Demonstration of regulatory CD8 T cell prevalence, phenotype, and functions in autoimmune patients treated with a tolerizing peptide vaccine

INTRODUCTION Others have described a subset of CD8 T cells with immunosuppressive characteristics in inflammatory disease settings. CD8 Treg activation, through a canonical T cell receptor, results in oligoclonal expansion and perforin dependent elimination of pathogenic CD4 T cells. We have demonstrated the CD8 Treg network in Celiac patients, and that CD8 Tregs can be modulated to enhance their cytolytic elimination of pathogenic CD4 T cells. Here, we evaluate culture conditions to enhance CD8 Treg functions, and describe the impact of a gluten tolerizing peptide vaccine on CD8 Treg in Celiac disease patients. METHODS We examined the phenotype and function of Celiac patient-derived peripheral blood CD8 Tregs using flow cytometry, multicolor immunohistochemical staining, supernatant analysis, and TCR sequencing. We then evaluated the impact of a gluten tolerizing peptide vaccine on the CD8 Treg network in Celiac patient derived peripheral blood and tissues. RESULTS Using our previously reported phenotypic and functional readouts to define CD8 Treg activity, we describe culture conditions that support oligoclonal CD8 Treg cell expansion, plasticity, and cytolytic function. In patients treated with a gluten tolerizing vaccine, we found evidence for CD8 Treg expansion and preferential recruitment to duodenal tissues; however, pathogenic CD4 T cells were still detectable, suggesting insufficient CD8 Treg functional activation. CONCLUSION We describe parameters that support cytolytic CD8 Treg function, as well as the impact of a gluten tolerizing vaccine on the mobilization of CD8 Treg. Collectively, our data support the potential for CD8 Treg directed therapies to eliminate pathogenic CD4 T cells in autoimmune diseases.