Thrombalexins: Cell-Localized Inhibition of Thrombin and its Effects in a Model of HighRisk Renal Transplantation

Allograft transplantation into sensitised recipients with anti-donor antibodies results in accelerated antibody-mediated rejection (AMR), complement activation and graft thrombosis. We have developed a membrane-localizing technology of wide applicability that enables therapeutic agents including anticoagulants to bind to cell surfaces and protect the donor endothelium. We describe here how this technology has been applied to thrombin inhibitors to generate a novel class of drugs termed thrombalexins (TLN). Using a rat model of hyperacute rejection we have investigated the potential of one such inhibitor (TLN-1) to prevent acute antibody-mediated thrombosis in the donor organ. TLN-1 alone was able to reduce intragraft thrombosis and significantly delay rejection. The results confirm a pivotal role for thrombin in AMR in vivo. This approach targets donor organs rather than the recipient and is intended to be directly translatable to clinical use

Thrombalexins: Cell-Localized Inhibition of Thrombin and its Effects in a Model of HighRisk Renal Transplantation

Allograft transplantation into sensitised recipients with anti-donor antibodies results in accelerated antibody-mediated rejection (AMR), complement activation and graft thrombosis. We have developed a membrane-localizing technology of wide applicability that enables therapeutic agents including anticoagulants to bind to cell surfaces and protect the donor endothelium. We describe here how this technology has been applied to thrombin inhibitors to generate a novel class of drugs termed thrombalexins (TLN). Using a rat model of hyperacute rejection we have investigated the potential of one such inhibitor (TLN-1) to prevent acute antibody-mediated thrombosis in the donor organ. TLN-1 alone was able to reduce intragraft thrombosis and significantly delay rejection. The results confirm a pivotal role for thrombin in AMR in vivo. This approach targets donor organs rather than the recipient and is intended to be directly translatable to clinical use

Homeostatic proliferation of lymphocytes results in augmented memory-like function and accelerated allograft rejection

Abstract Homeostatic proliferation is a normal physiological process triggered by lymphopenia to maintain a constant level of T cells. It becomes the predominant source of new T cells in adulthood after thymus regression. T cells that have undergone homeostatic proliferation acquire the memory phenotype, cause autoimmune disease, and are resistant to tolerance induction protocols. Transplantation is a rare example in which lymphopenia is deliberately induced for its immunosuppressive effect. However, it is not known whether the homeostatic proliferation that follows will have the opposite effect and accelerate rejection. We show that T cells that have undergone homeostatic proliferation acquire a memory phenotype, spontaneously skews toward the Th1 phenotype, even in the absence of antigenic stimulus. Interestingly, in contrast, the percentage of Foxp3+ regulatory T cells increased by 28-fold following homeostatic proliferation. Using a mouse life-sustaining kidney transplant model, we showed that T cells that have gone through homeostatic proliferation in lymphopenic hosts transformed chronic rejection to acute rejection of a single MHC class II-mismatched kidney allograft. T cells that have undergone homeostatic proliferation consistently cause reliable rejection even when bona fide memory T cells cannot. These functional changes are long-lasting and not restricted to the acute phase of homeostatic proliferation. Our findings have important implications for tolerance induction or graft-prolonging protocols involving leukocyte depletion such as irradiation bone marrow chimera, T cell-depleting Abs, and lymphopenia induced by infections such as CMV and HIV.</jats:p

Ex vivo delivery of Mirococept: A dose-finding study in pig kidney after showing a low dose is insufficient to reduce delayed graft function in human kidney

The complement system plays a pivotal role in the pathogenesis of ischemia\u2013reperfusion injury in solid organ transplantation. Mirococept is a potent membrane-localizing complement inhibitor that can be administered ex vivo to the donor kidney prior to transplantation. To evaluate the efficacy of Mirococept in reducing delayed graft function (DGF) in deceased donor renal transplantation, we undertook the efficacy of mirococept (APT070) for preventing ischaemia-reperfusion injury in the kidney allograft (EMPIRIKAL) trial (ISRCTN49958194). A dose range of 5-25\ua0mg would be tested, starting with 10\ua0mg in cohort 1. No significant difference between Mirococept at 10\ua0mg and control was detected; hence the study was stopped to enable a further dose saturation study in a porcine kidney model. The optimal dose of Mirococept in pig kidney was 80\ua0mg. This dose did not induce any additional histological damage compared to controls or after a subsequent 3\ua0hours of normothermic machine perfusion. The amount of unbound Mirococept postperfusion was found to be within the systemic dose range considered safe in the Phase I trial. The ex vivo administration of Mirococept is a safe and feasible approach to treat DGF in deceased donor kidney transplantation. The porcine kidney study identified an optimal dose of 80\ua0mg (equivalent to 120\ua0mg in human kidney) that provides a basis for further clinical development

Mucosal Tolerance Induced by an Immunodominant Peptide from Rat α3(IV)NC1 in Established Experimental Autoimmune Glomerulonephritis

Experimental autoimmune glomerulonephritis (EAG), an animal model of Goodpasture’s disease, can be induced in Wistar Kyoto (WKY) rats by immunization with the noncollagenous domain of the α 3 chain of type IV collagen, α3(IV)NC1. Recent studies have identified an immunodominant peptide, pCol (24-38), from the N-terminus of rat α3(IV)NC1; this peptide contains the major B- and T-cell epitopes in EAG and can induce crescentic nephritis. In this study, we investigated the mechanisms of mucosal tolerance in EAG by examining the effects of the nasal administration of this peptide after the onset of disease. A dose-dependent effect was observed: a dose of 300 μg had no effect, a dose of 1000 μg resulted in a moderate reduction in EAG severity, and a dose of 3000 μg produced a marked reduction in EAG severity accompanied by diminished antigen-specific, T-cell proliferative responses. These results demonstrate that mucosal tolerance in EAG can be induced by nasal administration of an immunodominant peptide from the N-terminus of α3(IV)NC1 and should be of value in designing new therapeutic strategies for patients with Goodpasture’s disease and other autoimmune disorders