QUANTITATION OF HUMAN ANTI-MOUSE ANTIBODY IN SERUM BY FLOW-CYTOMETRY

Clinical investigations utilizing murine monoclonal antibodies require techniques for the detection of the human anti-mouse antibody (HAMA) response in patient serum. We report here a flow cytometric assay for the quantitation of HAMA. Commercially available beads conjugated with goat anti-mouse antibody provide a solid phase matrix for a triple br idge immunoassay. The measurement of fluorescein labeled antibodies by flow cytometry allows accurate quantitation of the HAMA. The assay wi ll detect antibody levels of approximately 1.0 ng/ml. Antibody recover y in serum samples with known amounts of antibody added was greater th an 90% at levels greater-than-or-equal-to 10-mu-g/ml. Serum samples ob tained from 41 patients prior to and after single or multidose infusio ns of KS1/4-Desacetylvinblastine were analyzed. These results were com pared with HAMA titers previously determined by ELISA. With few except ions, patients with low titers as determined by ELISA demonstrated low HAMA potencies by flow cytometry and those with highest titers the hi ghest potencies. Patients with no detectable HAMA by ELISA were also n egative by flow analysis. The results of our studies demonstrate that HAMA levels can be accurately and quantitatively determined by flow cy tometry.