Background: The aim of our study is to investigate whether preproinsulin (PPI) could trigger a proinflammatory CD4+ T cell response in Chinese patients with type 1 diabetes (T1D).
Methods: Peripheral blood mononuclear cells were stimulated by a pool of 13 PPI peptides. Additional five PPI peptides previously proved to be antigenic in other cohorts of patients with T1D were also used. PPI reactive T cell responses were measured by interferon (IFN)-γ ELISPOT assay.
Results: Fifty-one Chinese patients with T1D were enrolled in this study and 72.34% of them were positive for at least one islet autoantibody. The stimulation index (SI) value of IFN-γ response to PPI peptide pool or peptides with dominant epitopes was below 3 in patients when SI≥3 was used as the positive cut-off value. Two peptides (B9-23 and C19-A3) restricted to DQ8 or DR4 molecule failed to induce positive IFN-γ response in patients with high-risk HLA-DQ8 or HLA-DR4/DR9 alleles. RNA-seq analysis of PPI specific CD4+ T cell lines further showed that most of the IFN-γ associated genes remained unchanged.
Conclusions: This is the first report of CD4+ T cell epitope mapping of PPI in Chinese T1D. The lack of positive IFN-γ response to PPI peptides indicates that PPI might not be the principal antigenic candidate for autoreactive CD4+ T cells in Chinese T1D. Therefore, the efficacy of PPI-based immunotherapies in attenuating proinflammatory CD4+ T cell response requires further investigation.
Keywords: IFN-γ; T cell response; overlapping peptides; preproinsulin; type 1 diabetes.
© 2019 The Authors. Diabetes/Metabolism Research and Reviews published by John Wiley & Sons Ltd.