scholarly journals The human cytomegalovirus protein UL147A downregulates the most prevalent MICA allele: MICA*008, to evade NK cell-mediated killing

2020 ◽  
Author(s):  
Einat Seidel ◽  
Liat Dassa ◽  
Esther Oiknine-Djian ◽  
Dana G. Wolf ◽  
Vu Thuy Khanh Le-Trilling ◽  
...  

AbstractNatural killer (NK) cells are innate immune lymphocytes capable of killing target cells without prior sensitization. NK cell activity is regulated by signals received from activating and inhibitory receptors. One pivotal activating NK receptor is NKG2D, which binds a family of eight ligands, including the major histocompatibility complex (MHC) class I-related chain A (MICA). Human cytomegalovirus (HCMV) is a ubiquitous betaherpesvirus causing morbidity and mortality in immunosuppressed patients and congenitally infected infants. HCMV encodes multiple antagonists of NK cell activation, including many mechanisms targeting MICA. However, only one of these mechanisms counters the most prevalent MICA allele, MICA*008. Here, we discover that a hitherto uncharacterized HCMV protein, UL147A, specifically targets MICA*008 to proteasomal degradation, thus hindering the elimination of HCMV-infected cells by NK cells. Mechanistic analyses disclose that the non-canonical GPI anchoring pathway of immature MICA*008 constitutes the determinant of UL147A specificity for this MICA allele. These findings advance our understanding of the complex and rapidly evolving HCMV immune evasion mechanisms, which may facilitate the development of antiviral drugs and vaccines.Author SummaryHuman cytomegalovirus (HCMV) is a common pathogen that usually causes asymptomatic infection in the immunocompetent population, but the immunosuppressed and fetuses infected in utero suffer mortality and disability due to HCMV disease. Current HCMV treatments are limited and no vaccine has been approved, despite significant efforts. HCMV encodes many genes of unknown function, and virus-host interactions are only partially understood. Here, we discovered that a hitherto uncharacterized HCMV protein, UL147A, downregulates the expression of an activating immune ligand allele named MICA*008, thus hindering the elimination of HCMV-infected cells. Elucidating HCMV immune evasion mechanisms could aid in the development of novel HCMV treatments and vaccines. Furthermore, MICA*008 is a highly prevalent allele implicated in cancer immune evasion, autoimmunity and graft rejection. In this work we have shown that UL147A interferes with MICA*008’s poorly understood, nonstandard maturation pathway. Study of UL147A may enable manipulation of its expression as a therapeutic measure against HCMV.

2021 ◽  
Vol 17 (5) ◽  
pp. e1008807
Author(s):  
Einat Seidel ◽  
Liat Dassa ◽  
Corinna Schuler ◽  
Esther Oiknine-Djian ◽  
Dana G. Wolf ◽  
...  

Natural killer (NK) cells are innate immune lymphocytes capable of killing target cells without prior sensitization. One pivotal activating NK receptor is NKG2D, which binds a family of eight ligands, including the major histocompatibility complex (MHC) class I-related chain A (MICA). Human cytomegalovirus (HCMV) is a ubiquitous betaherpesvirus causing morbidity and mortality in immunosuppressed patients and congenitally infected infants. HCMV encodes multiple antagonists of NK cell activation, including many mechanisms targeting MICA. However, only one of these mechanisms, the HCMV protein US9, counters the most prevalent MICA allele, MICA*008. Here, we discover that a hitherto uncharacterized HCMV protein, UL147A, specifically downregulates MICA*008. UL147A primarily induces MICA*008 maturation arrest, and additionally targets it to proteasomal degradation, acting additively with US9 during HCMV infection. Thus, UL147A hinders NKG2D-mediated elimination of HCMV-infected cells by NK cells. Mechanistic analyses disclose that the non-canonical GPI anchoring pathway of immature MICA*008 constitutes the determinant of UL147A specificity for this MICA allele. These findings advance our understanding of the complex and rapidly evolving HCMV immune evasion mechanisms, which may facilitate the development of antiviral drugs and vaccines.


Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 2411-2411
Author(s):  
Jack Fisher ◽  
Christopher J. Walker ◽  
Peter Johnson ◽  
Mark S Cragg ◽  
Francesco Forconi ◽  
...  

Abstract Introduction: Natural killer (NK) cells are powerful immune effectors which induce direct cytotoxicity, promote adaptive immune responses and mediate antibody dependent cellular cytotoxicity (ADCC). Enhancement of NK cell activity against cancer is currently the focus of intense research efforts and strategies include CAR-NK, stimulatory antibodies, cytokines and checkpoint inhibitors. Upregulation of exportin-1 (XPO1) is common in human cancers and high expression is negatively associated with survival in various cancers including diffuse large B cell lymphoma (DLBCL). Targeted inhibition of XPO1 by the selective inhibitor selinexor leads to cancer cell death via accumulation of tumour suppressor proteins in the nucleus, dysregulation of growth regulatory proteins and blockade of oncogene protein translation. The therapeutic efficacy of XPO1 inhibition has led to FDA approval of the oral XPO1 inhibitor selinexor for the treatment of multiple myeloma and DLBCL. The effect of selinexor on NK cell activity has not previously been investigated and was therefore addressed in this study. Methods: The B lymphoma cell lines JeKo-1, SU-DHL-4 and Ramos were incubated with selinexor (50-2000nM) for 18 hours before analysis. Flow cytometry was used to assess cell surface expression of activating and inhibitory ligands for NK cells. For NK based assays, peripheral blood derived NK cells were isolated from healthy donors and incubated with IL-15 (1ng/ml) overnight prior to co-culture with target lymphoma cells for a further 4 hours. Cytotoxicity was assessed using propidium iodide staining of target cells and degranulation of NK cells was assessed by measurement of CD107a. Whole blood samples from colorectal cancer patients (n=11) at pre-treatment and 3 weeks post selinexor monotherapy were assessed by flow cytometry for CD45+CD3-CD19-CD56+ NK cells. Results: Selinexor pre-treatment of target lymphoma cells significantly increased NK cell mediated cytotoxicity against SU-DHL-4 (2.2 Fold increase, p<0.01), JeKo-1 (2 Fold increase, p<0.01) and Ramos (1.7 Fold increase, p<0.01) cells. In accordance with this, selinexor pre-treatment of target cells also increased the activation of NK cells against SU-DHL-4, JeKo-1 and Ramos cells as measured by CD107a expression in both CD56 bright and CD56 dim NK cell sub-groups. To identify the mechanism behind this, we measured expression of activating and inhibitory ligands for NK cells on SU-DHL-4 cells after incubation with selinexor. No significant changes in expression of activating ligands (MICA/B, ULBP-2/5/6, ULBP-1, Vimentin, B7H6, CD54) were evident. In contrast, selinexor significantly (p<0.001) reduced the surface expression of HLA-E on SU-DHL-4 cells by 50%. Selinexor mediated downregulation of HLA-E was also evident in Ramos (60% reduction, p<0.001) and JeKo-1 cells (20% reduction, p<0.01). HLA-E binds the ITIM containing receptor NKG2A, a key inhibitory receptor for NK cells and subsets of T cells. In accordance with this, selinexor pre-treatment of SU-DHL-4 cells selectively increased NKG2A+ NK cell activation (p<0.01) following co-culture. To examine the effect of selinexor on NK cells in patients, we assessed the proportion of NK cells in the peripheral blood of 11 colorectal cancer patients at pre-treatment and three weeks post selinexor monotherapy. % NK cells of CD45+ peripheral blood lymphocytes following treatment with selinexor was increased 2-fold (Median 5% pre-treatment vs 10% post selinexor). In addition, increased abundance of the less mature and less cytotoxic CD56 bright subset of NK cells was associated with poor response to therapy (Median 4% responders (n=3) vs 20% non-responders (n=8)). Larger patient datasets are required to confirm these effects and this analysis is currently ongoing. The effect of selinexor on NK cells in patients with lymphoma is also currently under investigation. Conclusions: The NKG2A:HLA-E axis is a novel immune checkpoint target and our data identifies that selinexor sensitises lymphoma cells to NK cell mediated killing via disruption of this interaction. In addition, we provide initial evidence that NK cells may be associated with clinical response to selinexor. This data indicates that NK cells may contribute to the therapeutic efficacy of selinexor and that selinexor may synergise with NK cell targeted therapies for the treatment of lymphoma. Disclosures Walker: Karyopharm Therapeutics: Current Employment, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Johnson: Morphosys: Honoraria; Kymera: Honoraria; Kite Pharma: Honoraria; Incyte: Honoraria; Genmab: Honoraria; Celgene: Honoraria; Bristol-Myers: Honoraria; Epizyme: Consultancy, Research Funding; Boehringer Ingelheim: Consultancy; Novartis: Honoraria; Takeda: Honoraria; Oncimmune: Consultancy; Janssen: Consultancy. Cragg: BioInvent International: Consultancy, Research Funding; GSK: Research Funding; UCB: Research Funding; iTeos: Research Funding; Roche: Research Funding. Forconi: Novartis: Honoraria; Roche: Honoraria; Janssen: Consultancy, Honoraria, Speakers Bureau; AbbVie: Consultancy, Honoraria, Speakers Bureau; Gilead: Research Funding. Landesman: Karyopharm Therapeutics: Current Employment, Current equity holder in publicly-traded company. Blunt: Karyopharm Therapeutics: Research Funding.


2014 ◽  
Vol 89 (5) ◽  
pp. 2906-2917 ◽  
Author(s):  
Zeguang Wu ◽  
Christian Sinzger ◽  
Johanna Julia Reichel ◽  
Marlies Just ◽  
Thomas Mertens

ABSTRACTHuman cytomegalovirus (HCMV) transmission within the host is important for the pathogenesis of HCMV diseases. Natural killer (NK) cells are well known to provide a first line of host defense against virus infections. However, the role of NK cells in the control of HCMV transmission is still unknown. Here, we provide the first experimental evidence that NK cells can efficiently control HCMV transmission in different cell types. NK cells engage different mechanisms to control the HCMV transmission both via soluble factors and by cell contact. NK cell-produced interferon gamma (IFN-γ) suppresses HCMV production and induces resistance of bystander cells to HCMV infection. The UL16 viral gene contributes to an immune evasion from the NK cell-mediated control of HCMV transmission. Furthermore, the efficacy of the antibody-dependent NK cell-mediated control of HCMV transmission is dependent on a CD16-158V/F polymorphism. Our findings indicate that NK cells may have a clinical relevance in HCMV infection and highlight the need to consider potential therapeutic strategies based on the manipulation of NK cells.IMPORTANCEHuman cytomegalovirus (HCMV) infects 40% to 100% of the human population worldwide. After primary infection, mainly in childhood, the virus establishes a lifelong persistence with possible reactivations. Most infections remain asymptomatic; however, HCMV represents a major health problem since it is the most frequent cause of infection-induced birth defects and is responsible for high morbidity and mortality in immunocompromised patients. The immune system normally controls the infection by antibodies and immune effector cells. One type of effector cells are the natural killer (NK) cells, which provide a rapid response to virus-infected cells. NK cells participate in viral clearance by inducing the death of infected cells. NK cells also secrete antiviral cytokines as a consequence of the interaction with an infected cell. In this study, we investigated the mechanisms by which NK cells control HCMV transmission, from the perspectives of immune surveillance and immune evasion.


2019 ◽  
Vol 20 (15) ◽  
pp. 3715 ◽  
Author(s):  
Loredana Cifaldi ◽  
Margherita Doria ◽  
Nicola Cotugno ◽  
Sonia Zicari ◽  
Caterina Cancrini ◽  
...  

Natural Killer (NK) cells play a critical role in host defense against viral infections. The mechanisms of recognition and killing of virus-infected cells mediated by NK cells are still only partially defined. Several viruses induce, on the surface of target cells, the expression of molecules that are specifically recognized by NK cell-activating receptors. The main NK cell-activating receptors involved in the recognition and killing of virus-infected cells are NKG2D and DNAM-1. In particular, ligands for DNAM-1 are nectin/nectin-like molecules involved also in mechanisms allowing viral infection. Viruses adopt several immune evasion strategies, including those affecting NK cell-mediated immune surveillance, causing persistent viral infection and the development of virus-associated diseases. The virus’s immune evasion efficacy depends on molecules differently expressed during the various phases of infection. In this review, we overview the molecular strategies adopted by viruses, specifically cytomegalovirus (CMV), human immunodeficiency virus (HIV-1), herpes virus (HSV), Epstein-Barr virus (EBV) and hepatitis C virus (HCV), aiming to evade NK cell-mediated surveillance, with a special focus on the modulation of DNAM-1 activating receptor and its ligands in various phases of the viral life cycle. The increasing understanding of mechanisms involved in the modulation of activating ligands, together with those mediating the viral immune evasion strategies, would provide critical tools leading to design novel NK cell-based immunotherapies aiming at viral infection control, thus improving cure strategies of virus-associated diseases.


2003 ◽  
Vol 77 (8) ◽  
pp. 4539-4545 ◽  
Author(s):  
Jenny Odeberg ◽  
Helena Browne ◽  
Sunil Metkar ◽  
Christopher J. Froelich ◽  
Lars Brandén ◽  
...  

ABSTRACT Several reports have shown that human cytomegalovirus (HCMV)-infected cells are resistant to NK lysis. These studies have focused on receptor-ligand interactions, and different HCMV proteins have been indicated to mediate inhibitory NK signals. Here, we report that the HCMV protein UL16 is of major importance for the ability of HCMV-infected cells to resist NK cell-mediated cytotoxicity. Fibroblasts infected with the UL16 deletion mutant HCMV strain exhibited a 70% increased sensitivity to NK killing at 7 days postinfection compared to AD169-infected cells. Interestingly, HCMV-infected cells did not appear to engage inhibitory molecules on NK cells, since the levels of granzyme B were not reduced in supernatants obtained from NK cell cocultures with infected target cells compared to uninfected target cells. Furthermore, HCMV-infected cells, but not cells infected with the UL16 deletion mutant HCMV strain, exhibited a significantly increased resistance to the action of cytolytic proteins, including perforin, granzyme B, streptolysin O, and porcine NK lysin. In addition, fluorescence-activated cell sorting for UL16-positive transfected cells resulted in protection levels of 90% compared to control cells carrying the green fluorescent protein vector. Thus, the UL16 protein mediates an increased protection against the action of cytolytic proteins released by activated NK cells, possibly by a membrane-stabilizing mechanisms, rather than by delivering negative signals to NK cells.


Biomedicines ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 557
Author(s):  
Xuewen Deng ◽  
Hiroshi Terunuma ◽  
Mie Nieda

Natural killer (NK) cells are cytotoxic immune cells with an innate capacity for eliminating cancer cells and virus- infected cells. NK cells are critical effector cells in the immunosurveillance of cancer and viral infections. Patients with low NK cell activity or NK cell deficiencies are predisposed to increased risks of cancer and severe viral infections. However, functional alterations of human NK cells are associated with lifestyles and aging. Personal lifestyles, such as cigarette smoking, alcohol consumption, stress, obesity, and aging are correlated with NK cell dysfunction, whereas adequate sleep, moderate exercise, forest bathing, and listening to music are associated with functional healthy NK cells. Therefore, adherence to a healthy lifestyle is essential and will be favorable for immunosurveillance of cancer and viral infections with healthy NK cells.


2021 ◽  
Vol 22 (13) ◽  
pp. 6670
Author(s):  
Eva Prašnikar ◽  
Andrej Perdih ◽  
Jure Borišek

The innate immune system’s natural killer (NK) cells exert their cytolytic function against a variety of pathological challenges, including tumors and virally infected cells. Their activation depends on net signaling mediated via inhibitory and activating receptors that interact with specific ligands displayed on the surfaces of target cells. The CD94/NKG2C heterodimer is one of the NK activating receptors and performs its function by interacting with the trimeric ligand comprised of the HLA-E/β2m/nonameric peptide complex. Here, simulations of the all-atom multi-microsecond molecular dynamics in five immune complexes provide atomistic insights into the receptor–ligand molecular recognition, as well as the molecular events that facilitate the NK cell activation. We identify NKG2C, the HLA-Eα2 domain, and the nonameric peptide as the key elements involved in the molecular machinery of signal transduction via an intertwined hydrogen bond network. Overall, the study addresses the complex intricacies that are necessary to understand the mechanisms of the innate immune system.


2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Yan Feng ◽  
Yan Li ◽  
Ying Zhang ◽  
Bo-Hao Zhang ◽  
Hui Zhao ◽  
...  

Abstract Background Brain ischemia compromises natural killer (NK) cell-mediated immune defenses by acting on neurogenic and intracellular pathways. Less is known about the posttranscriptional mechanisms that regulate NK cell activation and cytotoxicity after ischemic stroke. Methods Using a NanoString nCounter® miRNA array panel, we explored the microRNA (miRNA) profile of splenic NK cells in mice subjected to middle cerebral artery occlusion. Differential gene expression and function/pathway analysis were applied to investigate the main functions of predicted miRNA target genes. miR-1224 inhibitor/mimics transfection and passive transfer of NK cells were performed to confirm the impact of miR-1224 in NK cells after brain ischemia. Results We observed striking dysregulation of several miRNAs in response to ischemia. Among those miRNAs, miR-1224 markedly increased 3 days after ischemic stroke. Transfection of miR-1224 mimics into NK cells resulted in suppression of NK cell activity, while an miR-1224 inhibitor enhanced NK cell activity and cytotoxicity, especially in the periphery. Passive transfer of NK cells treated with an miR-1224 inhibitor prevented the accumulation of a bacterial burden in the lungs after ischemic stroke, suggesting an enhanced immune defense of NK cells. The transcription factor Sp1, which controls cytokine/chemokine release by NK cells at the transcriptional level, is a predicted target of miR-1224. The inhibitory effect of miR-1224 on NK cell activity was blocked in Sp1 knockout mice. Conclusions These findings indicate that miR-1224 may serve as a negative regulator of NK cell activation in an Sp1-dependent manner; this mechanism may be a novel target to prevent poststroke infection specifically in the periphery and preserve immune defense in the brain.


1993 ◽  
Vol 178 (3) ◽  
pp. 961-969 ◽  
Author(s):  
M S Malnati ◽  
P Lusso ◽  
E Ciccone ◽  
A Moretta ◽  
L Moretta ◽  
...  

Natural killer (NK) cells provide a first line of defense against viral infections. The mechanisms by which NK cells recognize and eliminate infected cells are still largely unknown. To test whether target cell elements contribute to NK cell recognition of virus-infected cells, human NK cells were cloned from two unrelated donors and assayed for their ability to kill normal autologous or allogeneic cells before and after infection by human herpesvirus 6 (HHV-6), a T-lymphotropic herpesvirus. Of 132 NK clones isolated from donor 1, all displayed strong cytolytic activity against the NK-sensitive cell line K562, none killed uninfected autologous T cells, and 65 (49%) killed autologous T cells infected with HHV-6. A panel of representative NK clones from donors 1 and 2 was tested on targets obtained from four donors. A wide heterogeneity was observed in the specificity of lysis of infected target cells among the NK clones. Some clones killed none, some killed only one, and others killed more than one of the different HHV-6-infected target cells. Killing of infected targets was not due to complete absence of class I molecules because class I surface levels were only partially affected by HHV-6 infection. Thus, target cell recognition is not controlled by the effector NK cell alone, but also by polymorphic elements on the target cell that restrict NK cell recognition. Furthermore, NK clones from different donors display a variable range of specificities in their recognition of infected target cells.


2021 ◽  
Author(s):  
Andrew E. Greenstein ◽  
Mouhammed Amir Habra ◽  
Subhagya A. Wadekar ◽  
Andreas Grauer

Elevated glucocorticoid (GC) activity may limit tumor immune response and immune checkpoint inhibitor (ICI) efficacy. Adrenocortical carcinoma (ACC) provides a unique test case to assess correlates of GC activity, as approximately half of ACC patients exhibit excess GC production (GC+). ACC multi-omics were analyzed to identify molecular consequences of GC+ and assess the rationale for combining the glucocorticoid receptor (GR) antagonist relacorilant with an ICI. GC status, mRNA expression, and DNA mutation and methylation data from 71 adrenal tumors were accessed via The Cancer Genome Atlas. Expression of 858 genes differed significantly between GC- and GC+ ACC cases. KEGG pathway analysis showed higher gene expression of 3 pathways involved in steroid synthesis and secretion in GC+ cases. Fifteen pathways, most related to NK cells and other immune activity, showed lower expression. Hypomethylation was primarily observed in the steroid synthesis pathways. Tumor-infiltrating CD4+ memory (P=.003), CD8+ memory (P=.001), and NKT-cells (P=.014) were depleted in GC+ cases; tumor-associated neutrophils were enriched (P=.001). Given the pronounced differences between GC+ and GC- ACC, the effects of cortisol on NK cells were assessed in vitro (NK cells from human PBMCs stimulated with IL-2 or IL-12/15). Cortisol suppressed, and relacorilant restored, NK cell activation, proliferation, and direct tumor cell killing. Thus, GR antagonism may increase the abundance and function of NK and other immune cells in the tumor microenvironment, promoting immune response in GC+ ACC and other malignancies with GC+. This hypothesis will be tested in a phase 1 trial of relacorilant + ICI.


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