Effect of CTLA4-Ig gene transfer using adenoviral vector in organ and cell transplantation

Adenovirus-mediated CTLA4Ig gene inhibits infiltration of immune cells and cell apoptosis in rats after liver transplantation

AIM: To investigate the role of adenovirus-mediated CTLA4Ig gene therapy in inhibiting the infiltration of macrophages and CD8+T cells and cell apoptosis after liver transplantation.

METHODS: The rat orthotopic liver transplantation model was applied. The rats were divided into three groups: group I: rejection control (SD-to-Wistar); group II: acute rejection treated with intramuscular injection of CsA 3.0 mg/(kg·d) for 12 d (SD-to-Wistar+CsA); groupIII: injection of 1×10⁹ PFU adenovirus-mediated CTLA4Ig gene liquor in dorsal vein of penis 7 d before liver transplantation (SD-to-Wistar+CTLA4Ig). Immunohistochemistry and transferase-mediated dUTP nick-end labeling (TUNEL) were used to analyze the expression of CTLA4Ig gene in liver, infiltration of macrophages and CD8+T cells, cell apoptosis in grafts at different time-points after liver transplantation. Histopathological examination was done.

RESULTS: CTLA4Ig gene expression was positive in liver on d 7 after administering adenovirus-mediated CTLA4Ig gene via vein, and remained positive until day 60 after liver transplantation. Infiltration of macrophages and CD8+T cells in CTLA4Ig-treated group was less than in rejection control group and CsA-treated group. The apoptotic index of rejection group on d 3, 5, and 7 were significantly higher than that of CTLA4Ig-treated group. A good correlation was found between severity of rejection reaction and infiltration of immune activator cells or cell apoptotic index in grafts.

CONCLUSION: CTLA4Ig gene is constantly expressed in liver and plays an important role in inducing immune tolerance.

Antisense Oligonucleotides Down-Regulating Costimulation Confer Diabetes-Preventive Properties to Nonobese Diabetic Mouse Dendritic Cells

Phenotypically "immature" dendritic cells (DCs), defined by low cell surface CD40, CD80, and CD86 can elicit host immune suppression in allotransplantation and autoimmunity. Herein, we report the most direct means of achieving phenotypic immaturity in NOD bone marrow-derived DCs aiming at preventing diabetes in syngeneic recipients. CD40, CD80, and CD86 cell surface molecules were specifically down-regulated by treating NOD DCs ex vivo with a mixture of antisense oligonucleotides targeting the CD40, CD80, and CD86 primary transcripts. The incidence of diabetes was significantly delayed by a single injection of the engineered NOD DCs into syngeneic recipients. Insulitis was absent in diabetes-free recipients and their splenic T cells proliferated in response to alloantigen. Engineered DC promoted an increased prevalence of CD4(+)CD25(+) T cells in NOD recipients at all ages examined and diabetes-free recipients exhibited significantly greater numbers of CD4(+)CD25(+) T cells compared with untreated NOD mice. In NOD-scid recipients, antisense-treated NOD DC promoted an increased prevalence of these putative regulatory T cells. Collectively, these data demonstrate that direct interference of cell surface expression of the major costimulatory molecules at the transcriptional level confers diabetes protection by promoting, in part, the proliferation and/or survival of regulatory T cells. This approach is a useful tool by which DC-mediated activation of regulatory T cells can be studied as well as a potential therapeutic option for type 1 diabetes.

Prolonged cardiac allograft survival in rats systemically injected adenoviral vectors containing CTLA4Ig-gene

BACKGROUND

CTLA4Ig, a soluble recombinant fusion protein that contains the extracellular domain of the CTLA4 and Fc portion of IgG1, strongly adheres to the B7 molecule to block CD28-mediated costimulatory signals and inhibits in vitro and in vivo immune responses. In vivo gene transfer using adenovirus vector achieves a high transfection rate into organ cells that usually contain adenoviral receptors. In this study, we investigated expression levels of the transfected gene and the survival times of the allografts in cardiac recipients systemically administered adenoviral vectors containing CTLA4Ig.

METHODS

Hearts from DA rats (RT-1a) were transplanted into a cervical location in LEW recipients (RT1(1)). The adenoviral vectors containing CTLA4Ig was injected via a recipient vein immediately after grafting.

RESULTS

The serum level of CTLA4Ig reached to maximum at 51-93 microg/ml 3 to 7 days after gene-transfection and declined after 14 days, although detectable levels were observed up to 49 days. The median survival time of the allografts in the gene-transfected group were significantly prolonged (27 days) in compared to the control group (6 days). In addition, down-regulation of IL-2 and IFN-gamma mRNAs and persistence of IL-4 and IL-10 transcripts were observed in the graft infiltrating cells.

CONCLUSION

The adenovirous-mediated CTLA4Ig gene transfer into a recipient liver by systemic administration resulted in remarkable prolongation of cardiac allograft survival. Its action mechanisms may be mediated by inhibition of CD28-associated signal transduction, reduction of Th1-type cytokine production, and continuous expression of Th2-type cytokines in the activating lymphocytes.