As of today, there is no antiviral for the treatment of the SARS-CoV-2 infection, and the development of a vaccine might take several months or even years. The structural superposition of the hepatitis C virus polymerase bound to sofosbuvir, a nucleoside analog antiviral approved for hepatitis C virus infections, with the SARS-CoV polymerase shows that the residues that bind to the drug are present in the latter. Moreover, a multiple alignment of several SARS-CoV-2, SARS and MERS-related coronaviruses polymerases shows that these residues are conserved in all these viruses, opening the possibility to use sofosbuvir against these highly infectious pathogens.

Background: The rst case of a corona virus 2019 (COVID-19) infection in a Sri Lankan was reported on March 11, 2020. The situation in Sri Lanka changed with the rapid increase of personnel contracting COVID-19 in a Naval base camp that housed more than 4000 people. This provided a unique opportunity to study the effectiveness of hydroxychloroquine (HCQ) for post-exposure prophylaxis (PEP), while taking stringent, non-pharmacologic, public health measures to prevent spread. Our aim is to study the effectiveness and safety of HCQ for PEP among naval personnel with exposure to COVID-19 positive patients. Methods/design: This is a placebo-controlled, randomized, clinical trial carried out in the Naval base camp and quarantine centers of the Sri Lanka Navy, Ministry of Defense, Sri Lanka. Navy personnel who are exposed to a patient with con rmed COVID-19 infection but test negative for the virus on reverse, real-time polymerase chain reaction (rRT-PCR) at recruitment will be randomized, 200 to each arm, to receive HCQ or placebo, and monitored for the development of symptoms or rRT-PCR positivity for severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) virus for 14 days. Discussion: This trial will provide high-quality evidence of the effectiveness and safety of HCQ as PEP for COVID-19. The study design is unique due to the circumstances of the outbreak in a con ned area among otherwise healthy adults, at a relatively early stage of its spread.

In this review, we summarize the researches on animal reservoirs of the SARS coronavirus (SARS-CoV). Masked palm civets were suspected as the origin of the SARS outbreak in 2003 and was confirmed as the direct origin of SARS cases with mild symptom in 2004. Sequence analysis of the SARS-CoV-like virus in masked palm civets indicated that they were highly homologous to human SARS-CoV with nt identity over 99.6%, indicating the virus has not been circulating in the population of masked palm civets for a very long time. Alignment of 10 complete viral genome sequences from masked palm civets with those of human SARS-CoVs revealed 26 conserved single-nucleotide variations (SNVs) in the viruses from masked palm civets. These conserved SNVs were gradually lost from the genomes of viruses isolated from the early phase to late phase human patients of the 2003 SARS epidemic. In 2005, horseshoe bats were identified as the natural reservoir of a group of coronaviruses that are distantly related to SARS-CoV. The genome sequences of bat SARS-like coronavirus had about 88-92% nt identity with that of the SARS-CoV. The prevalence of antibodies and viral RNA in different bat species and the characteristics of the bat SARS-like coronavirus were elucidated. Apart from masked palm civets and bats, 29 other animal species had been tested for the SARS-CoV, and the results are summarized in this paper.

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For antiviral signaling mediated by retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs), the recruitment of cytosolic RLRs and downstream molecules (such as TBK1 and IKKε) to mitochondrial platform is a central event that facilitates the establishment of host antiviral state. Here, we present an example of viral targeting for immune evasion through spatial isolation of TBK1/IKKε from mitochondrial antiviral platform, which was employed by severe fever with thrombocytopenia syndrome virus (SFTSV), a deadly bunyavirus emerging recently. We showed that SFTSV nonstructural protein NSs functions as the interferon (IFN) antagonist, mainly via suppressing TBK1/IKKε-IRF3 signaling. NSs mediates the formation of cytoplasmic inclusion bodies (IBs), and the blockage of IB formation impairs IFN-inhibiting activity of NSs. We next demonstrate that IBs are utilized to compartmentalize TBK1/IKKε. The compartmentalization results in spatial isolation of the kinases from mitochondria, and deprived TBK1/IKKε may participate in antiviral complex assembly, leading to the blockage of IFN induction. This study proposes a new role of viral IBs as virus-built 'jail' for imprisoning cellular factors and presents a novel and likely common mechanism of viral immune evasion through spatial isolation of critical signaling molecules from the mitochondrial antiviral platform.

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease with a high case fatality rate of up to 30% (1-3). The causative agent is a novel phlebovirus of the Bunyaviridae family, namely, SFTS virus (SFTSV), which was identified first in China and subsequently was found in South Korea (4, 5) and Japan (6). Recently, another phlebovirus genetically closely related to SFTSV was isolated in the United States (7). Emerging bunyavirus infection has become a substantial threat to public health; however, the pathogenesis is largely unknown, and there are no vaccines or specific antivirals available. The SFTSV genome consists of three single-stranded RNA segments. The large (L) and medium (M) segments are of negative polarity and encode the RNA-dependent RNA polymerase and the glycoprotein precursor, respectively, while the small segment (S) encodes the nucleoprotein (NP) and the nonstructural protein (NSs) by an ambisense strategy. Although little is known on SFTSV-host interactions, studies have suggested that the NSs protein is implicated in viral suppression of host antiviral innate immunity; thus, it likely is contributing to viral pathogenesis (8-10).Antiviral innate immune response is initiated through the recognition of virus infection by cellular pattern recognition receptors (PRRs), such as transmembrane toll-like receptor 3 (TLR3) and cytosolic RIG-I-like receptors RIG-I and MDA5 (11). Upon recognition, PRRs trigger the signaling cascades that lead to the induction of type I interferons (IFNs) through the activation of transcription factors, such as interferon regulatory factors (IRFs) 3 and 7 and NF-B. The newly synthesized and secreted type I IFNs bind to their receptors on the cell surface and result in the phosphorylation of signal transducer and activator of transcription 2 (STAT2) and 1 (STAT1), transcription factors that are the key components of type I IFN signaling pathway, by Janus kinases (JAKs). The phosphorylated STATs then heterodimerize and as-

Five highly conserved per os infectivity factors, PIF1, PIF2, PIF3, PIF4, and P74, have been reported to be essential for oral infectivity of baculovirus occlusion-derived virus (ODV) in insect larvae. Three of these proteins, P74, PIF1, and PIF2, were thought to function in virus binding to insect midgut cells. In this paper evidence is provided that PIF1, PIF2, and PIF3 form a stable complex on the surface of ODV particles of the baculovirus Autographa californica multinucleocapsid nucleopolyhedrovirus (AcMNPV). The complex could withstand 2% SDS-5% ␤-mercaptoethanol with heating at 50°C for 5 min. The complex was not formed when any of the genes for PIF1, PIF2, or PIF3 was deleted, while reinsertion of these genes into AcMNPV restored the complex. Coimmunoprecipitation analysis independently confirmed the interactions of the three PIF proteins and revealed in addition that P74 is also associated with this complex. However, deletion of the p74 gene did not affect formation of the PIF1-PIF2-PIF3 complex. Electron microscopy analysis showed that PIF1 and PIF2 are localized on the surface of the ODV with a scattered distribution. This distribution did not change for PIF1 or PIF2 when the gene for PIF2 or PIF1 protein was deleted. We propose that PIF1, PIF2, PIF3, and P74 form an evolutionarily conserved complex on the ODV surface, which has an essential function in the initial stages of baculovirus oral infection.

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