MHC class Ia molecules facilitate MCK2-dependent MCMV infection of macrophages and virus dissemination to the salivary gland
Murine cytomegalovirus (MCMV) infection of macrophages relies on MCMV-encoded chemokine 2 (MCK2) through one or more unknown cellular receptors while infection of fibroblast occurs independent of MCK2 and is mediated by cell-expressed neuropilin 1. Applying a CRISPR screen, we now identified that the MHC-Ia/Beta-2-microglobulin (B2m) complex serves as an entry port for MCK2-mediated infection of macrophages. Further analyses revealed that MCK2-dependent infection requires expression of the MHC-Ia haplotypes H-2b and H-2d but not H-2k. The importance of the MCK2-MHC-I-pathway for primary infection and viral dissemination was highlighted by experiments with B2m-deficient mice, which lack surface expression of MHC-I molecules. In those mice, intranasally administered MCK2-proficient MCMV could not infect alveolar macrophages and subsequently failed to disseminate into the salivary glands. The identified molecular pathway used by MCMV to infect lung resident macrophages provides essential knowledge for understanding cytomegalovirus-induced pathogenesis, tissue targeting, and virus dissemination.