Tasmanian devil CD28 and CTLA4 capture CD80 and CD86 from adjacent cells

Abstract

Highlights 33  Key immune checkpoint receptor-ligand interactions are conserved in marsupials. 34  Live cell-based assays show Tasmanian devil CD28 and CTLA4 can capture CD80 35 and CD86 in trans from adjacent cells. 36  Mutation of the conserved CTLA4MYPPPY ligand binding motif to CTLA4MYPPPA 37 reduces binding to CD80 and intercellular protein transfer. 38  Removal of conserved CTLA4YVKM protein recycling binding motif in CTLA4 results 39 in bidirectional intercellular protein transfer between CTLA4 and CD80. 40  Highly successful human immune checkpoint immunotherapies have the potential to 41 be translated for veterinary and conservation medicine. 42 43 Abstract 44 Immune checkpoint immunotherapy is a pillar of human oncology treatment with potential for 45 non-human species. The first checkpoint immunotherapy approved for human cancers targeted 46 the CTLA4 protein. CTLA4 can inhibit T cell activation by capturing and internalizing CD80 47 and CD86 from antigen presenting cells, a process called trans-endocytosis. Similarly, CD28 48 can capture CD80 and CD86 via trogocytosis and retain the captured ligands on the surface of 49 the CD28-expressing cells. The wild Tasmanian devil (Sarcophilus harrisii) population has 50 declined by 77% due to transmissible cancers that evade immune defenses despite genetic 51 mismatches between the host and tumours. We used a live cell-based assay to demonstrate that 52 devil CTLA4 and CD28 can capture CD80 and CD86. Mutation of evolutionarily conserved 53 motifs in CTLA4 altered functional interactions with CD80 and CD86 in accordance with 54 patterns observed in other species. These results suggest that checkpoint immunotherapies can 55 be translated to evolutionarily divergent species. 56 57 Keywords 58 immune checkpoint, wild immunology, transmissible cancer, trans-endocytosis, trogocytosis, 59 intercellular protein transfer 60 Abbreviations 61 intercellular protein transfer (IPT), devil facial tumour (DFT), interferon gamma (IFNγ), major 62 histocompatibility complex (MHC), Cytotoxic T-Lymphocyte Associated Protein 4 (CTLA4), 63 blue fluorescent protein (BFP) 64 65 We Amanda Patchett, Camila Espejo, Chrissie Ong, Rob Gasperini, and Ruth Pye for 353 assistance in the laboratory and general advice on this project. 354 355

Mesenchymal plasticity of devil facial tumour cells during in vivo vaccine and immunotherapy trials

“…Upregulation of inhibitory checkpoint molecules, such as PDL1 and CTLA4 , was likely to have promoted host‐tumour equilibrium in this cancer by suppressing immune‐mediated killing. Previous analysis of immune checkpoint sequences and functional protein interactions has suggested that checkpoint receptor‐ligand interactions in devils are similar to humans and mice 51–53 . Tasmanian devil monoclonal antibodies previously produced against targets such as PD1 could effectively promote checkpoint blockade and subsequent tumour regression in DFT1 cancers exhibiting this immune‐enriched phenotype 54 …”

“…Previous analysis of immune checkpoint sequences and functional protein interactions has suggested that checkpoint receptor-ligand interactions in devils are similar to humans and mice. [51][52][53] Tasmanian devil monoclonal antibodies previously produced against targets such as PD1 could effectively promote checkpoint blockade and subsequent tumour regression in DFT1 cancers exhibiting this immune-enriched phenotype. 54 The ability of DFT1 cancers to dedifferentiate to a tolerogenic mesenchymal phenotype could be a key mechanism involved in the successful evasion of immune attack by these transmissible cancers.…”