Developing in vitro expanded CD45RA+ regulatory T cells as an adoptive cell therapy for Crohn's disease

Background and aim Thymus-derived regulatory T cells (T-regs) mediate dominant peripheral tolerance and treat experimental colitis. Tregs can be expanded from patient blood and were safely used in recent phase 1 studies in graft versus host disease and type 1 diabetes. T-reg cell therapy is also conceptually attractive for Crohn's disease (CD). However, barriers exist to this approach. The stability of T-regs expanded from Crohn's blood is unknown. The potential for adoptively transferred T-regs to express interleukin-17 and exacerbate Crohn's lesions is of concern. Mucosal T cells are resistant to T-reg-mediated suppression in active CD. The capacity for expanded T-regs to home to gut and lymphoid tissue is unknown. Methods To define the optimum population for T-reg cell therapy in CD, CD4(+)CD25(+)CD127(lo)CD45RA(+) and CD4(+)CD25(+)CD127(lo)CD45RA(-)T(reg) subsets were isolated from patients' blood and expanded in vitro using a workflow that can be readily transferred to a good manufacturing practice background. Results T-regs can be expanded from the blood of patients with CD to potential target dose within 22-24 days. Expanded CD45RA(+) T-regs have an epigenetically stable FOXP3 locus and do not convert to a Th17 phenotype in vitro, in contrast to CD45RA(-) T-regs. CD45RA(+) T-regs highly express alpha(4)beta(7) integrin, CD62L and CC motif receptor 7 (CCR7). CD45RA(+) T-regs also home to human small bowel in a C.B-17 severe combined immune deficiency (SCID) xenotransplant model. Importantly, in vitro expansion enhances the suppressive ability of CD45RA(+) T-regs. These cells also suppress activation of lamina propria and mesenteric lymph node lymphocytes isolated from inflamed Crohn's mucosa. Conclusions CD4(+)CD25(+)CD127(lo)CD45RA(+) T-regs may be the most appropriate population from which to expand T-regs for autologous T-reg therapy for CD, paving the way for future clinical trials.