Reduction of early graft loss after intraportal porcine islet transplantation in monkeys.

BACKGROUND: Pig islets constitute a possible resolution to the shortage of human islets for transplantation. After intraportal infusion of porcine islets in primates, many islets are lost through what has been termed the instant blood-mediated inflammatory reaction (IBMIR). We report on our experience with IBMIR. METHODS: Ten monkeys underwent intraportal porcine islet transplantation. Immunosuppressive therapy was with conventional agents (n=3) or based on costimulation blockade (n=7). Treatment specific for IBMIR was administered in eight monkeys; two additional monkeys received no such therapy (group 1). Cobra venom factor completely inhibited complement activity in four (group 2) and dextran sulfate provided anticoagulation in four (group 3). Islet graft function was monitored by following blood glucose, insulin requirement, and porcine C-peptide values. RESULTS: In monkeys that received neither cobra venom factor nor dextran sulfate (group 1), there was rapid destruction of islets indicated by severe hypoglycemia and the need for dextrose infusion; C-peptide levels were initially low and further reduction occurred within the first five days. In both groups 2 and 3, there was significantly less destruction of islets and some reversal of diabetes. However, when 40,000 IEQ/kg were infused, normoglycemia was lost within five days, but when 80,000 IEQ/kg were infused in one case, normoglycemia was more persistent. We observed that even when C-peptide levels were in the normal range for healthy nondiabetic pigs, these were not sufficient to maintain normoglycemia in the monkeys. CONCLUSIONS: Although pretransplantation complement depletion or anticoagulation reduces porcine islet xenograft loss significantly, neither alone is sufficient to prevent IBMIR.

Induction of diabetes in cynomolgus monkeys with high-dose streptozotocin: adverse effects and early responses.

OBJECTIVES: Streptozotocin (STZ) has been widely used to induce diabetes in nonhuman primates, although it has been found difficult to achieve complete diabetes without serious adverse effects. We have investigated different types and dosages of STZ to find a way to safely induce complete diabetes in cynomolgus monkeys. METHODS: After adequate hydration, 10 monkeys received STZ. Five monkeys received conventional STZ (Sigma) at a dosage of 1250 mg/m ("high dose"; n = 4) or 60 mg/kg ("low dose"; n = 1; Group 1). Five monkeys received Zanosar STZ (Sicor Pharmaceuticals, Irvine, CA) at 150 mg/kg (high dose; n = 5; Group 2). RESULTS: High-dose Group 1 monkeys became completely diabetic (n = 4), but a protein-losing nephropathy was observed in 3 of the 4 monkeys. The monkey that received 60 mg/kg STZ failed to become fully diabetic (C-peptide, > 1.86 ng/mL). Group 2 (high-dose Zanosar-treated) monkeys became completely diabetic but with no apparent adverse effects. A triphasic blood glucose response to STZ was documented in all the high-dose STZ-treated monkeys. Low-dose STZ failed to result in a triphasic response. CONCLUSIONS: (1) High-dose Zanosar STZ induced diabetes safely in cynomolgus monkeys without adverse effects. (2) A triphasic blood glucose response suggested the complete induction of diabetes.

Pancreas transplantation under alemtuzumab (Campath-1H) and tacrolimus: Correlation between low T-cell responses and infection.

BACKGROUND: Alemtuzumab induction and tacrolimus-based immunosuppression has been effective in pancreas transplantation. Despite the encouraging results of this minimalistic approach to immunosuppression, infection still remains a significant cause of morbidity. The Cylex ImmuKnow [corrected] assay was used in this study to compare pancreas recipient clinical states (stable, rejection, infection) with T cell responses. METHODS: Blood samples were taken from pancreas recipients pretransplant and at approximately three-month intervals posttransplant for analysis of T cell responses. When possible, T cell responses were also quantified during changes in clinical status (infection or rejection). RESULTS: A range between 100-300 ng/ml adenosine triphosphate (ATP) was found in stable patients (mean 194+/-123, n = 51) with good graft function and no infection or rejection. A low T cell response was highly correlated with infectious states. The fourteen patients with infections/posttransplant lymphoproliferative disease had a mean ATP of 48 ng/ml. Risk hazard analysis showed that patients with ATP levels <100 ng/ml were four to seven times more susceptible to infection compared to stable patients. Four patients with rejection showed a T cell response of 550 ng/ml ATP, which was statistically significant compared to stable patients, although the sampling numbers (9) were too small to be conclusive. CONCLUSION: The Cylex ImmuKnow [corrected] assay is a valuable tool to more precisely modulate immunosuppression in pancreas transplant patients. In particular, the assay is extremely useful in detecting overly immunosuppressed patients vulnerable to infections.