Nanoparticle-encapsulated allogeneic T cells mitigate graft-versus-host disease but retain graft-versus-leukemia activity

Aim Allogeneic hematopoietic stem cell transplantation （HSCT） has curable potential for hematopoietic malignancies through graft-versus-leukemia （GVL） effects but is often associated with life-threatening graft-versus-host disease （GVHD）. Donor T cells play an important role in the pathological process of GVHD. In this study, to determinate immunoisolation through encapsulating T cells with biomaterials could be a promising approach to atten- uate GVHD. Methods T cells were isolated from spleens of donor C57B1/6 mice by magnetic cell separation and coated by layer-by-layer in chitosan and alginate. BALB/c recipient mice were established by GVHD mode and leukemia mode. Xenogen IVIS imaging system was used for live animal imaging. Donor BMCs and T cell subsets were analyzed by flow cytometry. Results In this study, we successfully encapsulated T cells of mice in multilay- ers of chitosan and alginate. In vitro studies showed that the encapsulation did not change the phenotype of T cells as defined through the following parameters： size, viability, proliferation, antibody binding, cytokine secretion, and cytotoxicity. Mice transplanted with encapsulated allogeneic T cells exhibited less severe acute GVHD and pro- longed survival. The mice showed a lower GVHD score, less liver damage, a smaller CD8/CD4 T cell ratio, and a higher number of donor BM-derived cells following transplantation with encapsulated donor T cells. When this GVHD model was combined with implantation of A20 lymphoma cells, GVL of encapsulated T cells was not com- promised, while GVHD was still suppressed and the mouse survival also prolonged. Conclusion These studies demonstrate that encapsulation of T cells with bio-degradable materials could attenuate the severity of GVHD but re- taine GVL, which presents a novel and potentially safer and effective approach of allogeneic HSCT for future clini- cal application.