Type III IFNs production in type I classical dendritic cells to virus-infected cells
Tae Jin Yun1, Annesa Das1, Ai C. Ra2, Eduardo Esteva2, Sergei Kotenko3, Peter A. Sims4, Donna L. Farber5and Boris Reizis1
1Department of Medicine, Section of Rheumatology and the Center for Autoimmunity, University of Chicago, Chicago, IL 60637 USA; 2New York University Grossman School of Medicine, New York, NY 10016, USA; 3Rutgers New Jersey Medical School, Newark, NJ, USA; 4Department of Systems Biology, 5Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York City, NY, USA;
Type I dendritic cells (cDC1s) are specialized for antigen cross-presentation and resistant to viral infection. cDC1s were also shown to secrete type III IFNs in response to viral infection and it was suggested to be mediated by TLR3 pathway. However, the mechanisms by which they recognize virus to produce type III IFNs remain incompletely understood. Utilizing human and mouse cytomegalovirus (CMV/MCMV), we evaluated cDC1s responses to free MCMV particles, MCMV-infected cells, and TLR specific agonists. In addition to Poly(I:C)-mediated TLR3 activation triggering type III IFN production, both human and mouse cDC1s robustly secrete type III IFNs when co-cultured with virus-infected cells. In contrast, free MCMV particles and agonists for TLR2, TLR9, and TLR11 failed to elicit the response, demonstrating that this pathway is TLR2/9/11-independent and selectively driven by infected cells. Notably, type III IFNs induction strictly required direct interaction with viable infected cells, as physical separation in transwell assays or UV inactivation completely abolished type III IFN production. Furthermore, cDC1 uptake of EGFP-labeled viral particles was temperature-sensitive—abrogated at 4°C—confirming active viral transfer from infected cells to cDC1s. Together, these findings establish cDC1s alongside pDCs as crucial antiviral sentinels that mount a targeted type III IFN response requiring direct contact with virus-infected cells.