A KIR x CD8 targeting bispecific modulator enhances regulatory CD8 T cell functions, and reduces inflammation in models of autoimmune disease

Abstract INTRODUCTION: We have characterized a subset of CD8 T cells (CD8 Treg) with immunosuppressive characteristics in inflammatory disease settings. CD8 Treg activation results in their oligoclonal expansion and elimination of pathogenic CD4 T cells. Here we describe a bispecific CD8 Treg modulator that activates autoimmune patient derived CD8 Treg resulting in the cytolytic elimination of pathogenic CD4 T cell in vitro, ex vivo, and in vivo. METHODS: We tested target and cell binding of a novel bispecific CD8 Treg modulator by Octet and flow cytometry. The functional impact was evaluated using cytotoxicity assays and supernatant analysis in vitro, using Celiac patient derived biopsies ex vivo, and in acute GVHD studies using human PBMCs. RESULTS: We evaluated the efficacy and mechanism of action of a novel bispecific CD8 Treg modulator directed toward CD8 and inhibitory KIR2DL1/2/3. The modulator enhanced cytolytic CD8 Treg functions in vitro using autoimmune patient PBMCs, increased activated CD4 T cell death, and decreased pro-inflammatory cytokines. In Celiac patient derived duodenal tissues, the modulator increased CD8 Treg prevalence and reduced epithelial cell death after gliadin peptide stimulation. In acute GVHD studies, CD8 Treg modulator treated mice had CD8 Treg expansion in a dose dependent fashion and reduced inflammation. CONCLUSIONS: A novel KIR x CD8 targeting bispecific modulator restores cytolytic function of CD8 Treg, resulting in a decrease of pathogenic CD4 T cells. We postulate that the bispecific CD8 T cell modulator can reduce autoreactive CD4 T cell prevalence to reestablish immune balance and may represent a selective and broadly applicable therapeutic approach for the treatment of autoimmune disease.