Proteasome Inhibitor PS-341 Effectively Blocks Infection by the Severe Fever with Thrombocytopenia Syndrome Virus

Current insights into human pathogenic phenuiviruses and the host immune system

Phenuiviruses are a class of segmented negative-sense single-stranded RNA viruses, typically consisting of three RNA segments that encode four distinct proteins. The emergence of pathogenic phenuivirus strains, such as Rift Valley fever phlebovirus (RVFV) in sub-Saharan Africa, Severe Fever with Thrombocytopenia Syndrome Virus (SFTSV) in East and Southeast Asia, and Heartland Virus (HRTV) in the United States has presented considerable challenges to global public health in recent years. The innate immune system plays a crucial role as the initial defense mechanism of the host against invading pathogens. In addition to continued research aimed at elucidating the epidemiological characteristics of phenuivirus, significant advancements have been made in investigating its viral virulence factors (glycoprotein, non-structural protein, and nucleoprotein) and potential host-pathogen interactions. Specifically, efforts have focused on understanding mechanisms of viral immune evasion, viral assembly and egress, and host immune networks involving immune cells, programmed cell death, inflammation, nucleic acid receptors, etc. Furthermore, a plethora of technological advancements, including metagenomics, metabolomics, single-cell transcriptomics, proteomics, gene editing, monoclonal antibodies, and vaccines, have been utilized to further our understanding of phenuivirus pathogenesis and host immune responses. Hence, this review aims to provide a comprehensive overview of the current understanding of the mechanisms of host recognition, viral immune evasion, and potential therapeutic approaches during human pathogenic phenuivirus infections focusing particularly on RVFV and SFTSV.

The SFTSV Nonstructural Proteins Induce Autophagy to Promote Viral Replication via Interaction with Vimentin

Severe fever with thrombocytopenia syndrome virus (SFTSV) is a newly identified phlebovirus associated with severe hemorrhagic fever in humans. Studies have shown that SFTSV nucleoprotein (N) induces BECN1-dependent autophagy to promote viral assembly and release. However, the function of other SFTSV proteins in regulating autophagy has not been reported. In this study, we identify SFTSV NSs, a nonstructural protein that forms viroplasm-like structures in the cytoplasm of infected cells as the virus component mediating SFTSV-induced autophagy. We found that SFTSV NSs-induced autophagy was inclusion body independent, and most phenuivirus NSs had autophagy-inducing effects. Unlike N protein-induced autophagy, SFTSV NSs was key in regulating autophagy by interacting with the host's vimentin in an inclusion body-independent manner. NSs interacted with vimentin and induced vimentin degradation through the K48-linked ubiquitin-proteasome pathway. This negatively regulating Beclin1-vimentin complex formed and promoted autophagy. Furthermore, we identified the NSs-binding domain of vimentin and found that overexpression of wild-type vimentin antagonized the induced effect of NSs on autophagy and inhibited viral replication, suggesting that vimentin is a potential antiviral target. The present study shows a novel mechanism through which SFTSV nonstructural protein activates autophagy, which provides new insights into the role of NSs in SFTSV infection and pathogenesis. IMPORTANCE Severe fever with thrombocytopenia syndrome virus (SFTSV) is a newly emerging tick-borne pathogen that causes multifunctional organ failure and even death in humans. As a housekeeping mechanism for cells to maintain steady state, autophagy plays a dual role in viral infection and the host's immune response. However, the relationship between SFTSV infection and autophagy has not been described in detail yet. Here, we demonstrated that SFTSV infection induced complete autophagic flux and facilitated viral proliferation. We also identified a key mechanism underlying NSs-induced autophagy, in which NSs interacted with vimentin to inhibit the formation of the Beclin1-vimentin complex and induced vimentin degradation through K48-linked ubiquitination modification. These findings may help us understand the new functions and mechanisms of NSs and may aid in the identification of new antiviral targets.

Virus-host interactions during tick-borne bunyavirus infection

The Bunyavirales order is the largest grouping of RNA viruses, comprising emerging and re-emerging human, plant and animal pathogens. Bunyaviruses have a global distribution and many members of the order are transmitted by arthropods. They have evolved a plethora of mechanisms to manipulate the regulatory processes of the infected cell to facilitate their own replicative cycle, in hosts of disparate phylogenies. Interest in virus-vector interactions is growing rapidly. However, current understanding of tick-borne bunyavirus cellular interaction is heavily biased to studies conducted in mammalian systems. In this short review, we summarise current understandings of how tick-borne bunyaviruses utilise major cellular pathways (innate immunity, apoptosis and RNAi responses) in mammalian or tick cells to facilitate virus replication.

Antiviral Treatment Options for Severe Fever with Thrombocytopenia Syndrome Infections

Severe fever with thrombocytopenia syndrome virus (SFTSV) is a tick-borne virus that produces severe fever with thrombocytopenia syndrome (SFTS). It is widespread in Japan, South Korea, and Central and Eastern China. The epidemic has developed rapidly through China in recent years. SFTS cases have been reported in 25 provinces in China, mainly distributed in rural areas in mountainous and hilly areas. The infection has a high case fatality rate and no specific treatments or vaccinations. Therefore, early diagnosis and treatment of SFTS infection is important to survival and disease control. In this article, we provide an overview on different aspects of SFTS with an emphasis on management, to explore the current treatment and prophylactic measures further.

Immune escape mechanisms of severe fever with thrombocytopenia syndrome virus

Severe fever with thrombocytopenia syndrome (SFTS), which is caused by SFTS virus (SFTSV), poses a serious threat to global public health, with high fatalities and an increasing prevalence. As effective therapies and prevention strategies are limited, there is an urgent need to elucidate the pathogenesis of SFTS. SFTSV has evolved several mechanisms to escape from host immunity. In this review, we summarize the mechanisms through which SFTSV escapes host immune responses, including the inhibition of innate immunity and evasion of adaptive immunity. Understanding the pathogenesis of SFTS will aid in the development of new strategies for the treatment of this disease.

Dabie bandavirus Nonstructural Protein Interacts with Actin to Induce F-Actin Rearrangement and Inhibit Viral Adsorption and Entry

Dabie bandavirus (DBV) is an emerging Bandavirus that causes multiorgan failure with a high fatality rate in humans. While many viruses can manipulate the actin cytoskeleton to facilitate viral growth, the regulation pattern of the actin cytoskeleton and the molecular mechanisms involved in DBV entry into the host cells remain unclear. In this study, we demonstrate that expression of nonstructural protein (NSs) or infection with DBV induces actin rearrangement, which presents a point-like distribution, and this destruction is dependent on inclusion bodies (IBs). Further experiments showed that NSs inhibits viral adsorption by destroying the filopodium structure. In addition, NSs also compromised the viral entry by inhibiting clathrin aggregation on the cell surface and capturing clathrin into IBs. Furthermore, NSs induced clathrin light chain B (CLTB) degradation through the K48-linked ubiquitin proteasome pathway, which could negatively regulate clathrin-mediated endocytosis, inhibiting the viral entry. Finally, we confirmed that this NSs-induced antiviral mechanism is broadly applicable to other viruses, such as enterovirus 71 (EV71) and influenza virus, A/PR8/34 (PR8), which use the same clathrin-mediated endocytosis to enter host cells. In conclusion, our study provides new insights into the role of NSs in inhibiting endocytosis and a novel strategy for treating DBV infections. IMPORTANCEDabie bandavirus (DBV), a member of the Phenuiviridae family, is a newly emerging tick-borne pathogen that causes multifunctional organ failure and even death in humans. The actin cytoskeleton is involved in various crucial cellular processes and plays an important role in viral life activities. However, the relationship between DBV infection and the actin cytoskeleton has not been described in detail. Here, we show for the first time the interaction between NSs and actin to induce actin rearrangement, which inhibits the viral adsorption and entry. We also identify a key mechanism underlying NSs-induced entry inhibition in which NSs prevents clathrin aggregation on the cell surface by hijacking clathrin into the inclusion body and induces CLTB degradation through the K48-linked ubiquitination modification. This paper is the first to reveal the antiviral mechanism of NSs and provides a theoretical basis for the search for new antiviral targets.

Possible therapeutic effects of boron citrate and oleoylethanolamide supplementation in patients with COVID-19: A pilot randomized, double-blind, clinical trial

BACKGROUND

The present study aimed to assess the therapeutic effects of boron citrate and oleoylethanolamide supplementation in patients with COVID-19.

METHODS

Forty adult patients with a diagnosis of COVID-19 were recruited in the present study. Patients were randomized in a 1:1:1:1 allocation ratio to 1of 4 treatment groups: (A) 5 mg of boron citrate twice a day, (B) 200 mg of oleoylethanolamide twice a day, (C) both therapies, or (D) routine treatments without any study medications. At pre-and post-intervention phase, some clinical and biochemical parameters were assessed.

RESULTS

Supplementation with boron citrate alone or in combination with oleoylethanolamide significantly improved O2 saturation and respiratory rate (p < 0.01). At the end of the study, significant increases in white blood cell and lymphocyte count were observed in the boron citrate and combined groups (p < 0.001). Boron citrate supplementation led to a significant decrease in serum lactate dehydrogenase (p = 0.026) and erythrocyte sedimentation rate (p = 0.014), compared with other groups. Furthermore, boron citrate in combination with oleoylethanolamide resulted in a significant reduction in the high-sensitivity C-reactive protein and interleukin-1β concentrations (p = 0.031 and p = 0.027, respectively). No significant differences were found among four groups post-intervention, in terms of hemoglobin concentrations, platelet count, and serum interleukin-6 levels. At the end of the study, common symptoms of COVID-19 including cough, fatigue, shortness of breath, and myalgia significantly improved in the supplemented groups, compared to the placebo (p < 0.05).

CONCLUSION

Supplementation with boron citrate alone or in combination with oleoylethanolamide could improve some clinical and biochemical parameters in COVID-19 patients.

Tilorone confers robust in vitro and in vivo antiviral effects against severe fever with thrombocytopenia syndrome virus

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Tilorone dihydrochloride possesses robust anti-SFTSV activity in vitro and in vivo.

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Intraperitoneal administration of tilorone leads to protection against intracranial lethal challenge of SFTSV.

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The anti-SFTSV mechanism of tilorone is through stimulation of host innate immunity.

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Pre-treatment with tilorone can prevent mice from lethal SFTSV challenge.

Severe fever with thrombocytopenia syndrome virus (SFTSV)-host interactome screen identifies viral nucleoprotein-associated host factors as potential antiviral targets

Severe fever with thrombocytopenia syndrome virus (SFTSV) is an emerging tick-borne virus that causes severe infection in humans characterized by an acute febrile illness with thrombocytopenia and hemorrhagic complications, and a mortality rate of up to 30%. Understanding on virus-host protein interactions may facilitate the identification of druggable antiviral targets. Herein, we utilized liquid chromatography-tandem mass spectrometry to characterize the SFTSV interactome in human embryonic kidney-derived permanent culture (HEK-293T) cells. We identified 445 host proteins that co-precipitated with the viral glycoprotein N, glycoprotein C, nucleoprotein, or nonstructural protein. A network of SFTSV-host protein interactions based on reduced viral fitness affected upon host factor down-regulation was then generated. Screening of the DrugBank database revealed numerous drug compounds that inhibited the prioritized host factors in this SFTSV interactome. Among these drug compounds, the clinically approved artenimol (an antimalarial) and omacetaxine mepesuccinate (a cephalotaxine) were found to exhibit anti-SFTSV activity in vitro. The higher selectivity of artenimol (71.83) than omacetaxine mepesuccinate (8.00) highlights artenimol’s potential for further antiviral development. Mechanistic evaluation showed that artenimol interfered with the interaction between the SFTSV nucleoprotein and the host glucose-6-phosphate isomerase (GPI), and that omacetaxine mepesuccinate interfered with the interaction between the viral nucleoprotein with the host ribosomal protein L3 (RPL3). In summary, the novel interactomic data in this study revealed the virus-host protein interactions in SFTSV infection and facilitated the discovery of potential anti-SFTSV treatments.

Progress in the medicinal chemistry of organoboron compounds

The review aims to draw attention to the latest advances in the organoboron chemistry and therapeutic use of organoboron compounds. The synthetic strategies towards boron-containing compounds with proven in vitro and/or in vivo biological activities, including derivatives of boronic acids, benzoxaboroles, benzoxaborines and benzodiazaborines, are summarized. Approaches to the synthesis of hybrid structures containing an organoboron moiety as one of the pharmacophores are considered, and the effect of this modification on the pharmacological activity of the initial molecules is analyzed. On the basis of analysis of the published data, the most promising areas of research in the field of organoboron compounds are identified, including the latest methods of synthesis, modification and design of effective therapeutic agents.

The bibliography includes 246 references.

R, José M. SQ, D. FGE, Marvin A. SU. Docking Simulations Exhibit Bortezomib and other Boron-containing Peptidomimetics as Potential Inhibitors of SARS-CoV-2 Main Protease

Background::

Treatment of the COVID19 pandemic requires drug development. Boron- containing compounds are attractive chemical agents, some of them act as proteases inhibitors.

Objective::

The present study explores the role of boronic moieties in molecules interacting on the binding site of the SARS-CoV-2 main protease.

Methods::

Conventional docking procedure was applied by assaying boron-free and boron-containing compounds on the recently reported crystal structure of SARS-CoV-2 main protease (PDB code: 6LU7). The set of 150 ligands includes bortezomib and inhibitors of coronavirus proteases.

Results::

Most of the tested compounds share contact with key residues and pose on the cleavage pocket. The compounds with a boron atom in their structure are often estimated to have higher affinity than boron-free analogues.

Conclusion::

Interactions and the affinity of boron-containing peptidomimetics strongly suggest that boron-moieties increase affinity on the main protease, which is tested by in vitro assays. A Bis-boron-containing compound previously tested active on SARS-virus protease and bortezomib were identified as potent ligands. These advances may be relevant to drug designing, in addition to testing available boron-containing drugs in patients with COVID19 infection.

Severe fever with thrombocytopenia syndrome virus: a highly lethal bunyavirus

Severe fever with thrombocytopenia syndrome virus (SFTSV) is a novel bunyavirus. Since 2007, SFTS disease has been reported in China with high fatality rate up to 30%, which drew high attention from Centre for Disease Control and Prevention and government. SFTSV is endemic in the centra l and eastern China, Korea and Japan. There also have been similar cases reported in Vietnam. The number of SFTSV infection cases has a steady growth in these years. As SFTSV could transmitted from person to person, it will expose the public to infectious risk. In 2018 annual review of the Blueprint list of priority diseases, World Health Organisation has listed SFTSV infection as prioritised diseases for research and development in emergency contexts. However, the pathogenesis of SFTSV remains largely unclear. Currently, there are no specific therapeutics or vaccines to combat infections of SFTSV. This review discusses recent findings of epidemiology, transmission pathway, pathogenesis and treatments of SFTS disease.

Enzyme-Antibody-Modified Gold Nanoparticle Probes for the Ultrasensitive Detection of Nucleocapsid Protein in SFTSV

As humans and climate change continue to alter the landscape, novel disease risk scenarios have emerged. Sever fever with thrombocytopenia syndrome (SFTS), an emerging tick-borne infectious disease first discovered in rural areas of central China in 2009, is caused by a novel bunyavirus (SFTSV). The potential for SFTS to spread to other countries in combination with its high fatality rate, possible human-to-human transmission, and extensive prevalence among residents and domesticated animals in endemic regions make the disease a severe threat to public health. Because of the lack of preventive vaccines or useful antiviral drugs, diagnosis of SFTS is the key to prevention and control of the SFTSV infection. The development of serological detection methods will greatly improve our understanding of SFTSV ecology and host tropism. We describe a highly sensitive protein detection method based on gold nanoparticles (AuNPs) and enzyme-linked immunosorbent assay (ELISA)—AuNP-based ELISA. The optical sensitivity enhancement of this method is due to the high loading efficiency of AuNPs to McAb. This enhances the concentration of the HRP enzyme in each immune sandwich structure. The detection limit of this method to the nucleocapsid protein (NP) of SFTSV was 0.9 pg mL⁻¹ with good specificity and reproducibility. The sensitivity of AuNP-based ELISA was higher than that of traditional ELISA and was comparable to real-time quantitative polymerase chain reaction (qRT-PCR). The probes are stable for 120 days at 4 °C. This can be applied to diagnosis and hopefully can be developed into a commercial ELISA kit. The ultrasensitive detection of SFTSV will increase our understanding of the distribution and spread of SFTSV, thus helping to monitor the changes in tick-borne pathogen SFTSV risk in the environment.

Bortezomib inhibits chikungunya virus replication by interfering with viral protein synthesis

Chikungunya virus (CHIKV) is an alphavirus that causes a febrile illness accompanied by myalgia and arthralgia. Despite having re-emerged as a significant public health threat, there are no approved therapeutics or prophylactics for CHIKV infection. In this study, we explored the anti-CHIKV effects of proteasome inhibitors and their potential mechanism of antiviral action. A panel of proteasome inhibitors with different functional groups reduced CHIKV infectious titers in a dose-dependent manner. Bortezomib, which has been FDA-approved for multiple myeloma and mantle cell lymphoma, was further investigated in downstream studies. The inhibitory activities of bortezomib were confirmed using different cellular models and CHIKV strains. Time-of-addition and time-of-removal studies suggested that bortezomib inhibited CHIKV at an early, post-entry stage of replication. In western blot analysis, bortezomib treatment resulted in a prominent decrease in structural protein levels as early as 6 hpi. Contrastingly, nsP4 levels showed strong elevations across all time-points. NsP2 and nsP3 levels showed a fluctuating trend, with some elevations between 12 to 20 hpi. Finally, qRT-PCR data revealed increased levels of both positive- and negative-sense CHIKV RNA at late stages of infection. It is likely that the reductions in structural protein levels is a major factor in the observed reductions in virus titer, with the alterations in non-structural protein ratios potentially being a contributing factor. Proteasome inhibitors like bortezomib likely disrupt CHIKV replication through a variety of complex mechanisms and may display a potential for use as therapeutics against CHIKV infection. They also represent valuable tools for studies of CHIKV molecular biology and virus-host interactions.

The Severe Fever with Thrombocytopenia Syndrome Virus NSs Protein Interacts with CDK1 To Induce G2 Cell Cycle Arrest and Positively Regulate Viral Replication

Severe fever with thrombocytopenia syndrome virus (SFTSV) is a newly identified phlebovirus associated with severe hemorrhagic fever in humans. While many viruses subvert the host cell cycle to promote viral growth, it is unknown whether this is a strategy employed by SFTSV. In this study, we investigated how SFTSV manipulates the cell cycle and the effect of the host cell cycle on SFTSV replication. Our results suggest that cells arrest at the G₂/M transition following infection with SFTSV. The accumulation of cells at the G₂/M transition did not affect virus adsorption and entry but did facilitate viral replication. In addition, we found that SFTSV NSs, a nonstructural protein that forms viroplasm-like structures in the cytoplasm of infected cells and promotes virulence by modulating the interferon response, induces a large number of cells to arrest at the G₂/M transition by interacting with CDK1. The interaction between NSs and CDK1, which is inclusion body dependent, inhibits formation and nuclear import of the cyclin B1-CDK1 complex, thereby leading to cell cycle arrest. Expression of a CDK1 loss-of-function mutant reversed the inhibitive effect of NSs on the cell cycle, suggesting that this protein is a potential antiviral target. Our study provides new insight into the role of a specific viral protein in SFTSV replication, indicating that NSs induces G₂/M arrest of SFTSV-infected cells, which promotes viral replication.IMPORTANCE Severe fever with thrombocytopenia syndrome virus (SFTSV) is a tick-borne pathogen that causes severe hemorrhagic fever. Although SFTSV poses a serious threat to public health and was recently isolated, its pathogenesis remains unclear. In particular, the relationship between SFTSV infection and the host cell cycle has not been described. Here, we show for the first time that both asynchronized and synchronized SFTSV-susceptible cells arrest at the G₂/M checkpoint following SFTSV infection and that the accumulation of cells at this checkpoint facilitates viral replication. We also identify a key mechanism underlying SFTSV-induced G₂/M arrest, in which SFTSV NSs interacts with CDK1 to inhibit formation and nuclear import of the cyclin B1-CDK1 complex, thus preventing it from regulating cell cycle progression. Our study highlights the key role that NSs plays in SFTSV-induced G₂/M arrest.