Conformal Nanoencapsulation of Allogeneic T Cells Mitigates Graft-versus-Host Disease and Retains Graft-versus-Leukemia Activity.

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Allogeneic transplantation of hematopoietic stem cells (HSC) in combination with T cells has a curative potential for hematopoietic malignancies through graft-versus-leukemia (GVL) effects, but is often compromised by the notorious side effect of graft-versus-host disease (GVHD) resulting from alloreactivity of the donor T cells. Here, we tested if temporary immunoisolation achieved by conformally encapsulating the donor T cells within a biocompatible and biodegradable porous film (∼450 nm in thickness) of chitosan and alginate could attenuate GVHD without compromising GVL. The nanoencapsulation was found not to affect the phenotype of T cells in vitro in terms of size, viability, proliferation, cytokine secretion, and cytotoxicity against tumor cells. Moreover, the porous nature of the nanoscale film allowed the encapsulated T cells to communicate with their environment, as evidenced by their intact capability of binding to antibodies. Lethally irradiated mice transplanted with bone marrow cells (BMCs) and the conformally encapsulated allogeneic T cells exhibited significantly improved survival and reduced GVHD together with minimal liver damage and enhanced engraftment of donor BMCs, compared to the transplantation of BMCs and non-encapsulated allogeneic T cells. Moreover, the conformal nanoencapsulation did not compromise the GVL effect of the donor T cells. These data show that conformal nanoencapsulation of T cells within biocompatible and biodegradable nanoscale porous materials is a potentially safe and effective approach to improve allogeneic HSC transplantation for treating hematological malignancies and possibly other diseases.