Clinical implications of immune reconstitution following hematopoietic stem cell transplantation

Comparison of Immune Reconstitution After Allogeneic Versus Autologous Stem Cell Transplantation in 182 Pediatric Recipients

Hematopoietic stem cell transplantation (HSCT) is a life-saving procedure for children with a variety of malignant and nonmalignant conditions. However, even if immune reconstitution after HSCT has been studied extensively, until now, data on the comparison of immune reconstitution after autologous versus allogeneic HSCT are scarce, but might provide important clinical implications. We examined immune reconstitution (T cells, B cells, and NK cells) at defined timepoints in 147 children who received 182 HSCTs. Differences in the time course of immune reconstitution were analyzed in autologous versus allogeneic HSCT. We identified a quicker immune reconstitution in the T-cell compartment, especially in the CD4 and naive subset after autologous HSCT, whereas recipients of allogeneic transplants showed a higher TCRgd proportion. B-cell reconstitution showed a delayed immune reconstitution after allogeneic HSCT in the first 2 years after HSCT. However, a reconstitution of all lymphocyte subsets after HSCT could be achieved in all patients. Children undergoing an HSCT show a different pattern of immune reconstitution in the allogeneic and autologous setting. This might influence the outcome and should affect the clinical handling of infectious prophylaxis and revaccinations.

FOXN1 recombinant protein enhances T-cell regeneration after hematopoietic stem cell transplantation in mice

A prolonged period of T-cell recovery is the major challenge in hematopoietic stem cell transplantation (HSCT). Thymic epithelial cells (TECs) are the major component of the thymic microenvironment for T-cell generation. However, TECs undergo degeneration over time. FOXN1 plays a critical role in TEC development and is required to maintain adult TECs for thymopoiesis. To investigate the potential application of FOXN1, we have cloned and expressed recombinant FOXN1 protein (rFOXN1) that was fused with cell-penetrating peptides. We show here that the rFOXN1 protein can translocate from the cell surface into the cytoplasm and nucleus. Administration of rFOXN1 into both congenic and allogeneic HSCT recipient mice increased the number of TECs, resulting in enhanced thymopoiesis that led to an increased number of functional T cells in the periphery. The increased number of TECs is due to the enhanced survival and proliferation of TECs. Our results suggest that rFOXN1 has the potential to be used in enhancing T-cell regeneration in patients following HSCT.

Recombinant IL-7/HGFβ hybrid cytokine enhances T cell recovery in mice following allogeneic bone marrow transplantation

T cell immunodeficiency is a major complication of bone marrow (BM) transplantation (BMT). Therefore, approaches to enhance T cell reconstitution after BMT are required. We have purified a hybrid cytokine, consisting of IL-7 and the β-chain of hepatocyte growth factor (HGFβ) (IL-7/HGFβ), from a unique long-term BM culture system. We have cloned and expressed the IL-7/HGFβ gene in which the IL-7 and HGFβ genes are connected by a flexible linker to generate rIL-7/HGFβ protein. Here, we show that rIL-7/HGFβ treatment enhances thymopoiesis after allogeneic BMT. Although rIL-7 treatment also enhances the number of thymocytes, rIL-7/HGFβ hybrid cytokine was more effective than was rIL-7 and the mechanisms by which rIL-7 and rIL-7/HGFβ increase the numbers of thymocytes are different. rIL-7 enhances the survival of double negative (DN), CD4 and CD8 single positive (SP) thymocytes. In contrast, rIL-7/HGFβ enhances the proliferation of the DN, SP thymocytes, as well as the survival of CD4 and CD8 double positive (DP) thymocytes. rIL-7/HGFβ treatment also increases the numbers of early thymocyte progenitors (ETPs) and thymic epithelial cells (TECs). The enhanced thymic reconstitution in the rIL-7/HGFβ-treated allogeneic BMT recipients results in increased number and functional activities of peripheral T cells. Graft-versus-host-disease (GVHD) is not induced in the rIL-7/HGFβ-treated BMT mice. Therefore, rIL-7/HGFβ may offer a new tool for the prevention and/or treatment of T cell immunodeficiency following BMT.