Global transcriptional reprogramming by cytomegalovirus infection suppresses MHC class II antigen presentation while enhancing migration machinery in murine dendritic cells

Dendritic cells (DCs) serve dual roles in cytomegalovirus infection: orchestrating antiviral immunity and acting as vehicles for viral dissemination. DC-dependent systemic spread of mouse cytomegalovirus (MCMV) is dependent on the expression of a viral G protein-coupled receptor homologue, encoded by M33. We performed global transcriptional profiling of murine DCs infected with either WT mouse MCMV or an M33 mutant harbouring a single point mutation (R131Q; denoted M33NQY), which ablates constitutive G protein-dependent signalling. RNA-seq analysis revealed that MCMV induces substantial transcriptional reprogramming, with over 2,400 significantly altered genes affecting key immune and migration pathways. WT MCMV infection resulted in 1,883 upregulated and 658 downregulated genes, while M33NQY infection showed comparable effects with 1,905 upregulated and 668 downregulated genes. Both viruses systematically downregulated the MHC class II antigen presentation machinery, with substantial suppression of H2 molecules, peptide-loading components (<i>H2-DMa/H2-DMb1</i>) and the class II transactivator <i>Ciita</i> (log₂FC >-6.4). Pathway analysis revealed coordinated disruption of B cell receptor signalling, leucocyte transendothelial migration and antigen processing and presentation. A comparison between WT and M33NQY-infected DCs demonstrated that while both viruses similarly impair antigen presentation, M33 signalling specifically enhances the expression of genes involved in transendothelial migration, including <i>Spp1</i> (osteopontin, log₂FC=0.65), cytoskeletal components (<i>Actg1</i> and <i>Actb</i>), adhesion molecules (<i>Icam1</i>) and matrix interaction factors (<i>Tnc</i> and <i>Plau</i>). Network analysis identified critical hub genes, including <i>B2m</i>, <i>Itgb1</i>, <i>Itgam</i> and <i>Icam1</i>, as key regulatory nodes connecting antigen presentation and migration pathways. This provides molecular evidence for a sophisticated viral strategy that shields MCMV from immune detection while hijacking DC migratory machinery to facilitate dissemination, with M33 serving as a specific enhancer of migration-related pathways.