Intramuscular administration of expression plasmids encoding interferon-gamma receptor/IgG1 or IL-4/IgG1 chimeric proteins protects from autoimmunity

Background Interferon gamma (IFN gamma) is an inflammatory cytokine that pr omotes autoimmune insulitis and diabetes in NOD mice, while interleukin-4 ( IL-4) is protective. We constructed plasmids encoding either an IFN gamma, receptor/IgG1 (IFN gamma R/IgG1) chimeric protein which inhibits IFN gamma, or an IL-4/IgG1 chimeric protein with IL,-4 activity, for therapeutic gene transfer into NOD mice. Methods Murine IFN gamma R/IgG1 and IL-4/IgG1 cDNA segments were cloned int o the VICAL VR1255 expression plasmid. Naked plasmid DNA was injected i.m. into young NOD mice, which were then observed for development of insulitis and diabetes. Results After transient transfection of COS-7 cells, IFN gamma R/IgG1 and I L-4/IgG1 fusion proteins are secreted in vitro as disulfide-linked homodime rs, with the expected biological activity. Intramuscular injection of these vectors results in the production of the respective fusion proteins locall y in muscle. In serum, the IFN gamma R/IgG1 protein is present at > 200 ng/ ml over 130 days after the last of five DNA injections, but IL-4/IgG1 is un detectable in our assays (<10 pg/ml) at all time points. Both vectors prote ct NOD mice from autoimmune insulitis and diabetes, but the IL-4/IgG1 vecto r is more effective. Neutralization of IFN gamma with IFN gamma R/IgG1 was most protective when treatment was begun early (3 weeks of age). Conclusion Gene therapy by i.m. injection of these plasmids protects NOD mi ce from autoimmunity, and the IL-4/IgG1 vector is more effective despite lo w circulating protein levels. These chimeric proteins consist of nonimmunog enic self elements and are suitable for long-term therapy of autoimmune dis orders. Copyright (C) 1999 John Wiley & Sons, Ltd.