Transcriptome Profiling of the Virus-Induced Innate Immune Response in Pteropus vampyrus and Its Attenuation by Nipah Virus Interferon Antagonist Functions.

UNLABELLED: Bats are important reservoirs for several viruses, many of which cause lethal infections in humans but have reduced pathogenicity in bats. As the innate immune response is critical for controlling viruses, the nature of this response in bats and how it may differ from that in other mammals are of great interest. Using next-generation transcriptome sequencing (mRNA-seq), we profiled the transcriptional response of Pteropus vampyrus bat kidney (PVK) cells to Newcastle disease virus (NDV), an avian paramyxovirus known to elicit a strong innate immune response in mammalian cells. The Pteropus genus is a known reservoir of Nipah virus (NiV) and Hendra virus (HeV). Analysis of the 200 to 300 regulated genes showed that genes for interferon (IFN) and antiviral pathways are highly upregulated in NDV-infected PVK cells, including genes for beta IFN, RIG-I, MDA5, ISG15, and IRF1. NDV-infected cells also upregulated several genes not previously characterized to be antiviral, such as RND1, SERTAD1, CHAC1, and MORC3. In fact, we show that MORC3 is induced by both IFN and NDV infection in PVK cells but is not induced by either stimulus in human A549 cells. In contrast to NDV infection, HeV and NiV infection of PVK cells failed to induce these innate immune response genes. Likewise, an attenuated response was observed in PVK cells infected with recombinant NDVs expressing the NiV IFN antagonist proteins V and W. This study provides the first global profile of a robust virus-induced innate immune response in bats and indicates that henipavirus IFN antagonist mechanisms are likely active in bat cells. IMPORTANCE: Bats are the reservoir host for many highly pathogenic human viruses, including henipaviruses, lyssaviruses, severe acute respiratory syndrome coronavirus, and filoviruses, and many other viruses have also been isolated from bats. Viral infections are reportedly asymptomatic or heavily attenuated in bat populations. Despite their ecological importance to viral maintenance, research into their immune system and mechanisms for viral control has only recently begun. Nipah virus and Hendra virus are two paramyxoviruses associated with high mortality rates in humans and whose reservoir is the Pteropus genus of bats. Greater knowledge of the innate immune response of P. vampyrus bats to viral infection may elucidate how bats serve as a reservoir for so many viruses.

Hantavirus GnT elements mediate TRAF3 binding and inhibit RIG-I/TBK1-directed beta interferon transcription by blocking IRF3 phosphorylation.

Hantaviruses successfully replicate in primary human endothelial cells by restricting the early induction of beta interferon (IFN-ß) and interferon-stimulated genes (ISGs). Gn proteins from NY-1V, ANDV, and TULV, but not PHV, harbor elements in their 142-residue cytoplasmic tails (GnTs) that inhibit RIG-I/MAVS/TBK1-TRAF3-directed IFN-ß induction. Here, we define GnT interactions and residues required to inhibit TRAF3-TBK1-directed IFN-ß induction and IRF3 phosphorylation. We observed that GnTs bind TRAF3 via residues within the TRAF-N domain (residues 392 to 415) and that binding is independent of the MAVS-interactive TRAF-C domain (residues 415 to 568). We determined that GnT binding to TRAF3 is mediated by C-terminal degrons within NY-1V or ANDV GnTs and that mutations that add degrons to TULV or PHV GnTs confer TRAF3 binding. Further analysis of GnT domains revealed that TRAF3 binding is a discrete GnT function, independent of IFN regulation, and that residues 15 to 42 from the NY-1V GnT C terminus are required for inhibiting TBK1-directed IFN-ß transcription. Mutagenesis of the NY-1V GnT revealed that altering tyrosine 627 (Y627A/S/F) abolished GnT regulation of RIG-I/TBK1-directed IRF3 phosphorylation and transcriptional responses of ISRE, κB, and IFN-ß promoters. Moreover, GnTs from NY-1V, ANDV, and TULV, but not PHV, inhibited RIG-I-directed IRF3 phosphorylation. Collectively, these findings suggest a novel role for GnTs in regulating RIG-I/TBK1 pathway-directed IRF3 phosphorylation and IFN-ß induction and define virulence determinants within GnTs that may permit the attenuation of pathogenic hantaviruses. IMPORTANCE These findings provide a mechanism for selected hantavirus GnT interactions to regulate RIG-I/TBK1 signaling responses required for IFN-ß induction by inhibiting TBK1 phosphorylation of IRF3. These studies culminate in showing that a single GnT residue, Y627, is required for the NY-1V GnT to inhibit RIG-I/TBK1-directed IRF3 phosphorylation and IFN-ß induction. These findings define a potential virulence determinant within the NY-1V GnT that may permit hantavirus attenuation.

DRBP76 associates with Ebola virus VP35 and suppresses viral polymerase function.

The Zaire Ebola virus (EBOV) protein VP35 is multifunctional; it inhibits IFN-α/ß production and functions as a cofactor of the viral RNA polymerase. Mass spectrometry identified the double stranded RNA binding protein 76 (DRBP76/NFAR-1/NF90) as a cellular factor that associates with the VP35 C-terminal interferon inhibitory domain (IID). DRBP76 is described to regulate host cell protein synthesis and play an important role in host defense. The VP35-IID-DRBP76 interaction required the addition of exogenous dsRNA, but full-length VP35 associated with DRBP76 in the absence of exogenous dsRNA. Cells infected with a Newcastle disease virus (NDV)-expressing VP35 redistributed DRBP76 from the nucleus to the cytoplasm, the compartment in which EBOV replicates. Overexpression of DRBP76 did not alter the ability of VP35 to inhibit type I IFN production but did impair the function of the EBOV transcription/replication complex. These data suggest that DRBP76, via its association with VP35, exerts an anti-EBOV function.

Nebulized Tranexamic Acid in Secondary Post-Tonsillectomy Hemorrhage: Case Series and Review of the Literature.

INTRODUCTION: Post-tonsillectomy hemorrhage is a serious postoperative complication, and its acute management can present a challenge for the emergency provider. Although various strategies have been proposed, guidance on the best approach for management of this condition in the emergency department (ED) setting remains limited. Anecdotal reports of the use of nebulized tranexamic acid (TXA) for management of tonsillar bleeding have emerged over the past two years. Two recently published case reports describe the successful use of nebulized TXA for stabilization of post-tonsillectomy hemorrhage in an adult and a pediatric patient. CASE SERIES: Eight patients who presented to our ED with secondary post-tonsillectomy hemorrhage received nebulized TXA for hemostatic management. The most common TXA dose used was 500 milligrams, and all but one patient received a single dose of the medication in the ED. Hemostatic benefit was observed in six patients, with complete bleeding cessation observed in five cases. Interventions prior to nebulized TXA administration were attempted in three of the six patients and included ice water gargle, direct pressure with TXA-soaked gauze, and nebulized racemic epinephrine. All but one of the patients were taken to the operating room for definitive management after initial stabilization in the ED. CONCLUSION: Nebulized TXA may offer a hemostatic benefit and aid in stabilization of tonsillectomy hemorrhage in the acute care setting, prior to definitive surgical intervention. Consideration of general principles of nebulization and aerosol particle size may be an important factor for drug delivery to the target tissue site.

The safety of home discharge for low-risk emergency department patients presenting with coronavirus-like symptoms during the COVID-19 pandemic: A retrospective cohort study.

Objective: There is minimal evidence describing outcomes for emergency department (ED) patients with suspected coronavirus disease 2019 (COVID-19) infection who are not hospitalized. The study objective was to assess 30-day outcomes (ED revisit, admission, ICU admission, and death) for low-risk patients discharged after ED evaluation for COVID-19. Methods: This was a retrospective cohort study of patients triaged to a COVID-19 surge area within an urban ED and discharged between March 12 and April 6. Physicians were encouraged to discharge patients if they were well-appearing with few comorbidities. Data were collected from review of medical records and phone follow-up, and the analysis was descriptive. Results: Of 452 patients, the median age was 38, and 61.7% had no comorbidities. Chest radiographs were performed for 50.4% of patients and showed infiltrates in 14% of those tested. Polymerase chain reaction testing was performed for 28.3% of patients during the index ED visit and was positive in 35.9% of those tested. Follow-up was achieved for 75.4% of patients. ED revisits occurred for 13.7% of patients. The inpatient admission rate at 30 days was 4.6%, with 0.7% requiring intensive care. Median number of days between index ED evaluation and return for admission was 5 (interquartile range 3-7, range 1-17). There were no known deaths. Conclusions: A minority of low-risk patients with suspected COVID-19 will require hospitalization after being discharged home from the ED. Outpatient management is likely safe for well-appearing patients with normal vital signs, but patients should be instructed to return for worsening symptoms including labored breathing. Future work is warranted to develop and validate ED disposition guidelines.