cGAS-STING effectively restricts murine norovirus infection but antagonizes the antiviral action of N-terminus of RIG-I in mouse macrophages

Although cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling has been well recognized in defending DNA viruses, the role of cGAS-STING signaling in regulating infection of RNA viruses remains largely elusive. Noroviruses, as single-stranded RNA viruses, are the main causative agents of acute viral gastroenteritis worldwide. This study comprehensively investigated the role of cGAS-STING in response to murine norovirus (MNV) infection. We found that STING agonists potently inhibited MNV replication in mouse macrophages partially requiring the JAK/STAT pathway that induced transcription of interferon (IFN)-stimulated genes (ISGs). Loss- and gain-function assays revealed that both cGAS and STING were necessary for host defense against MNV propagation. Knocking out cGAS or STING in mouse macrophages led to defects in induction of antiviral ISGs upon MNV infection. Overexpression of cGAS and STING moderately increased ISG transcription but potently inhibited MNV replication in human HEK293T cells ectopically expressing the viral receptor CD300lf. This inhibitory effect was not affected by JAK inhibitor treatment or expression of different MNV viral proteins. Interestingly, STING but not cGAS interacted with mouse RIG-I, and attenuated its N-terminus-mediated anti-MNV effects. Our results implicate an essential role for mouse cGAS and STING in regulating innate immune response and defending MNV infection. This further strengthens the evidence of cGAS-STING signaling in response to RNA virus infection

The role of phosphatidylinositide-3-kinase in basal mitogen-activated protein kinase activity and cell survival

AbstractPhosphatidylinositide-3-OH-kinase (PI 3-kinase) is an upstream activator of p42/p44 mitogen-activated protein kinase (MAPK), but the role of PI 3-kinase-dependent MAPK remains obscure. Here we demonstrate that in a variety of different cell types, PI 3-kinase inhibition results in an inhibition of MAPK in unstimulated cells but does not interfere with growth factor-, or TPA-induced MAPK activity. Furthermore, inhibition of either PI 3-kinase or MEK/MAPK results in cell death in serum-starved cells. We concluded that basal, but not induced MAPK activity is mediated by PI 3-kinase and that this PI 3-kinase-mediated MEK/MAPK activity is essential for cell survival in quiescent cells

Disulfide-induced self-assembled targets:A novel strategy for the label free colorimetric detection of DNAs/RNAs via unmodified gold nanoparticles

A modified non-cross-linking gold-nanoparticles (Au-NPs) aggregation strategy has been developed for the label free colorimetric detection of DNAs/RNAs based on self-assembling target species in the presence of thiolated probes. Two complementary thiol-modified probes, each of which specifically binds at one half of the target introduced SH groups at both ends of dsDNA. Continuous disulfide bond formation at 3' and 5' terminals of targets leads to the self-assembly of dsDNAs into the sulfur-rich and flexible products with different lengths. These products have a high affinity for the surface of Au-NPs and efficiently protect the surface from salt induced aggregation. To evaluate the assay efficacy, a small part of the citrus tristeza virus (CTV) genome was targeted, leading to a detection limit of about 5 x 10(-9) mol. L-1 over a linear ranged from 20 x 10(-9) to 10 x 10(-7) mol. L-1. This approach also exhibits good reproducibility and recovery levels in the presence of plant total RNA or human plasma total circulating RNA extracts. Self-assembled targets can be then sensitively distinguished from non-assembled or mismatched targets after gel electrophoresis. The disulfide reaction method and integrating self-assembled DNAs/RNAs targets with bare AuNPs as a sensitive indicator provide us a powerful and simple visual detection tool for a wide range of applications

Lipopolysaccharide restricts murine norovirus infection in macrophages mainly through NF-kB and JAK-STAT signaling pathway

The inflammasome machinery has recently been recognized as an emerging pillar of innate immunity. However, little is known regarding the interaction between the classical interferon (IFN) response and inflammasome activation in response to norovirus infection. We found that murine norovirus (MNV-1) infection induces the transcription of IL-1β, a hallmark of inflammasome activation, which is further increased by inhibition of IFN response, but fails to trigger the release of mature IL-1β. Interestingly, pharmacological inflammasome inhibitors do not affect viral replication, but slightly reverse the inflammasome activator lipopolysaccharide (LPS)-mediated inhibition of MNV replication. LPS efficiently stimulates the transcription of IFN-β through NF-ĸB, which requires the transcription factors IRF3 and IRF7. This activates downstream antiviral IFN-stimulated genes (ISGs) via the JAK-STAT pathway. Moreover, inhibition of NF-ĸB and JAK-STAT signaling partially reverse LPS-mediated anti-MNV activity, suggesting additional antiviral mechanisms activated by NF-ĸB. This study reveals additional insight in host defense against MNV infection

Estimating the burden and modeling mitigation strategies of pork-related hepatitis E virus foodborne transmission in representative European countries

Hepatitis E virus (HEV) is an emerging zoonotic pathogen posing global health burden, and the concerns in Europe are tremendously growing. Pigs serve as a main reservoir, contributing to pork-related foodborne transmission. In this study, we aim to specifically simulate this foodborne transmission route and to assess potential interventions. We firstly established a dose-response relationship between the risk of transmission to human and the amount of ingested viruses. We further estimated the incidence of HEV infection specifically attributed to pork-related foodborne transmission in four representative European countries. Finally, we demonstrated a proof-of-concept of mitigating HEV transmission by implementing vaccination in human and pig populations. Our modeling approach bears essential implications for better understanding the transmission of pork-related foodborne HEV and for developing mitigation strategies

Kinase Activity Profiling of Gram-Negative Pneumonia

Pneumonia is a severe disease with high morbidity and mortality. A major causative pathogen is the Gram-negative bacterium Klebsiella (K.) pneumoniae. Kinases play an integral role in the transduction of intracellular signaling cascades and regulate a diverse array of biological processes essential to immune cells. The current study explored signal transduction events during murine Gram-negative pneumonia using a systems biology approach. Kinase activity arrays enable the analysis of 1,024 consensus sequences of protein kinase substrates. Using a kinase activity array on whole lung lysates, cellular kinase activities were determined in a mouse model of K. pneumoniae pneumonia. Notable kinase activities also were validated with phospho-specific Western blots. On the basis of the profiling data, mitogen-activated protein kinase (MAPK) signaling via p42 mitogen-activated protein kinase (p42) and p38 mitogen-activated protein kinase (p38) and transforming growth factor β (TGFβ) activity were reduced during infection, whereas v-src sarcoma (Schmidt-Ruppin A-2) viral oncogene homolog (avian) (SRC) activity generally was enhanced. AKT signaling was represented in both metabolic and inflammatory (mitogen-activated protein kinase kinase 2 [MKK], apoptosis signal-regulating kinase/mitogen-activated protein kinase kinase kinase 5 [ASK] and v-raf murine sarcoma viral oncogene homolog B1 [b-RAF]) context. This study reaffirms the importance of classic inflammation pathways, such as MAPK and TGFβ signaling and reveals less known involvement of glycogen synthase kinase 3β (GSK-3β), AKT and SRC signaling cassettes in pneumonia