Formation of neutralizing antibodies against natural interferon-β, but not against recombinant interferon-γ during adjuvant therapy for high-risk malignant melanoma patients

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Abstract
In an adjuvant clinical trial, 34 high‐risk malignant melanoma patients were treated with natural interferon (IFN)‐β and recombinant IFN‐γ. Patients with tumor location on head, neck, and trunk received 3 million IU IFN‐β intravenously (IV) three times weekly for 24 weeks. Patients with tumor location on the extremities received subcutaneous (SC) injection of 2 million IU of IFN‐β distal the locoregional lymph nodes instead. All patients were given 50 μg IFN‐γ SC on 3 consecutive days every 4 weeks. Antibody formation was detected by coincubation of IFN and patients' serum and assessment of the inhibition of the cytopathic effect by a virus suspension. Soluble interleukin‐2 receptors (sIL‐2R) were determined by enzymelinked immunosorbent assay (ELISA) technique. No antibodies against IFN‐γ were observed. The overall incidence of antibody formation to IFN‐β was 55.8% (19/34). Ninety‐two percent of the SC‐treated patients (13/14) and 30% (six of 20) of the IV‐treated patients developed antibodies. Soluble interleukin‐2 receptors were found to be significantly lower in antibody‐positive patients than in antibody‐negative patients. The authors conclude that IFN‐β antibody formation is frequent and might influence IFN induced sIL‐2R elevation in vivo.