Abstract
BackgroundThe NF-κB family of transcription factors and associated signalling pathways are abundant and ubiquitous in human immune responses. Activation of NF-κB transcription factors by viral pathogen-associated molecular patterns, such as viral RNA and DNA, is fundamental to anti-viral innate immune defences and pro-inflammatory cytokine production that steers adaptive immune responses. Diverse non-viral stimuli, such as lipopolysaccharide and cytokines, also activate NF-κB and the same anti-pathogen gene networks. Viruses adapted to human cells often encode multiple proteins targeting the NF-κB pathway to mitigate the anti-viral effects of NF-κB-dependent host immunity.ResultsIn this study we have demonstrated using a variety of assays, in a number of different cell types including primary cells, that plasmid-encoded or virus-delivered simian immunodeficiency virus (SIV) accessory protein Vpx is a broad antagonist of NF-κB signalling active against diverse innate NF-κB agonists. Using targeted Vpx mutagenesis, we showed that this novel Vpx phenotype is independent of known Vpx cofactor DCAF1 and other cellular binding partners, including SAMHD1, STING and the HUSH complex. We found that Vpx co-immunoprecipitated with canonical NF-κB transcription factor p65, but not NF-κB family members p50 or p100, preventing nuclear translocation of p65. We found that broad antagonism of NF-κB activation by Vpx was conserved across distantly related lentiviruses as well as for Vpr from SIV Mona monkey (SIVmon), which has Vpx-like SAMHD1-degradation activity.ConclusionsWe have discovered a novel mechanism by which lentiviruses antagonise NF-κB activation by targeting p65. These findings extend our knowledge of how lentiviruses manipulate universal regulators of immunity to avoid the anti-viral sequelae of pro-inflammatory gene expression stimulated by both viral and extra-viral agonists. Importantly our findings are also relevant to the gene therapy field where virus-like particle associated Vpx is routinely used to enhance vector transduction through antagonism of SAMHD1, and perhaps also through manipulation of NF-κB.Graphical
Highlights
The Nuclear factor kappa B (NF-κB) family of transcription factors and associated signalling pathways are abundant and ubiquitous in human immune responses
Vpx is a broad antagonist of NF‐κB activation Whilst investigating innate immune responses to SIVsm lineage viruses in primary human immune cells we noted that wild-type SIVsm infection of human monocyte-derived macrophages (MDM) did not induce NF-κB-dependent gene expression at the doses tested, basal expression of NF-κB-dependent genes such as tumour necrosis factor (TNF)α (Fig. 1A) and IL-8 (Fig. 1B) were significantly reduced in
We found that Vpx delivered by genome-free viruslike particles (VLPs) antagonised NF-κB-dependent gene expression activated by lipopolysaccharide (LPS) treatment of MDM (Fig. 1C), indicating that Vpx could antagonise NF-κB activation driven by exogenous nonviral agonists
Summary
The NF-κB family of transcription factors and associated signalling pathways are abundant and ubiquitous in human immune responses. Activation of NF-κB transcription factors by viral pathogen-associated molecular patterns, such as viral RNA and DNA, is fundamental to anti-viral innate immune defences and pro-inflammatory cytokine production that steers adaptive immune responses. Diverse non-viral stimuli, such as lipopolysaccharide and cytokines, activate NF-κB and the same anti-pathogen gene networks. Viruses adapted to human cells often encode multiple proteins targeting the NF-κB pathway to mitigate the anti-viral effects of NF-κB-dependent host immunity. Amongst diverse roles in immune signalling, NF-κB activation is fundamental to pro-inflammatory anti-viral innate defences. Emphasising the primacy of NF-κB TFs to host defences, viruses have evolved strategies to antagonise NF-κB signalling, often targeting pathway activation at multiple levels in complex ways [2]. HIV-1 suppresses NF-κB activation at the level of TF nuclear transport, through accessory protein HIV-1 Vpr interaction with karyopherins [17, 18]. This equivalent activity of HIV-1 Vpu or Vpr as broad NF-κB antagonists has not been studied for HIV-2
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