Adenovirus-Mediated Expression of Fas Ligand Induces Hepatic Apoptosis after Systemic Administration and Apoptosis ofEx Vivo-Infected Pancreatic Islet Allografts and Isografts

Abstract

Fas ligand (FasL) mediates apoptosis of Fas-bearing cells and is expressed on a limited number of tissues, predominantly activated T lymphocytes. We describe the construction and biological activity of a replication-deficient type-5 adenovirus encoding murine FasL under the control of the cytomegalovirus (CMV) promoter (adCMV-FasL). In vitro, Jurkat cells undergo apoptosis when co-incubated with adCMV-FasL-infected COS cells. Systemic administration of adCMV-FasL to Wistar rats or DBA/2J mice results in widespread hepatic apoptosis and death in a dose-dependent manner within 72 hr, an effect not seen in lpr mice, or animals administered equivalent doses of adCMV-βgal. Murine pancreatic islets also undergo apoptosis when infected ex vivo with adCMV-FasL, resulting in uniform primary nonfunction when transplanted into syngeneic or allogeneic diabetic recipients. These results indicate that adCMV-FasL is a potentially useful tool to study Fas/FasL biology. Expression of Fas ligand (FasL) has recently been associated with immune privilege, and has been shown to prolong pancreatic islet allograft survival when expressed on co-transplanted syngeneic myoblasts. To explore the possibility of using Fas-mediated apoptosis as a tool to destroy activated T cells in an organ transplant setting, we have generated a replication-deficient type-5 adenovirus encoding murine FasL under the control of the cytomegalovirus (CMV) promoter (adCMV-FasL). In this paper, we demonstrate that adCMV-FasL is a potent inducer of apoptosis in vitro and in vivo. Furthermore, ex vivo infection of pancreatic islet isografts and allografts with adCMV-FasL resulted in widespread apoptosis of the islets and dramatically reduced survival in a murine pancreatic islet transplant model. These data suggest that adCMV-FasL may be a useful tool to further study Fas/FasL biology, but its ability to induce apoptosis of transduced grafts effectively is detrimental in the transplant setting.