title: Inclusion of an IgG1-Fc spacer abrogates efficacy of CD19 CAR T cells in a xenograft mouse model.
abstract: Cancer therapy with T cells expressing chimeric antigen receptors (CARs) has produced remarkable clinical responses in recent trials, but also severe side effects. Whereas most protocols use permanently reprogrammed T cells, we have developed a platform for transient CAR expression by mRNA electroporation. This approach may be useful for safe clinical testing of novel receptors, or when a temporary treatment period is desirable. Herein, we investigated therapy with transiently redirected T cells in vitro and in a xenograft mouse model. We constructed a series of CD19-specific CARs with different spacers and co-stimulatory domains (CD28, OX40 or CD28-OX40). The CAR constructs all conferred T cells with potent CD19-specific activity in vitro. Unexpectedly, the constructs incorporating a commonly used IgG1-CH2CH3 spacer showed lack of anti-leukemia activity in vivo and induced severe, partly CD19-independent toxicity. By contrast, identical CAR constructs without the CH2-domain eradicated leukemia in vivo, without notable toxicity. Follow-up studies demonstrated that the CH2CH3-spacer bound soluble mouse Fcγ-receptor I and mediated off-target T-cell activation towards murine macrophages. Our findings highlight the importance of non-signalling CAR elements and of in vivo studies. Finally, the results show that transiently redirected T cells control leukemia in mice and support the rationale for developing an mRNA-CAR platform.
authors: Section for Cell Therapy, Department of Oncology, Oslo University Hospital Radiumhospitalet, Oslo, Norway.
authors: H
authors: H
authors: Almåsbak
authors: 1] Department of Immunology, Oslo University Hospital Radiumhospitalet, Oslo, Norway [2] Department of Cancer Biology, Scripps Research Institute, Jupiter, FL, USA.
authors: E
authors: E
authors: Walseng
authors: 1] Department of Tumor Biology, Oslo University Hospital Radiumhospitalet, Oslo, Norway [2] KG Jebsen Center for Breast Cancer Research, Institute for Clinical Medicine, University of Oslo, Oslo, Norway.
authors: A
authors: A
authors: Kristian
authors: Section for Cell Therapy, Department of Oncology, Oslo University Hospital Radiumhospitalet, Oslo, Norway.
authors: M R
authors: MR
authors: Myhre
authors: Section for Cell Therapy, Department of Oncology, Oslo University Hospital Radiumhospitalet, Oslo, Norway.
authors: E M
authors: EM
authors: Suso
authors: 1] Centre for Immune Regulation and Department of Immunology, Oslo University Hospital Rikshospitalet, Oslo, Norway [2] Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
authors: L A
authors: LA
authors: Munthe
authors: Centre for Immune Regulation and Department of Immunology, Oslo University Hospital Rikshospitalet, Oslo, Norway.
authors: J T
authors: JT
authors: Andersen
authors: Section for Cell Therapy, Department of Oncology, Oslo University Hospital Radiumhospitalet, Oslo, Norway.
authors: M Y
authors: MY
authors: Wang
authors: Section for Cell Therapy, Department of Oncology, Oslo University Hospital Radiumhospitalet, Oslo, Norway.
authors: G
authors: G
authors: Kvalheim
authors: Department of Immunology, Oslo University Hospital Radiumhospitalet, Oslo, Norway.
authors: G
authors: G
authors: Gaudernack
authors: Section for Cell Therapy, Department of Oncology, Oslo University Hospital Radiumhospitalet, Oslo, Norway.
authors: J A
authors: JA
authors: Kyte
mesh_terms: D000818:Animals; D018941:Antigens, CD19 / Q000235:genetics / Q000276:immunology; D018106:CD28 Antigens / Q000235:genetics / Q000276:immunology; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D015316:Genetic Therapy; D057809:HEK293 Cells; D006801:Humans; D016219:Immunotherapy, Adoptive; D007938:Leukemia / Q000628:therapy*; D008262:Macrophage Activation; D008264:Macrophages / Q000276:immunology; D051379:Mice; D016688:Mice, Inbred NOD; D011948:Receptors, Antigen, T-Cell / Q000235:genetics* / Q000276:immunology; D017452:Receptors, IgG / Q000235:genetics* / Q000276:immunology; D053262:Receptors, OX40 / Q000235:genetics / Q000276:immunology; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology* / Q000637:transplantation; D023041:Xenograft Model Antitumor Assays
chemical_list: D018941:Antigens, CD19; D018106:CD28 Antigens; D011948:Receptors, Antigen, T-Cell; D017452:Receptors, IgG; D053262:Receptors, OX40; D011994:Recombinant Proteins
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