Human pancreatic islets transfected to produce an inhibitor of TNF are protected against destruction by human leukocytes

The objective of this study was to determine whether transfection of human islets with an adenovirus construct encoding an inhibitor of tumor necrosis factor (TNFi) was effective at limiting damage to beta cells induced by hu man peripheral blood leukocytes (huPBL). Human islets transfected with TNFi or control islets were transplanted under the kidney capsule of NOD-scid m ice. After a 15-day engraftment period, half of the mice received injection s of activated huPBL and half received buffer injections. Islet graft funct ion was assessed by two different methods, both of which use a species-spec ific radioimmunoassay to determine human insulin. In some mice, insulin pro duction following intraperitoneal glucose injection was determined in serum . In other mice, tr,tal graft insulin content was determined by acid ethano l extraction. Histochemical stains were performed on some kidneys at the te rmination of the experiment to evaluate graft presence, transgene expressio n, and huPBL infiltration. In huPBL injected mice, graft performance was ma intained in mice whose grafts were transfected with TNFi but declined subst antially in control groups with sham transfected or beta -galactosidase tra nsfected islet grafts. Similar results were obtained using either glucose-s timulated insulin release or graft insulin content as a measure of graft su rvival. There was no significant difference in graft function between contr ol groups receiving buffer injections, regardless of whether the islets had been transfected. Human leukocytes were found in all huPBL groups regardle ss of islet transfection status. We conclude that transfection of human isl ets with an adenovirus encoding TNFi protects beta cells fi om destruction induced by human leukocytes. The local production of TNFi does not prevent graft infiltration by leukocytes, only the destruction of grafts by the inf iltrating leukocytes. These results raise the possibility that local expres sion of an inhibitor of the proinflammatory cytokine TNF-alpha may also pre vent graft failure in clinical islet transplantation.