Paired ADCC Reporter Bioassays Enable Differentiation of Antibody Fc Effector Activities via V158 and F158 Variant FcyRIIIa Receptors

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Antibody-dependent cell-mediated cytotoxicity (ADCC) contributes to clinical efficacy of a broad range of therapeutic antibodies. FcγRIIIa polymorphism of individual cancer patients are correlated with clinical efficacy of some of these antibody drugs. Classic ADCC cytotoxicity assays rely on primary effector cells, which are highly heterogeneous and variable. To quantitatively measure antibody activity and evaluate the impact of FcγRIIIa polymorphism, we developed a pair of reporter-based ADCC assays using two engineered effector cell lines in Jurkat that stably express an NFAT-RE driven luciferase reporter and either FcγRIIIa /V158 or FcγRIIIa /F158 polymorphism variant. Both cell lines were further developed in frozen, thaw-and-use format to reduce handling time and minimize assay variability. This reporter-based ADCC assay provides antibody biological activity ranking equivalent to that obtained in classic ADCC cytotoxicity assay. The V and F variant ADCC reporter assays showed appropriate IgG isotype specificity when testing various rituximab IgG isotypes. They are able to measure antibody potencies for therapeutic antibodies, with native target cells or genetically engineered target cell line such as a membrane-bound TNF cell line.

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