Specific detection of antibodies in cancer patients following immunotherapy with anti-idiotype

Abstract

Assays were compared for specificity and sensitivity in detecting in cancer patients' sera antibodies (Ab) raised during the course of immunotherapy with goat anti-idiotypic antibodies (Ab2) bearing the internal image of a colon carcinoma-associated antigen defined by monoclonal antibody (MAb) CO17-1A (Ab1). The human Ab were tested for binding to tumor cells, isolated tumor antigen (Ag), and Ab2, and for the capacity to inhibit binding of Ab2 to Ab1. Chimeric (human/mouse) MAb CO17-1A was used as a positive control in all assays. Of the four different cell binding assays used, the mixed hemadsorption assay (MHA) showed the highest specificity and sensitivity. For detection of Ag-binding human Ab, the enzyme-linked immunosorbent assay (ELISA) with Ag as target and peroxidase (PO)-labeled anti-human IgG antibodies as tracer for detection of human Ab binding to the target, showed higher specificity and sensitivity as compared to radioimmunoassay (RIA). For detection of human Ab binding specifically to Ab2, three different ELISAs and three RIAs were used. Best results were obtained in the ELISA with anti-human IgG antibodies as target and biotinylated Ab2 as tracer for detection of human Ab binding to the target. Of four different inhibition assays used, the ELISA which measures inhibition of binding of biotinylated Ab2 to Ab1 by human Ab or chimeric antibody at 37°C was the most sensitive and specific. These assays have general applicability for the characterization of human Ab responses in Ab2 vaccination approaches to various tumors and pathogens and therefore provide the basis for the establishment of a correlation between Ab responses and clinical outcome of the disease.