Adenovirus-mediated OX40Ig gene transfer induces long-term survival of orthotopic liver allograft in rats

Background: To discuss the effect and mechanism of adenovirus-mediated OX40Ig gene transfer in inducing long-term survival of liver allografts in rats. Methods: Orthotopic liver transplantation was performed from Lewis to Brown Norway (BN) rats through the modified two-cuffed technique, and all rats were randomly divided equally into four groups: control, AdEGFP, AdOX40Ig, and FK506. The survival times of the rats were recorded. The rats' liver function, serum cytokines, hepatocyte pathology, OX40Ig protein level, and mixed lymphocyte reaction (MLR) with or without recombinant interleukin-2 (rIL-2) were evaluated. Results: Compared with the control and AdEGFP groups, the rats in the AdOX40Ig and FK506 groups survived longer (P < 0.05), experienced less damage to hepatic function (P < 0.05), and showed milder hepatic cellular rejection and less hepatic cellular apoptosis. Interferon (IFN)-gamma and IL-2 content in the serum were lower after operation (P < .05) in the AdOX40Ig and FK506 groups. On the contrary, IL-4 and IL-10 content in the serum was higher after operation (P < 0.05) in the AdOX40Ig and FK506 groups. OX40Ig protein was significantly expressed in the AdOX40Ig group and reached the highest level on the 7th day after operation. With respect to the MLR between BN and Lewis rats, the AdOX40Ig group showed a lighter reaction for the same strain than the control and AdEGFP groups (P < 0.05), which is different from the MLR between BN and F344 rats. After adding rIL-2 to the MLR system between BN rats in the AdOX40Ig group and Lewis rats, MLR was aggravated. Conclusion: Through OX40/OX4OL pathways, OX40Ig created an immunosuppressive effect after liver transplantation in rats. This immunosuppressive effect is associated with reduced IL-2 and can be reversed by adding IL-2 with antigen specificity.