Immune control of murine cytomegalovirus salivary gland infection

• Applicant: Dr. Berislav Bosnjak
• Subject Area: Immunology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 563232125

Many viruses use saliva as an efficient conduit of transmission. Among them, human cytomegalovirus (HCMV) establishes persistent infection within the salivary gland, enabling the virus to spread for months following a primary infection. Mechanisms of virus persistency in the salivary gland can be studied in mice using murine cytomegalovirus (MCMV), which serves as a reliable model for HCMV. We recently discovered that MCMV infection of macrophages primarily relies on major-histocompatibility complex 1/beta-2 microglobulin (MHC-I/B2m) complexes. At the same time, neuropilin-1 is mainly involved in fibroblast infection. However, cellular receptors mediating MCMV infection of salivary gland cells and spread within the organ are unknown. Our preliminary unpublished data show that MCMV infection of newly established murine salivary gland pro-acinar and pro-ductal cell lines, as well as on endothelial cells, depends on the tetraspanin molecule CD81 and additional, still undescribed, cellular proteins. Our well-established CRISPR screen will allow us to characterize those additional cellular proteins on murine salivary gland pro-acinar cells involved in MCMV infection. To validate the CD81 role in viral dissemination and spread within salivary glands, we will compare the course of intranasal infection with MCMV chemokine 2 (MCK2)-proficient and -deficient MCMV strains between Cd81+/+ and Cd81-/- mice. Once MCMV enters the salivary glands, it replicates lytically for months due to inefficient MCMV-specific cytotoxic CD8 T cell control. Surprisingly, in preliminary experiments, we established that mice exhibit sex-based differences in MCMV infection of salivary glands. As salivary gland structure and leukocyte composition show strong sexual dimorphism in mice, our initial data offer an elegant experimental model for a better understanding of CD8 T cells’ antiviral control in this organ. To examine the dynamic interactions of CD8 T cells with infected salivary gland cells in detail, we will use two-photon microscopy to track individual CD8 T cells in state-of-the-art ex vivo culture of precision cut salivary gland slices and salivary glands explanted from MCMV-infected female and male mice. Furthermore, we will apply state-of-the-art CRISPR/Cas9-mediated gene editing of murine T cells to investigate T-cell entry and migration within the salivary glands. Altogether, this project aims to provide new insights into cellular receptors crucial for MCMV infection of salivary gland cells and mechanisms of CD8 T cell impairment within this organ. These results will provide a basis for a better understanding of HCMV persistency within human salivary glands.

• DFG Programme: Research Grants