Wdfy4-deficiency reveals a critical role for cross-presentation in anti-viral and anti-tumor responses

Abstract Cross-presentation allows for the presentation of exogenous viral and tumor antigens to CD8+ T cells by XCR1+ classical dendritic cells (cDC1s). Previously, the role of cross-presentation in cytotoxic T cell responses in vivo was unclear due to the lack of mouse models specifically deficient in cross-presentation. We developed a CRISPR-Cas9 screen to find novel regulators of cross-presentation and found that the protein WDFY4 is essential for cross-presentation of cell-associated antigens but not for direct presentation or presentation on MHCII. WDFY4-deficient mice had normal cDC1 development and were able to survive infections with Toxoplasma gondii through production of IL-12. However, WDFY4-deficient mice failed to prime CD8+ T cells to viral antigens and were completely unable to control immunogenic tumors. WDFY4 interacts with proteins related to vesicular formation and trafficking such as clathrin and HSP90ab1 and localizes near the cell surface, suggesting its involvement in vesicular targeting after antigen uptake during cross-presentation.