title: Anti-CD3-based bispecific antibody designed for therapy of human B-cell malignancy can induce T-cell activation by antigen-dependent and antigen-independent mechanisms.
abstract: Anti-CD3 x anti-B-cell antigen bispecific monoclonal antibodies (bsAbs) can redirect T-cell-mediated lysis toward malignant B cells. Clinical trials with CD3-based bsAbs have shown toxicity in patients which is likely related to nonspecific T-cell activation and targeting. Our current studies were designed to explore the mechanisms responsible for the observed in vivo toxicity by evaluating the immunologic effects of 2 different bsAb preparations in vitro. 1D10 was used as the tumor specific arm of the bsAbs. This antibody reacts with a variant of HLA-DR found on a majority of pre-B- and B-cell malignancies, and normal B cells in some individuals. Anti-CD3 served as the T-cell specific arm. A 1D10 x anti-CD3 bispecific IgG (bsIgG) produced using the hybrid-hybridoma method was compared to a 1D10 x anti-CD3 bispecific F(ab')2 [bsF(ab')2] produced using the leucine zipper technique. In cytotoxicity assays, both bsIgG and bsF(ab')2 induced lysis by pre-activated T cells of 1D10 (+) malignant B cells. bsIgG at high concentrations also induced lysis of 1D10 (-) tumor cells, while bsF(ab')2 did not. Proliferation of T cells induced by bsIgG and bsF(ab')2 was also evaluated. Both forms of bsAbs induced T-cell proliferation in the presence of antigen (+) Raji cells, while only bsIgG did so in the presence of antigen (-) malignant B cells. bsF(ab')2 induced T-cell activation in the absence of any tumor cells when testing was performed on samples where the 1D10 target antigen was present on normal peripheral blood B cells. We conclude that non-specific T-cell activation from bsAbs can occur in an antigen-independent manner due to the Fc/Fc receptor (FcR) interaction, or in an antigen-dependent manner when antigen is expressed on normal or tumor cells. Both mechanisms may have been responsible for the toxicity observed in prior clinical studies.
authors.affiliation: Department of Internal Medicine, University of Iowa Cancer Center, University of Iowa College of Medicine, Iowa City, USA. brian-link@uiowa.edu
authors.forename: B K
authors.initials: BK
authors.lastname: Link
authors.forename: S A
authors.initials: SA
authors.lastname: Kostelny
authors.forename: M S
authors.initials: MS
authors.lastname: Cole
authors.forename: W P
authors.initials: WP
authors.lastname: Fusselman
authors.forename: J Y
authors.initials: JY
authors.lastname: Tso
authors.forename: G J
authors.initials: GJ
authors.lastname: Weiner
mesh_terms: D000818:Animals; D018033:Antibodies, Bispecific / Q000276:immunology*; D000911:Antibodies, Monoclonal; D001402:B-Lymphocytes / Q000276:immunology*; D017252:CD3 Complex / Q000276:immunology*; D003602:Cytotoxicity, Immunologic; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000276:immunology*; D007074:Immunoglobulin G / Q000276:immunology; D019169:Jurkat Cells; D008213:Lymphocyte Activation; D051379:Mice; D011961:Receptors, Fc / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D014407:Tumor Cells, Cultured
chemical_list: D018033:Antibodies, Bispecific; D000911:Antibodies, Monoclonal; D017252:CD3 Complex; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D011961:Receptors, Fc