Expression of the bcl-2 gene from a defective HSV-1 amplicon vector protects pancreatic beta-cells from apoptosis

It has been suggested that the mechanism of pancreatic beta-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 beta-cells, we evaluated the use of replication defective HSV-1 amplicon vectors as gene transfer vehicles. Post-mitotic murine and human beta-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 beta-cell function, was unaffected by HSVlac transduction of a beta-cell line. A HSV amplicon vector that expressed bcl-2 (HSVbcl2) in beta-cells was constructed, and its effects on cytokine-mediated apoptosis in both a beta-cell line and primary murine beta-cells assessed by measuring internucleosomal fragmentation. beta-Cell apoptosis was blocked by transduction with HSVbcl2 but not HSVlac. The prevention of cytokine-induced apoptosis in beta-cells by bcl-2 expression has the potential both to ameliorate primary autoimmune beta-cell destruction as type I diabetes develops, and to prevent the destruction of transplanted beta-cells inside immunoisolation devices.