Localized combinatorial IL-4 and IL-10 gene therapy readjusts the balance of endogenous TH1/TH2 cytokines and induces the tolerance of the cardiac allografts

Abstract

The balance of Th1/Th2 cytokine plays an important role in the allograft tolerance, however, its operating mechanism remains unknown. Using a functional cervical heterotopic rabbit heart transplant model, we tested the hypothesis that liposome-mediated ex vivo intracoronary interleukin-4 (IL-4) and IL-10 combined gene therapy may induce localized IL-4 and IL-10 over expression that may synergistically regulates endogenous Th1/Th2 expression and induces allograft tolerance. The mean survival of cardiac allograft was prolonged from 7 ± 1 days in Control Group (CG) to 14 ± 3 days in IL-4 gene therapy group (IL4G), 28 ± 7 days in IL-10 gene therapy Group (IL10G) and 135 ± 20 days in IL-4 and IL-10 combined gene therapy Group (IL4&10G). The rejection score in IL4&10G was significantly lower (2.2 ± 0.2, p<0.05) than that of CG (3.6 ± 0.2) and IL-10G (2.7 ± 0.3) in POD3-6. In single cytokine gene therapy caused an excessive localized exogenous cytokine gene and protein expression which significantly downregulated the expression of the same endogenous cytokine, IL-4 or IL-10 gene (p<0.01), but in a certain extent upregulated the other Th2 cytokine genes expression (p<0.01). In IL4&10G, endogenous IL-4 and IL-10 gene expression was decreased in the early stage, then increased at POD 18-20 and remained in a high level for a long period of time. The expression of Th1 cytokine genes, IL-1b and TNF-a, were significantly decreased by the synergistic inhibition of IL-4 and IL-10, and maintained in the low level in the late stage. IFN-g gene expression level was increased in IL4G, decreased in IL10G. The slightly decreased IFN-g gene expression level observed in the combined gene therapy group that could be resulted from antagonistic immunoregulatory effects of two cytokines. We conclude that localized overexpression of exogenous IL-4 and IL-10 induced by ex vivo gene transfer could act synergistically for readjusting the balance of endogenous Th1/Th2 cytokines that may contribute to the allograft tolerance.