ADENOVIRAL VECTOR-MEDIATED INTERLEUKIN-10 EXPRESSION IN-VIVO - INTRAMUSCULAR GENE TRANSFERS INHIBITS CYTOKINE RESPONSES IN ENDOTOXEMIA

Interleukin-10 (IL-10) is a potent anti-inflammatory/immune cytokine a nd has received growing attention for ifs therapeutic potential. To ai d therapeutic studies of IL-10 in vivo, a replication-deficient adenov iral vector expressing mouse IL-10 was constructed and characterized. The transgene protein IL-10 was shown to markedly inhibit endotoxin-in duced tumor necrosis factor alpha (TNF alpha) production by mouse and rat macrophages in vitro. Intramuscular injection of this vector in mi ce resulted in efficient expression of transgene mRNA in the muscle an d active release of IL-10 protein into the bloodstream. To investigate the therapeutic potential of IL-10 using this vector, endotoxemia was induced by intraperitoneal injection of a sublethal dose of endotoxin . Expression of TNF alpha and IL-6 mRNA in the lung, spleen and heart and the circulating levels of these cytokines markedly increased in en dotoxemia. This toxin-induced TNF alpha and IL-6 up-regulation was how ever suppressed in mice expressing IL-10 after intramuscular gene tran sfer. While cytokine gene expression was inhibited to varying degrees in different organs, a maximal reduction was seen in the lung, thus al so indicating the efficacy of systemic IL-10 gene product at multiple tissue sites. Finally, we provided evidence that only when present in abnormally high concentrations in the circulation following intraperit oneal gene delivery, IL-10 by itself had some toxic effects of transie nt nature, primarily manifested by acute phase reaction and hemostatic disturbance. Thus, our studies demonstrate the usefulness of adenovir al vectors for therapeutic application of IL-10 in vivo.