Regulatory T cells engineered with a novel insulin-specific chimeric antigen receptor as a candidate immunotherapy for type 1 diabetes.

Adoptive immunotherapy with ex vivo expanded, polyspecific regulatory T cells (Tregs) is a promising treatment for graft-versus-host disease. Animal transplantation models used by us and others have demonstrated that the adoptive transfer of allospecific Tregs offers greater protection from graft rejection than that of polyclonal Tregs. This finding is in contrast to those of autoimmune models, where adoptive transfer of polyspecific Tregs had very limited effects, while antigen-specific Tregs were promising. However, antigen-specific Tregs in autoimmunity cannot be isolated in sufficient numbers. Chimeric antigen receptors (CARs) can modify T cells and redirect their specificity toward needed antigens and are currently clinically used in leukemia patients. A major benefit of CAR technology is its "off-the-shelf" usability in a translational setting in contrast to major histocompatibility complex (MHC)-restricted T cell receptors. We used CAR technology to redirect T cell specificity toward insulin and redirect T effector cells (Teffs) to Tregs by Foxp3 transduction. Our data demonstrate that our converted, insulin-specific CAR Tregs (cTregs) were functional stable, suppressive and long-lived in vivo. This is a proof of concept for both redirection of T cell specificity and conversion of Teffs to cTregs.

Early cell death induced by Clostridium difficile TcdB: Uptake and Rac1-glucosylation kinetics are decisive for cell fate.

Toxin A and Toxin B (TcdA/TcdB) are large glucosyltransferases produced by Clostridium difficile. TcdB but not TcdA induces reactive oxygen species-mediated early cell death (ECD) when applied at high concentrations. We found that nonglucosylated Rac1 is essential for induction of ECD since inhibition of Rac1 impedes this effect. ECD only occurs when TcdB is rapidly endocytosed. This was shown by generation of chimeras using the trunk of TcdB from a hypervirulent strain. TcdB from hypervirulent strain has been described to translocate from endosomes at higher pH values and thus, meaning faster than reference type TcdB. Accordingly, intracellular delivery of the glucosyltransferase domain of reference TcdB by the trunk of TcdB from hypervirulent strain increased ECD. Furthermore, proton transporters such as sodium/proton exchanger (NHE) or the ClC-5 anion/proton exchanger, both of which contribute to endosomal acidification, also affected cytotoxic potency of TcdB: Specific inhibition of NHE reduced cytotoxicity, whereas transfection of cells with the endosomal anion/proton exchanger ClC-5 increased cytotoxicity of TcdB. Our data suggest that both the uptake rate of TcdB into the cytosol and the status of nonglucosylated Rac1 are key determinants that are decisive for whether ECD or delayed apoptosis is triggered.

Umbilical cord as a long-term source of activatable mesenchymal stromal cells for immunomodulation.

BACKGROUND: Mesenchymal stromal cells (MSCs) are used in over 800 clinical trials mainly due to their immune inhibitory activity. Umbilical cord (UC), the second leading source of clinically used MSCs, is usually cut in small tissue pieces. Subsequent cultivation leads to a continuous outgrowth of MSC explant monolayers (MSC-EMs) for months. Currently, the first MSC-EM culture takes approximately 2 weeks to grow out, which is then expanded and applied to patients. The initiating tissue pieces are then discarded. However, when UC pieces are transferred to new culture dishes, MSC-EMs continue to grow out. In case the functional integrity of these cells is maintained, later induced cultures could also be expanded and used for cell therapy. This would drastically increase the number of available cells for each patient. To test the functionality of MSC-EMs from early and late induction time points, we compared the first cultures to those initiated after 2 months by investigating their clonality and immunomodulatory capacity. METHODS: We analyzed the clonal composition of MSC-EM cultures by umbilical cord piece transduction using integrating lentiviral vectors harboring genetic barcodes assessed by high-throughput sequencing. We investigated the transcriptome of these cultures by microarrays. Finally, the secretome was analyzed by multiplexed ELISAs, in vitro assays, and in vivo in mice. RESULTS: DNA barcode analysis showed polyclonal MSC-EMs even after months of induction cycles. A transcriptome and secretome analyses of early and late MSC cultures showed only minor changes over time. However, upon activation with TNF-α and IFN-γ, cells from both induction time points produced a multitude of immunomodulatory cytokines. Interestingly, the later induced MSC-EMs produced higher amounts of cytokines. To test whether the different cytokine levels were in a therapeutically relevant range, we used conditioned medium (CM) in an in vitro MLR and an in vivo killing assay. CM from late induced MSC-EMs was at least as immune inhibitory as CM from early induced MSC-EMs. CONCLUSION: Human umbilical cord maintains a microenvironment for the long-term induction of polyclonal and immune inhibitory active MSCs for months. Thus, our results would offer the possibility to drastically increase the number of therapeutically applicable MSCs for a substantial amount of patients.