A genome-wide CRISPR/Cas9 gene knockout screen identifies immunoglobulin superfamily DCC subclass member 4 as a key host factor that promotes influenza virus endocytosis

Influenza virus infection is dependent on host cellular factors, and identification of these factors and their underlying mechanisms can provide important information for the development of strategies to inhibit viral infection. Here, we used a highly pathogenic H5N1 influenza virus to perform a genome-wide CRISPR/Cas9 gene knockout screen in human lung epithelial cells (A549 cells), and found that knockout of transmembrane protein immunoglobulin superfamily DCC subclass member 4 (IGDCC4) significantly reduced the replication of the virus in A549 cells. Further studies showed that IGDCC4 interacted with the viral hemagglutinin protein and facilitated virus internalization into host cells. Animal infection studies showed that replication of H5N1 virus in the nasal turbinates, lungs, and kidneys of IGDCC4-knockout mice was significantly lower than that in the corresponding organs of wild-type mice. Half of the IGDCC4-knockout mice survived a lethal H5N1 virus challenge, whereas all of the wild-type mice died within 11 days of infection. Our study identifies a novel host factor that promotes influenza virus infection by facilitating internalization and provides insights that will support the development of antiviral therapies.
Author summary Influenza virus infection is initiated by the attachment of the viral HA protein to sialic acid receptors on the host cell surface; most of the virus particles enter cells through clathrin-mediated endocytosis (CME). However, it is still largely unknown which protein(s) play(s) a role in transmitting the signal of viral binding across the plasma membrane to initiate CME. In this study, we found that the single-pass type I transmembrane protein immunoglobulin superfamily DCC subclass member 4 (IGDCC4) plays a key role in influenza virus internalization into host cells. IGDCC4 knockout dramatically increased the ability of mice to resist influenza virus infection. Our study provides insights that will support the development of therapies against influenza.