Chikungunya virus nsP3 & nsP4 interacts with HSP-90 to promote virus replication: HSP-90 inhibitors reduce CHIKV infection and inflammation in vivo

Interaction of the endogenous antibody response with activating FcγRs enhance control of Mayaro virus through monocytes

Mayaro virus (MAYV) is an emerging arbovirus. Previous studies have shown antibody Fc effector functions are critical for optimal monoclonal antibody-mediated protection against alphaviruses; however, the requirement of Fc gamma receptors (FcγRs) for protection during natural infection has not been evaluated. Here, we showed mice lacking activating FcγRs (FcRγ-/-) developed prolonged clinical disease with increased MAYV in joint-associated tissues. Viral reduction was associated with anti-MAYV cell surface binding antibodies rather than neutralizing antibodies. Lack of Fc-FcγR engagement increased the number of monocytes present in the joint-associated tissue through chronic timepoints. Single-cell RNA sequencing showed elevated levels of pro-inflammatory monocytes in joint-associated tissue with increased MAYV RNA present in FcRγ-/- monocytes and macrophages. Transfer of FcRγ-/- monocytes into wild type animals was sufficient to increase virus in joint-associated tissue. Overall, this study suggests that engagement of antibody Fc with activating FcγRs promotes protective responses during MAYV infection and prevents a pro-viral role for monocytes.

Recent advances in phytocompounds as potential Chikungunya virus non-structural protein 2 protease antagonists: A systematic review

BACKGROUND

The mosquito-borne pathogenic alphavirus known as Chikungunya virus (CHIKV) is becoming a greater hazard to public health, which causes thousands of cases annually in both rural and urban areas of many different nations throughout the world. Finding and creating new leads for the CHIKV virus is crucial because there are currently no effective medications or vaccinations against it. The non-structural protein 2 (nsP2) protease has emerged as a promising target for therapeutic intervention due to its crucial role in viral replication.

PURPOSE

This systematic review aims to evaluate recent advances in natural products as inhibitors of the CHIKV nsP2 protease, summarizing current research, identifying promising compounds, and highlighting gaps in the existing knowledge.

STUDY DESIGN

A comprehensive literature search was conducted between January 2006, and June 2024 using databases including PubMed, Scopus, Science Direct, and Google Scholar. Search terms included CHIKV, nsP2 protease, antivirals, natural products, phytochemicals, and inhibitors. Studies were selected based on predefined inclusion and exclusion criteria, focusing on original research articles examining natural products as inhibitors of CHIKV nsP2 protease.

METHODS

Relevant studies were screened, and data were extracted regarding the source of natural compounds, methods of extraction, chemical structures, mechanisms of action, potency, and efficacy in inhibiting nsP2 protease or CHIKV replication.

RESULTS

The review included 40 studies, revealing a variety of natural products and their derivatives with inhibitory effects on CHIKV nsP2 protease. Several compounds demonstrated promising inhibitory activity with EC50 values in the micromolar range. Mechanistic studies revealed diverse modes of action, including inhibition of protease activity or interference with viral replication processes.

CONCLUSION

Natural products have gained attention for their diverse chemical structures and bioactivities, offering a rich source of compounds with antiviral potential. We summarize the current knowledge on natural products derived from various sources including flavonoids, alkaloids, terpenoids, polyphenols, and some derivative compounds that have demonstrated inhibitory effects against CHIKV through different mechanisms of action. Overall, this systematic review underscores the importance of exploring natural products as promising candidates for the development of effective therapeutics against Chikungunya fever, particularly through targeting the nsP2 protease.

Inhibitors of the Structural and Nonstructural Proteins of Alphaviruses

The Alphavirus genus includes viruses that cause encephalitis due to neuroinvasion and viruses that cause arthritis due to acute and chronic inflammation. There is no approved therapeutic for alphavirus infections, but significant efforts are ongoing, more so in recent years, to develop vaccines and therapeutics for alphavirus infections. This review article highlights some of the major advances made so far to identify small molecules that can selectively target the structural and the nonstructural proteins in alphaviruses with the expectation that persistent investigation of an increasingly expanding chemical space through a variety of structure-based design and high-throughput screening strategies will yield candidate drugs for clinical studies. While most of the works discussed are still in the early discovery to lead optimization stages, promising avenues remain for drug development against this family of viruses.

Damage-associated molecular patterns in viral infection: potential therapeutic targets

Frequent viral infections leading to infectious disease outbreaks have become a significant global health concern. Fully elucidating the molecular mechanisms of the immune response against viral infections is crucial for epidemic prevention and control. The innate immune response, the host's primary defense against viral infection, plays a pivotal role and has become a breakthrough in research mechanisms. A component of the innate immune system, damage-associated molecular patterns (DAMPs) are involved in inducing inflammatory responses to viral infections. Numerous DAMPs are released from virally infected cells, activating downstream signaling pathways via internal and external receptors on immune cells. This activation triggers immune responses and helps regulate viral host invasion. This review examines the immune regulatory mechanisms of various DAMPs, such as the S100 protein family, high mobility group box 1 (HMGB1), and heat shock proteins, in various viral infections to provide a theoretical basis for designing novel antiviral drugs.

Activating FcγRs on monocytes are necessary for optimal Mayaro virus clearance

Mayaro virus (MAYV) is an emerging arbovirus. Previous studies have shown antibody Fc effector functions are critical for optimal monoclonal antibody-mediated protection against alphaviruses; however, the requirement of Fc gamma receptors (FcγRs) for protection during natural infection has not been evaluated. Here, we showed mice lacking activating FcγRs (FcRγ-/-) developed prolonged clinical disease with more virus in joint-associated tissues. Viral clearance was associated with anti-MAYV cell surface binding rather than neutralizing antibodies. Lack of Fc-FcγR engagement increased the number of monocytes through chronic timepoints. Single cell RNA sequencing showed elevated levels of pro-inflammatory monocytes in joint-associated tissue with increased MAYV RNA present in FcRγ-/- monocytes and macrophages. Transfer of FcRγ-/- monocytes into wild type animals was sufficient to increase virus in joint-associated tissue. Overall, this study suggests that engagement of antibody Fc with activating FcγRs promotes protective responses during MAYV infection and prevents monocytes from being potential targets of infection.

Identification of RACK1 as a novel regulator of non-structural protein 4 of chikungunya virus

Chikungunya virus (CHIKV) is a neglected arthropod-borne and anthropogenic alphavirus. Over the past two decades, the CHIKV distribution has undergone significant changes worldwide, from the original tropics and subtropics regions to temperate regions, which has attracted global attention. However, the interactions between CHIKV and its host remain insufficiently understood, which dampens the need for the development of an anti-CHIKV strategy. In this study, on the basis of the optimal overexpression of non-structural protein 4 (nsP4), we explore host interactions of CHIKV nsP4 using mass spectrometry-based protein-protein interaction approaches. The results reveal that some cellular proteins that interact with nsP4 are enriched in the ubiquitin-proteasome pathway. Specifically, the scaffold protein receptor for activated C kinase 1 (RACK1) is identified as a novel host interactor and regulator of CHIKV nsP4. The inhibition of the interaction between RACK1 and nsP4 by harringtonolide results in the reduction of nsP4, which is caused by the promotion of degradation but not the inhibition of nsP4 translation. Furthermore, the decrease in nsP4 triggered by the RACK1 inhibitor can be reversed by the proteasome inhibitor MG132, suggesting that RACK1 can protect nsP4 from degradation through the ubiquitin-proteasome pathway. This study reveals a novel mechanism by which the host factor RACK1 regulates CHIKV nsP4, which could be a potential target for developing drugs against CHIKV.

Compounds from Natural Products Candidates to Drug for Chikungunya Virus Infection: A Systematic Review

INTRODUCTION

Chikungunya fever is a disease caused by infection with the Chikungunya virus, transmitted by Aedes aegypti and Aedes albopictus mosquitoes. Despite its self-limited character, more than 60% of patients have chronic recurrent arthralgia with debilitating pain that lasts for years.

AIM

The objective of this review was to gather and analyze evidence from the literature on potential therapeutic strategies with molecules from natural products for the treatment of Chikungunya fever.

METHODS

A search was performed for clinical trials, observational studies, in vitro or in vivo, without restriction of the year of publication or language in electronic databases (Medline/PubMed, EMBASE, Google Scholar, The Cochrane Library, LILACS (BVS), clinical trial registries (Clinical Trials.gov), digital libraries from CAPES theses and dissertations (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brazil) and conference abstracts. A quality assessment of the selected studies was performed using the SYRCLE, RoB2 and SciRAP tools.

RESULTS

42 studies were included, which showed molecules with potential antiviral pharmacological activity or with activity in reducing the joint complications caused by CHIKV infection.

CONCLUSIONS

Among the molecules found in the survey of references, regarding the class of secondary metabolites, flavonoids stood out and for this reason, the molecules may be promising candidates for future clinical trials. Overall, evidence from in vitro studies was of acceptable quality; in vivo and intervention studies showed a high risk of bias, which is a limitation of these studies.

Glucose-regulated protein 94 facilitates the proliferation of the Bombyx mori nucleopolyhedrovirus via inhibiting apoptosis

Glucose regulatory protein 94 (GRP94) is an endoplasmic reticulum (ER)-resident member of the heat shock protein 90 (HSP90) family, that plays an important role in secreted protein folding. Bombyx mori nuclear polyhedrosis virus (BmNPV) is one of the main pathogens in sericulture, causing serious economic losses every year. Previous studies showed that HSP90 members promote BmNPV replication in silkworm, but the function of BmGRP94 in BmNPV infection and proliferation is still not understood. In this study, we investigated the interplay between BmGRP94 and BmNPV infection in silkworm. We first identified a single gene of BmGRP94 in the Bombyx mori genome, which encodes a polypeptide with 810 amino acids in length. Spatio-temporal expression profiles showed that BmGRP94 was highly expressed in hemocytes and midgut, and was significantly induced by BmNPV infection. Furthermore, overexpression of BmGRP94 facilitates viral proliferation, while BmGRP94 inhibition evidently decreased BmNPV proliferation in BmN cells and in silkworm midgut. Mechanistically, BmGRP94 inhibition triggers ER stress, as judged by increased expression of PERK/ATF4/ERO1, H2O2 production, and ER calcium efflux, which promotes cell apoptosis to restrict BmNPV replication in silkworm. These results suggest that BmGRP94 plays an important role in facilitating BmNPV proliferation, and provides a potential molecular target for BmNPV prevention.

Anthracyclines inhibit SARS-CoV-2 infection

Vaccines and drugs are two effective medical interventions to mitigate SARS-CoV-2 infection. Three SARS-CoV-2 inhibitors, remdesivir, paxlovid, and molnupiravir, have been approved for treating COVID-19 patients, but more are needed, because each drug has its limitation of usage and SARS-CoV-2 constantly develops drug resistance mutations. In addition, SARS-CoV-2 drugs have the potential to be repurposed to inhibit new human coronaviruses, thus help to prepare for future coronavirus outbreaks. We have screened a library of microbial metabolites to discover new SARS-CoV-2 inhibitors. To facilitate this screening effort, we generated a recombinant SARS-CoV-2 Delta variant carrying the nano luciferase as a reporter for measuring viral infection. Six compounds were found to inhibit SARS-CoV-2 at the half maximal inhibitory concentration (IC50) below 1 μM, including the anthracycline drug aclarubicin that markedly reduced viral RNA-dependent RNA polymerase (RdRp)-mediated gene expression, whereas other anthracyclines inhibited SARS-CoV-2 by activating the expression of interferon and antiviral genes. As the most commonly prescribed anti-cancer drugs, anthracyclines hold the promise of becoming new SARS-CoV-2 inhibitors.

Host Factor Nucleophosmin 1 (NPM1/B23) Exerts Antiviral Effects against Chikungunya Virus by Its Interaction with Viral Nonstructural Protein 3

Chikungunya virus (CHIKV) hijacks host cell machinery to support its replication. Nucleophosmin 1 (NPM1/B23), a nucleolar phosphoprotein, is one of the host proteins known to restrict CHIKV infection; however, the mechanistic details of the antiviral role of NPM1 are not elucidated. It was seen in our experiments that the level of NPM1 expression affected the expression levels of interferon-stimulated genes (ISGs) that play antiviral roles in CHIKV infection, such as IRF1, IRF7, OAS3, and IFIT1, indicating that one of the antiviral mechanisms could be through modulation of interferon-mediated pathways. Our experiments also identified that for CHIKV restriction, NPM1 must move from the nucleus to the cytoplasm. A deletion of the nuclear export signal (NES), which confines NPM1 within the nucleus, abolishes its anti-CHIKV action. We observed that NPM1 binds CHIKV nonstructural protein 3 (nsP3) strongly via its macrodomain, thereby exerting a direct interaction with viral proteins to limit infection. Based on site-directed mutagenesis and coimmunoprecipitation studies, it was also observed that amino acid residues N24 and Y114 of the CHIKV nsP3 macrodomain, known to be involved in virus virulence, bind ADP-ribosylated NPM1 to inhibit infection. Overall, the results show a key role of NPM1 in CHIKV restriction and indicate it as a promising host target for developing antiviral strategies against CHIKV. IMPORTANCE Chikungunya, a recently reemerged mosquito-borne infection caused by a positive-sense, single-stranded RNA virus, has caused explosive epidemics in tropical regions. Unlike the classical symptoms of acute fever and debilitating arthralgia, incidences of neurological complications and mortality were reported. Currently there are no antivirals or commercial vaccines available against chikungunya. Like all viruses, CHIKV uses host cellular machinery for establishment of infection and successful replication. To counter this, the host cell activates several restriction factors and innate immune response mediators. Understanding these host-virus interactions helps to develop host-targeted antivirals against the disease. Here, we report the antiviral role of the multifunctional host protein NPM1 against CHIKV. The significant inhibitory effect of this protein against CHIKV involves its increased expression and movement from its natural location within the nucleus to the cytoplasm. There, it interacts with functional domains of key viral proteins. Our results support ongoing efforts toward development of host-directed antivirals against CHIKV and other alphaviruses.

Preparing for the next viral threat with broad-spectrum antivirals

There is a large global unmet need for the development of countermeasures to combat hundreds of viruses known to cause human disease and for the establishment of a therapeutic portfolio for future pandemic preparedness. Most approved antiviral therapeutics target proteins encoded by a single virus, providing a narrow spectrum of coverage. This, combined with the slow pace and high cost of drug development, limits the scalability of this direct-acting antiviral (DAA) approach. Here, we summarize progress and challenges in the development of broad-spectrum antivirals that target either viral elements (proteins, genome structures, and lipid envelopes) or cellular proviral factors co-opted by multiple viruses via newly discovered compounds or repurposing of approved drugs. These strategies offer new means for developing therapeutics against both existing and emerging viral threats that complement DAAs.

Hsp90 could promote BmNPV proliferation by interacting with Actin-4 and enhance its expression

As a highly infectious pathogen, Bombyx mori nuclear polyhedrosis virus (BmNPV) has a high lethality rate in silkworm. Our previous study have confirmed that Hsp90 plays a positive role in BmNPV proliferation and Hsp90 inhibitor, geldanamycin (GA) can decrease the replication of BmNPV in vitro. However, its molecular mechanism is not fully understood. In the present study, first, we found that GA could inhibit the proliferation of BmNPV in a dose-dependent manner and delay the pathogenesis of BmNPV in vivo possibly by altering the transcript level of genes associated with cell apoptosis and immune pathways. Furthermore, by immunoprecipitation (IP) and mass spectrometry analysis, we identified a series of proteins potentially interacting with Hsp90 including two BmNPV encoded proteins. Subsequently, by Co-IP we confirmed the interaction between BmActin-4 and BmHsp90. Knocking down Bmhsp90 by small interfering RNA inhibited the protein expression level of BmActin-4. Over-expression of Bmactin-4 promoted the replication of BmNPV whereas knockdown of Bmactin-4 suppressed BmNPV replication. In addition, decrease of the transcript level of Bmhsp90 in Bmactin-4 knocking down BmN cells was also detected. Taken together, BmHsp90 can interact with BmActin-4 and promote its expression, thereby promoting BmNPV proliferation. Our findings may enrich the molecular mechanism of Hsp90 for promoting virus proliferation and provide new clues to elucidate the interact mechanism between silkworm and virus.

Mode of Action of Heat Shock Protein (HSP) Inhibitors against Viruses through Host HSP and Virus Interactions

Misfolded proteins after stress-induced denaturation can regain their functions through correct re-folding with the aid of molecular chaperones. As a molecular chaperone, heat shock proteins (HSPs) can help client proteins fold correctly. During viral infection, HSPs are involved with replication, movement, assembly, disassembly, subcellular localization, and transport of the virus via the formation of macromolecular protein complexes, such as the viral replicase complex. Recent studies have indicated that HSP inhibitors can inhibit viral replication by interfering with the interaction of the virus with the HSP. In this review, we describe the function and classification of HSPs, the transcriptional mechanism of HSPs promoted by heat shock factors (HSFs), discuss the interaction between HSPs and viruses, and the mode of action of HSP inhibitors at two aspects of inhibiting the expression of HSPs and targeting the HSPs, and elaborate their potential use as antiviral agents.

Growth in chikungunya virus-related research in ASEAN and South Asian countries from 1967 to 2022 following disease emergence: a bibliometric and graphical analysis

BACKGROUND

ASEAN (Association of Southeast Asian Nations) is composed of ten Southeast Asian countries bound by socio-cultural ties that promote regional peace and stability. South Asia, located in the southern subregion of Asia, includes nine countries sharing similarities in geographical and ethno-cultural factors. Chikungunya is one of the most significant problems in Southeast and South Asian countries. Much of the current chikungunya epidemic in Southeast Asia is caused by the emergence of a virus strain that originated in Africa and spread to Southeast Asia. Meanwhile, in South Asia, three confirmed lineages are in circulation. Given the positive correlation between research activity and the improvement of the clinical framework of biomedical research, this article aimed to examine the growth of chikungunya virus-related research in ASEAN and South Asian countries.

METHODS

The Scopus database was used for this bibliometric analysis. The retrieved publications were subjected to a number of analyses, including those for the most prolific countries, journals, authors, institutions, and articles. Co-occurrence mapping of terms and keywords was used to determine the current state, emerging topics, and future prospects of chikungunya virus-related research. Bibliometrix and VOSviewer were used to analyze the data and visualize the collaboration network mapping.

RESULTS

The Scopus search engine identified 1280 chikungunya-related documents published by ASEAN and South Asian countries between 1967 and 2022. According to our findings, India was the most productive country in South Asia, and Thailand was the most productive country in Southeast Asia. In the early stages of the study, researchers investigated the vectors and outbreaks of the chikungunya virus. In recent years, the development of antivirus agents has emerged as a prominent topic.

CONCLUSIONS

Our study is the first to present the growth of chikungunya virus-related research in ASEAN and South Asian countries from 1967 to 2022. In this study, the evaluation of the comprehensive profile of research on chikungunya can serve as a guide for future studies. In addition, a bibliometric analysis may serve as a resource for healthcare policymakers.

Targeting the alphavirus virus replication process for antiviral development

Many alphaviruses, including chikungunya virus (CHIKV) are known human pathogens that lack specific and effective antivirals or vaccines available. The upstream portion of the positive-sense single-stranded RNA genome of alphaviruses encodes four nonstructural proteins: nsP1 to nsP4. They are expressed and autoprocessed to nonstructural proteins which assemble into a replication complex (RC) playing multiple essential roles on viral RNA replication and communication with the host components. The assembly of alphavirus RC and its RNA genome initiates the membrane-derived ultrastructure known as spherule which facilitates viral RNA synthesis protected from host immune responses. Recent advances in the molecular understanding of the high-resolution CHIKV RC heteromeric ultrastructure have provided new insights into the viral replication process. Hence, alphavirus RC presents as an ideal multi-enzyme target for the development of structure-based antiviral drugs. Moreover, the alphavirus RC has therapeutic potential in the form of self-amplifying RNA technology against both infectious and non-infectious diseases.

Regional mutations in CHIKV-ECSA genomes and detection of other viruses in the serum of acute febrile patients by a metagenomic approach in Mato Grosso, Central-Western Brazil, 2018

Mato Grosso (MT) State is part of central western Brazil and has a tropical permissive environment that favors arbovirus outbreaks. A metagenomic approach was used to identify viral genomes in seven pools of serum from patients (n=65) with acute febrile disease. Seven chikungunya virus (CHIKV) genomes were determined, showing four amino acid changes found only in CHIKV genomes obtained in MT since 2018: nsP2:T31I, nsP3: A388V, E3:T201I and E3:H57R, in addition to other mutations in E1, nsP2 and nsP4. Six parvovirus B19 (B19V) genotype I genomes (4771-5131 nt) showed four aa alterations (NS1:N473D, R579Q; VP1:I716T; and 11 kDa:V44A) compared to most similar B19V from the USA. Coinfection between CHIKV and B19V was evidenced in 22/65 (33.8%) patients by RT‒PCR and PCR, respectively. Other viruses found in these pools include human pegivirus C, torque teno virus 3, an unclassified TTV and torque teno mini virus. Metagenomics represents a useful approach to detect viruses in the serum of acute febrile patients suspected of arbovirus disease.

Host cell stress response as a predictor of COVID-19 infectivity and disease progression

The coronavirus disease (COVID-19) caused by a coronavirus identified in December 2019 has caused a global pandemic. COVID-19 was declared a pandemic in March 2020 and has led to more than 6.3 million deaths. The pandemic has disrupted world travel, economies, and lifestyles worldwide. Although vaccination has been an effective tool to reduce the severity and spread of the disease there is a need for more concerted approaches to fighting the disease. COVID-19 is characterised as a severe acute respiratory syndrome . The severity of the disease is associated with a battery of comorbidities such as cardiovascular diseases, cancer, chronic lung disease, and renal disease. These underlying diseases are associated with general cellular stress. Thus, COVID-19 exacerbates outcomes of the underlying conditions. Consequently, coronavirus infection and the various underlying conditions converge to present a combined strain on the cellular response. While the host response to the stress is primarily intended to be of benefit, the outcomes are occasionally unpredictable because the cellular stress response is a function of complex factors. This review discusses the role of the host stress response as a convergent point for COVID-19 and several non-communicable diseases. We further discuss the merits of targeting the host stress response to manage the clinical outcomes of COVID-19.

A first glimpse into the transcriptomic changes induced by the PaV1 infection in the gut of Caribbean spiny lobsters, Panulirus argus (Latreille, 1804) (Decapoda: Achelata: Palinuridae)

The Caribbean spiny lobster, Panulirus argus (Latreille, 1804) supports important fisheries in the Caribbean region. This species is affected by a deadly virus, Panulirus argus Virus 1 (PaV1), the only known pathogenic virus for this species. As infection progresses, the effects of PaV1 on its host become systemic, with far reaching impacts on the host's physiology, including structural injuries to its gastrointestinal organs, such as the hepatopancreas and the gut. This last one becomes highly compromised in the last stages of infection. Since the gut is a key organ for the physiological stability of lobsters, we compared the transcriptomic changes in the gut of juvenile individuals of Panulirus argus naturally infected with PaV1. In the RNA-Seq analysis, we obtained a total of 485 × 10⁶ raw reads. After cleaning, reads were de novo assembled into 68,842 transcripts and 50,257 unigenes. The length of unigenes ranged from 201 bp to 28,717 bp, with a N50 length of 2079, and a GC content of 40.61%. In the differential gene expression analysis, we identified a total of 3,405 non redundant differential transcripts, of which 1,920 were up-regulated and 1,485 were down-regulated. We found alterations in transcripts encoding for proteins involved in transcriptional regulation, splicing, postraductional regulation, protein signaling, transmembrane transport, cytoskeletal regulation, and proteolysis, among others. This is the first insight into the transcriptomic regulation of PaV1-P. argus interaction. The information generated can help to unravel the molecular mechanisms that may intervene in the gut during PaV1 infection.

Oral Hsp90 inhibitor SNX-5422 attenuates SARS-CoV-2 replication and dampens inflammation in airway cells

Currently available SARS-CoV-2 therapeutics are targeted toward moderately to severely ill patients and require intravenous infusions, with limited options for exposed or infected patients with no or mild symptoms. Although vaccines have demonstrated protective efficacy, vaccine hesitancy and logistical distribution challenges will delay their ability to end the pandemic. Hence, there is a need for rapidly translatable, easy-to-administer-therapeutics that can prevent SARS-CoV-2 disease progression, when administered in the early stages of infection. We demonstrate that an orally bioavailable Hsp90 inhibitor, SNX-5422, currently in clinical trials as an anti-cancer therapeutic, inhibits SARS-CoV-2 replication in vitro at a high selectivity index. SNX-5422 treatment of human primary airway epithelial cells dampened expression of inflammatory pathways previously associated with poor SARS-CoV-2 disease outcomes. In addition, SNX-5422 interrupted expression of host factors demonstrated to be crucial for SARS-CoV-2 replication. Development of SNX-5422 as SARS-CoV-2-early-therapy will dampen disease severity, resulting in better clinical outcomes and reduced hospitalizations.

MK2a inhibitor CMPD1 abrogates chikungunya virus infection by modulating actin remodeling pathway

Chikungunya virus (CHIKV) epidemics around the world have created public health concern with the unavailability of effective drugs and vaccines. This emphasizes the need for molecular understanding of host-virus interactions for developing effective targeted antivirals. Microarray analysis was carried out using CHIKV strain (Prototype and Indian) infected Vero cells and two host isozymes, MAPK activated protein kinase 2 (MK2) and MAPK activated protein kinase 3 (MK3) were selected for further analysis. The substrate spectrum of both enzymes is indistinguishable and covers proteins involved in cytokines production, endocytosis, reorganization of the cytoskeleton, cell migration, cell cycle control, chromatin remodeling and transcriptional regulation. Gene silencing and drug treatment were performed in vitro and in vivo to unravel the role of MK2/MK3 in CHIKV infection. Gene silencing of MK2 and MK3 abrogated around 58% CHIKV progeny release from the host cell and a MK2 activation inhibitor (CMPD1) treatment demonstrated 68% inhibition of viral infection suggesting a major role of MAPKAPKs during late CHIKV infection in vitro. Further, it was observed that the inhibition in viral infection is primarily due to the abrogation of lamellipodium formation through modulation of factors involved in the actin cytoskeleton remodeling pathway. Moreover, CHIKV-infected C57BL/6 mice demonstrated reduction in the viral copy number, lessened disease score and better survivability after CMPD1 treatment. In addition, reduction in expression of key pro-inflammatory mediators such as CXCL13, RAGE, FGF, MMP9 and increase in HGF (a CHIKV infection recovery marker) was observed indicating the effectiveness of the drug against CHIKV. Taken together it can be proposed that MK2 and MK3 are crucial host factors for CHIKV infection and can be considered as important target for developing effective anti-CHIKV strategies.

Chikungunya virus has been a dreaded disease from the first time it occurred in 1952 Tanzania. Since then it has been affecting the different parts of the world at different time periods in large scale. It is typically transmitted to humans by bites of Aedes aegypti and Aedes albopictus mosquitoes. Although, studies have been undertaken to combat its prevalence still there are no effective strategies like vaccines or antivirals against it. Therefore it is essential to understand the virus and host interaction to overcome this hurdle. In this study two host factors MK2 and MK3 have been taken into consideration to see how they affect the multiplication of the virus. The in vitro and in vivo experiments conducted demonstrated that inhibition of MK2 and MK3 not only restricted viral release but also decreased the disease score and allowed better survivability. Therefore, MK2 and MK3 could be considered as the key targets in the anti CHIKV approach.

Overview on Chikungunya Virus Infection: From Epidemiology to State-of-the-Art Experimental Models

Chikungunya virus (CHIKV) is currently one of the most relevant arboviruses to public health. It is a member of the Togaviridae family and alphavirus genus and causes an arthritogenic disease known as chikungunya fever (CHIKF). It is characterized by a multifaceted disease, which is distinguished from other arbovirus infections by the intense and debilitating arthralgia that can last for months or years in some individuals. Despite the great social and economic burden caused by CHIKV infection, there is no vaccine or specific antiviral drugs currently available. Recent outbreaks have shown a change in the severity profile of the disease in which atypical and severe manifestation lead to hundreds of deaths, reinforcing the necessity to understand the replication and pathogenesis processes. CHIKF is a complex disease resultant from the infection of a plethora of cell types. Although there are several in vivo models for studying CHIKV infection, none of them reproduces integrally the disease signature observed in humans, which is a challenge for vaccine and drug development. Therefore, understanding the potentials and limitations of the state-of-the-art experimental models is imperative to advance in the field. In this context, the present review outlines the present knowledge on CHIKV epidemiology, replication, pathogenesis, and immunity and also brings a critical perspective on the current in vitro and in vivo state-of-the-art experimental models of CHIKF.

Antiviral strategies targeting host factors and mechanisms obliging +ssRNA viral pathogens

The ongoing COVID-19 pandemic, periodic recurrence of viral infections, and the emergence of challenging variants has created an urgent need of alternative therapeutic approaches to combat the spread of viral infections, failing to which may pose a greater risk to mankind in future. Resilience against antiviral drugs or fast evolutionary rate of viruses is stressing the scientific community to identify new therapeutic approaches for timely control of disease. Host metabolic pathways are exquisite reservoir of energy to viruses and contribute a diverse array of functions for successful replication and pathogenesis of virus. Targeting the host factors rather than viral enzymes to cease viral infection, has emerged as an alternative antiviral strategy. This approach offers advantage in terms of increased threshold to viral resistance and can provide broad-spectrum antiviral action against different viruses. The article here provides substantial review of literature illuminating the host factors and molecular mechanisms involved in innate/adaptive responses to viral infection, hijacking of signalling pathways by viruses and the intracellular metabolic pathways required for viral replication. Host-targeted drugs acting on the pathways usurped by viruses are also addressed in this study. Host-directed antiviral therapeutics might prove to be a rewarding approach in controlling the unprecedented spread of viral infection, however the probability of cellular side effects or cytotoxicity on host cell should not be ignored at the time of clinical investigations.

Diversity in heat shock protein families: functional implications in virus infection with a comprehensive insight of their role in the HIV-1 life cycle

Heat shock proteins (HSPs) are a group of cellular proteins that are induced during stress conditions such as heat stress, cold shock, UV irradiation and even pathogenic insult. They are classified into families based on molecular size like HSP27, 40, 70 and 90 etc, and many of them act as cellular chaperones that regulate protein folding and determine the fate of mis-folded or unfolded proteins. Studies have also shown multiple other functions of these proteins such as in cell signalling, transcription and immune response. Deregulation of these proteins leads to devastating consequences, such as cancer, Alzheimer's disease and other life threatening diseases suggesting their potential importance in life processes. HSPs exist in multiple isoforms, and their biochemical and functional characterization still remains a subject of active investigation. In case of viral infections, several HSP isoforms have been documented to play important roles with few showing pro-viral activity whereas others seem to have an anti-viral role. Earlier studies have demonstrated that HSP40 plays a pro-viral role whereas HSP70 inhibits HIV-1 replication; however, clear isoform-specific functional roles remain to be established. A detailed functional characterization of all the HSP isoforms will uncover their role in cellular homeostasis and also may highlight some of them as potential targets for therapeutic strategies against various viral infections. In this review, we have tried to comprehend the details about cellular HSPs and their isoforms, their role in cellular physiology and their isoform-specific functions in case of virus infection with a specific focus on HIV-1 biology.

Role of Heat Shock Proteins (HSP70 and HSP90) in Viral Infection

Heat shock proteins (HSPs) are a large group of chaperones found in most eukaryotes and bacteria. They are responsible for the correct protein folding, protection of the cell against stressors, presenting immune and inflammatory cytokines; furthermore, they are important factors in regulating cell differentiation, survival and death. Although the biological function of HSPs is to maintain cell homeostasis, some of them can be used by viruses both to fold their proteins and increase the chances of survival in unfavorable host conditions. Folding viral proteins as well as replicating many different viruses are carried out by, among others, proteins from the HSP70 and HSP90 families. In some cases, the HSP70 family proteins directly interact with viral polymerase to enhance viral replication or they can facilitate the formation of a viral replication complex and/or maintain the stability of complex proteins. It is known that HSP90 is important for the expression of viral genes at both the transcriptional and the translational levels. Both of these HSPs can form a complex with HSP90 and, consequently, facilitate the entry of the virus into the cell. Current studies have shown the biological significance of HSPs in the course of infection SARS-CoV-2. A comprehensive understanding of chaperone use during viral infection will provide new insight into viral replication mechanisms and therapeutic potential. The aim of this study is to describe the molecular basis of HSP70 and HSP90 participation in some viral infections and the potential use of these proteins in antiviral therapy.

Hsp90 Is Required for Snakehead Vesiculovirus Replication via Stabilization of the Viral L Protein

Snakehead vesiculovirus (SHVV), a kind of fish rhabdovirus isolated from diseased hybrid snakehead fish, has caused great economic losses in snakehead fish culture in China. The large (L) protein, together with its cofactor phosphoprotein (P), forms a P/L polymerase complex and catalyzes the transcription and replication of viral genomic RNA. In this study, the cellular heat shock protein 90 (Hsp90) was identified as an interacting partner of SHVV L protein. Hsp90 activity was required for the stability of SHVV L because Hsp90 dysfunction caused by using its inhibitor destabilized SHVV L and thereby suppressed SHVV replication via reducing viral RNA synthesis. SHVV L expressed alone was detected mainly in the insoluble fraction, and the insoluble L was degraded by Hsp90 dysfunction through the proteasomal pathway, while the presence of SHVV P promoted the solubility of SHVV L and the soluble L was degraded by Hsp90 dysfunction through the autophagy pathway. Collectively, our data suggest that Hsp90 contributes to the maturation of SHVV L and ensures the effective replication of SHVV, which exhibits an important anti-SHVV target. This study will help us to understand the role of Hsp90 in stabilizing the L protein and regulating the replication of negative-stranded RNA viruses. IMPORTANCE It has long been proposed that cellular proteins are involved in viral RNA synthesis via interacting with the viral polymerase protein. This study focused on identifying cellular proteins interacting with the SHVV L protein, studying the effects of their interactions on SHVV replication, and revealing the underlying mechanisms. We identified Hsp90 as an interacting partner of SHVV L and found that Hsp90 activity was required for SHVV replication. Hsp90 functioned in maintaining the stability of SHVV L. Inhibition of Hsp90 activity with its inhibitor degraded SHVV L through different pathways based on the solubility of SHVV L due to the presence or absence of SHVV P. Our data provide important insights into the role of Hsp90 in SHVV polymerase maturation, which will help us to understand the polymerase function of negative-stranded RNA viruses.

Antivirals against the Chikungunya Virus

Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that has re-emerged in recent decades, causing large-scale epidemics in many parts of the world. CHIKV infection leads to a febrile disease known as chikungunya fever (CHIKF), which is characterised by severe joint pain and myalgia. As many patients develop a painful chronic stage and neither antiviral drugs nor vaccines are available, the development of a potent CHIKV inhibiting drug is crucial for CHIKF treatment. A comprehensive summary of current antiviral research and development of small-molecule inhibitor against CHIKV is presented in this review. We highlight different approaches used for the identification of such compounds and further discuss the identification and application of promising viral and host targets.

Current Status of Chikungunya in India

Chikungunya fever (CHIKF) is an arbovirus disease caused by chikungunya virus (CHIKV), an alphavirus of Togaviridae family. Transmission follows a human-mosquito-human cycle starting with a mosquito bite. Subsequently, symptoms develop after 2-6 days of incubation, including high fever and severe arthralgia. The disease is self-limiting and usually resolve within 2 weeks. However, chronic disease can last up to several years with persistent polyarthralgia. Overlapping symptoms and common vector with dengue and malaria present many challenges for diagnosis and treatment of this disease. CHIKF was reported in India in 1963 for the first time. After a period of quiescence lasting up to 32 years, CHIKV re-emerged in India in 2005. Currently, every part of the country has become endemic for the disease with outbreaks resulting in huge economic and productivity losses. Several mutations have been identified in circulating strains of the virus resulting in better adaptations or increased fitness in the vector(s), effective transmission, and disease severity. CHIKV evolution has been a significant driver of epidemics in India, hence, the need to focus on proper surveillance, and implementation of prevention and control measure in the country. Presently, there are no licensed vaccines or antivirals available; however, India has initiated several efforts in this direction including traditional medicines. In this review, we present the current status of CHIKF in India.

Radicicol Inhibits Chikungunya Virus Replication by Targeting Nonstructural Protein 2

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that causes a debilitating febrile illness characterized by persistent muscle and joint pain. The widespread distribution of transmission-competent vectors, Aedes species mosquitoes, indicates the potential risk of large-scale epidemics with high attack rates that can severely impact public health globally. Despite this, currently, there are no antivirals available for the treatment of CHIKV infections. Thus, we aimed to identify potential drug candidates by screening a chemical library using a cytopathic effect-based high-throughput screening assay. As a result, we identified radicicol, a heat shock protein 90 (Hsp90) inhibitor that effectively suppressed CHIKV replication by blocking the synthesis of both positive- and negative-strand viral RNA as well as expression of viral proteins. Interestingly, selection for viral drug-resistant variants and mutational studies revealed nonstructural protein 2 (nsP2) as a putative molecular target of radicicol. Moreover, coimmunoprecipitation and in silico modeling analyses determined that G641D mutation in the methyltransferase (MT)-like domain of nsP2 is essential for its interaction with cytoplasmic Hsp90β chaperone. Our findings collectively support the potential application of radicicol as an anti-CHIKV agent. The detailed study of the underlying mechanism of action further contributes to our understanding of virus-host interactions for novel therapeutics against CHIKV infection.

Chikungunya and Zika Viruses: Co-Circulation and the Interplay between Viral Proteins and Host Factors

Chikungunya and Zika viruses, both transmitted by mosquito vectors, have globally re-emerged over for the last 60 years and resulted in crucial social and economic concerns. Presently, there is no specific antiviral agent or vaccine against these debilitating viruses. Understanding viral-host interactions is needed to develop targeted therapeutics. However, there is presently limited information in this area. In this review, we start with the updated virology and replication cycle of each virus. Transmission by similar mosquito vectors, frequent co-circulation, and occurrence of co-infection are summarized. Finally, the targeted host proteins/factors used by the viruses are discussed. There is an urgent need to better understand the virus-host interactions that will facilitate antiviral drug development and thus reduce the global burden of infections caused by arboviruses.

Prophylactic strategies to control chikungunya virus infection

Chikungunya virus (CHIKV) is a (re)emerging arbovirus and the causative agent of chikungunya fever. In recent years, CHIKV was responsible for a series of outbreaks, some of which had serious economic and public health impacts in the affected regions. So far, no CHIKV-specific antiviral therapy or vaccine has been approved. This review gives a brief summary on CHIKV epidemiology, spread, infection and diagnosis. It furthermore deals with the strategies against emerging diseases, drug development and the possibilities of testing antivirals against CHIKV in vitro and in vivo. With our review, we hope to provide the latest information on CHIKV, disease manifestation, as well as on the current state of CHIKV vaccine development and post-exposure therapy.

Current and Promising Antivirals Against Chikungunya Virus

Chikungunya virus (CHIKV) is the causative agent of chikungunya fever (CHIKF) and is categorized as a(n) (re)emerging arbovirus. CHIKV has repeatedly been responsible for outbreaks that caused serious economic and public health problems in the affected countries. To date, no vaccine or specific antiviral therapies are available. This review gives a summary on current antivirals that have been investigated as potential therapeutics against CHIKF. The mode of action as well as possible compound targets (viral and host targets) are being addressed. This review hopes to provide critical information on the in vitro efficacies of various compounds and might help researchers in their considerations for future experiments.

Small-Molecule Inhibitors of Chikungunya Virus: Mechanisms of Action and Antiviral Drug Resistance

Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that has spread to more than 60 countries worldwide. CHIKV infection leads to a febrile illness known as chikungunya fever (CHIKF), which is characterized by long-lasting and debilitating joint and muscle pain. CHIKV can cause large-scale epidemics with high attack rates, which substantiates the need for development of effective therapeutics suitable for outbreak containment. In this review, we highlight the different strategies used for developing CHIKV small-molecule inhibitors, ranging from high-throughput cell-based screening to in silico screens and enzymatic assays with purified viral proteins.

Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that has spread to more than 60 countries worldwide. CHIKV infection leads to a febrile illness known as chikungunya fever (CHIKF), which is characterized by long-lasting and debilitating joint and muscle pain. CHIKV can cause large-scale epidemics with high attack rates, which substantiates the need for development of effective therapeutics suitable for outbreak containment. In this review, we highlight the different strategies used for developing CHIKV small-molecule inhibitors, ranging from high-throughput cell-based screening to in silico screens and enzymatic assays with purified viral proteins. We further discuss the current status of the most promising molecules, including in vitro and in vivo findings. In particular, we focus on describing host and/or viral targets, mode of action, and mechanisms of antiviral drug resistance and associated mutations. Knowledge of the key molecular determinants of drug resistance will aid selection of the most promising antiviral agent(s) for clinical use. For these reasons, we also summarize the available information about drug-resistant phenotypes in Aedes mosquito vectors. From this review, it is evident that more of the active molecules need to be evaluated in preclinical and clinical models to address the current lack of antiviral treatment for CHIKF.

Inhibition of orf virus replication in goat skin fibroblast cells by the HSPA1B protein, as demonstrated by iTRAQ-based quantitative proteome analysis

Orf virus (ORFV) infects sheep and goat tissues, resulting in severe proliferative lesions. To analyze cellular protein expression in ORFV-infected goat skin fibroblast (GSF) cells, we used two-dimensional liquid chromatography-tandem mass spectrometry coupled with isobaric tags for relative and absolute quantification (iTRAQ). The proteomics approach was used along with quantitative reverse transcription polymerase chain reaction (RT-qPCR) to detect differentially expressed proteins in ORFV-infected GSF cells and mock-infected GSF cells. A total of 282 differentially expressed proteins were identified. It was found that 222 host proteins were upregulated and 60 were downregulated following viral infection. We confirmed that these proteins were differentially expressed and found that heat shock 70-kDa protein 1B (HSPA1B) was differentially expressed and localized in the cytoplasm. It was also noted that HSPA1B caused inhibition of viral proliferation, in the middle and late stages of viral infection. The differentially expressed proteins were associated with the biological processes of viral binding, cell structure, signal transduction, cell adhesion, and cell proliferation.

Andrographolide Mitigates Unfolded Protein Response Pathway and Apoptosis Involved in Chikungunya Virus Infection

BACKGROUND

Chikungunya virus (CHIKV) is an arthropod-borne RNA virus which induces host Endoplasmic Reticulum (ER) stress by accumulating unfolded or misfolded proteins. ER stress activates the unfolded protein response (UPR) pathway to enable proper protein folding and maintain cellular homeostasis. There is no approved drug or vaccine available for CHIKV treatment, therefore, a pharmacological countermeasure is warranted for preventing CHIKV infection.

OBJECTIVE

With a view to find a treatment modality for chikungunya infection, "andrographolide", a plant-derived diterpenoid with reported antiviral, anti-inflammatory and immunomodulatory effects, was used to investigate its role in chikungunya induced unfolded protein stress and apoptosis.

METHODS

Cells and supernatant collected on andrographolide and VER-155008, a GRP78 inhibitor, treatment in CHIKV infected and mock-infected THP-1 cells were tested for differential expression of UPR pathway proteins including GRP78, PERK, EIF-2α, IRE-1α, XBP-1 and ATF6. Furthermore, the inflammasome and apoptosis pathway proteins, i.e., caspase-1, caspase-3 and PARP, were tested by immunoblotting, and cytokines, i.e., IL-1β, IL-6 and IFN-γ were tested by ELISA.

RESULTS

Andrographolide treatment in CHIKV infected THP-1 cells significantly reduced IRE1α and downstream spliced XBP1 protein expression. Furthermore, CHIKV induced apoptosis and viral protein expression were also reduced on andrographolide treatment. A comparative analysis of andrographolide versus VER-155008, confirmed that andrographolide surpasses the effects of VER-155008 in suppressing the CHIKV induced ER stress.

CONCLUSION

The study, therefore, confirms that andrographolide is a potential remedy for chikungunya infection and suppresses CHIKV induced ER stress and apoptosis.

Stress proteins: the biological functions in virus infection, present and challenges for target-based antiviral drug development

Stress proteins (SPs) including heat-shock proteins (HSPs), RNA chaperones, and ER associated stress proteins are molecular chaperones essential for cellular homeostasis. The major functions of HSPs include chaperoning misfolded or unfolded polypeptides, protecting cells from toxic stress, and presenting immune and inflammatory cytokines. Regarded as a double-edged sword, HSPs also cooperate with numerous viruses and cancer cells to promote their survival. RNA chaperones are a group of heterogeneous nuclear ribonucleoproteins (hnRNPs), which are essential factors for manipulating both the functions and metabolisms of pre-mRNAs/hnRNAs transcribed by RNA polymerase II. hnRNPs involve in a large number of cellular processes, including chromatin remodelling, transcription regulation, RNP assembly and stabilization, RNA export, virus replication, histone-like nucleoid structuring, and even intracellular immunity. Dysregulation of stress proteins is associated with many human diseases including human cancer, cardiovascular diseases, neurodegenerative diseases (e.g., Parkinson’s diseases, Alzheimer disease), stroke and infectious diseases. In this review, we summarized the biologic function of stress proteins, and current progress on their mechanisms related to virus reproduction and diseases caused by virus infections. As SPs also attract a great interest as potential antiviral targets (e.g., COVID-19), we also discuss the present progress and challenges in this area of HSP-based drug development, as well as with compounds already under clinical evaluation.

Computer-Aided Design, Synthesis, and Antiviral Evaluation of Novel Acrylamides as Potential Inhibitors of E3-E2-E1 Glycoproteins Complex from Chikungunya Virus

Chikungunya virus (CHIKV) causes an infectious disease characterized by inflammation and pain of the musculoskeletal tissues accompanied by swelling in the joints and cartilage damage. Currently, there are no licensed vaccines or chemotherapeutic agents to prevent or treat CHIKV infections. In this context, our research aimed to explore the potential in vitro anti-CHIKV activity of acrylamide derivatives. In silico methods were applied to 132 Michael's acceptors toward the six most important biological targets from CHIKV. Subsequently, the ten most promising acrylamides were selected and synthesized. From the cytotoxicity MTT assay, we verified that LQM330, 334, and 336 demonstrate high cell viability at 40 µM. Moreover, these derivatives exhibited anti-CHIKV activities, highlighting the compound LQM334 which exhibited an inhibition value of 81%. Thus, docking simulations were performed to suggest a potential CHIKV-target for LQM334. It was observed that the LQM334 has a high affinity towards the E3-E2-E1 glycoproteins complex. Moreover, LQM334 reduced the percentage of CHIKV-positive cells from 74.07 to 0.88%, 48h post-treatment on intracellular flow cytometry staining. In conclusion, all virtual simulations corroborated with experimental results, and LQM334 could be used as a promising anti-CHIKV scaffold for designing new drugs in the future.

The Host Cell ViroCheckpoint: Identification and Pharmacologic Targeting of Novel Mechanistic Determinants of Coronavirus-Mediated Hijacked Cell States

Most antiviral agents are designed to target virus-specific proteins and mechanisms rather than the host cell proteins that are critically dysregulated following virus-mediated reprogramming of the host cell transcriptional state. To overcome these limitations, we propose that elucidation and pharmacologic targeting of host cell Master Regulator proteins-whose aberrant activities govern the reprogramed state of coronavirus-infected cells-presents unique opportunities to develop novel mechanism-based therapeutic approaches to antiviral therapy, either as monotherapy or as a complement to established treatments. Specifically, we propose that a small module of host cell Master Regulator proteins (ViroCheckpoint) is hijacked by the virus to support its efficient replication and release. Conventional methodologies are not well suited to elucidate these potentially targetable proteins. By using the VIPER network-based algorithm, we successfully interrogated 12h, 24h, and 48h signatures from Calu-3 lung adenocarcinoma cells infected with SARS-CoV, to elucidate the time-dependent reprogramming of host cells and associated Master Regulator proteins. We used the NYS CLIA-certified Darwin OncoTreat algorithm, with an existing database of RNASeq profiles following cell perturbation with 133 FDA-approved and 195 late-stage experimental compounds, to identify drugs capable of virtually abrogating the virus-induced Master Regulator signature. This approach to drug prioritization and repurposing can be trivially extended to other viral pathogens, including SARS-CoV-2, as soon as the relevant infection signature becomes available.

Inhibition of heat shock protein 90 suppresses Bombyx mori nucleopolyhedrovirus replication in B. mori

Heat shock protein 90 (Hsp90) plays a very important role in facilitating the replication of many viruses. Until now, little has been known about the role of Hsp90 in Bombyx mori virus infection. In this study, we explored the role of BmHsp90 in B. mori nucleopolyhedrovirus (BmNPV) replication. We found that BmHsp90 inhibition by geldanamycin (GA) significantly reduced the BmNPV titre, the protein expression level of BmNPV nucleocapsid protein 39 (VP39) and the transcript level of BmNPV genes. Silencing the hsp90 gene in BmN cells by small interfering RNA suppressed BmNPV replication whereas overexpression of hsp90 promoted the replication of BmNPV. After inhibition of Hsp90, the expression of three key genes [signal transducing activator of transcription (stat), suppressor of cytokine signalling protein 2 (socs2), socs6] involved in the Janus kinase/STAT pathway significantly changed, with up-regulation of stat and down-regulation of socs2 and socs6. In addition, the expression of two antiapoptosis genes, BmNPV inhibitor of apoptosis protein1 (BmNPV-iap1) and Bmiap2, was greatly decreased in GA-treated cells, whereas their expression was significantly increased in hsp90-overexpressed silkworm larvae. Our results indicated that inhibition of Hsp90 can suppress BmNPV proliferation in B. mori. Our findings may provide new clues to elucidate the molecular mechanisms of silkworm-virus interactions.

Medicinal chemistry strategies toward host targeting antiviral agents

Direct‐acting antiviral agents (DAAs) represent a class of drugs targeting viral proteins and have been demonstrated to be very successful in combating viral infections in clinic. However, DAAs suffer from several inherent limitations, including narrow‐spectrum antiviral profiles and liability to drug resistance, and hence there are still unmet needs in the treatment of viral infections. In comparison, host targeting antivirals (HTAs) target host factors for antiviral treatment. Since host proteins are probably broadly required for various viral infections, HTAs are not only perceived, but also demonstrated to exhibit broad‐spectrum antiviral activities. In addition, host proteins are not under the genetic control of viral genome, and hence HTAs possess much higher genetic barrier to drug resistance as compared with DAAs. In recent years, much progress has been made to the development of HTAs with the approval of chemokine receptor type 5 antagonist maraviroc for human immunodeficiency virus treatment and more in the pipeline for other viral infections. In this review, we summarize various host proteins as antiviral targets from a medicinal chemistry prospective. Challenges and issues associated with HTAs are also discussed.

Antiviral drug discovery against arthritogenic alphaviruses: Tools and molecular targets

Alphaviruses are (mainly) arthropod-borne viruses that belong to the family of the Togaviridae. Based on the disease they cause, alphaviruses are divided into an arthritogenic and an encephalitic group. Arthritogenic alphaviruses such as the chikungunya virus (CHIKV), the Ross River virus (RRV) and the Mayaro virus (MAYV) have become a serious public health concern in recent years. Epidemics are associated with high morbidity and the infections cause in many patients debilitating joint pain that can persist for months to years. The recent (2013-2014) introduction of CHIKV in the Americas resulted in millions of infected persons. Massive outbreaks of CHIKV and other arthritogenic alphaviruses are likely to occur in the future. Despite the worldwide (re-)emergence of these viruses, there are no antivirals or vaccines available for the treatment or prevention of infections with alphaviruses. It is therefore of utmost importance to develop antiviral strategies against these viruses. We here review the possible molecular targets in the replication cycle of these viruses for the development of antivirals. In addition, we provide an overview of the currently available in vitro systems and mouse infection models that can be used to assess the potential antiviral effect against these viruses.

Heat Shock Protein 90 Ensures the Integrity of Rubella Virus p150 Protein and Supports Viral Replication

Two viral nonstructural proteins, p150 and p90, are expressed in rubella virus (RUBV)-infected cells and mediate viral genome replication, presumably using various host machineries. Molecular chaperones are critical host factors for the maintenance of cellular proteostasis, and certain viral proteins use this chaperone system. The RUBV p150 and p90 proteins are generated from a precursor polyprotein, p200, via processing by the protease activity of its p150 region. This processing is essential for RUBV genome replication. Here we show that heat shock protein 90 (HSP90), a molecular chaperone, is an important host factor for RUBV genome replication. The treatment of RUBV-infected cells with the HSP90 inhibitors 17-allylamino-17-desmethoxygeldanamycin (17-AAG) and ganetespib suppressed RUBV genome replication. HSP90α physically interacted with p150, but not p90. Further analyses into the mechanism of action of the HSP90 inhibitors revealed that HSP90 activity contributes to p150 functional integrity and promotes p200 processing. Collectively, our data demonstrate that RUBV p150 is a client of the HSP90 molecular chaperone and that HSP90 functions as a key host factor for RUBV replication.IMPORTANCE Accumulating evidence indicates that RNA viruses use numerous host factors during replication of their genomes. However, the host factors involved in rubella virus (RUBV) genome replication are largely unknown. In this study, we demonstrate that the HSP90 molecular chaperone is needed for the efficient replication of the RUBV genome. Further, we reveal that HSP90 interacts with RUBV nonstructural protein p150 and its precursor polyprotein, p200. HSP90 contributes to the stability of p150 and the processing of p200 via its protease domain in the p150 region. We conclude that the cellular molecular chaperone HSP90 is a key host factor for functional maturation of nonstructural proteins for RUBV genome replication. These findings provide novel insight into this host-virus interaction.

The role of heat shock protein 90 in regulating pain, opioid signaling, and opioid antinociception

Heat shock protein 90 (Hsp90) is one of the central signal transduction regulators of the cell. Via client interactions with hundreds of proteins, including receptors, receptor regulatory kinases, and downstream signaling regulators, Hsp90 has a crucial and wide-ranging impact on signaling in response to numerous drugs with impacts on resultant physiology and behavior. Despite this importance, however, Hsp90 has barely been studied in the context of pain and the opioid receptor system, leaving open the possibility that Hsp90 could be manipulated to improve pain therapeutic outcomes, a current area of massive medical need. In this review, we will highlight the known roles of Hsp90 in directly regulating the initiation and maintenance of the pain state. We will also explore how Hsp90 regulates signaling and antinociceptive responses to opioid analgesic drugs, with a special emphasis on ERK MAPK signaling. Understanding this new and growing area will improve our understanding of how Hsp90 regulates signaling and physiology, and also may provide new ways to treat pain, and perhaps reduce the severe impact of the ongoing opioid addiction and overdose crisis.

Viral Induced Oxidative and Inflammatory Response in Alzheimer's Disease Pathogenesis with Identification of Potential Drug Candidates: A Systematic Review using Systems Biology Approach

Alzheimer's disease (AD) is genetically complex with multifactorial etiology. Here, we aim to identify the potential viral pathogens leading to aberrant inflammatory and oxidative stress response in AD along with potential drug candidates using systems biology approach. We retrieved protein interactions of amyloid precursor protein (APP) and tau protein (MAPT) from NCBI and genes for oxidative stress from NetAge, for inflammation from NetAge and InnateDB databases. Genes implicated in aging were retrieved from GenAge database and two GEO expression datasets. These genes were individually used to create protein-protein interaction network using STRING database (score≥0.7). The interactions of candidate genes with known viruses were mapped using virhostnet v2.0 database. Drug molecules targeting candidate genes were retrieved using the Drug- Gene Interaction Database (DGIdb). Data mining resulted in 2095 APP, 116 MAPT, 214 oxidative stress, 1269 inflammatory genes. After STRING PPIN analysis, 404 APP, 109 MAPT, 204 oxidative stress and 1014 inflammation related high confidence proteins were identified. The overlap among all datasets yielded eight common markers (AKT1, GSK3B, APP, APOE, EGFR, PIN1, CASP8 and SNCA). These genes showed association with hepatitis C virus (HCV), Epstein- Barr virus (EBV), human herpes virus 8 and Human papillomavirus (HPV). Further, screening of drugs targeting candidate genes, and possessing anti-inflammatory property, antiviral activity along with a suggested role in AD pathophysiology yielded 12 potential drug candidates. Our study demonstrated the role of viral etiology in AD pathogenesis by elucidating interaction of oxidative stress and inflammation causing candidate genes with common viruses along with the identification of potential AD drug candidates.

Proteomics analysis reveals heat shock proteins involved in caprine parainfluenza virus type 3 infection

BACKGROUND

Caprine parainfluenza virus type 3 (CPIV3) is major pathogen of goat herds causing serious respiratory tract disease and economic losses to the goat industry in China. We analyzed the differential proteomics of CPIV3-infected Madin-Darby bovine kidney (MDBK) cells using quantitative iTRAQ coupled LC-MS/MS. In addition, four DEPs were validated by qRT-PCR and western blot analysis.

RESULTS

Quantitative proteomics analysis revealed 163 differentially expressed proteins (DEPs) between CPIV3-infected and mock-infected groups (p-value < 0.05 and fold change > 1.2), among which 91 were down-regulated and 72 were up-regulated. Gene ontology (GO) analysis showed that these DEPs were involved in molecular functions, cellular components and biological processes. Biological functions in which the DEPs were involved in included diseases, genetic information processing, metabolism, environmental information processing, cellular processes, and organismal systems. STRING analysis revealed that four heat shock proteins (HSPs) included HSPA5, HSPA1B, HSP90B1 and HSPA6 may be associated with proliferation of CPIV3 in MDBK cells. qRT-PCR and western blot analysis showed that the selected HSPs were identical to the quantitative proteomics data.

CONCLUSION

To our knowledge, this is the first report of the proteomic changes in MDBK cells after CPIV3 infection.

Molecular detection of Hsp90 inhibitor suppressing PCV2 replication in host cells

Porcine Circovirus Type 2 (PCV2) is a pathogen that has the ability to cause devastating disease manifestations in pig populations with major economic implications. Our previous research found that Hsp90 is required for PCV2 production in PK-15 and 3D4/31 cells. The aim of this study was to evaluate the effect of Hsp90 inhibitor regulating PCV2 replication and to explore its underlying mechanism. In PK-15 and 3D4/31 cells treated with 17-AAG after viral adsorption, replication of PCV2 was attenuated as assessed by quantitating the expression of viral protein. Following NF-κB activation it was observed that 24hpi with PCV2 was significantly inhibited in the presence of 17-AAG. The expression of Hsp90 associated client proteins in PCV2-infected cells were also reduced in the presence of 17-AAG. However, treatment with MG-132 failed to rescue 17-AAG mediated reduction of PCV2 production in host cells. Thus, Hsp90 regulates PCV2 by modulating cellular signaling proteins. These results highlight the importance of cellular proteins during PCV2 infection and the possibility of targeting cellular chaperones for developing new anti-rotaviral strategies.

Spectrum of candidate molecules against Chikungunya virus - an insight into the antiviral screening platforms

INTRODUCTION

Chikungunya disease has undergone a phenomenal transition in its status from being recognized as a sporadic infection to acquiring a global prominence over the last couple of decades. The causative agent behind the explosive epidemics worldwide is the re-emerging pathogen, Chikungunya virus (CHIKV). Areas covered: The current review discusses all the possible avenues of antiviral research towards combating CHIKV infection. Aspects of antiviral drug discovery such as antiviral targets, candidate molecules screened, and the various criteria to be a potential inhibitor are all discussed at length. Existing antiviral drug screening tools for CHIKV and their applications are thoroughly described. Clinical trial status of agents with therapeutic potential has been updated with special mention of candidate molecules under patent approval. Databases such as PubMed, Google Scholar, ScienceDirect, Google Patent, and Clinical Trial Registry platforms were referred. Expert opinion: The massive outbreaks of Chikungunya viral disease in the recent past and the serious health concerns imposed thereby, have driven the search for effective therapeutics. The greatest challenge being the non-availability of robust, reproducible, cost-effective and biologically accurate assay models. Nevertheless, there is a need to identify good models mimicking the appropriate microenvironment of an infectious setting.

Chikungunya Virus Fidelity Variants Exhibit Differential Attenuation and Population Diversity in Cell Culture and Adult Mice

Chikungunya virus (CHIKV) is a reemerging global health threat that produces debilitating arthritis in people. Like other RNA viruses with high mutation rates, CHIKV produces populations of genetically diverse genomes within a host. While several known CHIKV mutations influence disease severity in vertebrates and transmission by mosquitoes, the role of intrahost diversity in chikungunya arthritic disease has not been studied. In this study, high- and low-fidelity CHIKV variants, previously characterized by altered in vitro population mutation frequencies, were used to evaluate how intrahost diversity influences clinical disease, CHIKV replication, and antibody neutralization in immunocompetent adult mice inoculated in the rear footpads. Both high- and low-fidelity mutations were hypothesized to attenuate CHIKV arthritic disease, replication, and neutralizing antibody levels compared to wild-type (WT) CHIKV. Unexpectedly, high-fidelity mutants elicited more severe arthritic disease than the WT despite comparable CHIKV replication, whereas a low-fidelity mutant produced attenuated disease and replication. Serum antibody developed against both high- and low-fidelity CHIKV exhibited reduced neutralization of WT CHIKV. Using next-generation sequencing (NGS), the high-fidelity mutations were demonstrated to be genetically stable but produced more genetically diverse populations than WT CHIKV in mice. This enhanced diversification was subsequently reproduced after serial in vitro passage. The NGS results contrast with previously reported population diversities for fidelity variants, which focused mainly on part of the E1 gene, and highlight the need for direct measurements of mutation rates to clarify CHIKV fidelity phenotypes.IMPORTANCE CHIKV is a reemerging global health threat that elicits debilitating arthritis in humans. There are currently no commercially available CHIKV vaccines. Like other RNA viruses, CHIKV has a high mutation rate and is capable of rapid intrahost diversification during an infection. In other RNA viruses, virus population diversity associates with disease progression; however, potential impacts of intrahost viral diversity on CHIKV arthritic disease have not been studied. Using previously characterized CHIKV fidelity variants, we addressed whether CHIKV population diversity influences the severity of arthritis and host antibody response in an arthritic mouse model. Our findings show that CHIKV populations with greater genetic diversity can cause more severe disease and stimulate antibody responses with reduced neutralization of low-diversity virus populations in vitro The discordant high-fidelity phenotypes in this study highlight the complexity of inferring replication fidelity indirectly from population diversity.