P281

Tissue-specific chimeric antigen receptor modified regulatory T cells for the therapy of inflammatory bowel diseases

KARSLI Ü. ¹, SÄTZLER V. ¹, RIET T. ^1,2, SCHIENKE A. ¹, HAGEDORN M. ¹, LIEBER M. ¹, HUST M. ³, BUITRAGO-MOLINA L. ¹, WEDEMEYER H. ¹, NOYAN F. ¹, JAECKEL E. ^1,4, HARDTKE-WOLENSKI M. ^1,5

¹ Dept. of Gastroenterology, Hepatology, Infectious Diseases and Endocrinology, Hannover Medical School, Hannover, Germany; ² Clinic I for Internal Medicine, Uniklinik Koeln, Koeln, Germany; ³ Institute for Biochemistry, Biotechnology and Bioinformatics, Technical University Braunschweig, Braunschweig, Germany; ⁴ Ajmera Transplant Centre, Toronto General Hospital, Toronto, Canada; ⁵ Institute of Medical Microbiology, University Hospital Essen, University Duisburg-Essen, Essen, Germany

Inflammatory bowel diseases (IBD), including Crohn’s disease and ulcerative colitis, are characterized by chronic inflammation of the gastrointestinal tract. As the prevalence and incidence of both forms of the disease are high in industrialized countries in Europe and North America, they represent a major global health problem. Various immunological factors, environmental changes, gene variants, abnormal gut microbiota, and dysregulation of the immune response may be responsible for the development of IBD. An altered balance between regulatory T cells (Tregs) and T effector cells in the intestinal microenvironment may also contribute to the pathogenesis of IBD.
Although polyclonal Tregs are effective in treating graft-versus-host disease, they are insufficient for treating autoimmune disorders or graft rejection. However, antigen-specific Tregs were more effective under these conditions.

Therefore, we propose the use of chimeric antigen receptors (CARs) consisting of enterocyte-specific single chain variable fragments (scFvs) to change the specificity of peripheral Tregs for gut-specific antigens. To this end, enterocyte-specific scFv MRU54-A1 was generated using a phage-display approach. The scFv was cloned into different second-generation CAR backbones consisting of antigen-binding domains, hinge regions, and transmembrane domains linked to intracellular CD3ζ and CD28 signaling domains. Downstream signaling is activated through the specific binding of scFvs to an antigen, which leads to a phenotype-specific stimulus inside the T cells. The ability of CARs to activate T cells was demonstrated by transduction into reporter T-cell hybridomas expressing eGFP under the minimal IL-2 promoter with the NFAT response element.
In proof-of-concept studies, CAR-Tregs showed efficient homing to sites of inflammation in vivo. Furthermore, the enterocyte-specific CAR-modified cells were effective in disease-relevant long-term IBD mouse models.

Thus, long-term local persistence of CAR-Tregs in the gut should ensure long-lasting immune control with regeneration of the intestinal barrier without compromising general immunocompetence.