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Humanized mice are a powerful tool for the study of human hematopoiesis and immune function in vivo. However, the existing models cannot support robust adaptive immune responses, especially the generation of class-switched, antigen-specific antibody responses. Here we describe a new mouse strain, in which human interleukin 6 (IL-6) gene encoding the cytokine that is important for B- and T-cell differentiation was knocked into its respective mouse locus. The provision of human IL-6 not only enhanced thymopoiesis and periphery T-cell engraftment, but also significantly increased class switched memory B cells and serum immunoglobulin G (IgG). In addition, immunization with ovalbumin (OVA) induced OVA-specific B cells only in human IL-6 knock-in mice. These OVA-specific antibodies displayed the highest frequency of somatic mutation, further suggesting that human IL-6 is important for efficient B-cell activation and selection. We conclude that human IL-6 knock-in mice represent a novel and improved model for human adaptive immunity without relying on complex surgery to transplant human fetal thymus and liver. These mice can therefore be used to exploit or evaluate immunization regimes that would be unethical or untenable in humans., (© 2017 by The American Society of Hematology.)

Lentiviral vectors (LVs)-mediated gene transfer is an efficient method for ex vivo and in vivo gene therapy. Actually, LVs have been used in several clinical trials and therapeutic correction was reached in affected patients. However, in order to be effective gene therapy needs to be efficient without detrimental effects for target cells. Successful cell transduction by LVs can be hampered by several factors such as the activation of innate immune sensors during cell transduction and different restriction factors (RFs) inhibiting viral replication inside the cells. Therefore, a better knowledge of host-vector interactions is important for the development of more efficient gene therapy strategies improving the LVs platform by limiting harmful responses., (Copyright © 2016. Published by Elsevier B.V.)

Haploidentical hematopoietic stem cell transplantation (haplo-HSCT) is a treatment option for patients with hematopoietic malignancies that is hampered by treatment-related morbidity and mortality, in part the result of opportunistic infections, a direct consequence of delayed T-cell recovery. Thymic output can be improved by facilitation of thymic immigration, known to require precommitment of CD34(+) cells. We demonstrate that Delta-like ligand-mediated predifferentiation of mobilized CD34(+) cells in vitro results in a population of thymocyte-like cells arrested at a T/natural killer (NK)-cell progenitor stage. On intrahepatic transfer to Rag2(-/-)gamma(c)(-/-) mice, these cells selectively home to the thymus and differentiate toward surface T-cell receptor-alphabeta(+) mature T cells considerably faster than animals transplanted with noncultured CD34(+) cells. This finding creates the opportunity to develop an early T-cell reconstitution therapy to combine with HSCT.

Dendritic cells (DCs) are considered critical for the induction of graft-versus-host disease (GVHD) after bone marrow transplantation (BMT). In addition to their priming function, dendritic cells have been shown to induce organ-tropism through induction of specific homing molecules on T cells. Using adoptive transfer of CFSE-labeled cells, we first demonstrated that alloreactive T cells differentially up-regulate specific homing molecules in vivo. Host-type dendritic cells from the GVHD target organs liver and spleen or skin- and gut-draining lymph nodes effectively primed naive allogeneic T cells in vitro with the exception of liver-derived dendritic cells, which showed less stimulatory capacity. Gut-derived dendritic cells induced alloreactive donor T cells with a gut-homing phenotype that caused increased GVHD mortality and morbidity compared with T cells stimulated with dendritic cells from spleen, liver, and peripheral lymph nodes in an MHC-mismatched murine BMT model. However, in vivo analysis demonstrated that the in vitro imprinting of homing molecules on alloreactive T cells was only transient. In conclusion, organ-derived dendritic cells can efficiently induce specific homing molecules on alloreactive T cells. A gut-homing phenotype correlates with increased GVHD mortality and morbidity after murine BMT, underlining the importance of the gut in the pathophysiology of GVHD.

Tumor necrosis factor (TNF) plays an important role in graft-versus-host disease (GVHD) and graft-versus-tumor (GVT) activity after allogeneic bone marrow transplantation (allo-BMT). TNF can be expressed in a membrane-bound form (memTNF) and as a soluble (solTNF) molecule after being cleaved by the TNF-alpha converting enzyme (TACE). To study the contribution of donor T-cell-derived memTNF versus solTNF in GVHD and GVT, we used mice containing a noncleavable allele in place of endogenous TNF (memTNF(Delta/Delta)) as donors in murine BMT models. Recipients of memTNF T cells developed significantly less GVHD than recipients of wild-type (wt) T cells. In contrast, GVT activity mediated by memTNF T cells remained intact, and alloreactive memTNF T cells showed no defects in proliferation, activation, and cytotoxicity. These data suggest that suppressing the secretion of solTNF by donor T cells significantly decreases GVHD without impairing GVT activity.