Specific activation of resting T cells against tumour cells by bispecific antibodies and CD28-mediated costimulation is accompanied by Th1 differentiation and recruitment of MHC-independent cytotoxicity

Abstract

SUMMARYSpecific activation of resting lymphocytes for tumour targeting can be achieved by bispecific monoclonal antibodies (bi-MoAbs) with specificity for tumour antigens and T cell-activating antigens in combination with a costimulatory anti-CD28 antibody. In this study we focus on the immunomodulatory function of an anti-CD3/CA19-9 bi-MoAb in combination with a costimulatory anti-CD28 antibody which may result not only in antigen-specific, T cell-mediated tumour cell lysis but also in recruitment of other cellular effector functions. In combination with costimulatory anti-CD28 antibodies, resting peripheral lymphocytes could be activated specifically to secrete high amounts of Th1 cytokines (IL-2, interferon-gamma (IFN-g)) characterizing a cellular immune response. In contrast, no IL-4 and only low amounts of IL-10 could be detected. Furthermore, bi-MoAb-mediated CA19-9-specific activation of T cells was accompanied by recruitment of MHC-and CA19-9-independent cytotoxicity, as was determined by lysis of different CA19-9 ¹ cell lines. This MHC-independent cytotxicity was mediated at least in part by activated natural killer (NK) cells, as depletion of CD16 þ NK cells resulted in substantial decrease of cytotoxicity against CA19-9 ¹ targets. Our results indicate that specific activation of resting T cells with CD3-associated bi-MoAbs in combination with an anti-CD28 antibody leads to a Th1 differentiation pathway and is accompanied by recruitment of MHCindependent lymphokine-activated killer (LAK) cell cytotoxicity which can possibly be directed against a heterogeneous tumour.

Optimization studies for the coupling of bispecific antibodies to viral anchor molecules of a tumor vaccine

“…Following the concept of the use of bispecific singlechain antibodies (18,23,24), T cells can be activated only if the targeted receptor proteins (e.g. CD3 and CD28) become cross-linked.…”

Targeting T Cells with Bispecific Antibodies for Cancer Therapy

“…Co-stimulation with anti-CD28 alone or anti-CD28×anti-TAA induces enhanced signaling, [140,141] cytokine synthesis, [142] enhanced killing in leukemia/lymphoma models, [95,98,105] and cytotoxicity in colon cell lines. [143] It has also been reported that BiAb and CD28 co-stimulation induces T h 1 differentiation. [143] However, it remains unclear whether co-stimulation correlates with more effective long-term clinically relevant immune responses.…”

“…[143] It has also been reported that BiAb and CD28 co-stimulation induces T h 1 differentiation. [143] However, it remains unclear whether co-stimulation correlates with more effective long-term clinically relevant immune responses.…”

NK cell depletion diminish tumour-specific B cell responses

“…YAC-1 cells were Europium labelled as described elsewhere [12] and extensively washed to remove extracellular Europium traces. The E/T-ratio was ranging from 3:1 until 200:1.…”