A pilot study of preproinsulin peptides reactivity in Chinese patients with type 1 diabetes

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.