Inhibition of cyclooxygenase activity reduces rotavirus infection at a postbinding step

ML241 Antagonizes ERK 1/2 Activation and Inhibits Rotavirus Proliferation

Rotavirus (RV) is the main pathogen that causes severe diarrhea in infants and children under 5 years of age. No specific antiviral therapies or licensed anti-rotavirus drugs are available. It is crucial to develop effective and low-toxicity anti-rotavirus small-molecule drugs that act on novel host targets. In this study, a new anti-rotavirus compound was selected by ELISA, and cell activity was detected from 453 small-molecule compounds. The anti-RV effects and underlying mechanisms of the screened compounds were explored. In vitro experimental results showed that the small-molecule compound ML241 has a good effect on inhibiting rotavirus proliferation and has low cytotoxicity during the virus adsorption, cell entry, and replication stages. In addition to its in vitro effects, ML241 also exerted anti-RV effects in a suckling mouse model. Transcriptome sequencing was performed after adding ML241 to cells infected with RV. The results showed that ML241 inhibited the phosphorylation of ERK1/2 in the MAPK signaling pathway, thereby inhibiting IκBα, activating the NF-κB signaling pathway, and playing an anti-RV role. These results provide an experimental basis for specific anti-RV small-molecule compounds or compound combinations, which is beneficial for the development of anti-RV drugs.

Aspirin inhibits rotavirus replication and alters rat gut microbial composition

BACKGROUND

Aspirin is widely used to treat various clinical symptoms. Evidence suggests that aspirin has antiviral properties, but little is known about its specific effect against rotavirus.

METHODS

MA104, Caco-2, and CV-1 cells were infected with rotavirus, and aspirin was added after 12 h. Viral mRNA and titer levels were measured by qRT-PCR and immunofluorescence assays. For in vivo validation, forty specific-pathogen-free SD rats were randomly divided into oral aspirin (ASP) groups and control (NC) groups. 16 S rRNA gene sequencing was performed to identify gut microbiota. After 6 months of continuous ASP/NC administration, the rats were infected with rotavirus. Fecal samples were collected over a 30-day time course, and viral levels were quantified. Proinflammatory cytokines/chemokine levels were measured by ELISA.

RESULTS

Aspirin inhibited rotavirus infection in cell lines and in rats. The effects of aspirin on viral replication were associated with the alteration of gut microbiota composition by aspirin, including increased abundance of Firmicutes and decreased abundance of Bacteroidetes after aspirin treatment. Mechanistically, aspirin reduced IL-2 and IL-10 levels, and increased IRF-1 and COX-2 levels. Aspirin blocked rotavirus replication in vitro and in vivo, which might be related to effects on IRF-1, COX-2, chemokines, and gut microbial composition.

CONCLUSION

These results indicate that long-term oral aspirin administration reduces rotavirus infection. Intestinal virus infection may be suppressed in elderly patients who take aspirin for a long time. The change of their Gut microbiota may lead to functional disorder of the intestinal tract, which may provide some reference for clinical adjuvant probiotics treatment.

Prediction and Verification of Curcumin as a Potential Drug for Inhibition of PDCoV Replication in LLC-PK1 Cells

Porcine deltacoronavirus (PDCoV) is an emerging swine enteropathogenic coronavirus (CoV) that causes lethal watery diarrhea in neonatal pigs and poses economic and public health burdens. Currently, there are no effective antiviral agents against PDCoV. Curcumin is the active ingredient extracted from the rhizome of turmeric, which has a potential pharmacological value because it exhibits antiviral properties against several viruses. Here, we described the antiviral effect of curcumin against PDCoV. At first, the potential relationships between the active ingredients and the diarrhea-related targets were predicted through a network pharmacology analysis. Twenty-three nodes and 38 edges were obtained using a PPI analysis of eight compound-targets. The action target genes were closely related to the inflammatory and immune related signaling pathways, such as the TNF signaling pathway, Jak-STAT signaling pathway, and so on. Moreover, IL-6, NR3C2, BCHE and PTGS2 were identified as the most likely targets of curcumin by binding energy and 3D protein-ligand complex analysis. Furthermore, curcumin inhibited PDCoV replication in LLC-PK1 cells at the time of infection in a dose-dependent way. In poly (I:C) pretreated LLC-PK1 cells, PDCoV reduced IFN-β production via the RIG-I pathway to evade the host's antiviral innate immune response. Meanwhile, curcumin inhibited PDCoV-induced IFN-β secretion by inhibiting the RIG-I pathway and reduced inflammation by inhibiting IRF3 or NF-κB protein expression. Our study provides a potential strategy for the use of curcumin in preventing diarrhea caused by PDCoV in piglets.

Advances in the development of antivirals for rotavirus infection

Rotavirus (RV) causes 200,000 deaths per year and imposes a serious burden to public health and livestock farming worldwide. Currently, rehydration (oral and intravenous) remains the main strategy for the treatment of rotavirus gastroenteritis (RVGE), and no specific drugs are available. This review discusses the viral replication cycle in detail and outlines possible therapeutic approaches including immunotherapy, probiotic-assisted therapy, anti-enteric secretory drugs, Chinese medicine, and natural compounds. We present the latest advances in the field of rotavirus antivirals and highlights the potential use of Chinese medicine and natural compounds as therapeutic agents. This review provides an important reference for rotavirus prevention and treatment.

Candida albicans-enteric viral interactions-The prostaglandin E2 connection and host immune responses

The human microbiome comprises trillions of microorganisms residing within different mucosal cavities and across the body surface. The gut microbiota modulates host susceptibility to viral infections in several ways, and microbial interkingdom interactions increase viral infectivity within the gut. Candida albicans, a frequently encountered fungal species in the gut, produces highly structured biofilms and eicosanoids such as prostaglandin E₂ (PGE₂), which aid in viral protection and replication. These biofilms encompass viruses and provide a shield from antiviral drugs or the immune system. PGE₂ is a key modulator of active inflammation with the potential to regulate interferon signaling upon microbial invasion or viral infections. In this review, we raise the perspective of gut interkingdom interactions involving C. albicans and enteric viruses, with a special focus on biofilms, PGE₂, and viral replication. Ultimately, we discuss the possible implications of C. albicans-enteric virus associations on host immune responses, particularly the interferon signaling pathway.

Lacticaseibacillus rhamnosus GG Counteracts Rotavirus-Induced Ion Secretion and Enterocyte Damage by Inhibiting Oxidative Stress and Apoptosis Through Specific Effects of Living and Postbiotic Preparations

Background

Administration of Lacticaseibacillus rhamnosus GG (LGG) to children with gastroenteritis is recommended by universal guidelines. Rotavirus (RV) causes diarrhea through combined cytotoxic and enterotoxic effects. Aim of this study was to evaluate the mechanisms of efficacy of LGG in an in-vitro model of RV diarrhea in its viable form (LGG) and conditioned medium (mLGG).

Methods

Ion secretion corresponding to the NSP4 enterotoxic effect, was evaluated by short circuit current (Isc) and the cytotoxic effect by transepithelial electrical resistance (TEER) in Ussing chambers, upon exposure to RV in Caco-2 enterocyte monolayers treated or not with living probiotic or its culture supernatant. Mechanisms of enterotoxic and cytotoxic damage were evaluated including oxidative stress measured by reactive oxygen species, apoptosis evaluated by DAPI and nuclear staining, NFkβ immunofluorescence.

Results

RV induced Isc increase and TEER decrease, respectively indicating ion secretion and epithelial damage, the two established pathways of diarrhea. Both probiotic preparations reduced both diarrheal effects, but their potency was different. Live LGG was equally effective on both enterotoxic and cytotoxic effect whereas mLGG was highly effective on ion secretion and showed minimal protective effects on cytoskeleton, apoptosis and NFkβ.

Conclusions

LGG counteracts RV-induced diarrhea by inhibiting both cytotoxic and enterotoxic pathogenic mechanisms. Namely, LGG inhibits chloride secretion by specific moieties secreted in the medium with a direct pharmacologic-like action. This is considered a postbiotic effect. Subsequently, live bacteria exert a probiotic effect protecting the enterocyte structure.

Rotavirus-Mediated Prostaglandin E2 Production in MA104 Cells Promotes Virus Attachment and Internalisation, Resulting in an Increased Viral Load

Rotaviruses are one of the leading causes of severe dehydrating diarrhoea in infants and children under the age of five. Despite the introduction of vaccines, disease burden remains high in sub-Saharan Africa, with no known anti-viral treatments available. During early infection rotavirus attaches to several cellular receptors and enters the cells by either clathrin-dependent or -independent endocytosis. Prostaglandin E_2, an abundant eicosanoid, is produced from arachidonic acid during rotavirus infection and inhibition of prostaglandin E₂ formation have a deleterious effect on rotavirus infection. In this study, MA104 cells were supplemented with γ-linolenic acid (GLA), a precursor of arachidonic acid. Infection of supplemented cells with rotavirus SA11 led to a depletion in the relative percentages of GLA and arachidonic acid which coincided with an increased production of prostaglandin E₂ as monitored by ELISA. Confocal microscopy demonstrated that prostaglandin E₂ co-localises with the viroplasm-forming proteins, NSP5 and NSP2. Due to the known association of viroplasms with lipid droplets and the fact that lipid droplets are sites for prostaglandin E₂ production, our results indicate a possible role for viroplasms in the production of rotavirus-induced prostaglandin E₂. Replication kinetics showed that inhibitors, targeting the biosynthesis of prostaglandin E₂, had negative effects on rotavirus yield, especially during the early stages of infection. Using flow cytometry and prostaglandin E₂ addback experiments, we show that prostaglandin E₂ enhances the attachment and internalisation of rotavirus in MA104 cells indicating a possible role for prostaglandin E₂ during clathrin-mediated rotavirus entry. The production of prostaglandin E₂ during rotavirus infection could serve as a possible target for anti-viral treatment.

Delineation of altered brain proteins associated with furious rabies virus infection in dogs by quantitative proteomics

Rabies is a fatal zoonotic disease caused by rabies virus (RABV). Despite the existence of control measures, dog-transmitted human rabies accounts for ˃95% reported cases due to unavailability of sensitive diagnostic methods, inadequate understanding of disease progression and absence of therapeutics. In addition, host factors and their role in RABV infection are poorly understood. In this study, we used 8-plex iTRAQ coupled with HRMS approach to identify differentially abundant proteins (DAPs) of dog brain associated with furious rabies virus infection. Total 40 DAPs including 26 down-regulated and 14 up-regulated proteins were statistically significant in infected samples. GO annotation and IPA showed that calcium signaling and calcium transport, efficient neuronal function, metabolic pathway associated proteins were mostly altered during this infection. Total 34 proteins including 10 down-regulated proteins pertaining to calcium signaling and calcium transport pathways were successfully verified by qRT-PCR and two proteins were verified by western blot, thereby suggesting these pathways may play an important role in this infection. This study provides the map of altered brain proteins and some insights into the molecular pathophysiology associated with furious rabies virus infection. However, further investigations are required to understand their role in disease mechanism. SIGNIFICANCE: Transmission of rabies by dogs poses the greatest hazard world-wide and the rare survival of post-symptomatic patients as well as severe neurological and immunological problems pose a question to understand the molecular mechanism involved in rabies pathogenesis. However, information regarding host factors and their function in RABV infection is still inadequate. Our study has used an advanced quantitative proteomics approach i.e. 8-plex iTRAQ coupled with HRMS and identified 40 DAPs in furious rabies infected dog brain tissues compared to the controls. Further analysis showed that calcium signaling and transport pathway, efficient neuronal functions and metabolic pathway associated brain proteins were most altered during furious rabies virus infection. This data provides a map of altered brain proteins which may have role in furious rabies virus infection. Hence, this will improve our understanding of the molecular pathogenesis of RABV infection.

Lipid droplets and lipid mediators in viral infection and immunity

Lipid droplets (LDs) contribute to key pathways important for the physiology and pathophysiology of cells. In a homeostatic view, LDs regulate the storage of neutral lipids, protein sequestration, removal of toxic lipids and cellular communication; however, recent advancements in the field show these organelles as essential for various cellular stress response mechanisms, including inflammation and immunity, with LDs acting as hubs that integrate metabolic and inflammatory processes. The accumulation of LDs has become a hallmark of infection, and is often thought to be virally driven; however, recent evidence is pointing to a role for the upregulation of LDs in the production of a successful immune response to viral infection. The fatty acids housed in LDs are also gaining interest due to the role that these lipid species play during viral infection, and their link to the synthesis of bioactive lipid mediators that have been found to have a very complex role in viral infection. This review explores the role of LDs and their subsequent lipid mediators during viral infections and poses a paradigm shift in thinking in the field, whereby LDs may play pivotal roles in protecting the host against viral infection.

Network pharmacology approach to decipher signaling pathways associated with target proteins of NSAIDs against COVID-19

Non-steroidal anti-inflammatory drugs (NSAIDs) showed promising clinical efficacy toward COVID-19 (Coronavirus disease 2019) patients as potent painkillers and anti-inflammatory agents. However, the prospective anti-COVID-19 mechanisms of NSAIDs are not evidently exposed. Therefore, we intended to decipher the most influential NSAIDs candidate(s) and its novel mechanism(s) against COVID-19 by network pharmacology. FDA (U.S. Food & Drug Administration) approved NSAIDs (19 active drugs and one prodrug) were used for this study. Target proteins related to selected NSAIDs and COVID-19 related target proteins were identified by the Similarity Ensemble Approach, Swiss Target Prediction, and PubChem databases, respectively. Venn diagram identified overlapping target proteins between NSAIDs and COVID-19 related target proteins. The interactive networking between NSAIDs and overlapping target proteins was analyzed by STRING. RStudio plotted the bubble chart of the KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment analysis of overlapping target proteins. Finally, the binding affinity of NSAIDs against target proteins was determined through molecular docking test (MDT). Geneset enrichment analysis exhibited 26 signaling pathways against COVID-19. Inhibition of proinflammatory stimuli of tissues and/or cells by inactivating the RAS signaling pathway was identified as the key anti-COVID-19 mechanism of NSAIDs. Besides, MAPK8, MAPK10, and BAD target proteins were explored as the associated target proteins of the RAS. Among twenty NSAIDs, 6MNA, Rofecoxib, and Indomethacin revealed promising binding affinity with the highest docking score against three identified target proteins, respectively. Overall, our proposed three NSAIDs (6MNA, Rofecoxib, and Indomethacin) might block the RAS by inactivating its associated target proteins, thus may alleviate excessive inflammation induced by SARS-CoV-2.

A small molecule compound berberine as an orally active therapeutic candidate against COVID-19 and SARS: A computational and mechanistic study

The novel coronavirus disease, COVID-19, has grown into a global pandemic and a major public health threat since its breakout in December 2019. To date, no specific therapeutic drug or vaccine for treating COVID-19 and SARS has been FDA approved. Previous studies suggest that berberine, an isoquinoline alkaloid, has shown various biological activities that may help against COVID-19 and SARS, including antiviral, anti-allergy and inflammation, hepatoprotection against drug- and infection-induced liver injury, as well as reducing oxidative stress. In particular, berberine has a wide range of antiviral activities such as anti-influenza, anti-hepatitis C, anti-cytomegalovirus, and anti-alphavirus. As an ingredient recommended in guidelines issued by the China National Health Commission for COVID-19 to be combined with other therapy, berberine is a promising orally administered therapeutic candidate against SARS-CoV and SARS-CoV-2. The current study comprehensively evaluates the potential therapeutic mechanisms of berberine in preventing and treating COVID-19 and SARS using computational modeling, including target mining, gene ontology enrichment, pathway analyses, protein-protein interaction analysis, and in silico molecular docking. An orally available immunotherapeutic-berberine nanomedicine, named NIT-X, has been developed by our group and has shown significantly increased oral bioavailability of berberine, increased IFN-γ production by CD8+ T cells, and inhibition of mast cell histamine release in vivo, suggesting a protective immune response. We further validated the inhibition of replication of SARS-CoV-2 in lung epithelial cells line in vitro (Calu3 cells) by berberine. Moreover, the expression of targets including ACE2, TMPRSS2, IL-1α, IL-8, IL-6, and CCL-2 in SARS-CoV-2 infected Calu3 cells were significantly suppressed by NIT-X. By supporting protective immunity while inhibiting pro-inflammatory cytokines; inhibiting viral infection and replication; inducing apoptosis; and protecting against tissue damage, berberine is a promising candidate in preventing and treating COVID-19 and SARS. Given the high oral bioavailability and safety of berberine nanomedicine, the current study may lead to the development of berberine as an orally, active therapeutic against COVID-19 and SARS.

Potential therapeutic and pharmacological strategies for SARS-CoV2

BACKGROUND

At the end of 2019, the new Coronavirus disease 2019 (COVID-19) strain causing severe acute respiratory syndrome swept the world. From November 2019 till February 2021, this virus infected nearly 104 million, with more than two million deaths and about 25 million active cases. This has prompted scientists to discover effective drugs to combat this pandemic.

AREA COVERED

Drug repurposing is the magic bullet for treating severe acute respiratory syndrome coronavirus 2 (SARS-CoV2). Therefore, several drugs have been investigated in silico, in vitro, as well as through human trials such as anti-SARS-CoV2 agents, or to prevent the complications resulting from the virus. In this review, the mechanisms of action of different therapeutic strategies are summarized. According to the WHO, different classes of drugs can be used, including anti-malarial, antiviral, anti-inflammatory, and anti-coagulant drugs, as well as angiotensin-converting enzyme inhibitors, antibiotics, vitamins, zinc, neutralizing antibodies, and convalescent plasma therapy. Recently, there are some vaccines which are approved against SARS-CoV2.

EXPERT OPINION

A complete understanding of the structure and function of all viral proteins that play a fundamental role in viral infection, which contribute to the therapeutic intervention and the development of vaccine in order to reduce the mortality rate.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40005-021-00520-4.

Perspective Adjunctive Therapies for COVID-19: Beyond Antiviral Therapy

The coronavirus disease 2019 (COVID-19) pandemic is the largest health crisis ever faced worldwide. It has resulted in great health and economic costs because no effective treatment is currently available. Since infected persons vary in presentation from healthy asymptomatic mild symptoms to those who need intensive care support and eventually succumb to the disease, this illness is considered to depend primarily on individual immunity. Demographic distribution and disease severity in several regions of the world vary; therefore, it is believed that natural inherent immunity provided through dietary sources and traditional medicines could play an important role in infection prevention and disease progression. People can boost their immunity to prevent them from infection after COVID-19 exposure and can reduce their inflammatory reactions to protect their organ deterioration in case suffering from the disease. Some drugs with in-situ immunomodulatory and anti-inflammatory activity are also identified as adjunctive therapy in the COVID-19 era. This review discusses the importance of COVID-19 interactions with immune cells and inflammatory cells; and further emphasizes the possible pathways related with traditional herbs, medications and nutritional products. We believe that such pathophysiological pathway approach treatment is rational and important for future development of new therapeutic agents for prevention or cure of COVID-19 infection.

Potential Anti-SARS-CoV-2 Therapeutics That Target the Post-Entry Stages of the Viral Life Cycle: A Comprehensive Review

The coronavirus disease-2019 (COVID-19) pandemic continues to challenge health care systems around the world. Scientists and pharmaceutical companies have promptly responded by advancing potential therapeutics into clinical trials at an exponential rate. Initial encouraging results have been realized using remdesivir and dexamethasone. Yet, the research continues so as to identify better clinically relevant therapeutics that act either as prophylactics to prevent the infection or as treatments to limit the severity of COVID-19 and substantially decrease the mortality rate. Previously, we reviewed the potential therapeutics in clinical trials that block the early stage of the viral life cycle. In this review, we summarize potential anti-COVID-19 therapeutics that block/inhibit the post-entry stages of the viral life cycle. The review presents not only the chemical structures and mechanisms of the potential therapeutics under clinical investigation, i.e., listed in clinicaltrials.gov, but it also describes the relevant results of clinical trials. Their anti-inflammatory/immune-modulatory effects are also described. The reviewed therapeutics include small molecules, polypeptides, and monoclonal antibodies. At the molecular level, the therapeutics target viral proteins or processes that facilitate the post-entry stages of the viral infection. Frequent targets are the viral RNA-dependent RNA polymerase (RdRp) and the viral proteases such as papain-like protease (PLpro) and main protease (Mpro). Overall, we aim at presenting up-to-date details of anti-COVID-19 therapeutics so as to catalyze their potential effective use in fighting the pandemic.

Indomethacin and resveratrol as potential treatment adjuncts for SARS-CoV-2/COVID-19

The ongoing pandemic caused by severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2, also known as COVID-19) has led to unprecedented challenges for the global healthcare system. This novel coronavirus disease phenotype ranges from asymptomatic carriage to fulminant cytokine storm with respiratory failure, polyorgan dysfunction and death. Severe disease is characterised by exuberant inflammation resulting from high circulating cytokines such as interleukin-6 and tumour necrosis factor. These inflammatory mediators are responsible for the detrimental effects on the immune, hematologic, respiratory, renal, gastrointestinal and other body systems. In addition to inhibition of viral replication, blunting this inflammatory response before overt cytokine storm is important to improve outcomes. Although there are upcoming promising agents such as remdesivir and convalescent plasma, inexpensive, safe and widely available adjunct treatments to ameliorate disease burden would be welcome. Two potential anti-inflammatory agents include indomethacin, which has been shown in experimental models to decrease canine coronavirus levels in dogs and exhibit antiviral activity against several other viruses and the polyphenol, resveratrol, a potent antioxidant that has shown antiviral activity against several viruses.

Urinary PGE2 metabolite levels in hospitalised infants with infections compared to age-matched controls

AIM

To determine the urinary tetranor-prostaglandin E₂ metabolite in healthy infants and in hospitalised infants with upper and lower respiratory tract as well as gastrointestinal infections.

METHODS

A prospective cross-sectional study to determine baseline concentrations of urinary tetranor-prostaglandin E₂ metabolite was conducted in 81 healthy infants aged one week to one year and in 142 hospitalised infants with infections. Prostaglandin metabolite levels were measured by liquid chromatography tandem mass spectrometry.

RESULTS

In healthy infants, urinary prostaglandin E₂ metabolite levels decreased with age and did not differ between girls and boys. Infections of the lower respiratory (n = 78) and gastrointestinal tract (n = 12) correlated with increased levels of the prostaglandin E₂ metabolite. In contrast, infants hospitalised with upper respiratory tract infections (n = 23) exhibited similar levels as healthy, age-matched controls. Lower prostaglandin E₂ levels were found after treatment with acetaminophen in hospitalised children. Prostaglandin E₂ metabolite levels did not correlate with length of hospitalisation or need for respiratory support.

CONCLUSION

This study first provides normal levels of urinary prostaglandin E₂ metabolite in infants and secondly demonstrates elevated levels in hospitalised children with lower respiratory tract and gastrointestinal infections.

Rotavirus Induces Formation of Remodeled Stress Granules and P Bodies and Their Sequestration in Viroplasms To Promote Progeny Virus Production

Rotavirus replicates in unique virus-induced cytoplasmic inclusion bodies called viroplasms (VMs), the composition and structure of which have yet to be understood. Based on the analysis of a few proteins, earlier studies reported that rotavirus infection inhibits stress granule (SG) formation and disrupts P bodies (PBs). However, the recent demonstration that rotavirus infection induces cytoplasmic relocalization and colocalization with VMs of several nuclear hnRNPs and AU-rich element-binding proteins (ARE-BPs), which are known components of SGs and PBs, suggested the possibility of rotavirus-induced remodeling of SGs and PBs, prompting us to analyze a large number of the SG and PB components to understand the status of SGs and PBs in rotavirus-infected cells. Here we demonstrate that rotavirus infection induces molecular triage by selective exclusion of a few proteins of SGs (G3BP1 and ZBP1) and PBs (DDX6, EDC4, and Pan3) and sequestration of the remodeled/atypical cellular organelles, containing the majority of their components, in the VM. The punctate SG and PB structures are seen at about 4 h postinfection (hpi), coinciding with the appearance of small VMs, many of which fuse to form mature large VMs with progression of infection. By use of small interfering RNA (siRNA)-mediated knockdown and/or ectopic overexpression, the majority of the SG and PB components, except for ADAR1, were observed to inhibit viral protein expression and virus growth. In conclusion, this study demonstrates that VMs are highly complex supramolecular structures and that rotavirus employs a novel strategy of sequestration in the VM and harnessing of the remodeled cellular RNA recycling bins to promote its growth.IMPORTANCE Rotavirus is known to replicate in specialized virus-induced cytoplasmic inclusion bodies called viroplasms (VMs), but the composition and structure of VMs are not yet understood. Here we demonstrate that rotavirus interferes with normal SG and PB assembly but promotes formation of atypical SG-PB structures by selective exclusion of a few components and employs a novel strategy of sequestration of the remodeled SG-PB granules in the VMs to promote virus growth by modulating their negative influence on virus infection. Rotavirus VMs appear to be complex supramolecular structures formed by the union of the triad of viral replication complexes and remodeled SGs and PBs, as well as other host factors, and designed to promote productive virus infection. These observations have implications for the planning of future research with the aim of understanding the structure of the VM, the mechanism of morphogenesis of the virus, and the detailed roles of host proteins in rotavirus biology.

Therapeutics and Immunoprophylaxis Against Noroviruses and Rotaviruses: The Past, Present, and Future

Background:

Noroviruses and rotaviruses are important viral etiologies of severe gastroenteritis. Noroviruses are the primary cause of nonbacterial diarrheal outbreaks in humans, whilst rotaviruses are a major cause of childhood diarrhea. Although both enteric pathogens substantially impact human health and economies, there are no approved drugs against noroviruses and rotaviruses so far. On the other hand, whilst the currently licensed rotavirus vaccines have been successfully implemented in over 100 countries, the most advanced norovirus vaccine has recently completed phase-I and II trials.

Methods:

We performed a structured search of bibliographic databases for peer-reviewed research litera-ture on advances in the fields of norovirus and rotavirus therapeutics and immunoprophylaxis.

Results:

Technological advances coupled with a proper understanding of viral morphology and replication over the past decade has facilitated pioneering research on therapeutics and immunoprophylaxis against noroviruses and rotaviruses, with promising outcomes in human clinical trials of some of the drugs and vaccines. This review focuses on the various developments in the fields of norovirus and rotavirus thera-peutics and immunoprophylaxis, such as potential antiviral drug molecules, passive immunotherapies (oral human immunoglobulins, egg yolk and bovine colostral antibodies, llama-derived nanobodies, and anti-bodies expressed in probiotics, plants, rice grains and insect larvae), immune system modulators, probiot-ics, phytochemicals and other biological substances such as bovine milk proteins, therapeutic nanoparti-cles, hydrogels and viscogens, conventional viral vaccines (live and inactivated whole virus vaccines), and genetically engineered viral vaccines (reassortant viral particles, virus-like particles (VLPs) and other sub-unit recombinant vaccines including multi-valent viral vaccines, edible plant vaccines, and encapsulated viral particles).

Conclusions:

This review provides important insights into the various approaches to therapeutics and im-munoprophylaxis against noroviruses and rotaviruses..

Cytoplasmic Relocalization and Colocalization with Viroplasms of Host Cell Proteins, and Their Role in Rotavirus Infection

Rotavirus replicates in the cytoplasm of infected cells in unique virus-induced cytoplasmic inclusion bodies called viroplasms (VMs), which are nucleated by two essential viral nonstructural proteins, NSP2 and NSP5. However, the precise composition of the VM, the intracellular localization of host proteins during virus infection, and their association with VMs or role in rotavirus growth remained largely unexplored. Mass spectrometry analyses revealed the presence of several host heterogeneous nuclear ribonucleoproteins (hnRNPs), AU-rich element-binding proteins (ARE-BPs), and cytoplasmic proteins from uninfected MA104 cell extracts in the pulldown (PD) complexes of the purified viroplasmic proteins NSP2 and NSP5. Immunoblot analyses of PD complexes from RNase-treated and untreated cell extracts, analyses of coimmunoprecipitation complexes using RNase-treated infected cell lysates, and direct binding assays using purified recombinant proteins further demonstrated that the interactions of the majority of the hnRNPs and ARE-BPs with viroplasmic proteins are RNA independent. Time course immunoblot analysis of the nuclear and cytoplasmic fractions from rotavirus-infected and mock-infected cells and immunofluorescence confocal microscopy analyses of virus-infected cells revealed a surprising sequestration of the majority of the relocalized host proteins in viroplasms. Analyses of ectopic overexpression and small interfering RNA (siRNA)-mediated downregulation of expression revealed that host proteins either promote or inhibit viral protein expression and progeny virus production in virus-infected cells. This study demonstrates that rotavirus induces the cytoplasmic relocalization and sequestration of a large number of nuclear and cytoplasmic proteins in viroplasms, subverting essential cellular processes in both compartments to promote rapid virus growth, and reveals that the composition of rotavirus viroplasms is much more complex than is currently understood.IMPORTANCE Rotavirus replicates exclusively in the cytoplasm. Knowledge on the relocalization of nuclear proteins to the cytoplasm or the role(s) of host proteins in rotavirus infection is very limited. In this study, it is demonstrated that rotavirus infection induces the cytoplasmic relocalization of a large number of nuclear RNA-binding proteins (hnRNPs and AU-rich element-binding proteins). Except for a few, most nuclear hnRNPs and ARE-BPs, nuclear transport proteins, and some cytoplasmic proteins directly interact with the viroplasmic proteins NSP2 and NSP5 in an RNA-independent manner and become sequestered in the viroplasms of infected cells. The host proteins differentially affected viral gene expression and virus growth. This study demonstrates that rotavirus induces the relocalization and sequestration of a large number of host proteins in viroplasms, affecting host processes in both compartments and generating conditions conducive for virus growth in the cytoplasm of infected cells.

Activation of PI3K, Akt, and ERK during early rotavirus infection leads to V-ATPase-dependent endosomal acidification required for uncoating

The cellular PI3K/Akt and/or MEK/ERK signaling pathways mediate the entry process or endosomal acidification during infection of many viruses. However, their roles in the early infection events of group A rotaviruses (RVAs) have remained elusive. Here, we show that late-penetration (L-P) human DS-1 and bovine NCDV RVA strains stimulate these signaling pathways very early in the infection. Inhibition of both signaling pathways significantly reduced production of viral progeny due to blockage of virus particles in the late endosome, indicating that neither of the two signaling pathways is involved in virus trafficking. However, immunoprecipitation assays using antibodies specific for pPI3K, pAkt, pERK and the subunit E of the V-ATPase co-immunoprecipitated the V-ATPase in complex with pPI3K, pAkt, and pERK. Moreover, Duolink proximity ligation assay revealed direct association of the subunit E of the V-ATPase with the molecules pPI3K, pAkt, and pERK, indicating that both signaling pathways are involved in V-ATPase-dependent endosomal acidification. Acidic replenishment of the medium restored uncoating of the RVA strains in cells pretreated with inhibitors specific for both signaling pathways, confirming the above results. Isolated components of the outer capsid proteins, expressed as VP4-VP8* and VP4-VP5* domains, and VP7, activated the PI3K/Akt and MEK/ERK pathways. Furthermore, psoralen-UV-inactivated RVA and CsCl-purified RVA triple-layered particles triggered activation of the PI3K/Akt and MEK/ERK pathways, confirming the above results. Our data demonstrate that multistep binding of outer capsid proteins of L-P RVA strains with cell surface receptors phosphorylates PI3K, Akt, and ERK, which in turn directly interact with the subunit E of the V-ATPase to acidify the late endosome for uncoating of RVAs. This study provides a better understanding of the RVA-host interaction during viral uncoating, which is of importance for the development of strategies aiming at controlling or preventing RVA infections.

Viral particles must transport their genome into the cytoplasm or the nucleus of host cells to initiate successful infection. Knowledge of how viruses may pirate host cell signaling cascades or molecules to promote their own replication can facilitate the development of antiviral drugs. Group A rotavirus (RVA) is a major etiological agent of acute gastroenteritis in young children and the young of various mammals. RVA enters cells by a complex multistep process. However, the cellular signaling cascades or molecules that facilitate these processes are incompletely understood. Here, we demonstrate that infection with late-penetration RVA strains results in phosphorylation of PI3K, Akt, and ERK signaling molecules at an early stage of infection, a process mediated by the multistep binding of RVAs outer capsid proteins. Specific inhibitors for PI3K/Akt and MEK/ERK signaling pathways trap the viral particles in late endosome, and acidic replenishment restores and releases them. Moreover, the RVA-induced phosphorylated PI3K, Akt, and ERK directly interact with the subunit E of the V-ATPase proton pump, required for endosomal acidification and RVA uncoating. Understanding how RVA-induced early activation of cellular signaling molecules mediates the V-ATPase-dependent endosomal acidification required for uncoating of viral particles opens up opportunities for targeted interventions against rotavirus entry.

Prostaglandin E2 As a Modulator of Viral Infections

Viral infections are a major cause of infectious diseases worldwide. Inflammation and the immune system are the major host defenses against these viral infection. Prostaglandin E2 (PGE2), an eicosanoid generated by cyclooxygenases, has been shown to modulate inflammation and the immune system by regulating the expression/concentration of cytokines. The effect of PGE2 on viral infection and replication is cell type- and virus-family-dependent. The host immune system can be modulated by PGE2, with regards to immunosuppression, inhibition of nitrogen oxide (NO) production, inhibition of interferon (IFN) and apoptotic pathways, and inhibition of viral receptor expression. Furthermore, PGE2 can play a role in viral infection directly by increasing the production and release of virions, inhibiting viral binding and replication, and/or stimulating viral gene expression. PGE2 may also have a regulatory role in the induction of autoimmunity and in signaling via Toll-like receptors. In this review the known effects of PGE2 on the pathogenesis of various infections caused by herpes simplex virus, rotavirus, influenza A virus and human immunodeficiency virus as well the therapeutic potential of PGE2 are discussed.

PPARγ Agonists as an Anti-Inflammatory Treatment Inhibiting Rotavirus Infection of Small Intestinal Villi

Rotavirus infection has been reported to induce an inflammatory response in the host cell accompanied by the increased expression or activation of some cellular molecules including ROS, NF-κB, and COX-2. PPARγ stimulation and N-acetylcysteine (NAC) treatment have been found to interfere with viral infections including rotavirus infection. Small intestinal villi isolated from in vivo infected mice with rotavirus ECwt were analyzed for the percentage of ECwt-infected cells, the presence of rotavirus antigens, and infectious virion yield following treatment with pioglitazone. Isolated villi were also infected in vitro and treated with PPARγ agonists (PGZ, TZD, RGZ, DHA, and ALA), all-trans retinoic acid (ATRA), and NAC. After treatments, the expression of cellular proteins including PPARγ, NF-κB, PDI, Hsc70, and COX-2 was analyzed using immunochemistry, ELISA, immunofluorescence, and Western blotting. The results showed that rotavirus infection led to an increased accumulation of the cellular proteins studied and ROS. The virus infection-induced accumulation of the cellular proteins studied and ROS was reduced upon pioglitazone treatment, causing also a concomitant reduction of the infectious virion yield. We hypothesized that rotavirus infection is benefiting from the induction of a host cell proinflammatory response and that the interference of the inflammatory pathways involved leads to decreased infection.

Inflammatory and oxidative stress in rotavirus infection

Rotaviruses are the single leading cause of life-threatening diarrhea affecting children under 5 years of age. Rotavirus entry into the host cell seems to occur by sequential interactions between virion proteins and various cell surface molecules. The entry mechanisms seem to involve the contribution of cellular molecules having binding, chaperoning and oxido-reducing activities. It appears to be that the receptor usage and tropism of rotaviruses is determined by the species, cell line and rotavirus strain. Rotaviruses have evolved functions which can antagonize the host innate immune response, whereas are able to induce endoplasmic reticulum (ER) stress, oxidative stress and inflammatory signaling. A networking between ER stress, inflammation and oxidative stress is suggested, in which release of calcium from the ER increases the generation of mitochondrial reactive oxygen species (ROS) leading to toxic accumulation of ROS within ER and mitochondria. Sustained ER stress potentially stimulates inflammatory response through unfolded protein response pathways. However, the detailed characterization of the molecular mechanisms underpinning these rotavirus-induced stressful conditions is still lacking. The signaling events triggered by host recognition of virus-associated molecular patterns offers an opportunity for the development of novel therapeutic strategies aimed at interfering with rotavirus infection. The use of N-acetylcysteine, non-steroidal anti-inflammatory drugs and PPARγ agonists to inhibit rotavirus infection opens a new way for treating the rotavirus-induced diarrhea and complementing vaccines.

Diminished COX-2/PGE2-Mediated Antiviral Response Due to Impaired NOX/MAPK Signaling in G6PD-Knockdown Lung Epithelial Cells

Glucose-6-phosphate dehydrogenase (G6PD) provides the reducing agent NADPH to meet the cellular needs for reductive biosynthesis and the maintenance of redox homeostasis. G6PD-deficient cells experience a high level of oxidative stress and an increased susceptibility to viral infections. Cyclooxygenase-2 (COX-2) is a key mediator in the regulation of viral replication and inflammatory response. In the current study, the role of G6PD on the inflammatory response was determined in both scramble control and G6PD-knockdown (G6PD-kd) A549 cells upon tumor necrosis factor-α (TNF-α) stimulation. A decreased expression pattern of induced COX-2 and reduced production of downstream PGE₂ occurred upon TNF-α stimulation in G6PD-kd A549 cells compared with scramble control A549 cells. TNF-α-induced antiviral activity revealed that decreased COX-2 expression enhanced the susceptibility to coronavirus 229E infection in G6PD-kd A549 cells and was a result of the decreased phosphorylation levels of MAPK (p38 and ERK1/2) and NF-κB. The impaired inflammatory response in G6PD-kd A549 cells was found to be mediated through NADPH oxidase (NOX) signaling as elucidated by cell pretreatment with a NOX2-siRNA or NOX inhibitor, diphenyleneiodonium chloride (DPI). In addition, NOX activity with TNF-α treatment in G6PD-kd A549 cells was not up-regulated and was coupled with a decrease in NOX subunit expression at the transcriptional level, implying that TNF-α-mediated NOX signaling requires the participation of G6PD. Together, these data suggest that G6PD deficiency affects the cellular inflammatory response and the decreased TNF-α-mediated antiviral response in G6PD-kd A549 cells is a result of dysregulated NOX/MAPK/NF-κB/COX-2 signaling.

Protective effect of resveratrol against pseudorabies virus-induced reproductive failure in a mouse model

Resveratrol (RES), a natural polyphenol that is abundant in grapes, exerts anti-inflammatory, anti-oxidative, and antiviral bioactive effects. Protective effects of RES against pseudorabies virus (PrV)- induced reproductive failure were investigated in a mice model. Injection of PrV partially induced stillbirth and abortion, and caused poor growth of progeny. Treatment with RES attenuated the reproductive failure induced by the virus with recovery of the serum progesterone level. RES improved the growth performance of newborn mice. RES can attenuate the reproductive failure induced by PrV in mice.

Inhibition of viral protein translation by indomethacin in vesicular stomatitis virus infection: role of eIF2α kinase PKR

Indomethacin, a cyclooxygenase‐1 and ‐2 inhibitor widely used in the clinic for its potent anti‐inflammatory/analgesic properties, possesses antiviral activity against several viral pathogens; however, the mechanism of antiviral action remains elusive. We have recently shown that indomethacin activates the double‐stranded RNA (dsRNA)‐dependent protein kinase R (PKR) in human colon cancer cells. Because of the important role of PKR in the cellular defence response against viral infection, herein we investigated the effect of indomethacin on PKR activity during infection with the prototype rhabdovirus vesicular stomatitis virus. Indomethacin was found to activate PKR in an interferon‐ and dsRNA‐independent manner, causing rapid (< 5 min) phosphorylation of eukaryotic initiation factor‐2 α‐subunit (eIF2α). These events resulted in shutting off viral protein translation and blocking viral replication (IC₅₀ = 2 μM) while protecting host cells from virus‐induced damage. Indomethacin did not affect eIF2α kinases PKR‐like endoplasmic reticulum‐resident protein kinase (PERK) and general control non‐derepressible‐2 (GCN2) kinase, and was unable to trigger eIF2α phosphorylation in the presence of PKR inhibitor 2‐aminopurine. In addition, small‐interfering RNA‐mediated PKR gene silencing dampened the antiviral effect in indomethacin‐treated cells. The results identify PKR as a critical target for the antiviral activity of indomethacin and indicate that eIF2α phosphorylation could be a key element in the broad spectrum antiviral activity of the drug.

Inhibition of rotavirus ECwt infection in ICR suckling mice by N-acetylcysteine, peroxisome proliferator-activated receptor gamma agonists and cyclooxygenase-2 inhibitors

Live attenuated vaccines have recently been introduced for preventing rotavirus disease in children. However, alternative strategies for prevention and treatment of rotavirus infection are needed mainly in developing countries where low vaccine coverage occurs. In the present work, N-acetylcysteine (NAC), ascorbic acid (AA), some nonsteroidal anti-inflammatory drugs (NSAIDs) and peroxisome proliferator-activated receptor gamma (PPARγ) agonists were tested for their ability to interfere with rotavirus ECwt infectivity as detected by the percentage of viral antigen-positive cells of small intestinal villi isolated from ECwt-infected ICR mice. Administration of 6 mg NAC/kg every 8 h for three days following the first diarrhoeal episode reduced viral infectivity by about 90%. Administration of AA, ibuprofen, diclofenac, pioglitazone or rosiglitazone decreased viral infectivity by about 55%, 90%, 35%, 32% and 25%, respectively. ECwt infection of mice increased expression of cyclooxygenase-2, ERp57, Hsc70, NF-κB, Hsp70, protein disulphide isomerase (PDI) and PPARγ in intestinal villus cells. NAC treatment of ECwt-infected mice reduced Hsc70 and PDI expression to levels similar to those observed in villi from uninfected control mice. The present results suggest that the drugs tested in the present work could be assayed in preventing or treating rotaviral diarrhoea in children and young animals.

Rotavirus infection induces G1 to S phase transition in MA104 cells via Ca⁺²/Calmodulin pathway

Viruses, obligate cellular parasites rely on host cellular functions and target the host cell cycle for their own benefit. In this study, effect of rotavirus infection on cell cycle machinery was explored. We found that rotavirus (RV) infection in MA104 cells induces the expression of cyclins and cyclin dependent kinases and down-regulates expression of CDK inhibitors, resulting in G1 to S phase transition. The rotavirus induced S phase accumulation was found to be concurrent with induction in expression of calmodulin and activation of CaMKI which is reported as inducer of G1-S phase transition. This cell cycle manipulation was found to be Ca(+2)/Calmodulin pathway dependent. The physiological relevance of G1 to S phase transition was established when viral gene expressions as well as viral titers were found to be increased in S phase synchronized cells and decreased in G0/G1 phase synchronized cells compared to unsynchronized cells during rotavirus infection.

Rotavirus infection increases intestinal motility but not permeability at the onset of diarrhea

The disease mechanisms associated with onset and secondary effects of rotavirus (RV) diarrhea remain to be determined and may not be identical. In this study, we investigated whether onset of RV diarrhea is associated with increased intestinal permeability and/or motility. To study the transit time, fluorescent fluorescein isothiocyanate (FITC)-dextran was given to RV-infected adult and infant mice. Intestinal motility was also studied with an opioid receptor agonist (loperamide) and a muscarinic receptor antagonist (atropine). To investigate whether RV increases permeability at the onset of diarrhea, fluorescent 4- and 10-kDa dextran doses were given to infected and noninfected mice, and fluorescence intensity was measured subsequently in serum. RV increased transit time in infant mice. Increased motility was detected at 24 h postinfection (h p.i.) and persisted up to 72 h p.i in pups. Both loperamide and atropine decreased intestinal motility and attenuated diarrhea. Analysis of passage of fluorescent dextran from the intestine into serum indicated unaffected intestinal permeability at the onset of diarrhea (24 to 48 h p.i.). We show that RV-induced diarrhea is associated with increased intestinal motility via an activation of the myenteric nerve plexus, which in turn stimulates muscarinic receptors on intestinal smooth muscles.

IMPORTANCE

We show that RV-infected mice have increased intestinal motility at the onset of diarrhea, and that this is not associated with increased intestinal permeability. These new observations will contribute to a better understanding of the mechanisms involved in RV diarrhea.

Prostaglandin E2 reduces the release and infectivity of new cell-free virions and cell-to-cell HIV-1 transfer

Background

The course of human immunodeficiency virus type-1 (HIV-1) infection is influenced by a complex interplay between viral and host factors. HIV infection stimulates several proinflammatory genes, such as cyclooxigense-2 (COX-2), which leads to an increase in prostaglandin (PG) levels in the plasma of HIV-1-infected patients. These genes play an indeterminate role in HIV replication and pathogenesis. The effect of prostaglandin E₂ (PGE₂) on HIV infection is quite controversial and even contradictory, so we sought to determine the role of PGE₂ and the signal transduction pathways involved in HIV infection to elucidate possible new targets for antiretrovirals.

Results

Our results suggest that PGE₂ post-infection treatment acts in the late stages of the viral cycle to reduce HIV replication. Interestingly, viral protein synthesis was not affected, but a loss of progeny virus production was observed. No modulation of CD4 CXCR4 and CCR5 receptor expression, cell proliferation, or activation after PGE₂ treatment was detected. Moreover, PGE₂ induced an increase in intracellular cAMP (cyclic AMP) levels through the EP2/EP4 receptors. PGE₂ effects were mimicked by dbcAMP and by a specific Epac (exchange protein directly activated by cyclic AMP) agonist, 8-Cpt-cAMP. Treatment with PGE₂ increased Rap1 activity, decreased RhoA activity and subsequently reduced the polymerization of actin by approximately 30% compared with untreated cells. In connection with this finding, polarized viral assembly platforms enriched in Gag were disrupted, altering HIV cell-to-cell transfer and the infectivity of new virions.

Conclusions

Our results demonstrate that PGE₂, through Epac and Rap activation, alters the transport of newly synthesized HIV-1 components to the assembly site, reducing the release and infectivity of new cell-free virions and cell-to-cell HIV-1 transfer.

Identification of cellular calcium binding protein calmodulin as a regulator of rotavirus A infection during comparative proteomic study

Rotavirus (RV) being the major diarrhoegenic virus causes around 527000 children death (<5years age) worldwide. In cellular environment, viruses constantly adapt and modulate to survive and replicate while the host cell also responds to combat the situation and this results in the differential regulation of cellular proteins. To identify the virus induced differential expression of proteins, 2D-DIGE (Two-dimensional Difference Gel Electrophoresis) based proteomics was used. For this, HT-29 cells were infected with RV strain SA11 for 0 hours, 3 hours and 9 hours post infection (hpi), differentially expressed spots were excised from the gel and identified using MALDI-TOF/TOF mass spectrometry. 2D-DIGE based proteomics study identified 32 differentially modulated proteins, of which 22 were unique. Some of these were validated in HT-29 cell line and in BALB/c mice model. One of the modulated cellular proteins, calmodulin (CaM) was found to directly interact with RV protein VP6 in the presence of Ca²⁺. Ca²⁺-CaM/VP6 interaction positively regulates RV propagation since both CaM inhibitor (W-7) and Ca²⁺ chelator (BAPTA-AM) resulted in decreased viral titers. This study not only identifies differentially modulated cellular proteins upon infection with rotavirus in 2D-DIGE but also confirmed positive engagement of cellular Ca²⁺/CaM during viral pathogenesis.

Inhibition of rotavirus infection in cultured cells by N-acetyl-cysteine, PPARγ agonists and NSAIDs

Although the current rotavirus vaccines have shown good tolerance and significant efficacy, it would be useful to develop alternative or complementary strategies aimed at preventing or treating acute diarrhoeal disease caused by this viral agent. A variety of antiviral strategies other than vaccines have been assayed for rotavirus infection management. The recently demonstrated sensitivity of rotavirus infectivity to thiol/disulfide reagents prompted assays for screening drugs that potentially affect cellular redox reactions. MA104 or Caco-2 cells were inoculated with the rotavirus strains RRV, Wa, Wi or M69 and then incubated with different concentrations of drugs belonging to a selected group of 60 drugs that are currently used in humans for purposes other than rotavirus infection treatment. Eighteen of these drugs were able to inhibit rotavirus infectivity to different extents. A more systematic evaluation was performed with drugs that could be used in children such as N-acetylcysteine and ascorbic acid, in addition to ibuprofen, pioglitazone and rosiglitazone, all of which affecting cellular pathways potentially needed by the rotavirus infection process. Evidence is provided here that rotavirus infectivity is significantly inhibited by NAC in different cell-culture systems. These findings suggest that NAC has the potential to be used as a therapeutic tool for treatment and prevention of rotavirus disease in children.

Active participation of cellular chaperone Hsp90 in regulating the function of rotavirus nonstructural protein 3 (NSP3)

Heat shock protein 90 (Hsp90) has been reported to positively regulate rotavirus replication by modulating virus induced PI3K/Akt and NFκB activation. Here, we report the active association of Hsp90 in the folding and stabilization of rotavirus nonstructural protein 3 (NSP3). In pCD-NSP3-transfected cells, treatment with Hsp90 inhibitor (17-N,N-dimethylethylenediamine-geldanamycin (17DMAG)) resulted in the proteasomal degradation of NSP3. Sequence analysis and deletion mutations revealed that the region spanning amino acids 225-258 within the C-terminal eIF4G-binding domain of NSP3 is a putative Hsp90 binding region. Co-immunoprecipitation and mammalian two-hybrid experiments revealed direct interaction of the C-terminal 12-kDa domain of Hsp90 (C90) with residues 225-258 of NSP3. NSP3-Hsp90 interaction is important for the formation of functionally active mature NSP3, because full-length NSP3 in the presence of the Hsp90 inhibitor or NSP3 lacking the amino acid 225-258 region did not show NSP3 dimers following in vitro coupled transcription-translation followed by chase. Disruption of residues 225-258 within NSP3 also resulted in poor RNA binding and eIF4G binding activity. In addition, inhibition of Hsp90 by 17DMAG resulted in reduced nuclear translocation of poly(A)-binding protein and translation of viral proteins. These results highlight the crucial role of Hsp90 chaperone in the regulation of assembly and functionality of a viral protein during the virus replication and propagation in host cells.

Rotavirus nonstructural protein 1 suppresses virus-induced cellular apoptosis to facilitate viral growth by activating the cell survival pathways during early stages of infection

Following virus infection, one of the cellular responses to limit the virus spread is induction of apoptosis. In the present study, we report role of rotavirus nonstructural protein 1 (NSP1) in regulating apoptosis by activating prosurvival pathways such as phosphatidylinositol 3-kinase (PI3K)/Akt and NF-kappaB (nuclear factor kappaB) during early hours of infections (2 to 8 hpi). The NSP1 mutant strain A5-16 induces weak and transient activation of Akt (protein kinase B) and p65 NF-kappaB compared to the isogenic wild-type strain A5-13 in MA104 or HT29 cells. The weak NF-kappaB promoter activity or Akt phosphorylation after A5-16 infection could be complemented in cells transfected with plasmid expressing NSP1 after infection with the rotavirus A5-16 strain. In cells either infected with A5-13 or transfected with pcD-NSP1, coimmunoprecipitation of NSP1 with phosphoinositide 3-kinase (PI3K) was observed, indicating that strong activation of PI3K/Akt could be due to its interaction with NSP1. In addition, after infection with same multiplicity of infection, A5-16 showed reduced number of viral particles compared to the A5-13 strain at the end of the replication cycle. A lower growth rate could be due to weak induction of PI3K/Akt and NF-kappaB, since the A5-13 strain also showed reduced growth in the presence of PI3K or NF-kappaB inhibitors. This effect was interferon independent; however, it was partly due to significantly higher caspase-3 activity, poly-ADP ribose polymerase (PARP) cleavage, and apoptosis during earlier stages of infection with the NSP1 mutant. Thus, our data suggest that NSP1 positively supports rotavirus growth by suppression of premature apoptosis for improved virus growth after infection.

Eicosanoids influence insect susceptibility to nucleopolyhedroviruses

Nine pharmaceutical inhibitors of eicosanoid biosynthesis (e.g., bromophenacyl bromide, clotrimazole, diclofenamic acid, esculetin, flufenamic acid, indomethacin, nimesulide, sulindac, tolfenamic acid) that increased the susceptibility of the gypsy moth, Lymantria dispar (L.), to the nucleopolyhedrovirus LdMNPV were tested against the beet armyworm Spodoptera exigua (Hübner), the corn earworm Helicoverpa zea (Boddie) and the fall armyworm Spodoptera frugiperda (J.E. Smith) and their respective NPVs to determine whether these compounds also alter the susceptibility of these insects. The susceptibility of the beet armyworm was increased by six inhibitors (bromophenacyl bromide, clotrimazole, diclofenic acid, esculetin, flufenamic acid, nimesulide). The susceptibility of the fall armyworm was increased by seven inhibitors, (bromophenacyl bromide, diclofenamic acid, esculetin, indomethacin, nimesulide, sulindac, tolfenamic acid), whereas the susceptibility of the corn earworm was increased by only one inhibitor (sulindac). The influence of the cyclooxygenase inhibitor, indomethacin was expressed in a concentration-related manner in beet armyworms. We infer from these findings that eicosanoids, including prostaglandins and lipoxygenase products, act in insect anti-viral defenses.

The molecular chaperone heat shock protein-90 positively regulates rotavirus infectionx

Rotaviruses are the major cause of severe dehydrating gastroenteritis in children worldwide. In this study, we report a positive role of cellular chaperone Hsp90 during rotavirus infection. A highly specific Hsp90 inhibitor, 17-allylamono-demethoxygeldanamycin (17-AAG) was used to delineate the functional role of Hsp90. In MA104 cells treated with 17-AAG after viral adsorption, replication of simian (SA11) or human (KU) strains was attenuated as assessed by quantitating both plaque forming units and expression of viral genes. Phosphorylation of Akt and NFkappaB observed 2-4 hpi with SA11, was strongly inhibited in the presence of 17-AAG. Direct Hsp90-Akt interaction in virus infected cells was also reduced in the presence of 17-AAG. Anti-rotaviral effects of 17-AAG were due to inhibition of activation of Akt that was confirmed since, PI3K/Akt inhibitors attenuated rotavirus growth significantly. Thus, Hsp90 regulates rotavirus by modulating cellular signaling proteins. The results highlight the importance of cellular proteins during rotavirus infection and the possibility of targeting cellular chaperones for developing new anti-rotaviral strategies.

Immunomodulators released during rotavirus infection of polarized caco-2 cells

Rotavirus preferentially replicates in enterocytes and "danger signals" released by these cells are likely to modulate viral immunity. As a model of these events, we studied selected immunomodulators released during rotavirus infection of polarized Caco-2 cells grown in transwell cultures (TW). At early time points post-infection the virus was detected mainly in the apical side of the TWs, but this tendency was progressively lost concomitantly with disruption of the cell monolayer and cell death. Rotavirus-infected cells released IL-8, PGE(2), small quantities of TGF-beta1, and the constitutive and inducible heat shock proteins HSC70 and HSP70, but not IL-1beta, IL-6, IL-10, IL-12p70, or TNF-alpha. This set of immunomodulators is known to induce a non-inflammatory (non-Th-1) immune response, and may be determining, in part, the relatively low T-cell immune response observed in blood samples after RV infection.

Differential effects of triptolide and tetrandrine on activation of COX-2, NF-kappaB, and AP-1 and virus production in dengue virus-infected human lung cells

Most virus infections induce cycloxygenase-2 (COX-2) expression and subsequent prostaglandin E₂ (PGE₂) production in cells, an inflammatory response that might be detrimental to virus replication and pathogenesis. This response in dengue virus infection remains to be elucidated. Triptolide and tetrandrine, compounds derived from two commonly used Chinese herbs, both demonstrate anti-inflammatory and immunosuppressive effects partly through modulation of COX-2 expression and, hence, may have antiviral effects. In this study, we examined, firstly, the immune response to dengue virus infection with respect to COX-2 expression and PGE₂ production in human lung cells (A549), liver cells (HepG2) and dendritic cells. Secondly, we assessed the potential antiviral effects of triptolide and tetrandrine on dengue virus infection vis-à-vis expression of COX-2, PGE₂, transcription factors, as well as virus production. We found that dengue virus infection enhanced COX-2 expression and PGE₂ production in A549 cells, similarly to the response in dendritic cells, but not in HepG2 cells. In dengue virus-infected A549 cells, nuclear factor κB (NF-κB) and activator protein 1 (AP-1) were also activated, and both were dose-dependently inhibited by triptolide (0.5–4 ng/ml). Tetrandrine (1–10 μM) had no similar immunosuppressive effects and, moreover, at higher concentrations, enhanced NF-κB and AP-1 activity, COX-2 expression and PGE₂ production. However, unexpectedly, tetrandrine, but not triptolide, dose-dependently suppressed dengue virus production in A549 cells, independent of PGE₂ level. Our findings imply that triptolide and tetrandrine may attenuate dengue virus infection in human lung cells, but through distinct pathways.

Acetylsalicylic acid inhibits hepatitis C virus RNA and protein expression through cyclooxygenase 2 signaling pathways

It has been reported that salicylates (sodium salicylate and aspirin) inhibit the replication of flaviviruses, such as Japanese encephalitis virus and dengue virus. Therefore, we considered it important to test whether acetylsalicylic acid (ASA) had anti-hepatitis C virus (HCV) activity. To this end, we examined the effects of ASA on viral replication and protein expression, using an HCV subgenomic replicon cell culture system. We incubated Huh7 replicon cells with 2-8 mM ASA for different times and measured HCV-RNA and protein levels by northern blot, real-time polymerase chain reaction, and western analysis, respectively. We found that ASA had a suppressive effect on HCV-RNA and protein levels (nearly 58%). ASA-dependent inhibition of HCV expression was not mediated by the 5'-internal ribosome entry site or 3'-untranslated regions, as determined by transfection assays using bicistronic constructs containing these regulatory regions. However, we found that HCV-induced cyclooxygenase 2 (COX-2) messenger RNA and protein levels and activity and these effects were down-regulated by ASA, possibly by a nuclear factor kappa B-independent mechanism. We also observed that the ASA-dependent inhibition of viral replication was due in part to inhibition of COX-2 and activation of p38 and mitogen-activated protein kinase/extracellular signal-regulated kinase kinase 1/2 (MEK1/2) mitogen-activated protein kinases (MAPKs). Inhibition of these kinases by SB203580 and U0126, respectively, and by short interfering RNA silencing of p38 and MEK1 MAPK prevented the antiviral effect of ASA. Taken together, our findings suggest that the anti-HCV effect of ASA in the Huh7 replicon cells is due to its inhibitory effect on COX-2 expression, which is mediated in part by the activation of MEK1/2/p38 MAPK.

CONCLUSION

These findings suggest the possibility that ASA could be an excellent adjuvant in the treatment of chronic HCV infection.

Leukotriene B4-mediated release of antimicrobial peptides against cytomegalovirus is BLT1 dependent

Leukotriene B4 (LTB(4)) is a potent lipid mediator of inflammation that possesses antiviral activities. Here we provide evidence that LTB(4)-mediated defense against in vitro cytomegalovirus (CMV) infection of human leukocytes involves activation of the high-affinity LTB(4) receptor (BLT1) and neutrophil degranulation. Treatment of CMV-infected peripheral blood leukocytes with LTB(4) (10 nM) leads to a significant reduction in viral titers. This activity involves neutrophil activation through the BLT1 receptor, because no reduction in viral titers was observed after neutrophil depletion from cellular preparation or when leukocytes were pretreated with the BLT1 antagonist U75,302. Direct stimulation of neutrophils with LTB(4) (in the presence or absence of CMV) leads to the release of myeloperoxidase, alpha-defensins, eosinophil-derived neurotoxin, and the human cathelicidin LL-37 in a BLT1-dependent manner. LTB(4) does not act exclusively on the secretion of preformed antimicrobial peptides, but also acts on the synthesis of selected peptides as reflected by the increase in transcriptional levels of eosinophil-derived neurotoxin (EDN) and LL-37 in LTB(4)-treated neutrophils. Treatment of cell cultures with neutralizing antibodies directed against alpha-defensins, EDN, and LL-37 significantly reduces the antiviral effect of LTB(4), suggesting that LTB(4) may act through the release of antimicrobial peptides. Ex vivo experiments using LTB(4)-treated neutrophils from peritoneal washing of wild-type and BLT1 knockout mice further supported the role played by antimicrobial peptides in LTB(4)-mediated antiviral activity toward CMV. These results provide evidence of a mechanism by which LTB(4) induces host defense against viral infection.

Combination of indomethacin and statin compared with indomethacin and placebo in patients with a first episode of acute pericarditis: preliminary findings

The aim of the present study was to evaluate the safety and efficacy of the combination of indomethacin and statin compared with indomethacin plus placebo in patients with a first episode of pericarditis. A total of 55 consecutive patients with acute pericarditis were randomized in a double-blind manner into two groups: group 1 (statin group) was treated with 150 mg of indomethacin plus 10 mg of rosuvastatin, and group 2 (placebo group) was treated with 150 mg of indomethacin plus placebo. Both groups received treatment up to the normalization of inflammation markers and for the following week. Clinical and laboratory assessments [white cell count, ESR (erythrocyte sedimentation rate) and CRP (C-reactive protein), troponin I, creatine kinase and brain natriuretic peptide plasma levels], ECG and echocardiogram were performed at baseline and daily up to discharge. All of the patients were followed as outpatients for 3 months to evaluate any recurrence of pericarditis. The two groups were similar in age, sex and laboratory parameters [group 1 (the statin group), n=28 patients; gender, 18 male and ten female; and age, 29.5+/-5.7 years; group 2 (placebo group), n=27 patients; gender, 16 male/11 female; and age, 29.2+/-4.8 years]. The statin group, when compared with the placebo group, had a significantly faster reduction in CRP values (5.0+/-1.0 compared with 6.0+/-2.0 days respectively; P=0.022), ST segment normalization (3.5+/-1.0 compared with 4.5+/-1.0 days respectively; P=0.001), pericardial effusion (4.5+/-1.0 compared with 5.5+/-1.0 days respectively; P=0.001) and ESR (5.0+/-1 compared with 6.0+/-2 days respectively; P=0.022). Our results show that the combination of statin and indomethacin treatment in patients with acute pericarditis is feasible, with a significant reduction in inflammatory markers and a favourable trend in hospitalization time (5.5+/-2.0 compared with 6.5+/-2.0 days respectively; P=0.069). However, these preliminary findings require further studies in a larger sample of patients.

Prevention and treatment of enteric viral infections: possible benefits of probiotic bacteria

The structure and function of the intestinal epithelium is briefly described, with the principal mechanisms involved in diarrhea. Human enteric viruses and probiotics are presented. We then review how probiotic bacteria could interfere with virus-induced pathology, we present our own view and describe specific interactions that would be valuable targets for future studies.

MAPK signaling contributes to rotaviral-induced cholangiocyte injury and viral replication

BACKGROUND

Biliary atresia is a disease of newborns that results in obliteration of the biliary tree. Infection of mice with rhesus rotavirus (RRV) results in a cholangiopathy mirroring human disease. The Mitogen Associated Protein Kinase (MAPK) signaling pathway can be activated by viral binding to cell-surface receptors. We hypothesized that RRV infection of cholangiocytes results in activation of MAPK signaling.

METHODS

Extrahepatic bile ducts from BALB/c pups or immortalized cholangiocytes subjected to RRV infection or control were analyzed, using Western blots, for phosphorylated members of the MAPK family: p38, ERK 1/2, JNK 1/2, and downstream transcription factors. Inhibitors of the MAPK were used to downregulate activity. Viral replication and cytolysis in cholangiocytes were evaluated post-MAPK inhibition.

RESULTS

Phosphorylation of all MAPK increased in RRV-infected mice and cholangiocytes. Several downstream transcription factors had increased activity in vitro. Inhibition of p38 and ERK 1/2 resulted in decreased viral replication. ERK 1/2 inhibition decreased cytolysis without affecting viral entry or binding.

CONCLUSIONS

RRV infection of cholangiocytes resulted in increased MAPK signaling. Inhibition of p38 and ERK 1/2 influenced the ability of rotavirus to replicate. These novel findings provide insight into the signaling cascade involved in RRV-induced cholangiocyte injury.

Isoflavones at concentrations present in soy infant formula inhibit rotavirus infection in vitro

Rotavirus (RV) infections are a major cause of acute gastroenteritis in children and domestic animals, infecting virtually all children within their first 5 y of life. Infants consuming soy-based infant formula (SBIF) are exposed to high levels of isoflavones that exhibit antiviral activity on numerous viruses in vitro and in vivo. Thus, the hypothesis that isoflavones would inhibit RV infection was tested. All isoflavones at SBIF concentrations were tested individually and as a mixture (MIX). Virus infectivity was assessed in MA-104 cells using a focus forming unit assay. Genistin and MIX significantly reduced RV infectivity by 33-62% and 66-74%, respectively, compared with the control and across a wide range of RV concentrations. When tested without genistin, the MIX lost its anti-RV activity, suggesting that genistin is the biologically active isoflavone in our model. In a dose response assay, genistin significantly reduced RV infectivity at a concentration as low as 30 mumol/L. We investigated several possible mechanisms of action. Isoflavones decreased RV infectivity by modulating virion attachment to the host cells and by modulating a postbinding step. Isoflavones did not alter RV triple-layered structure and genistin did not act through inhibition of protein tyrosine kinases and topoisomerase II or by mimicking the effect of estrogens. To our knowledge, this is the first study showing the inhibition of RV infectivity by isoflavones present in SBIF. The modulation of SBIF isoflavone composition and concentration represents novel nutritional approaches to potentially reduce the severity of RV infection in human and production animals.

Cyclooxygenase activity is important for efficient replication of mouse hepatitis virus at an early stage of infection

Cyclooxygenases (COXs) play a significant role in many different viral infections with respect to replication and pathogenesis. Here we investigated the role of COXs in the mouse hepatitis coronavirus (MHV) infection cycle. Blocking COX activity by different inhibitors or by RNA interference affected MHV infection in different cells. The COX inhibitors reduced MHV infection at a post-binding step, but early in the replication cycle. Both viral RNA and viral protein synthesis were affected with subsequent loss of progeny virus production. Thus, COX activity appears to be required for efficient MHV replication, providing a potential target for anti-coronaviral therapy.

Role of MAPK in the regulation of double-stranded RNA- and encephalomyocarditis virus-induced cyclooxygenase-2 expression by macrophages

In response to virus infection or treatment with dsRNA, macrophages express the inducible form of cyclooxygenase-2 (COX-2) and produce proinflammatory prostaglandins. Recently, we have shown that NF-kappaB is required for encephalomyocarditis virus (EMCV)- and dsRNA-stimulated COX-2 expression in mouse macrophages. The dsRNA-dependent protein kinase R is not required for EMCV-stimulated COX-2 expression, suggesting the presence of protein kinase R-independent pathways in the regulation of this antiviral gene. In this study, the role of MAPK in the regulation of macrophage expression of cyclooxygenase-2 (COX)-2 in response to EMCV infection was examined. Treatment of mouse macrophages or RAW-264.7 cells with dsRNA or infection with EMCV stimulates the rapid activation of the MAPKs p38, JNK, and ERK. Inhibition of p38 and JNK activity results in attenuation while ERK inhibition does not modulate dsRNA- and EMCV-induced COX-2 expression and PGE2 production by macrophages. JNK and p38 appear to selectively regulate COX-2 expression, as inhibition of either kinase fails to prevent dsRNA- or EMCV-stimulated inducible NO synthase expression by macrophages. Using macrophages isolated from TLR3-deficient mice, we show that p38 and JNK activation and COX-2 expression in response to EMCV or poly(IC) does not require the presence the dsRNA receptor TLR3. These findings support a role for p38 and JNK in the selective regulation of COX-2 expression by macrophages in response to virus infection.

Natural products that reduce rotavirus infectivity identified by a cell-based moderate-throughput screening assay

Background

There is widespread interest in the use of innate immune modulators as a defense strategy against infectious pathogens. Using rotavirus as a model system, we developed a cell-based, moderate-throughput screening (MTS) assay to identify compounds that reduce rotavirus infectivity in vitro, toward a long-term goal of discovering immunomodulatory agents that enhance innate responses to viral infection.

Results

A natural product library consisting of 280 compounds was screened in the assay and 15 compounds that significantly reduced infectivity without cytotoxicity were identified. Time course analysis of four compounds with previously characterized effects on inflammatory gene expression inhibited replication with pre-treatment times as minimal as 2 hours. Two of these four compounds, α-mangostin and 18-β-glycyrrhetinic acid, activated NFκB and induced IL-8 secretion. The assay is adaptable to other virus systems, and amenable to full automation and adaptation to a high-throughput format.

Conclusion

Identification of several compounds with known effects on inflammatory and antiviral gene expression that confer resistance to rotavirus infection in vitro suggests the assay is an appropriate platform for discovery of compounds with potential to amplify innate antiviral responses.