Immunogenic potential of mutations in mitochondrial DNA and possible implications in autoimmune disease

To seek the underlying cause of autoimmune diseases we tested the hypothesis that mutated self proteins from mitochondria are seen as foreign proteins. A total of 21 mitochondrial peptides were identified using epitope prediction tool, SYFPEITHI as likely HLA-A2 restricted peptides. In vitro T cell line assays were conducted based on MHC stabilization of the peptides on T2 cells. Ten peptides were identified and the significant correlations were observed between the insilico and in vitro binding affinities. To determine the frequency of T cellular memory for the identified mutated peptides, PBMCs from healthy donors were tested in INF gamma-ELISpot assays. Frequencies of T cells recognizing mutated self peptide ranged from as few as 10 in 200,000 to 90 in 200,000 of the PBMCs plated. Among A2-donors, significant T cell responses were seen with mean age of 61 years. Of the 21 peptides two peptides, named as P10 and P14 were identified to be immuno-dominant peptides based on the immunogenic response by most of the donors (both A2 and non-A2) tested. To further determine the phenotype of the responding T cells, T cell co-stimulation assays were done for selected peptides based on T2 binding and Elispot assay results. T cell co-stimulation assays further confirmed Elispot results and interestingly, both interferon gamma producing CD8+T cells and CD4+ T cells were identified. We propose and will discuss the role of these immunogenic peptides as “Enemies with-in”.