Ex Vivo Expanded Human Non-Cytotoxic CD8+CD45RClow/\textminus Tregs Efficiently Delay Skin Graft Rejection and GVHD in Humanized Mice

International audienc

Ex Vivo Expanded Human Non-Cytotoxic CD8+CD45RClow/\textminus Tregs Efficiently Delay Skin Graft Rejection and GVHD in Humanized Mice

International audienc

Anti-CD28 Antibody and Belatacept Exert Differential Effects on Mechanisms of Renal Allograft Rejection

International audienceBelatacept is a biologic that targets CD80/86 and prevents its interaction with CD28 and its alternative ligand, cytotoxic T lymphocyte antigen 4 (CTLA-4). Clinical experience in kidney transplantation has revealed a high incidence of rejection with belatacept, especially with intensive regimens, suggesting that blocking CTLA-4 is deleterious. We performed a head to head assessment of FR104 (n=5), a selective pegylated Fab9 antibody fragment antagonist of CD28 that does not block the CTLA-4 pathway, and belatacept (n=5) in kidney allotransplantation in baboons. The biologics were supplemented with an initial 1-month treatment with low-dose tacrolimus. In cases of acute rejection, animals also received steroids. In the belatacept group, four of five recipients developed severe, steroid-resistant acute cellular rejection, whereas FR104-treated animals did not. Assessment of regulatory T cell-specific demethylated region methylation status in 1-month biopsy samples revealed a nonsignificant trend for higher regulatory T cell frequencies in FR104-treated animals. Transcriptional analysis did not reveal significant differences in Th17 cytokines but did reveal higher levels of IL-21, the main cytokine secreted by CD4 T follicular helper (Tfh) cells, in belatacept-treated animals. In vitro, FR104 controlled the proliferative response of human preex-isting Tfh cells more efficiently than belatacept. In mice, selective CD28 blockade also controlled Tfh memory cell responses to KLH stimulation more efficiently than CD80/86 blockade. Our data reveal that selective CD28 blockade and belatacept exert different effects on mechanisms of renal allograft rejection, particularly at the level of Tfh cell stimulation

Survival and Differentiation of Adenovirus-Generated Induced Pluripotent Stem Cells Transplanted into the Rat Striatum

International audienceInduced pluripotent stem cells (iPSCs) offer certain advantages over embryonic stem cells in cell replacement therapy for a variety of neurological disorders. However, reliable procedures, whereby transplanted iPSCs can survive and differentiate into functional neurons, without forming tumors, have yet to be devised. Currently, retroviral or lentiviral reprogramming methods are often used to reprogram somatic cells. Although the use of these viruses has proven to be effective, formation of tumors often results following in vivo transplantation, possibly due to the integration of the reprogramming genes. The goal of the current study was to develop a new approach, using an adenovirus for reprogramming cells, characterize the iPSCs in vitro, and test their safety, survivability, and ability to differentiate into region-appropriate neurons following transplantation into the rat brain. To this end, iPSCs were derived from bone marrow-derived mesenchymal stem cells and tail-tip fibro-blasts using a single cassette lentivirus or a combination of adenoviruses. The reprogramming efficiency and levels of pluripotency were compared using immunocytochemistry, flow cytometry, and real-time polymerase chain reaction. Our data indicate that adenovirus-generated iPSCs from tail-tip fibroblasts are as efficient as the method we used for lentiviral reprogramming. All generated iPSCs were also capable of differentiating into neuronal-like cells in vitro. To test the in vivo survivability and the ability to differentiate into region-specific neurons in the absence of tumor formation, 400,000 of the iPSCs derived from tail-tip fibroblasts that were transfected with the adenovirus pair were transplanted into the striatum of adult, immune-competent rats. We observed that these iPSCs produced region-specific neuronal phenotypes, in the absence of tumor formation, at 90 days posttransplantation. These results suggest that adenovirus-generated iPSCs may provide a safe and viable means for neuronal replacement therapies

Human Tolerogenic Dendritic Cells Regulate Immune Responses through Lactate Synthesis

Cell therapy is a promising strategy for treating patients suffering from autoimmune or inflammatory diseases or receiving a transplant. Based on our preclinical studies, we have generated human autologous tolerogenic dendritic cells (ATDCs), which are being tested in a first-in-man clinical trial in kidney transplant recipients. Here, we report that ATDCs represent a unique subset of monocyte-derived cells based on phenotypic, transcriptomic, and metabolic analyses. ATDCs are characterized by their suppression of T cell proliferation and their expansion of Tregs through secreted factors. ATDCs produce high levels of lactate that shape T cell responses toward tolerance. Indeed, T cells take up ATDC-secreted lactate, leading to a decrease of their glycolysis. In vivo, ATDCs promote elevated levels of circulating lactate and delay graft-versus-host disease by reducing T cell proliferative capacity. The suppression of T cell immunity through lactate production by ATDCs is a novel mechanism that distinguishes ATDCs from other cell-based immunotherapies