Long-term survival and function of intrahepatic islet allografts in rhesus monkeys treated with humanized anti-CD154

Abstract

Reported effects of anti-CD154 treatment on autoimmunity, alloreactivity, and inflammatory events mediated by macrophages and endothelial cells indicated that it might be an ideal agent for the prevention of intrahepatic islet allograft failure. This hypothesis was tested in MHC-mismatched rhesus monkeys. Transplantation of an adequate number of viable islets resulted in engraftment and insulin independence in six of six recipients treated with anti-CD154 (hu5c8) induction plus monthly maintenance therapy (post-operative day >125, >246, >266, >405, >419, >476). Anti-CD154 (hu5c8) displayed no inhibitory effect on islet cell function. For monkeys followed for >100 days, continued improvement in graft function, as determined by first phase insulin release in response to intravenous glucose, was observed after the first 100 days post-transplant. No evidence of toxicity or infectious complications has been observed. All recipients treated with anti-CD154 became specifically nonresponsive to donor cells in mixed lymphocyte reactions. Furthermore, three monkeys are now off therapy (>113, >67, and >54 days off anti-CD154), with continued insulin independence and donor-specific mixed lymphocyte reaction hyporeactivity. In striking contrast to all previously tested strategies, transplantation of an adequate number of functional islets under the cover of anti-CD154 (hu5c8) monotherapy consistently allows for allogeneic islet engraftment and long-term insulin independence in this highly relevant preclinical model.

Figure 1

Fasting (Left) and post-prandial (Right) blood glucose values for the two longest surviving recipients of allogeneic islets. RH-01 occasionally received a dose of 0.5 units of insulin during the first 2 weeks post-transplant to maintain PPG < 200 mg/dl but was subsequently insulin independent.

Figure 2

Fasting and PPG values for a nontreated, control recipient of allogeneic islets. This monkey required insulin beginning on POD 6 and was maintained on >4 units/kg/day. Note the variable nature of the blood glucose values, demonstrating that, in the absence of islet function, it was difficult to maintain normal fasting blood glucose levels, despite intensive insulin therapy (three insulin injections per day). C-peptide was positive on POD 3 but negative on POD 10, thus verifying rejection of the islet allograft.

Figure 3

Insulin release in response to intravenous glucose tolerance testing of RH-01. Ketamine doses (mg/kg) were as follows: 28.6 pre-transplant, 31.7 on POD 42, 23.3 on POD 99, 22.8 on POD155, 20.5 on POD 227, 18.2 on POD 296, and 15.2 on POD 367.

Figure 4

Insulin release in response to intravenous glucose tolerance testing of a recipient of two islet transplants from unrelated donors. Note the low insulin production subsequent to the first transplant. FPIR is clearly enhanced subsequent to the second transplant and has been maintained through POD 363.