PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-3 (3)
 

Clipboard (0)
None

Select a Filter Below

Journals
Authors
more »
Year of Publication
Document Types
1.  Chikungunya Virus Induces IPS-1-Dependent Innate Immune Activation and Protein Kinase R-Independent Translational Shutoff▿  
Journal of Virology  2010;85(1):606-620.
Chikungunya virus (CHIKV) is an arthritogenic mosquito-transmitted alphavirus that is undergoing reemergence in areas around the Indian Ocean. Despite the current and potential danger posed by this virus, we know surprisingly little about the induction and evasion of CHIKV-associated antiviral immune responses. With this in mind we investigated innate immune reactions to CHIKV in human fibroblasts, a demonstrable in vivo target of virus replication and spread. We show that CHIKV infection leads to activation of the transcription factor interferon regulatory factor 3 (IRF3) and subsequent transcription of IRF3-dependent antiviral genes, including beta interferon (IFN-β). IRF3 activation occurs by way of a virus-induced innate immune signaling pathway that includes the adaptor molecule interferon promoter stimulator 1 (IPS-1). Despite strong transcriptional upregulation of these genes, however, translation of the corresponding proteins is not observed. We further demonstrate that translation of cellular (but not viral) genes is blocked during infection and that although CHIKV is found to trigger inactivation of the translational molecule eukaryotic initiation factor subunit 2α by way of the double-stranded RNA sensor protein kinase R, this response is not required for the block to protein synthesis. Furthermore, overall diminution of cellular RNA synthesis is also observed in the presence of CHIKV and transcription of IRF3-dependent antiviral genes appears specifically blocked late in infection. We hypothesize that the observed absence of IFN-β and antiviral proteins during infection results from an evasion mechanism exhibited by CHIKV that is dependent on widespread shutoff of cellular protein synthesis and a targeted block to late synthesis of antiviral mRNA transcripts.
doi:10.1128/JVI.00767-10
PMCID: PMC3014158  PMID: 20962078
2.  Activation of the Interferon Response by Human Cytomegalovirus Occurs via Cytoplasmic Double-Stranded DNA but Not Glycoprotein B ▿  
Journal of Virology  2010;84(17):8913-8925.
In vitro infection of cells with the betaherpesvirus human cytomegalovirus (HCMV) stimulates an innate immune response characterized by phosphorylation of the transcription factor interferon regulatory factor 3 (IRF3) and subsequent expression of IRF3-dependent genes. While previous work suggests that HCMV envelope glycoprotein B is responsible for initiating this reaction, the signaling pathways stimulated by virus infection that lead to IRF3 phosphorylation have largely been uncharacterized. Recently, we identified Z DNA binding protein 1 (ZBP1), a sensor of cytoplasmic DNA, as an essential protein for this response. We now describe a human fibroblast cell line exhibiting a recessive defect that results in the absence of activation of IRF3 following treatment with HCMV but not Sendai virus or double-stranded RNA. In addition, we show that while exposure of these cells to soluble HCMV glycoprotein B is capable of triggering IRF3-dependent gene transcription, transfection of the cells with double-stranded DNA is not. Furthermore, we show that overexpression of ZBP1 in these cells reestablishes their ability to secrete interferon in response to HCMV and that multiple ZBP1 transcriptional variants exist in both wild-type and mutant cells. These results have two major implications for the understanding of innate immune stimulation by HCMV. First, they demonstrate that HCMV glycoprotein B is not the essential molecular pattern that induces an IRF3-dependent innate immune response. Second, IRF3-terminal signaling triggered by HCMV particles closely resembles that which is activated by cytoplasmic double-stranded DNA.
doi:10.1128/JVI.00169-10
PMCID: PMC2919031  PMID: 20573816
3.  Human Cytomegalovirus Induces the Interferon Response via the DNA Sensor ZBP1▿  
Journal of Virology  2009;84(1):585-598.
Human cytomegalovirus (HCMV) is a member of the betaherpesvirus family that, unlike other herpesviruses, triggers a strong innate immune response in infected cells that includes transcription of the beta interferon gene via activation of interferon regulatory factor 3 (IRF3). IRF3 activation requires signaling from pattern recognition receptors that is initiated by their interaction with specific pathogen-associated molecules. However, while IRF3-activating pathways are increasingly well characterized, the cellular molecules involved in HCMV-mediated IRF3-dependent beta interferon transcription are virtually unknown. We undertook a systematic examination of new and established IRF3-terminal pathway components to identify those that are essential to HCMV-triggered IRF3 activation. We show here that IRF3 activation induced by HCMV infection involves the newly identified protein STING but, in contrast to infections with other herpesviruses, occurs independently of the adaptor molecule IPS-1. We also show that the protein DDX3 contributes to HCMV-triggered expression of beta interferon. Moreover, we identify Z-DNA binding protein 1 (ZBP1) as being essential for IRF3 activation and interferon beta expression triggered by HCMV, as well as being sufficient to enhance HCMV-stimulated beta interferon transcription and secretion. ZBP1 transcription was also found to be induced following exposure to HCMV in a JAK/STAT-dependent manner, thus perhaps also contributing to a positive feedback signal. Finally, we show that constitutive overexpression of ZBP1 inhibits HCMV replication. ZBP1 was recently identified as a cytosolic pattern recognition receptor of double-stranded DNA, and thus, we propose a model for HCMV-mediated IRF3 activation that involves HCMV-associated DNA as the principal innate immune-activating pathogen-associated molecular pattern.
doi:10.1128/JVI.01748-09
PMCID: PMC2798427  PMID: 19846511

Results 1-3 (3)