Berberine Promotes Induction of Immunological Tolerance to an Allograft via Downregulating Memory CD8+ T-Cells Through Altering the Gut Microbiota

Emerging evidence has linked the gut microbiota dysbiosis to transplant rejection while memory T-cells pose a threat to long-term transplant survival. However, it's unclear if the gut microbiome alters the formation and function of alloreactive memory T-cells. Here we studied the effects of berberine, a narrow-spectrum antibiotic that is barely absorbed when orally administered, on the gut microbiota, memory T-cells, and allograft survival. In this study, C57BL/6 mice transplanted with islets or a heart from BALB/c mice were treated orally with berberine. Allograft survival was observed, while spleen, and lymph node T-cells from recipient mice were analyzed using a flow cytometer. High-throughput sequencing and qPCR were performed to analyze the gut microbiota. CD8+ T-cells from recipients were cultured with the bacteria to determine potential T-cell memory cross-reactivity to a specific pathogen. We found that berberine suppressed islet allograft rejection, reduced effector CD8+CD44highCD62Llow and central memory CD8+CD44highCD62Lhigh T-cells (TCM), altered the gut microbiota composition and specifically lowered Bacillus cereus abundance. Further, berberine promoted long-term islet allograft survival induced by conventional costimulatory blockade and induced cardiac allograft tolerance as well. Re-colonization of B. cereus upregulated CD8+ TCM cells and reversed long-term islet allograft survival induced by berberine plus the conventional costimulatory blockade. Finally, alloantigen-experienced memory CD8+ T-cells from transplanted recipients rapidly responded to B. cereus in vitro. Thus, berberine prolonged allograft survival by repressing CD8+ TCM through regulating the gut microbiota. We have provided the first evidence that donor-specific memory T-cell generation is linked to a specific microbe and uncovered a novel mechanism underlying the therapeutic effects of berberine. This study may be implicated for suppressing human transplant rejection since berberine is already used in clinic to treat intestinal infections.

Low Dose IL-2 Combined with Rapamycin Led to an Expansion of CD4+CD25+FOXP3+ Tregs and Prolonged Human Islet-allograft Survival in Humanized Mice

<a>Islet transplantation is an emerging therapy for type 1 diabetes (T1D) and hypoglycaemic unawareness. However, a key challenge for islet transplantation is cellular rejection and the requirement for long-term immunosuppression. In this study we established a diabetic-humanizedNOD-scidIL2Rnull(NSG) mouse model of T cell mediated human islet-allograft rejection and developed a therapeutic regimen of low-dose recombinant human interleukin2(IL-2) combined with low-dose rapamycin to prolong graft survival. NSG-mice that had received renal-subcapsular human islet-allografts and were transfused with 1×107 of human-spleen-mononuclear-cells (hSPMCs), reconstituted human CD45+ cells that were predominantly CD3+ T cells and rejected their grafts with a median survival time of 27 days. IL-2 alone (0.3×106 IU/m2 or 1×106 IU/m2), or rapamycin alone (0.5-1mg/kg) for 3 weeks did not prolong survival. However, the combination of rapamycin with IL-2 for 3 weeks significantly prolonged human islet-allograft survival. Graft survival was associated with expansion of CD4+CD25+FOXP3+ Tregs and enhanced TGF-β production by CD4+ T cells. CD8+ T cells showed reduced IFN-γ production and reduced expression of perforin-1. The combination of IL-2 and rapamycin has the potential to inhibit human islet-allograft rejection by expanding CD4+FOXP3+ Tregs in vivo and supressing effector cell function, and could be the basis of effective tolerance-based regimens.</a>

Low Dose IL-2 Combined with Rapamycin Led to an Expansion of CD4+CD25+FOXP3+ Tregs and Prolonged Human Islet-allograft Survival in Humanized Mice

<a>Islet transplantation is an emerging therapy for type 1 diabetes (T1D) and hypoglycaemic unawareness. However, a key challenge for islet transplantation is cellular rejection and the requirement for long-term immunosuppression. In this study we established a diabetic-humanizedNOD-scidIL2Rnull(NSG) mouse model of T cell mediated human islet-allograft rejection and developed a therapeutic regimen of low-dose recombinant human interleukin2(IL-2) combined with low-dose rapamycin to prolong graft survival. NSG-mice that had received renal-subcapsular human islet-allografts and were transfused with 1×107 of human-spleen-mononuclear-cells (hSPMCs), reconstituted human CD45+ cells that were predominantly CD3+ T cells and rejected their grafts with a median survival time of 27 days. IL-2 alone (0.3×106 IU/m2 or 1×106 IU/m2), or rapamycin alone (0.5-1mg/kg) for 3 weeks did not prolong survival. However, the combination of rapamycin with IL-2 for 3 weeks significantly prolonged human islet-allograft survival. Graft survival was associated with expansion of CD4+CD25+FOXP3+ Tregs and enhanced TGF-β production by CD4+ T cells. CD8+ T cells showed reduced IFN-γ production and reduced expression of perforin-1. The combination of IL-2 and rapamycin has the potential to inhibit human islet-allograft rejection by expanding CD4+FOXP3+ Tregs in vivo and supressing effector cell function, and could be the basis of effective tolerance-based regimens.</a>