Utilization of leukapheresis and CD4 positive selection in Treg isolation and the ex-vivo expansion for a clinical application in transplantation and autoimmune disorders

Abstract

Adoptive transfer of T regulatory cells (Tregs) is of great interest as a novel immunosuppressive therapy in autoimmune disorders and transplantation. Obtaining a sufficient number of stable and functional Tregs generated according to current Good Manufacturing Practice (cGMP) requirements has been a major challenge in introducing Tregs as a clinical therapy. Here, we present a protocol involving leukapheresis and CD4⁺ cell pre-enrichment prior to Treg sorting, which allows a sufficient number of Tregs for a clinical application to be obtained. With this method there is a decreased requirement for ex- vivo expansion. The protocol was validated in cGMP conditions. Our final Treg product passed all release criteria set for clinical applications. Moreover, during expansion Tregs presented their stable phenotype: percentage of CD4⁺CD25^hiCD127⁻ and CD4⁺FoxP3⁺ Tregs was > 95% and > 80%, respectively, and Tregs maintained proper immune suppressive function in vitro. Our results suggest that utilization of leukapheresis and CD4 positive selection during Treg isolation improves the likelihood of obtaining a sufficient number of high quality Treg cells during subsequent ex-vivo expansion and they can be applied clinically.