Generation and functional characterization of anti-clonotype antibodies to human T-cell receptors

Biophysical and Immunological Characterization and In Vivo Pharmacokinetics and Toxicology in Nonhuman Primates of the Anti-PD-1 Antibody Pembrolizumab

The programmed cell death 1 (PD-1) pathway represents a major immune checkpoint, which may be engaged by cells in the tumor microenvironment to overcome active T-cell immune surveillance. Pembrolizumab (Keytruda®, MK-3475) is a potent and highly selective humanized mAb of the IgG4/kappa isotype designed to directly block the interaction between PD-1 and its ligands, PD-L1 and PD-L2. This blockade enhances the functional activity of T cells to facilitate tumor regression and ultimately immune rejection. Pembrolizumab binds to human and cynomolgus monkey PD-1 with picomolar affinity and blocks the binding of human and cynomolgus monkey PD-1 to PD-L1 and PD-L2 with comparable potency. Pembrolizumab binds both the C'D and FG loops of PD-1. Pembrolizumab overcomes human and cynomolgus monkey PD-L1-mediated immune suppression in T-cell cultures by enhancing IL2 production following staphylococcal enterotoxin B stimulation of healthy donor and cancer patient cells, and IFNγ production in human primary tumor histoculture. Ex vivo and in vitro studies with human and primate T cells show that pembrolizumab enhances antigen-specific T-cell IFNγ and IL2 production. Pembrolizumab does not mediate FcR or complement-driven effector function against PD-1-expressing cells. Pembrolizumab displays dose-dependent clearance and half-life in cynomolgus monkey pharmacokinetic and toxicokinetic studies typical for human IgG4 antibodies. In nonhuman primate toxicology studies, no findings of toxicologic significance were observed. The preclinical data for pembrolizumab are consistent with the clinical anticancer activity and safety that has been demonstrated in human clinical trials.

Generation and characterization of a clonotypic antibody specific for the T cell receptor of an arthritogenic T cell clone--studies in adjuvant arthritis

Adjuvant Arthritis (AA) can be induced by passive transfer of a T cell clone (A2b) derived from arthritic rats, specific for Heat Shock Protein 60, HSP60 176-190. Furthermore, a crucial role for T cells with HSP60 176-190 specificity in AA was shown by induction of tolerance using HSP60 176-190 or by immunization with an altered peptide ligand based on the same sequence. To study clonal expansion of A2b-like T cells during AA and to determine their role in AA induction, we generated a clonotypic antibody, 16C4, specific for the TCR of the A2b T cell clone (TCR AV11S1/BV18). This antibody stained A2b T cells in flow cytometry experiments, induced proliferation of A2b cells when fixed on a solid support, and inhibited antigen-induced A2b proliferation when added in solution. A2b-like T cells were detected in a low frequency in lymphoid organs of arthritic rats. Thus, as in vivo administration of 16C4 did not inhibit AA, cells containing the determinant recognized by 16C4 are possibly not the sole contributors to AA development. Furthermore, epitope specific interventions by antigen administration may be possible even in cases where the epitope specific T cell clonotype is of low frequency.

T-cell anergy induced by clonotype-specific antibodies: modulation of an autoreactive human T-cell clone in vitro

Monoclonal antibodies (mAb) specific for the clonotype of an autoreactive T cell may be useful reagents in the modulation of autoimmune disease. We have previously reported the generation of a set of mAb specific for the clonotypic structure of a human T-cell clone recognizing an epitope of human cartilage gp-39. This glycoprotein was recently identified as a candidate autoantigen in rheumatoid arthritis. Here, we demonstrate for the first time that small amounts of immobilized anticlonotype mAb can induce anergy in the autoreactive clone. Following the anergic stimulus, T cells failed to proliferate upon restimulation as a result of a lack of interleukin-2 (IL-2) gene transcription. In addition, a diminished interferon-gamma (IFN-gamma) production was found. Our data indicate that anergy was not a result of T-cell receptor (TCR) downmodulation or the absence of free TCR. The anergic state was induced independent of costimulation or the presence of IL-2 and no protein synthesis was required for the induction of anergy. Anticlonotype mAb-induced anergy was prevented by cyclosporin A, suggesting that active signalling via the calcium/calcineurin pathway was required for the induction of anergy. In coculture experiments, anergic T cells were found to suppress the response of reactive cells from the same clone. This bystander suppression led to 90% inhibition of peptide-induced proliferation. Together, these findings suggest that mAb to the clonotypic structure of autoreactive T cells may be suitable reagents for the functional inactivation of these T cells in autoimmune diseases.