DNAM-1 and NKG2D mediate natural killer cell activation in response to dengue virus Julia L. McKechnie1, Davis Beltrán2,3,4, Arcelys Pitti2, Henry Puerta-Guardo5, Daniela Pajek5, Simona Zompi5, Eva Harris5, Lewis L. Lanier6, Sandra López Vergès2,3*, Catherine Blish1* 1Stanford University, Stanford, California; 2Gorgas Memorial Institute of Health Studies, Panama City, Panama; 3INDICASAT-AIP, Panama City, Panama; 4Acharya-Nagarjuna University, Guntur, India; 5University of California Berkeley, Berkeley, California; 6University of California San Francisco, San Francisco, California
Natural killer (NK) cells are innate lymphoid cells whose activation in response to virally infected cells is dependent on the balance of activating and inhibitory signals from numerous germline-encoded receptors. Upon activation, NK cells not only shape the initial anti-viral immune response by directly killing infected cells, but also influence the downstream adaptive immune response through secretion of cytokines. Consequently, elucidating the mechanisms by which viruses activate or evade NK cells is critical to our understanding of the immune response to viral infection. Previous reports have shown that dengue virus (DENV), a flavivirus that two-thirds of the world's population is at risk of contracting, activates NK cells. To identify the receptor-ligand interactions mediating this activation, we used cytometry by time of flight (CyTOF) to profile the expression of NK cell receptors and their known ligands in a cohort of acute DENV-infected patients. Our analysis showed increased NK cell expression of perforin, a functional marker of degranulation, in patients compared to healthy controls. Additionally, we identified an association between infection and expression of activating NK cell receptor NKG2D, its ligands MICA/B, and Nectin-2, a ligand for the activating NK cell receptor DNAM-1. We confirmed that NK cells degranulate in response to DENV-infected cells using an autologous in vitro NK co-culture system with DENV-2-infected monocyte-derived immature dendritic cells (imDCs). RT-qPCR analysis of infected imDCs showed an increase in mRNA levels of NKG2D ligands MICA and ULBP-2, -3, -4, -5 at various time points. The same was true for DNAM-1 ligands Nectin-2 and PVR. These results suggest a novel mechanism for NK cell recognition of DENV-infected cells via DNAM-1 and NKG2D interaction with their respective ligands, leading to NK cell degranulation.
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