An inhibitor of interferon action: I. Physical association of the inhibitor with interferon-gamma

Interferon inhibitor factor predicting success of plasmapheresis in patients with multiple sclerosis

Interferons (IFN) are biological molecules with antiviral, antiproliferative, and immunomodulatory actions. Plasmapheresis (PP) combined with IFN therapy in 24 multiple sclerosis (MS) patients was associated with a rapid increase in detectable IFN levels. We describe the presence of a detectable factor in the serum of MS patients which decreases the efficacy of IFN therapy in these patients. We call this factor "interferon inhibitor factor" (IIF). Standard IFN assay indicates inhibition of WISH cell protection by IFN owing to the presence of IIF in patient's serum. Similar results were also obtained with human fibroblast and human leukocyte IFNs. The best results were obtained with an IFN mixture; results with 1:20 diluted patient's sera showed elevation of 120% greater than 1:10 dilution. With 1:40 dilution, an elevation of 1,041% was noticed. The IIF from patient sera collected during PP was purified and characterized. Native gel electrophoresis of IIF indicates a single protein band; further analysis on SDS gels indicates two bands at the 200 and 21-kD range. ELISA failed to reveal the presence of any anti-IFN antibodies. This study demonstrates the presence of IIF in MS patients' sera which are removed from the circulation by PP. Removal of IIF from circulation was associated with increased IFN levels and clinical improvement as measured by Kurtzke's disability status scale (KDSS).

Interferon inactivator(s) in patients with AIDS and AIDS-unrelated Kaposi's sarcoma

Interferon inhibitory activity was found in the plasma of 11 of 14 patients with the acquired immune deficiency syndrome (AIDS). This was not seen in 75 normal persons, including six whose specimens were randomly and blindly interspersed among the patient samples. Plasma from a single patient with the AIDS prodrome (AIDS-related complex), who later demonstrated AIDS, did not contain interferon inhibitors but did contain high levels of interferon. Three patients with AIDS-unrelated Kaposi's sarcoma had neither significant levels of interferon nor interferon inhibitory activity. The existence of interferon inhibitory activity in the plasma has to be taken into account when interferon preparations are administered therapeutically.

An inhibitor of interferon action: II. Biological properties of the IFN-gamma-associated inhibitor of interferon action

Previously an inhibitor of interferon action had been isolated from mitogen stimulated mouse spleen cells. This inhibitor was associated with the IFN-gamma molecule and might possibly represent an altered IFN-gamma molecule which can no longer induce an effective antiviral state. This report further investigates the biological properties of this inhibitor. Inhibitor activity is independent of the virus used in the interferon assay. Inhibitor activity has also been found to be species specific. Mouse inhibitor does not inhibit the antiviral activity of either human IFN-gamma or human IFN-beta. However, inhibitor production is not limited to the mouse system. Inhibitor is also present in preparations of human IFN-gamma. The inhibitor does not appear to directly compete with IFN-gamma for a specific cell surface receptor since inhibitor activity is independent of interferon concentration. The presence of inhibitor allows a unique, albeit reduced level of antiviral protection to develop. Increasing concentrations of interferon do not increase the level of antiviral protection allowed by the inhibitor. This inhibitor of interferon action may represent a natural mechanism whereby IFN-gamma-induced effects are regulated in vivo.