West Nile virus infection of human monocyte-derived dendritic cells

West Nile virus (WNV) is a neurotropic flavivirus and the leading cause of mosquito-borne encephalitis in the United States. Recent studies in humans have found that dysfunctional T cell responses strongly correlate with development of severe WNV neuroinvasive disease. However, the contributions of human dendritic cells (DCs) in priming WNV-specific T cell immunity remains poorly understood. Here, we demonstrate that human monocyte derived DCs (moDCs) support productive viral replication following infection with a pathogenic strain of WNV. Antiviral effector gene transcription was strongly induced during the log-phase viral growth, while secretion of type I interferons (IFN) occurred with delayed kinetics. Activation of RIG-I like receptor (RLR) or type I IFN signaling prior to log-phase viral growth significantly diminished viral replication, suggesting that early activation of antiviral programs can block WNV infection. In contrast to the induction of antiviral responses, WNV infection did not promote transcription or secretion of pro-inflammatory (IL-6, GM-CSF, CCL3, CCL5, CXCL9) or T cell modulatory cytokines (IL-4, IL-12, IL-15). There was also minimal induction of molecules associated with antigen presentation and T cell priming, including the co-stimulatory molecules CD80, CD86, and CD40. Functionally, WNV-infected moDCs dampened allogenic CD4 and CD8 T cell activation and proliferation. Combined, we propose a model where WNV subverts human DC activation to compromise priming of WNV-specific T cell immunity. Overall design: Human monocyte-derived DCs moDCs were generated from 5 donors and treated with innate immune agonists for 12hr (RIG-I, MDA5, or IFNß) or infected with WNV (12hpi and 24hpi). Time matched mocks were left untreated and collected at 12 and 24 hours post-treatment. RIG-I agonist- 100 ng RNA derived from the 3'UTR of Hepatitis C virus, MDA5 agonist- 100 ng high molecular weight poly-I:C, IFN- 100 IU/ml IFNb and West Nile virus(WNV)-TX lineage 1 strain.