NK cell activation has been shown to be metabolically regulated in vitro; however, the role of metabolism during in vivo NK cell responses to infection is unknown. We examined the role of glycolysis ...in NK cell function during murine cytomegalovirus (MCMV) infection and the ability of IL-15 to prime NK cells during CMV infection. The glucose metabolism inhibitor 2-deoxy-ᴅ-glucose (2DG) impaired both mouse and human NK cell cytotoxicity following priming in vitro. Similarly, MCMV-infected mice treated with 2DG had impaired clearance of NK-specific targets in vivo, which was associated with higher viral burden and susceptibility to infection on the C57BL/6 background. IL-15 priming is known to alter NK cell metabolism and metabolic requirements for activation. Treatment with the IL-15 superagonist ALT-803 rescued mice from otherwise lethal infection in an NK-dependent manner. Consistent with this, treatment of a patient with ALT-803 for recurrent CMV reactivation after hematopoietic cell transplant was associated with clearance of viremia. These studies demonstrate that NK cell-mediated control of viral infection requires glucose metabolism and that IL-15 treatment in vivo can reduce this requirement and may be effective as an antiviral therapy.
Because NK cells secrete cytotoxic granules and cytokines that can destroy surrounding cells and help shape the subsequent immune response, they must be kept under tight control. Several mechanisms, ...at different levels, are in place to control NK cell function. In this study, we describe a novel mechanism regulating NK cell function in which NK cells acquire ligands for activating receptors from target cells by trogocytosis, rendering the NK cells hyporesponsive. In this model, murine NK cells acquire m157, the murine CMV-encoded ligand for the Ly49H-activating receptor, from target cells both in vitro and in vivo. Although acquisition of m157 requires cell-to-cell contact, it does not require the expression of the Ly49H receptor by the NK cell. Acquired m157 protein is expressed on the NK cell surface with a glycosylphosphatidylinisotol linkage and interacts with the Ly49H receptor expressed on the NK cell. This interaction results in blocking the Ly49H receptor that prevents the NK cells from recognizing m157-expressing targets and continuous engagement of the Ly49H-activating receptor, which results in the hyporesponsiveness of the Ly49H(+) NK cell to stimulation through other activating receptors. Thus, NK cell acquisition of a ligand for an activation receptor by trogocytosis renders them hyporesponsive. This mechanism, by which mature NK cell function can be altered, has important implications in regard to how NK cells respond to tumors in specific microenvironments as well as the use of expanded NK cells in treating various malignancies.
Natural killer (NK) cell tolerance mechanisms are incompletely understood. One possibility is that they possess self-specific activation receptors that result in hyporesponsiveness unless modulated ...by self-major histocompatability complex (MHC)-specific inhibitory receptors. As putative self-specific activation receptors have not been well characterized, we studied a transgenic C57BL/6 mouse that ubiquitously expresses m157 (m157-Tg), which is the murine cytomegalovirus (MCMV)-encoded ligand for the Ly49H NK cell activation receptor. The transgenic mice were more susceptible to MCMV infection and were unable to reject m157-Tg bone marrow, suggesting defects in Ly49H(+) NK cells. There was a reversible hyporesponsiveness of Ly49H(+) NK cells that extended to Ly49H-independent stimuli. Continuous Ly49H-m157 interaction was necessary for the functional defects. Interestingly, functional defects occurred when mature wild-type NK cells were adoptively transferred to m157-Tg mice, suggesting that mature NK cells may acquire hyporesponsiveness. Importantly, NK cell tolerance caused by Ly49H-m157 interaction was similar in NK cells regardless of expression of Ly49C, an inhibitory receptor specific for a self-MHC allele in C57BL/6 mice. Thus, engagement of self-specific activation receptors in vivo induces an NK cell tolerance effect that is not affected by self-MHC-specific inhibitory receptors.
Natural killer (NK) cells play an important role in the innate immune response. The summation of activation and inhibitory signals delivered through cell surface membrane receptors determines NK cell ...function. However, the continuous engagement of an activating receptor on NK cells appears to render the cells hyporesponsive to stimulation through other unrelated activating receptors. The mechanism by which this takes place remains unclear. Herein we demonstrate that continuous
engagement of the Ly49H receptor with its ligand, m157, results in Ly49H
NK cells that are hyporesponsive to further stimulation by other ITAM-dependent and independent receptors, while Ly49H
NK cells remain unaffected. The hyporesponsiveness of the NK cell correlates with the degree of Ly49H receptor downmodulation on its cell surface. We observe defects in calcium flux in the hyporesponsive NK cells following stimulation through the NK1.1 receptor. In addition, we observe differences in signaling molecules that play a role in calcium flux, including spleen tyrosine kinase (Syk) at baseline and phosphorylated phospholipase C gamma 2 (p-PLCγ2) at both baseline and following stimulation through NK1.1. We also demonstrate that various ITAM associated activation receptors, including Ly49H, remain associated with their respective adaptor molecules. With regard to
NK cell function, we did not find differences in the formation of metastatic lung lesions following IV injection of B16 melanoma cells. However, we did observe defects in rejection of missing-self targets
. The data suggest that continuous engagement of the Ly49H activating receptor on NK cells results in hyporesponsiveness of the NK cells to all of the ITAM-dependent and independent receptors we analyzed due to altered signaling pathways downstream of the receptor and adaptor molecule.
NK cells are important mediators of viral control with the capacity to form adaptive immune features following infection. However, studies of infection-induced adaptive NK cells require adoptive cell ...transfer to lower the precursor frequency of "Ag-specific" NK cells, potentially limiting the diversity of the NK cell response. In seeking an unmanipulated model to probe the adaptive NK cells, we interrogated a wide range of Collaborative Cross (CC) inbred mice, inbred mouse strains that exhibit broad genetic diversity across strains. Our assessment identified and validated a putative "ideal" CC strain, CC006, which does not require manipulation to generate and maintain adaptive NK cells. Critically, CC006 mice, in contrast to C57BL/6 mice, are capable of developing enhanced NK cell-mediated protective responses to murine CMV infection following m157-mediated vaccination. This work both furthers our understanding of adaptive NK cells and demonstrates the utility of CC mice in the development and interrogation of immunologic models.
Continuous engagement of the Ly49H activating receptor with its ligand (m157) in a transgenic mouse expressing m157 (m157‐Tg) results in hyporesponsiveness of Ly49H+ NK cells. The same interaction, ...during murine cytomegalovirus (MCMV) infection, leads to activation of Ly49H+ NK cells. MCMV infection results in decreased MHC class I (MHC‐I) expression on the infected cell as well as inflammatory responses, both of which do not take place in the uninfected m157‐Tg mouse, potentially allowing for activation of NK cells in the context of MCMV infection. In this study, we demonstrated that viral infection transiently reverses activation receptor‐mediated NK cell hyporesponsiveness in an MHC‐I‐independent mechanism. Furthermore, Ly49H+ NK cells in an MHC‐I‐deficient environment remained hyporesponsive in the context of m157 expression, even when mature WT splenocytes were transferred into m157‐Tg mice in an MHC‐I‐deficient environment. However, the administration of cytokines TNF‐α, IL‐12, and IFN‐β resulted in a partial recovery from activation receptor‐induced hyporesponsiveness. Thus, the release of the aforementioned cytokines during MCMV infection and not the downregulation of MHC‐I expression appears to be responsible for partial resolution of Ly49H receptor‐induced NK cell hyporesponsiveness.
NK cell responses are determined by signals received through activating and inhibitory cell surface receptors. Ly49H is an NK cell-specific activating receptor that accounts for the genetic ...resistance to murine CMV (MCMV). The Ly49H receptor has been shown to interact with two adaptor proteins (DAP12 and DAP10). In the context of MCMV infection, interaction of m157 (the MCMV-encoded ligand for Ly49H) with Ly49H results in activation of Ly49H-expressing NK cells. Chronic exposure of Ly49H with m157, however, induces tolerance in these same cells. The mechanism of this tolerance remains poorly understood. Using a transgenic mouse model, we demonstrate that induction of tolerance in Ly49H(+) NK cells by chronic exposure to m157, in vivo, requires signaling through the Ly49H adaptor protein DAP12, but not the DAP10 adaptor protein. Furthermore, mature Ly49H-expressing NK cells from wild-type mice can acquire a tolerant phenotype by 24 h posttransfer into a transgenic C57BL/6 mouse that expresses m157. The tolerant phenotype can be reversed, in vivo, if tolerant NK cells are transferred to mice that do not express the m157 protein. Thus, continuous activating receptor engagement can induce a transient tolerance in mature NK cells in vivo. These observations provide new insight into how activating receptor engagement shapes NK cell function and has important implications in how NK cells respond to tumors and during chronic viral infection.
Species from the genus Phytophthora are well represented among organisms causing serious diseases on trees. Phytophthora plurivora has been implicated in long-term decline of woodland trees across ...Europe. Here we present a draft genome sequence of P. plurivora, originally isolated from diseased European beech (Fagus sylvatica) in Malmö, Sweden. When compared with other sequenced Phytophthora species, the P. plurivora genome assembly is relatively compact, spanning 41 Mb. This is organized in 1,919 contigs and 1,898 scaffolds, encompassing 11,741 predicted genes, and has a repeat content of approximately 15%. Comparison of allele frequencies revealed evidence for tetraploidy in the sequenced isolate. As in other sequenced Phytophthora species, P. plurivora possesses genes for pathogenicity-associated RXLR and Crinkle and Necrosis effectors, predominantly located in gene-sparse genomic regions. Comparison of the P. plurivora RXLR effectors with orthologs in other sequenced species in the same clade (Phytophthora multivora and Phytophthora capsici) revealed that the orthologs were likely to be under neutral or purifying selection.
The use of replication-defective adenoviruses (RDAd) for human gene therapy has been limited by host immune responses that result in transient recombinant gene expression in vivo. It remained unclear ...whether these immune responses were directed predominantly against viral proteins or, alternatively, against foreign transgene-encoded proteins. In this report, we have compared the stability of recombinant gene expression in adult immunocompetent mice following intramuscular (i.m.) injection with identical RDAd encoding self (murine) or foreign (human) erythropoietin. Our results demonstrate that immune responses direct against foreign transgene-encoded proteins are the major determinants of the stability of gene expression following i.m. injection of RDAd. Moreover, we demonstrate long-term recombinant gene expression in immunocompetent animals following a single i.m. injection of RDAd encoding a self protein. These findings are important for the design of future preclinical and clinical gene therapy trials.
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