Anti-CD1C monoclonal antibody, clone 3C4

Background The study of dendritic cell (DC) biology in the rhesus macaque is becoming increasingly important but is limited by incomplete characterization and the lack of a rapid assay to quantify cells. Methods We characterized the surface phenotype of myeloid (mDC) and plasmacytoid DC (pDC) subsets in healthy rhesus macaque blood and developed a flow cytometry-based assay for absolute DC determinations. Results Rhesus CD11c(+) mDC were CD16(+) CD11b(+) CD56(lo) CD8(-) CD1c(-) whereas CD123(+) pDC lacked expression of these markers. Precise DC determinations were performed using a rapid two-step assay combining the analysis of whole blood and peripheral blood leukocytes (PBL). Conclusions Antibodies to CD11b, CD56 and CD16 must be omitted from the lineage antibody cocktail to prevent inadvertent gating-out of DC when analyzing rhesus blood. The combined whole-blood/PBL quantification assay will be invaluable for the rapid and repeated monitoring of blood DC counts in this species.

Strong innate and adaptive immune responses are paramount in combating viral infections. Dendritic cells (DCs) detect viral infections via cytosolic RIG-I like receptors (RLRs) RIG-I and MDA5 leading to MAVS-induced immunity. The DEAD-box RNA helicase DDX3 senses abortive human immunodeficiency virus 1 (HIV-1) transcripts and induces MAVS-dependent type I interferon (IFN) responses, suggesting that abortive HIV-1 RNA transcripts induce antiviral immunity. Little is known about the induction of antiviral immunity by DDX3-ligand abortive HIV-1 RNA. Here we synthesized a 58 nucleotide-long capped RNA (HIV-1 Cap-RNA(58)) that mimics abortive HIV-1 RNA transcripts. HIV-1 Cap-RNA(58) induced potent type I IFN responses in monocyte-derived DCs, monocytes, macrophages and primary CD1c(+) DCs. Compared with RLR agonist poly-I:C, HIV-1 Cap-RNA(58) induced comparable levels of type I IFN responses, identifying HIV-1 Cap-RNA(58) as a potent trigger of antiviral immunity. In monocyte-derived DCs, HIV-1 Cap-RNA(58) activated the transcription factors IRF3 and NF-kappa B. Moreover, HIV-1 Cap-RNA(58) induced DC maturation and the expression of pro-inflammatory cytokines. HIV-1 Cap-RNA(58)-stimulated DCs induced proliferation of CD4(+) and CD8(+) T cells and differentiated naive T helper (T-H) cells toward a T(H)2 phenotype. Importantly, treatment of DCs with HIV-1 Cap-RNA(58) resulted in an efficient antiviral innate immune response that reduced ongoing HIV-1 replication in DCs. Our data strongly suggest that HIV-1 Cap-RNA(58) induces potent innate and adaptive immune responses, making it an interesting addition in vaccine design strategies.