Activated iNKT Cells Promote Memory CD8+ T Cell Differentiation during Viral Infection

α-galactosylceramide (α-GalCer) is the prototypical lipid ligand for invariant NKT cells. Recent studies have proposed that α-GalCer is an effective adjuvant in vaccination against a range of immune challenges, however its mechanism of action has not been completely elucidated. A variety of delivery methods have been examined including pulsing dendritic cells with α-GalCer to optimize the potential of α-GalCer. These methods are currently being used in a variety of clinical trials in patients with advanced cancer but cannot be used in the context of vaccine development against pathogens due to their complexity. Using a simple delivery method, we evaluated α-GalCer adjuvant properties, using the mouse model for cytomegalovirus (MCMV). We measured several key parameters of the immune response to MCMV, including inflammation, effector, and central memory CD8+ T cell responses. We found that α-GalCer injection at the time of the infection decreases viral titers, alters the kinetics of the inflammatory response, and promotes both increased frequencies and numbers of virus-specific memory CD8+ T cells. Overall, our data suggest that iNKT cell activation by α-GalCer promotes the development of long-term protective immunity through increased fitness of central memory CD8+ T cells, as a consequence of reduced inflammation

Human cytomegalovirus immediate-early 1 protein rewires upstream STAT3 to downstream STAT1 signaling switching an IL6-type to an IFNγ-like response

MN and CP were supported by the Wellcome Trust (www.wellcome.ac.uk) Institutional Strategic Support Fund and CP was supported by the Deutsche Forschungsgemeinschaft (PA 815/2-1; www.dfg.de).The human cytomegalovirus (hCMV) major immediate-early 1 protein (IE1) is best known for activating transcription to facilitate viral replication. Here we present transcriptome data indicating that IE1 is as significant a repressor as it is an activator of host gene expression. Human cells induced to express IE1 exhibit global repression of IL6- and oncostatin M-responsive STAT3 target genes. This repression is followed by STAT1 phosphorylation and activation of STAT1 target genes normally induced by IFNγ. The observed repression and subsequent activation are both mediated through the same region (amino acids 410 to 445) in the C-terminal domain of IE1, and this region serves as a binding site for STAT3. Depletion of STAT3 phenocopies the STAT1-dependent IFNγ-like response to IE1. In contrast, depletion of the IL6 receptor (IL6ST) or the STAT kinase JAK1 prevents this response. Accordingly, treatment with IL6 leads to prolonged STAT1 instead of STAT3 activation in wild-type IE1 expressing cells, but not in cells expressing a mutant protein (IE1dl410-420) deficient for STAT3 binding. A very similar STAT1-directed response to IL6 is also present in cells infected with a wild-type or revertant hCMV, but not an IE1dl410-420 mutant virus, and this response results in restricted viral replication. We conclude that IE1 is sufficient and necessary to rewire upstream IL6-type to downstream IFNγ-like signaling, two pathways linked to opposing actions, resulting in repressed STAT3- and activated STAT1-responsive genes. These findings relate transcriptional repressor and activator functions of IE1 and suggest unexpected outcomes relevant to viral pathogenesis in response to cytokines or growth factors that signal through the IL6ST-JAK1-STAT3 axis in hCMV-infected cells. Our results also reveal that IE1, a protein considered to be a key activator of the hCMV productive cycle, has an unanticipated role in tempering viral replication.Publisher PDFPeer reviewe

Human Cytomegalovirus IE1 Protein Elicits a Type II Interferon-Like Host Cell Response That Depends on Activated STAT1 but Not Interferon-γ

Human cytomegalovirus (hCMV) is a highly prevalent pathogen that, upon primary infection, establishes life-long persistence in all infected individuals. Acute hCMV infections cause a variety of diseases in humans with developmental or acquired immune deficits. In addition, persistent hCMV infection may contribute to various chronic disease conditions even in immunologically normal people. The pathogenesis of hCMV disease has been frequently linked to inflammatory host immune responses triggered by virus-infected cells. Moreover, hCMV infection activates numerous host genes many of which encode pro-inflammatory proteins. However, little is known about the relative contributions of individual viral gene products to these changes in cellular transcription. We systematically analyzed the effects of the hCMV 72-kDa immediate-early 1 (IE1) protein, a major transcriptional activator and antagonist of type I interferon (IFN) signaling, on the human transcriptome. Following expression under conditions closely mimicking the situation during productive infection, IE1 elicits a global type II IFN-like host cell response. This response is dominated by the selective up-regulation of immune stimulatory genes normally controlled by IFN-γ and includes the synthesis and secretion of pro-inflammatory chemokines. IE1-mediated induction of IFN-stimulated genes strictly depends on tyrosine-phosphorylated signal transducer and activator of transcription 1 (STAT1) and correlates with the nuclear accumulation and sequence-specific binding of STAT1 to IFN-γ-responsive promoters. However, neither synthesis nor secretion of IFN-γ or other IFNs seems to be required for the IE1-dependent effects on cellular gene expression. Our results demonstrate that a single hCMV protein can trigger a pro-inflammatory host transcriptional response via an unexpected STAT1-dependent but IFN-independent mechanism and identify IE1 as a candidate determinant of hCMV pathogenicity

Simulator­based testing environment for avionics software: a feasibility study

International audienceHardware execution targets are widely used for software testing in the avionics industry to ensure that the tests represent the behaviour on the actual aircraft's calculators to a maximum degreeAt the same time, software simulators of the Integrated Modular Avionics structure are used on several system integration benches for calculator validation or as a part of full flight simulators.We substituted a hardware target with a specific software simulator in order to create a new testing platform that provides application developers with features not found on hardware­based environments. Such features include greater availability of testing platforms, debugging capabilities and an easier and faster testing process. Our goal was to evaluate the feasibility of a full migration to the resulting simulator­based testing environment. We identified several industrial constraints and technical problems to achieve this migration and approached them by developing progressive prototypes of the components of the new testing system and of the interfaces between them. Our project’s validation plan included comparing the results of both hardware­based and simulator­based platforms when executing a set of representative avionics tests

Efficient priming of antigen-specific cytotoxic T lymphocytes by human cord blood dendritic cells.

Previous studies have suggested that defective immune responses in early life may be related to the immaturity of neonatal antigen-presenting cells. To test this hypothesis, we assessed the capacity of neonatal dendritic cells (DC) to prime and polarize in vitro human naive antigen-specific T cells. We report that mature cord blood DC efficiently prime an oligoclonal population of antigen-specific CD8 T cells, capable of cytolytic activity and IFN-gamma secretion. In contrast, cells primed by immature cord blood DC do not acquire cytolytic activity and secrete lower amounts of IFN-gamma. Upon priming by either immature or mature DC, neonatal T cells acquire markers of activation and differentiation towards effector-memory cells. Our results demonstrate that, if appropriately activated, neonatal DC can prime efficient cytotoxic T lymphocyte (CTL) responses. Furthermore, these findings have important implications for the development of vaccine strategies in early life and for the reconstitution of a functional CTL repertoire after bone marrow transplantation.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

A detrimental role for invariant natural killer T cells in the pathogenesis of experimental Dengue virus infection

Dengue virus (DENY), a member of the mosquito-borne flaviviruses, is a serious public health problem in many tropical countries. We assessed the in vivo physiologic contribution of invariant natural killer T (iNKT) cells, a population of nonconventional lipid-reactive alpha beta T lymphocytes, to the host response during experimental DENY infection. We used a mouse-adapted DENY serotype 2 strain that causes a disease that resembles severe dengue in humans. On DENY challenge, splenic and hepatic iNKT cells became activated insofar as CD69 and Fas ligand up-regulation and interferon-gamma production. C57BL/6 mice deficient in iNKT cells (J alpha 18(-/-)) were more resistant to lethal infection than were wild-type animals, and the phenotype was reversed by adoptive transfer of iNKT cells to J alpha 18(-/-) animals. The absence of iNKT cells in J alpha 18(-/-) mice was associated with decreased systemic and local inflammatory responses, less liver injury, diminished vascular leak syndrome, and reduced activation of natural killer cells and neutrophils. iNKT cell functions were not necessary for control of primary DENY infection, after either natural endogenous activation or exogenous activation with the canonical iNKT cell agonist alpha-galactosylceramide. Together, these data reveal a novel and critical role for iNKT cells in the pathogenesis of severe experimental dengue disease

The Human Fetal Immune Response to Hepatitis C Virus Exposure in Utero

Background. Although the rate of mother-to-child transmission of hepatitis C virus (HCV) is low, the effect of HCV exposure in utero on the fetal immune system is unknown