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Hanssens H, Meeus F, De Vlaeminck Y, Lecocq Q, Puttemans J, Debie P, De Groof TWM, Goyvaerts C, De Veirman K, Breckpot K, Devoogdt N. Scrutiny of chimeric antigen receptor activation by the extracellular domain: experience with single domain antibodies targeting multiple myeloma cells highlights the need for case-by-case optimization. Front Immunol 2024; 15:1389018. [PMID: 38720898 PMCID: PMC11077437 DOI: 10.3389/fimmu.2024.1389018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Accepted: 04/02/2024] [Indexed: 05/12/2024] Open
Abstract
Introduction Multiple myeloma (MM) remains incurable, despite the advent of chimeric antigen receptor (CAR)-T cell therapy. This unfulfilled potential can be attributed to two untackled issues: the lack of suitable CAR targets and formats. In relation to the former, the target should be highly expressed and reluctant to shedding; two characteristics that are attributed to the CS1-antigen. Furthermore, conventional CARs rely on scFvs for antigen recognition, yet this withholds disadvantages, mainly caused by the intrinsic instability of this format. VHHs have been proposed as valid scFv alternatives. We therefore intended to develop VHH-based CAR-T cells, targeting CS1, and to identify VHHs that induce optimal CAR-T cell activation together with the VHH parameters required to achieve this. Methods CS1-specific VHHs were generated, identified and fully characterized, in vitro and in vivo. Next, they were incorporated into second-generation CARs that only differ in their antigen-binding moiety. Reporter T-cell lines were lentivirally transduced with the different VHH-CARs and CAR-T cell activation kinetics were evaluated side-by-side. Affinity, cell-binding capacity, epitope location, in vivo behavior, binding distance, and orientation of the CAR-T:MM cell interaction pair were investigated as predictive parameters for CAR-T cell activation. Results Our data show that the VHHs affinity for its target antigen is relatively predictive for its in vivo tumor-tracing capacity, as tumor uptake generally decreased with decreasing affinity in an in vivo model of MM. This does not hold true for their CAR-T cell activation potential, as some intermediate affinity-binding VHHs proved surprisingly potent, while some higher affinity VHHs failed to induce equal levels of T-cell activation. This could not be attributed to cell-binding capacity, in vivo VHH behavior, epitope location, cell-to-cell distance or binding orientation. Hence, none of the investigated parameters proved to have significant predictive value for the extent of CAR-T cell activation. Conclusions We gained insight into the predictive parameters of VHHs in the CAR-context using a VHH library against CS1, a highly relevant MM antigen. As none of the studied VHH parameters had predictive value, defining VHHs for optimal CAR-T cell activation remains bound to serendipity. These findings highlight the importance of screening multiple candidates.
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Affiliation(s)
- Heleen Hanssens
- Laboratory of Molecular Imaging and Therapy (MITH), Department of Biomedical Sciences, Vrije Universiteit Brussel, Brussels, Belgium
- Laboratory for Molecular and Cellular Therapy (LMCT), Translational Oncology Research Center, Department of Biomedical Sciences, Vrije Universiteit Brussel, Brussels, Belgium
- Laboratory for Hematology and Immunology (HEIM), Translational Oncology Research Center, Department of Biomedical Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Fien Meeus
- Laboratory for Molecular and Cellular Therapy (LMCT), Translational Oncology Research Center, Department of Biomedical Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Yannick De Vlaeminck
- Laboratory for Molecular and Cellular Therapy (LMCT), Translational Oncology Research Center, Department of Biomedical Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Quentin Lecocq
- Laboratory for Molecular and Cellular Therapy (LMCT), Translational Oncology Research Center, Department of Biomedical Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Janik Puttemans
- Laboratory of Molecular Imaging and Therapy (MITH), Department of Biomedical Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Pieterjan Debie
- Laboratory of Molecular Imaging and Therapy (MITH), Department of Biomedical Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Timo W. M. De Groof
- Laboratory of Molecular Imaging and Therapy (MITH), Department of Biomedical Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Cleo Goyvaerts
- Laboratory for Molecular and Cellular Therapy (LMCT), Translational Oncology Research Center, Department of Biomedical Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Kim De Veirman
- Laboratory for Hematology and Immunology (HEIM), Translational Oncology Research Center, Department of Biomedical Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Karine Breckpot
- Laboratory for Molecular and Cellular Therapy (LMCT), Translational Oncology Research Center, Department of Biomedical Sciences, Vrije Universiteit Brussel, Brussels, Belgium
| | - Nick Devoogdt
- Laboratory of Molecular Imaging and Therapy (MITH), Department of Biomedical Sciences, Vrije Universiteit Brussel, Brussels, Belgium
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Czajka TF, Vance DJ, Davis S, Rudolph MJ, Mantis NJ. Single-domain antibodies neutralize ricin toxin intracellularly by blocking access to ribosomal P-stalk proteins. J Biol Chem 2022; 298:101742. [PMID: 35182523 PMCID: PMC8941211 DOI: 10.1016/j.jbc.2022.101742] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Revised: 02/10/2022] [Accepted: 02/14/2022] [Indexed: 12/27/2022] Open
Abstract
During ricin intoxication in mammalian cells, ricin's enzymatic (RTA) and binding (RTB) subunits disassociate in the endoplasmic reticulum. RTA is then translocated into the cytoplasm where, by virtue of its ability to depurinate a conserved residue within the sarcin-ricin loop (SRL) of 28S rRNA, it functions as a ribosome-inactivating protein. It has been proposed that recruitment of RTA to the SRL is facilitated by ribosomal P-stalk proteins, whose C-terminal domains interact with a cavity on RTA normally masked by RTB; however, evidence that this interaction is critical for RTA activity within cells is lacking. Here, we characterized a collection of single-domain antibodies (VHHs) whose epitopes overlap with the P-stalk binding pocket on RTA. The crystal structures of three such VHHs (V9E1, V9F9, and V9B2) in complex with RTA revealed not only occlusion of the ribosomal P-stalk binding pocket but also structural mimicry of C-terminal domain peptides by complementarity-determining region 3. In vitro assays confirmed that these VHHs block RTA-P-stalk peptide interactions and protect ribosomes from depurination. Moreover, when expressed as "intrabodies," these VHHs rendered cells resistant to ricin intoxication. One VHH (V9F6), whose epitope was structurally determined to be immediately adjacent to the P-stalk binding pocket, was unable to neutralize ricin within cells or protect ribosomes from RTA in vitro. These findings are consistent with the recruitment of RTA to the SRL by ribosomal P-stalk proteins as a requisite event in ricin-induced ribosome inactivation.
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Affiliation(s)
- Timothy F Czajka
- Department of Biomedical Sciences, University at Albany, Albany, New York, USA
| | - David J Vance
- Department of Biomedical Sciences, University at Albany, Albany, New York, USA; Division of Infectious Diseases, Wadsworth Center, New York State Department of Health, Albany, New York, USA
| | - Simon Davis
- New York Structural Biology Center, New York, New York, USA
| | | | - Nicholas J Mantis
- Department of Biomedical Sciences, University at Albany, Albany, New York, USA; Division of Infectious Diseases, Wadsworth Center, New York State Department of Health, Albany, New York, USA.
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