Adoptive Therapy with Cord Blood Regulatory T Cells Does Not Impair Anti-Leukemia Activity of Infused Donor Cells

Abstract

IntroductionCord blood derived ex vivo expanded regulatory T cells(CB-Tregs) have been verified that they can effectively prevent xenogenic graft-versus-host disease(GVHD) in NSG mice, which provide evidence to further investigate the effect of CB-Tregs in clinical setting. However, due to the potent suppression function of CB-Tregs, it needs to elucidate the concerning about whether CB-Tregs worsen leukemia or dampen anti-leukemia activity of donor cells. Beatrice et al. report donor derived in vitro expanded Treg can also prevent GVHD successfully while allowing a powerful graft-versus-leukemia(GVL) in murine models. We hypothesize cord blood derived ex vivo Treg are effective in preventing GVHD without compromising GVL.MethodsTregs are isolated from cord blood and expanded with CD3CD28 beads and IL-2 in SCGM medium. Then the cells are harvested on day14 after culturing. We use CD4+CD25+CD127low or - Foxp3+ to confirm Tregs, viabilty and purification on flow cytometry. The suppresive assay of CB-Tregs are based on CFSE. 3 or 10 million HL-60 cells are used to build AML model in NSG mouse. AML VS AML+Tregs or AML+PBMC/Tcons VS AML+PBMC/Tcons+Tregs are set up in each experiments. The primary end point is survival, secondary point is AML percentage and weight loss as well as the cytokines in the serum and tissue pathology.Results62-135 folds of CB-Tregs compared original number are harvested on day14, >90% cells are CD4+CD25+CD127low or - Foxp3+, There is no any difference in weight loss, AML percentage of peripheral blood and survival between AML+PBMC and AML+PBMC+Treg (Figure1 a, b,c and d,e,f). There is no significant difference in AML percentage between AML+PBMC/Tcons +Treg and AML+PBMC/Tcons, but mice in AML+Tcons+Treg survived longer than mice in AML+Tcons (Figure 2a,b,c,d).ConclusionCB-Tregs do not deteriorate the development of AML, they also do not impair anti-leukemia activity of PBMC or Tcons while they provide protection from GVHD. Our findings lay down the basis for testing impact CB-Tregs on CAR T cell activity in Vivo. DisclosuresNo relevant conflicts of interest to declare.