The NS1 protein of influenza A virus is a major virulence factor that is essential for pathogenesis. NS1 functions to impair innate and adaptive immunity by inhibiting host signal transduction and gene expression, but its mechanisms of action remain to be fully elucidated. We show here that NS1 forms an inhibitory complex with NXF1/TAP, p15/NXT, Rae1/mrnp41, and E1B-AP5, which are key constituents of the mRNA export machinery that interact with both mRNAs and nucleoporins to direct mRNAs through the nuclear pore complex. Increased levels of NXF1, p15, or Rae1 revert the mRNA export blockage induced by NS1. Furthermore, influenza virus down-regulates Nup98, a nucleoporin that is a docking site for mRNA export factors. Reduced expression of these mRNA export factors renders cells highly permissive to influenza virus replication, demonstrating that proper levels of key constituents of the mRNA export machinery protect against influenza virus replication. Because Nup98 and Rae1 are induced by interferons, downregulation of this pathway is likely a viral strategy to promote viral replication. These findings demonstrate previously undescribed influenza-mediated viral-host interactions and provide insights into potential molecular therapies that may interfere with influenza infection.NS1 ͉ nucleoporin ͉ nuclear transport ͉ mRNA nuclear export

A chemical genetics approach was taken to identify inhibitors of NS1, a major influenza A virus virulence factor that inhibits host gene expression. A high-throughput screen of 200,000 synthetic compounds identified small molecules that reverted NS1-mediated inhibition of host gene expression. A counter-screen for suppression of influenza virus cytotoxicity identified naphthalimides that inhibited replication of influenza virus and vesicular stomatitis virus. The mechanism of action was through activation of REDD1 expression and concomitant inhibition of mTORC1 via TSC1/TSC2 complex. The antiviral activity of naphthalimides was abolished in REDD1−/− cells. Viruses inhibited REDD1 expression, resulting in activation of the mTORC1 pathway. REDD1−/− cells prematurely up-regulated viral proteins via mTORC1 activation and were permissive to virus replication. In contrast, cells conditionally expressing high levels of REDD1 down-regulated viral protein levels. Thus, REDD1 is a novel host defense factor and chemical activation of REDD1 expression represents a potent antiviral intervention strategy.

Viral hemorrhagic fevers, because of their high mortality rates, the lack of medical countermeasures, and their potential use as instruments of bioterrorism, pose a significant threat to the developed and the developing areas of the world. The key to preventing the spread of these diseases is early and accurate detection. For decades, the gold-standard immunoassay for hemorrhagic fever detection has been the enzyme-linked immunosorbent assay (ELISA); however, newer technologies are emerging with increased sensitivities. One such technology is the Luminex MagPix platform using xMAP microspheres. Here, we compare the MagPix platform with a traditional ELISA for IgM and antigen detection of infections from Lassa and Ebola viruses (LASV and EBOV, respectively). For IgM detection in nonhuman primate samples, the MagPix platform was 5 and 25 times more sensitive in detecting LASV and EBOV, respectively, compared to that with ELISA. For antigen detection in buffer, the MagPix platform was 25 and 2.5 times more sensitive in detecting lower levels of LASV and EBOV, respectively. In both IgM and antigen detection assays, the MagPix platform demonstrated excellent reproducibility at the lower limit of detection (LLOD). These findings demonstrate that the MagPix platform is a viable diagnostic replacement for the ELISA for viral hemorrhagic fevers.KEYWORDS ELISA, MagPix, Ebola virus, immunoassays, Lassa virus, viral hemorrhagic fever H emorrhagic fevers are a part of the normal disease burden in Africa. In the developed world, they are a concern because of their potential use as bioterrorism agents. Lassa virus (family, Arenaviridae) and ebolaviruses (family, Filoviridae) are hemorrhagic fever viruses that are endemic in several African countries (1, 2). Disease outbreaks with these viruses have significant medical and social impacts. Case fatality rates can be as high as 65% for Lassa virus (LASV) and as high as 90% for ebolaviruses (3,4). Their high mortality rates combined with their ease of transmission and the lack of vaccines or effective treatments render them extremely dangerous pathogens.Early during an infection, hemorrhagic fever viruses have a clinical presentation that is similar to other more common febrile illnesses (5, 6). A rapid and accurate diagnosis of hemorrhagic fever viruses is critical for limiting the spread of disease and enabling an earlier more effective treatment. Traditionally, enzyme-linked immunosorbent assays (ELISAs) have been used for the detection of a virus-specific antigen and/or IgM antibodies (7,8).ELISA immunodiagnostics are the standard by which other diagnostics are evaluated. ELISA has been commonly used for the detection of LASV and Ebola virus (EBOV) for many years; however, newer immunodiagnostic platforms that offer multiplex

Influenza A virus infects 5–20% of the population annually, resulting in ∼35,000 deaths and significant morbidity. Current treatments include vaccines and drugs that target viral proteins. However, both of these approaches have limitations, as vaccines require yearly development and the rapid evolution of viral proteins gives rise to drug resistance. In consequence additional intervention strategies, that target host factors required for the viral life cycle, are under investigation. Here we employed arrayed whole-genome siRNA screening strategies to identify cell-autonomous molecular components that are subverted to support H1N1 influenza A virus infection of human bronchial epithelial cells. Integration across relevant public data sets exposed druggable gene products required for epithelial cell infection or required for viral proteins to deflect host cell suicide checkpoint activation. Pharmacological inhibition of representative targets, RGGT and CHEK1, resulted in significant protection against infection of human epithelial cells by the A/WS/33 virus. In addition, chemical inhibition of RGGT partially protected against H5N1 and the 2009 H1N1 pandemic strain. The observations reported here thus contribute to an expanding body of studies directed at decoding vulnerabilities in the command and control networks specified by influenza virulence factors.

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