+T cells in human type 1 diabetes, and provided pathogenesis theory of T1DM.