Gene transfer of antisense B7.1 attenuates acute rejection against splenic allografts in rats

The Role of Co-stimulatory/Co-inhibitory Signals in Graft-vs.-Host Disease

Allogeneic hematopoietic cell transplantation (allo-HCT) is an effective immunotherapeutic approach for various hematologic and immunologic ailments. Despite the beneficial impact of allo-HCT, its adverse effects cause severe health concerns. After transplantation, recognition of host cells as foreign entities by donor T cells induces graft-vs.-host disease (GVHD). Activation, proliferation and trafficking of donor T cells to target organs and tissues are critical steps in the pathogenesis of GVHD. T cell activation is a synergistic process of T cell receptor (TCR) recognition of major histocompatibility complex (MHC)-anchored antigen and co-stimulatory/co-inhibitory signaling in the presence of cytokines. Most of the currently used therapeutic regimens for GVHD are based on inhibiting the allogeneic T cell response or T-cell depletion (TCD). However, the immunosuppressive drugs and TCD hamper the therapeutic potential of allo-HCT, resulting in attenuated graft-vs.-leukemia (GVL) effect as well as increased vulnerability to infection. In view of the drawback of overbroad immunosuppression, co-stimulatory, and co-inhibitory molecules are plausible targets for selective modulation of T cell activation and function that can improve the effectiveness of allo-HCT. Therefore, this review collates existing knowledge of T cell co-stimulation and co-inhibition with current research that may have the potential to provide novel approaches to cure GVHD without sacrificing the beneficial effects of allo-HCT.

Gene transfer of antisense B7.1 attenuates acute rejection against liver allografts in rats

OBJECTIVE

Blockade of CD80-CD28 costimulatory pathway induces unresponsiveness of T cells to alloantigens and protects allografts against immune rejection. The aim of this study was to investigate whether downregulating the expression of B7.1 (CD80) in the donor livers by antisense B7.1 gene transfer could attenuate the acute immune rejection against liver allografts in rats.

METHODS

The liver grafts from 60 Dark Agouti rats were intraportally perfused with antisense B7.1 expression vector, before they were transplanted into Lewis rats. Empty vector pcDNA3 served as control to be perfused into livers of another group of 60 Dark Agouti rats. The orthotopic liver transplantation was performed. The rats were randomly sacrificed at scheduled time points to collect liver allografts, or monitored to record the survival rate. The livers were histologically examined to calculate Banff rejection activity index, or subjected to Western blot analysis or immunohistochemistry for examining the expression of B7.1, or counting CD4+ and CD8+ cells.

RESULTS

Antisense gene transfer resulted in markedly downregulation of B7.1 in the donor livers, attenuated acute immune rejection against liver allografts, prolonged the survival time of rats, and decreased the number of infiltrating CD4+ and CD8+ cells in livers.

CONCLUSIONS

Blocking expression of B7.1 in liver by antisense gene therapy may represent a potential strategy to attenuate acute rejection against liver allografts.