Therapeutic potency of IL2-caspase 3 targeted treatment in a murine experimental model of inflammatory bowel disease

Abstract

IL2-caspase 3 chimeric protein may provide a novel approach to the therapy of human IBD, and a possible suggested treatment for other pathological conditions that involve uncontrolled expansion of activated T cells.

Targeting of IL-2 receptor with a caspase fusion protein disrupts autoimmunity in prediabetic and diabetic NOD mice

“…First, direct introduction of toxic moieties through the IL-2/ IL-2 receptor complex overcomes the relative resistance of NOD lymphocytes to apoptosis (as compared with wildtype mice) [49,50], and the decreased susceptibility of diabetogenic cells to Treg-mediated inhibition [33,51,52]. Inasmuch as B cell lymphoma protein 2 (BCL-2) is associated with the survival of islet-infiltrating T cells [18], IL2-cas was found to reduce the BCL-2/apoptosis regulator BAX ratio in a model of toxic colitis [25], suggesting that the fusion protein sensitises pathogenic lymphocytes to apoptosis. Thus, fusion proteins comprising IL-2 and toxic moieties are of therapeutic value irrespective of concomitant depletion of CD25 + Treg in NOD mice and models of inflammatory colitis [22,23], which are associated with aberrant sensitivity of the pathogenic cells to apoptosis.…”

“…The glucose tolerance test was performed by intraperitoneal administration of 2 g glucose and measurement of blood glucose at 30, 60 and 120 min. IL2-cas is composed of full-frame IL-2 conjugated head to tail to fullframe caspase-3 (without the leading procaspase segment) [23,25]. The sequence was inserted into a PET-28 plasmid under control of the T7 promoter and protein retrieved from the inclusion bodies of Escherichia coli was purified under denatured conditions and refolded to a biologically active molecule.…”

“…On the one hand, an agent that mediates targeted killing of CD25 + T cells is expected to precipitate early onset of diabetes similar to cyclophosphamide [4][5][6] and anti-CD25 antibodies [27,28]. On the other hand, decreased activity of reactive cells suggests that the fusion protein might ameliorate the course of insulitis as observed with diphtheria toxin in NOD mice [20] and IL2-cas in inflammatory colitis [22,23,25]. Our female NOD colony was monitored over an extended period of time to determine onset of diabetes at age 14 weeks, with an overall incidence of 83% diabetic mice at the age of 30 weeks (n=312).…”

“…Administration of one dose of cyclophosphamide (Cy) has been long recognised to induce diabetes in NOD mice. While causing transient lymphodepletion [4,5], this agent is particularly toxic to naturally occurring Treg that express cluster of differentiation (CD) 25 and Forkhead box P3 (FOXP3), causing both their depletion and functional inactivation in the pancreas and its draining lymph nodes [4]. Subsequent administration of agents that stimulate immuno-haematopoietic reconstitution partially reverse the toxic effects of Cy by increasing the pool of suppressor cells [6], as does adoptive transfer of Treg [4].…”

“…Homeostatic expansion of effector cells outpaces the recovery of Treg under conditions of lymphopenia [24], creating a transient period of instability with predominant autoimmune effector activity [9,10]. In variance, a fusion protein composed of IL-2 and activated caspase-3 (IL2-cas) provided the same defence against inflammatory colitis without causing lymphopenia [23,25]. In this study we evaluated the effect of IL2-cas in NOD mice, where targeted deletion of cells expressing the IL-2 receptor has two possible outcomes.…”