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

Immune checkpoint immunotherapy is a pillar of human oncology treatment with potential for non-human species. The first checkpoint immunotherapy approved for human cancers targeted the CTLA4 protein. CTLA4 can inhibit T cell activation by capturing and internalizing CD80 and CD86 from antigen presenting cells, a process called trans-endocytosis. Similarly, CD28 can capture CD80 and CD86 via trogocytosis and retain the captured ligands on the surface of the CD28-expressing cells. The wild Tasmanian devil ( Sarcophilus harrisii ) population has declined by 77% due to transmissible cancers that evade immune defenses despite genetic mismatches between the host and tumours. We used a live cell-based assay to demonstrate that devil CTLA4 and CD28 can capture CD80 and CD86. Mutation of evolutionarily conserved motifs in CTLA4 altered functional interactions with CD80 and CD86 in accordance with patterns observed in other species. These results suggest that checkpoint immunotherapies can be translated to evolutionarily divergent species. Highlights Key immune checkpoint receptor-ligand interactions are conserved in marsupials. Live cell-based assays show Tasmanian devil CD28 and CTLA4 can capture CD80 and CD86 in trans from adjacent cells. Mutation of the conserved CTLA4 MYPPPY ligand binding motif to CTLA4 MYPPPA reduces binding to CD80 and intercellular protein transfer. Removal of conserved CTLA4 YVKM protein recycling binding motif in CTLA4 results in bidirectional intercellular protein transfer between CTLA4 and CD80. Highly successful human immune checkpoint immunotherapies have the potential to be translated for veterinary and conservation medicine.