Expression of the bcl-2 Gene from a Defective HSV-1 Amplicon Vector Protects Pancreatic β -Cells from Apoptosis

Abstract

It has been suggested that the mechanism of pancreatic β-cell death in autoimmune diabetes mellitus and in immunoisolated transplantation devices involves cytokine-induced apoptosis. To explore the feasibility of a gene transfer strategy to protect β-cells, we evaluated the use of replication defective HSV-1 amplicon vectors as gene transfer vehicles. Post-mitotic murine and human β-cells were efficiently transduced by a herpes simplex virus (HSV) vector that expresses the reporting gene Escherichia coli lacZ under the transcriptional control of a HSV promoter (HSVlac) both as islets and as single cells. Insulin secretion, a marker of β-cell function, was unaffected by HSVlac transduction of a β-cell line. A HSV amplicon vector that expressed bcl-2 (HSVbcl2) in β-cells was constructed, and its effects on cytokine-mediated apoptosis in both a β-cell line and primary murine β-cells assessed by measuring internucleosomal fragmentation. β-Cell apoptosis was blocked by transduction with HSVbcl2 but not HSVlac. The prevention of cytokine-induced apoptosis in β-cells by bcl-2 expression has the potential both to ameliorate primary autoimmune β-cell destruction as type I diabetes develops, and to prevent the destruction of transplanted β-cells inside immunoisolation devices.

Overview summary

Apoptotic cell death is implicated in immune destruction of pancreatic β-cells mediated by cytokines. To develop a gene therapeutic strategy to ameliorate cell death, we used replication-defective HSV amplicon vectors to transfer genes into β-cell lines and primary murine and human β-cells. Gene transfer efficiency, monitored by the expression of the lacZ gene, into primary β-cells of both species was highly efficient. Gene transfer and expression did not alter stimulated and regulated insulin release. Finally, transfer of the anti-apoptotic gene bcl-2 significantly attenuated cytokine-mediated cell death. These studies suggest the feasibility of gene transfer approaches to block immune associated pancreatic β-cell apoptosis.