title: Serial killing of tumor cells by cytotoxic T cells redirected with a CD19-/CD3-bispecific single-chain antibody construct.
abstract: Certain bispecific antibodies exhibit an extraordinary potency and efficacy for target cell lysis by eliciting a polyclonal T-cell response. One example is a CD19-/CD3-bispecific single-chain antibody construct (bscCD19xCD3), which at femtomolar concentrations can redirect cytotoxic T cells to eliminate human B lymphocytes, B lymphoma cell lines and patient-derived malignant B cells. Here we have further explored the basis for this high potency. Using video-assisted microscopy, bscCD19xCD3 was found to alter the motility and activity of T cells from a scanning to a killing mode. Individual T cells could eliminate multiple target cells within a 9 hr time period, resulting in nuclear fragmentation and membrane blebbing of target cells. Complete target cell elimination was observed within 24 hr at effector-to-target cell ratios as low as 1:5. Under optimal conditions, cell killing started within minutes after addition of bscCD19xCD3, suggesting that the rate of serial killing was mostly determined by T-cell movement and target cell scanning and lysis. At all times, T cells remained highly motile, and no clusters of T and target cells were induced by the bispecific antibody. Bystanding target-negative cells were not detectably affected. Repeated target cell lysis by bscCD19xCD3-activated T cells increased the proportion of CD19/CD3 double-positive T cells, which was most likely a consequence of transfer of CD19 from B to T cells during cytolytic synapse formation. To our knowledge, this is the first study showing that a bispecific antibody can sustain multiple rounds of target cell lysis by T cells.
authors.affiliation: Micromet AG, Munich, Germany.
authors.forename: Patrick
authors.initials: P
authors.lastname: Hoffmann
authors.forename: Robert
authors.initials: R
authors.lastname: Hofmeister
authors.forename: Klaus
authors.initials: K
authors.lastname: Brischwein
authors.forename: Christian
authors.initials: C
authors.lastname: Brandl
authors.forename: Sandrine
authors.initials: S
authors.lastname: Crommer
authors.forename: Ralf
authors.initials: R
authors.lastname: Bargou
authors.forename: Christian
authors.initials: C
authors.lastname: Itin
authors.forename: Nadja
authors.initials: N
authors.lastname: Prang
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Baeuerle
mesh_terms: D018033:Antibodies, Bispecific / Q000737:chemistry; D018941:Antigens, CD19 / Q000096:biosynthesis*; D001402:B-Lymphocytes / Q000276:immunology; D017252:CD3 Complex / Q000096:biosynthesis*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D003602:Cytotoxicity, Immunologic; D004305:Dose-Response Relationship, Drug; D005434:Flow Cytometry; D006801:Humans; D007128:Immunoglobulin Fragments / Q000737:chemistry*; D007167:Immunotherapy / Q000379:methods*; D007376:Interleukin-2 / Q000378:metabolism; D007700:Kinetics; D008213:Lymphocyte Activation; D018715:Microscopy, Video; D009369:Neoplasms / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D013997:Time Factors
chemical_list: D018033:Antibodies, Bispecific; D018941:Antigens, CD19; D017252:CD3 Complex; D007128:Immunoglobulin Fragments; D007376:Interleukin-2