Proteomic profiling of chikungunya virus-infected human muscle cells: reveal the role of cytoskeleton network in CHIKV replication

Research progress of vimentin in viral infections

Vimentin, a type III intermediate filament protein, has become a focal point in the research of viral infections. It participates in multiple crucial processes during the viral life cycle and the host's antiviral response. During viral entry, it may function as a receptor or co-receptor and interact with viral entry proteins, also influencing endocytic pathways. Furthermore, vimentin engages with replication complexes and modulates the intracellular environment in viral replication. Moreover, vimentin plays significant roles in immune responses and inflammatory reactions during viral infections. This review thoroughly analyzes the recent progress in understanding vimentin's functions during viral infections, covering aspects such as viral entry, replication, and the immune response to achieve a cohesive comprehension of the underlying mechanisms. The antiviral strategies based on vimentin are also discussed, aiming to promote the development of more effective preventive and treatment strategies for viral diseases.

Mitochondrial protein BNIP3 regulates Chikungunya virus replication in the early stages of infection

Chikungunya virus (CHIKV) is a human pathogen causing outbreaks of febrile illness for which vaccines and specific treatments remain unavailable. Autophagy-related (ATG) proteins and autophagy receptors are a set of host factors that participate in autophagy, but have also shown to function in other unrelated cellular pathways. Although autophagy is reported to both inhibit and enhance CHIKV replication, the specific role of individual ATG proteins remains largely unknown. Here, a siRNA screen was performed to evaluate the importance of the ATG proteome and autophagy receptors in controlling CHIKV infection. We observed that 7 out of 50 ATG proteins impact the replication of CHIKV. Among those, depletion of the mitochondrial protein and autophagy receptor BCL2 Interacting Protein 3 (BNIP3) increased CHIKV infection. Interestingly, BNIP3 controls CHIKV independently of autophagy and cell death. Detailed analysis of the CHIKV viral cycle revealed that BNIP3 interferes with the early stages of infection. Moreover, the antiviral role of BNIP3 was found conserved across two distinct CHIKV genotypes and the closely related Semliki Forest virus. Altogether, this study describes a novel and previously unknown function of the mitochondrial protein BNIP3 in the control of the early stages of the alphavirus viral cycle.

Calpain-2 protein influences chikungunya virus replication and regulates vimentin rearrangement caused by chikungunya virus infection

Chikungunya fever (CHIF), a vector-borne disease transmitted mainly by Aedes albopictus and Aedes aegypti, is caused by Chikungunya virus (CHIKV) infection. To date, it is estimated that 39% of the world's population is at risk of infection for living in countries and regions where CHIKV is endemic. However, at present, the cellular receptors of CHIKV remains not clear, and there are no specific drugs and vaccines for CHIF. Here, the cytotoxicity of calpain-2 protein activity inhibitor III and specific siRNA was detected by MTT assays. The replication of CHIKV was detected by qPCR amplification and plaque assay. Western blot was used to determine the level of the calpain-2 protein and vimentin protein. Immunofluorescence was also operated for detecting the rearrangement of vimentin protein. Our results indicated that calpain-2 protein activity inhibitor III and specific siRNA might suppress CHIKV replication. Furthermore, CHIKV infection led to vimentin remodeling and formation of cage-like structures, which could be inhibited by the inhibitor III. In summary, we confirmed that calpain-2 protein influenced chikungunya virus replication and regulated vimentin rearrangement caused by chikungunya virus infection, which could be important for understanding the biological significance of CHIKV replication and the future development of antiviral strategies.

A Review of Omics Studies on Arboviruses: Alphavirus, Orthobunyavirus and Phlebovirus

Since the intricate and complex steps in pathogenesis and host-viral interactions of arthropod-borne viruses or arboviruses are not completely understood, the multi-omics approaches, which encompass proteomics, transcriptomics, genomics and metabolomics network analysis, are of great importance. We have reviewed the omics studies on mosquito-borne viruses of the Togaviridae, Peribuyaviridae and Phenuiviridae families, specifically for Chikungunya, Mayaro, Oropouche and Rift Valley Fever viruses. Omics studies can potentially provide a new perspective on the pathophysiology of arboviruses, contributing to a better comprehension of these diseases and their effects and, hence, provide novel insights for the development of new antiviral drugs or therapies.

Evidence of chikungunya virus infections among febrile patients at three secondary health facilities in the Ashanti and the Bono Regions of Ghana

BACKGROUND

Chikungunya is now of public health concern globally due to its re-emergence in endemic areas and introduction into new areas of the world. Worldwide, the vectors for transmission of the chikungunya virus are Aedes mosquitoes and these are prevalent in Ghana. Despite its global significance, the true burden of chikungunya virus infection in Ghana is largely unknown and the threat of outbreak remains high owing to international travel. This study sought to determine chikungunya virus infection among febrile patients suspected of having malaria infections at some selected health facilities in the Ashanti, Bono East, and Bono Regions of Ghana.

METHODOLOGY

This cross-sectional study recruited six hundred (600) febrile patients suspected of having malaria who submitted their clinical samples to the laboratories of the selected health facilities for the diagnosis of their infections. Five to ten millilitres (5-10ml) of venous blood were collected from each study participant. Sera were separated and tested for anti-chikungunya (IgM and IgG) antibodies using InBios ELISA kit following the manufacturer's instruction. Samples positive for chikungunya IgM and IgG were selected and tested for chikungunya virus RNA using Reverse Transcription-quantitative Polymerase Chain Reaction. Malaria Rapid Diagnostic Test kits were used to screen the participants for malaria. Structured questionnaires were administered to obtain demographic and clinical information of the study participants.

RESULT

Of the 600 samples tested, the overall seroprevalence of chikungunya was 6%. The seroprevalence of chikungunya IgM and IgG antibodies were 1.8% and 4.2% respectively. None of the chikungunya IgM and IgG positive samples tested positive for chikungunya RNA by RT-qPCR. Of the 600 samples, tested 32.3% (194/600) were positive for malaria parasites. Malaria and chikungunya co-infection was detected in 1.8% (11/600) of the participants.

CONCLUSION

Findings from the current study indicate low-level exposure to the chikungunya virus suggesting the virus is circulating and potentially causing morbidity in Ghana.

Acrylamide inhibits vaccinia virus through vimentin-independent anti-viral granule formation

The replication and assembly of vaccinia virus (VACV), the prototypic poxvirus, occurs exclusively in the cytoplasm of host cells. While the role of cellular cytoskeletal components in these processes remains poorly understood, vimentin-a type III intermediate filament-has been shown to associate with viral replication sites and to be incorporated into mature VACV virions. Here, we employed chemical and genetic approaches to further investigate the role of vimentin during the VACV lifecycle. The collapse of vimentin filaments, using acrylamide, was found to inhibit VACV infection at the level of genome replication, intermediate- and late-gene expression. However, we found that CRISPR-mediated knockout of vimentin did not impact VACV replication. Combining these tools, we demonstrate that acrylamide treatment results in the formation of anti-viral granules (AVGs) known to mediate translational inhibition of many viruses. We conclude that vimentin is dispensable for poxvirus replication and assembly and that acrylamide, as a potent inducer of AVGs during VACV infection, serves to bolster cell's anti-viral response to poxvirus infection.

Rediscovering the chikungunya virus

El virus de chikunguña (CHIKV) es un Alfavirus perteneciente al grupo denominado del Viejo Mundo; estos son virus artritogénicos que causan una enfermedad febril caracterizada por artralgias y mialgias. Aunque la muerte por CHIKV es poco frecuente, la enfermedad puede llegar a ser incapacitante y generar un amplio espectro de manifestaciones atípicas, como complicaciones cardiovasculares, respiratorias, oculares, renales y dérmicas, entre otras. Cuando el dolor articular persiste por tres o más meses, da lugar a la forma crónica de la enfermedad denominada reumatismo inflamatorio crónico poschikunguña, el cual es la principal secuela de la enfermedad. Se considera que este virus no es neurotrópico, sin embargo, puede afectar el sistema nervioso central y generar secuelas graves y permanentes, principalmente, en niños y ancianos.

En África, Asia y Europa se habían reportado anteriormente brotes epidémicos por CHIKV, pero solo hasta finales del 2013 se documentó la introducción del virus a las Américas; desde entonces, el virus se ha propagado a 45 países o territorios del continente y el número de casos acumulados ascendió a cerca de dos millones en dos años.

Esta revisión describe de manera general la biología molecular del virus, sus manifestaciones clínicas, su patogénesis y las principales complicaciones posteriores a la infección. Además, reúne la información de la epidemia en Colombia y el continente americano publicada entre el 2014 y el 2020.

Orchestrated efforts on host network hijacking: Processes governing virus replication

With the high pervasiveness of viral diseases, the battle against viruses has never ceased. Here we discuss five cellular processes, namely "autophagy", "programmed cell death", "immune response", "cell cycle alteration", and "lipid metabolic reprogramming", that considerably guide viral replication after host infection in an orchestrated manner. On viral infection, "autophagy" and "programmed cell death" are two dynamically synchronized cell survival programs; "immune response" is a cell defense program typically suppressed by viruses; "cell cycle alteration" and "lipid metabolic reprogramming" are two altered cell housekeeping programs tunable in both directions. We emphasize on their functionalities in modulating viral replication, strategies viruses have evolved to tune these processes for their benefit, and how these processes orchestrate and govern cell fate upon viral infection. Understanding how viruses hijack host networks has both academic and industrial values in providing insights toward therapeutic strategy design for viral disease control, offering useful information in applications that aim to use viral vectors to improve human health such as gene therapy, and providing guidelines to maximize viral particle yield for improved vaccine production at a reduced cost.

Arboviruses and Muscle Disorders: From Disease to Cell Biology

Infections due to arboviruses (arthropod-borne viruses) have dramatically increased worldwide during the last few years. In humans, symptoms associated with acute infection of most arboviruses are often described as "dengue-like syndrome", including fever, rash, conjunctivitis, arthralgia, and muscular symptoms such as myalgia, myositis, or rhabdomyolysis. In some cases, muscular symptoms may persist over months, especially following flavivirus and alphavirus infections. However, in humans the cellular targets of infection in muscle have been rarely identified. Animal models provide insights to elucidate pathological mechanisms through studying viral tropism, viral-induced inflammation, or potential viral persistence in the muscle compartment. The tropism of arboviruses for muscle cells as well as the viral-induced cytopathic effect and cellular alterations can be confirmed in vitro using cellular models. This review describes the link between muscle alterations and arbovirus infection, and the underlying mechanisms.

Expanding the canon: Non-classical mosquito genes at the interface of arboviral infection

Mosquito transmitted viruses cause significant morbidity and mortality in human populations. Despite the use of insecticides and other measures of vector control, arboviral diseases are on the rise. One potential solution for limiting disease transmission to humans is to render mosquitoes refractory to viral infection through genetic modification. Substantial research effort in Drosophila, Aedes and Anopheles has helped to define the major innate immune pathways, including Toll, IMD, Jak/Stat and RNAi, however we still have an incomplete picture of the mosquito antiviral response. Transcriptional profiles of virus-infected insects reveal a much wider range of pathways activated by the process of infection. Within these lists of genes are unexplored mosquito candidates of viral defense. Wolbachia species are endosymbiotic bacteria that naturally limit arboviral infection in mosquitoes. Our understanding of the Wolbachia-mediated viral blocking mechanism is poor, but it does not appear to operate via the classical immune pathways. Herein, we reviewed the transcriptomic response of mosquitoes to multiple viral species and put forth consensus gene types/families outside the immune canon whose expression responds to infection, including cytoskeleton and cellular trafficking, the heat shock response, cytochromes P450, cell proliferation, chitin and small RNAs. We then examine emerging evidence for their functional role in viral resistance in diverse insect and mammalian hosts and their potential role in Wolbachia-mediated viral blocking. These candidate gene families offer novel avenues for research into the nature of insect viral defense.

SAMHD1 Enhances Chikungunya and Zika Virus Replication in Human Skin Fibroblasts

Chikungunya virus (CHIKV) and Zika virus (ZIKV) are emerging arboviruses that pose a worldwide threat to human health. Currently, neither vaccine nor antiviral treatment to control their infections is available. As the skin is a major viral entry site for arboviruses in the human host, we determined the global proteomic profile of CHIKV and ZIKV infections in human skin fibroblasts using Stable Isotope Labelling by Amino acids in Cell culture (SILAC)-based mass-spectrometry analysis. We show that the expression of the interferon-stimulated proteins MX1, IFIT1, IFIT3 and ISG15, as well as expression of defense response proteins DDX58, STAT1, OAS3, EIF2AK2 and SAMHD1 was significantly up-regulated in these cells upon infection with either virus. Exogenous expression of IFITs proteins markedly inhibited CHIKV and ZIKV replication which, accordingly, was restored following the abrogation of IFIT1 or IFIT3. Overexpression of SAMHD1 in cutaneous cells, or pretreatment of cells with the virus-like particles containing SAMHD1 restriction factor Vpx, resulted in a strong increase or inhibition, respectively, of both CHIKV and ZIKV replication. Moreover, silencing of SAMHD1 by specific SAMHD1-siRNA resulted in a marked decrease of viral RNA levels. Together, these results suggest that IFITs are involved in the restriction of replication of CHIKV and ZIKV and provide, as yet unreported, evidence for a proviral role of SAMHD1 in arbovirus infection of human skin cells.

Implication of B23/NPM1 in Viral Infections, Potential Uses of B23/NPM1 Inhibitors as Antiviral Therapy

BACKGROUND

B23/nucleophosmin (B23/NPM1) is an abundant multifunctional protein mainly located in the nucleolus but constantly shuttling between the nucleus and cytosol. As a consequence of its constitutive expression, intracellular dynamics and binding capacities, B23/NPM1 interacts with multiple cellular factors in different cellular compartments, but also with viral proteins from both DNA and RNA viruses. B23/NPM1 influences overall viral replication of viruses like HIV, HBV, HCV, HDV and HPV by playing functional roles in different stages of viral replication including nuclear import, viral genome transcription and assembly, as well as final particle formation. Of note, some virus modify the subcellular localization, stability and/or increases B23/NPM1 expression levels on target cells, probably to foster B23/NPM1 functions in their own replicative cycle.

RESULTS

This review summarizes current knowledge concerning the interaction of B23/NPM1 with several viral proteins during relevant human infections. The opportunities and challenges of targeting this well-conserved host protein as a potentially new broad antiviral treatment are discussed in detail. Importantly, although initially conceived to treat cancer, a handful of B23/NPM1 inhibitors are currently available to test on viral infection models.

CONCLUSION

As B23/NPM1 partakes in key steps of viral replication and some viral infections remain as unsolved medical needs, an appealing idea may be the expedite evaluation of B23/NPM1 inhibitors in viral infections. Furthermore, worth to be addressed is if the up-regulation of B23/NPM1 protein levels that follows persistent viral infections may be instrumental to the malignant transformation induced by virus like HBV and HCV.

The Interplay of Viral and Host Factors in Chikungunya Virus Infection: Targets for Antiviral Strategies

Chikungunya virus (CHIKV) has re-emerged as one of the many medically important arboviruses that have spread rampantly across the world in the past decade. Infected patients come down with acute fever and rashes, and a portion of them suffer from both acute and chronic arthralgia. Currently, there are no targeted therapeutics against this debilitating virus. One approach to develop potential therapeutics is by understanding the viral-host interactions. However, to date, there has been limited research undertaken in this area. In this review, we attempt to briefly describe and update the functions of the different CHIKV proteins and their respective interacting host partners. In addition, we also survey the literature for other reported host factors and pathways involved during CHIKV infection. There is a pressing need for an in-depth understanding of the interaction between the host environment and CHIKV in order to generate potential therapeutics.

Conflict in the Intracellular Lives of Endosymbionts and Viruses: A Mechanistic Look at Wolbachia-Mediated Pathogen-blocking

At the forefront of vector control efforts are strategies that leverage host-microbe associations to reduce vectorial capacity. The most promising of these efforts employs Wolbachia, a maternally transmitted endosymbiotic bacterium naturally found in 40% of insects. Wolbachia can spread through a population of insects while simultaneously inhibiting the replication of viruses within its host. Despite successes in using Wolbachia-transfected mosquitoes to limit dengue, Zika, and chikungunya transmission, the mechanisms behind pathogen-blocking have not been fully characterized. Firstly, we discuss how Wolbachia and viruses both require specific host-derived structures, compounds, and processes to initiate and maintain infection. There is significant overlap in these requirements, and infection with either microbe often manifests as cellular stress, which may be a key component of Wolbachia’s anti-viral effect. Secondly, we discuss the current understanding of pathogen-blocking through this lens of cellular stress and develop a comprehensive view of how the lives of Wolbachia and viruses are fundamentally in conflict with each other. A thorough understanding of the genetic and cellular determinants of pathogen-blocking will significantly enhance the ability of vector control programs to deploy and maintain effective Wolbachia-mediated control measures.

Nucleophosmin (NPM1)/B23 in the Proteome of Human Astrocytic Cells Restricts Chikungunya Virus Replication

Chikungunya virus (CHIKV), a positive-stranded RNA virus, can cause neurological complications by infecting the major parenchymal cells of the brain such as neurons and astrocytes. A proteomic analysis of CHIKV-infected human astrocytic cell line U-87 MG revealed tight functional associations among the modulated proteins. The predominant cellular pathways involved were of transcription-translation machinery, cytoskeletol reorganization, apoptosis, ubiquitination, and metabolism. In the proteome, we could also identify a few proteins that are reported to be involved in host-virus interactions. One such protein, Nucleophosmin (NPM1)/B23, a nucleolar protein, showed enhanced cytoplasmic aggregation in CHIKV-infected cells. NPM1 aggregation was predominantly localized in areas wherein CHIKV antigen could be detected. Furthermore, we observed that inhibition of this aggregation using a specific NPM1 oligomerization inhibitor, NSC348884, caused a significant dose-dependent enhancement in virus replication. There was a marked increase in the amount of intracellular viral RNA, and ∼10⁵-fold increase in progeny virions in infected cells. Our proteomic analysis provides a comprehensive spectrum of host proteins modulated in response to CHIKV infection in astrocytic cells. Our results also show that NPM1/B23, a multifunctional chaperone, plays a critical role in restricting CHIKV replication and is a possible target for antiviral strategies.

Pixuna virus modifies host cell cytoskeleton to secure infection

Pixuna virus (PIXV) is an enzootic member of the Venezuelan Equine Encephalitis Virus complex and belongs to the New World cluster of alphaviruses. Herein we explore the role of the cellular cytoskeleton during PIXV replication. We first identified that PIXV undergoes an eclipse phase consisting of 4 h followed by 20 h of an exponential phase in Vero cells. The infected cells showed morphological changes due to structural modifications in actin microfilaments (MFs) and microtubules (MTs). Cytoskeleton-binding agents, that alter the architecture and dynamics of MFs and MTs, were used to study the role of cytoskeleton on PIXV replication. The virus production was significantly affected (p < 0.05) after treatment with paclitaxel or nocodazole due to changes in the MTs network. Interestingly, disassembly of MFs with cytochalasin D, at early stage of PIXV replication cycle, significantly increased the virus yields in the extracellular medium (p < 0.005). Furthermore, the stabilization of actin network with jasplakinolide had no effect on virus yields. Our results demonstrate that PIXV relies not only on intact MTs for the efficient production of virus, but also on a dynamic actin network during the early steps of viral replication.

Systems Biology Reveals NS4B-Cyclophilin A Interaction: A New Target to Inhibit YFV Replication

Yellow fever virus (YFV) replication is highly dependent on host cell factors. YFV NS4B is reported to be involved in viral replication and immune evasion. Here interactions between NS4B and human proteins were determined using a GST pull-down assay and analyzed using 1-DE and LC-MS/MS. We present a total of 207 proteins confirmed using Scaffold 3 Software. Cyclophilin A (CypA), a protein that has been shown to be necessary for the positive regulation of flavivirus replication, was identified as a possible NS4B partner. 59 proteins were found to be significantly increased when compared with a negative control, and CypA exhibited the greatest difference, with a 22-fold change. Fisher's exact test was significant for 58 proteins, and the p value of CypA was the most significant (0.000000019). The Ingenuity Systems software identified 16 pathways, and this analysis indicated sirolimus, an mTOR pathway inhibitor, as a potential inhibitor of CypA. Immunofluorescence and viral plaque assays showed a significant reduction in YFV replication using sirolimus and cyclosporine A (CsA) as inhibitors. Furthermore, YFV replication was strongly inhibited in cells treated with both inhibitors using reporter BHK-21-rep-YFV17D-LucNeoIres cells. Taken together, these data suggest that CypA-NS4B interaction regulates YFV replication. Finally, we present the first evidence that YFV inhibition may depend on NS4B-CypA interaction.

Global expansion of chikungunya virus: mapping the 64-year history

Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that is emerging as a global threat because of the highly debilitating nature of the associated disease and unprecedented magnitude of its spread. Chikungunya originated in Africa and has since spread across the entire globe causing large numbers of epidemics that have infected millions of people in Asia, the Indian subcontinent, Europe, the Americas, and Pacific Islands. Phylogenetic analysis has identified four different genotypes of CHIKV: Asian, West African, East/Central/South African (ECSA), and Indian Ocean Lineage (IOL). In the absence of well-designed epidemiological studies, the aim of this review article was to summarize the global epidemiology of CHIKV and to provide baseline data for future research on the treatment, prevention, and control of this life-threatening disease.

Japanese encephalitis virus induces human neural stem/progenitor cell death by elevating GRP78, PHB and hnRNPC through ER stress

Japanese encephalitis virus (JEV), which is a causative agent of sporadic encephalitis, harbours itself inside the neural stem/progenitor cells. It is a well-known fact that JEV infects neural stem/progenitor cells and decreases their proliferation capacity. With mass spectrometry-based quantitative proteomic study, it is possible to reveal the impact of virus on the stem cells at protein level. Our aim was to perceive the stem cell proteomic response upon viral challenge. We performed a two-dimensional gel electrophoresis-based proteomic study of the human neural stem cells (hNS1 cell line) post JEV infection and found that 13 proteins were differentially expressed. The altered proteome profile of hNS1 cell line revealed sustained endoplasmic reticulum stress, which deteriorated normal cellular activities leading to cell apoptosis. The proteomic changes found in hNS1 cell line were validated in vivo in the subventricular zone of JE infected BALB/c mice. Congruent alterations were also witnessed in multipotent neural precursor cells isolated from human foetus and in autopsy samples of human brain clinically diagnosed as cases of JE patients. Endoplasmic reticulum resident chaperone GRP78, mitochondrial protein Prohibitin and heterogeneous nuclear ribonucleoprotein hnRNPC (C1/C2) have been shown to interact with viral RNA. Hence it is proposed that these are the principle candidates governing endoplasmic reticulum stress-induced apoptosis in JEV infection.

Chemical Methods for Probing Virus-Host Proteomic Interactions

Interactions between host and pathogen proteins constitute an important aspect of both infectivity and the host immune response. Different viruses have evolved complex mechanisms to hijack host-cell machinery and metabolic pathways to redirect resources and energy flow toward viral propagation. These interactions are often critical to the virus, and thus understanding these interactions at a molecular level gives rise to opportunities to develop novel antiviral strategies for therapeutic intervention. This review summarizes current advances in chemoproteomic methods for studying these molecular altercations between different viruses and their hosts.

Establishment of a Novel Primary Human Skeletal Myoblast Cellular Model for Chikungunya Virus Infection and Pathogenesis

Chikungunya virus (CHIKV) is a re-emerging arbovirus known to cause chronic myalgia and arthralgia and is now considered endemic in countries across Asia and Africa. The tissue tropism of CHIKV infection in humans remains, however, ill-defined. Due to the fact that myositis is commonly observed in most patients infected with CHIKV, we sought to develop a clinically relevant cellular model to better understand the pathogenesis of CHIKV infection. In this study, primary human skeletal muscle myoblasts (HSMM) were established as a novel human primary cell line that is highly permissive to CHIKV infection, with maximal amounts of infectious virions observed at 16 hours post infection. Genome-wide microarray profiling analyses were subsequently performed to identify and map genes that are differentially expressed upon CHIKV infection. Infection of HSMM cells with CHIKV resulted in altered expressions of host genes involved in skeletal- and muscular-associated disorders, innate immune responses, cellular growth and death, host metabolism and virus replication. Together, this study has shown the establishment of a clinically relevant primary human cell model that paves the way for the further analysis of host factors and their involvement in the various stages of CHIKV replication cycle and viral pathogenesis.

Early Events in Chikungunya Virus Infection-From Virus Cell Binding to Membrane Fusion

Chikungunya virus (CHIKV) is a rapidly emerging mosquito-borne alphavirus causing millions of infections in the tropical and subtropical regions of the world. CHIKV infection often leads to an acute self-limited febrile illness with debilitating myalgia and arthralgia. A potential long-term complication of CHIKV infection is severe joint pain, which can last for months to years. There are no vaccines or specific therapeutics available to prevent or treat infection. This review describes the critical steps in CHIKV cell entry. We summarize the latest studies on the virus-cell tropism, virus-receptor binding, internalization, membrane fusion and review the molecules and compounds that have been described to interfere with virus cell entry. The aim of the review is to give the reader a state-of-the-art overview on CHIKV cell entry and to provide an outlook on potential new avenues in CHIKV research.

Quantification of the host response proteome after herpes simplex virus type 1 infection

Viruses employ numerous host cell metabolic functions to propagate and manage to evade the host immune system. For herpes simplex virus type 1 (HSV1), a virus that has evolved to efficiently infect humans without seriously harming the host in most cases, the virus-host interaction is specifically interesting. This interaction can be best characterized by studying the proteomic changes that occur in the host during infection. Previous studies have been successful at identifying numerous host proteins that play important roles in HSV infection; however, there is still much that we do not know. This study identifies host metabolic functions and proteins that play roles in HSV infection, using global quantitative stable isotope labeling by amino acids in cell culture (SILAC) proteomic profiling of the host cell combined with LC-MS/MS. We showed differential proteins during early, mid and late infection, using both cytosolic and nuclear fractions. We identified hundreds of differentially regulated proteins involved in fundamental cellular functions, including gene expression, DNA replication, inflammatory response, cell movement, cell death, and RNA post-transcriptional modification. Novel differentially regulated proteins in HSV infections include some previously identified in other virus systems, as well as fusion protein, involved in malignant liposarcoma (FUS) and hypoxia up-regulated 1 protein precursor (HYOU1), which have not been identified previously in any virus infection.

High throughput proteomic analysis and a comparative review identify the nuclear chaperone, Nucleophosmin among the common set of proteins modulated in Chikungunya virus infection

Global re-emergence of Chikungunya virus (CHIKV) has renewed the interest in its cellular pathogenesis. We subjected CHIKV-infected Human Embryo Kidney cells (HEK293), a widely used cell-based system for CHIKV infection studies, to a high throughput expression proteomics analysis by Liquid Chromatography–tandem mass spectrometry. A total of 1047 differentially expressed proteins were identified in infected cells, consistently in three biological replicates. Proteins involved in transcription, translation, apoptosis and stress response were the major ones among the 209 proteins that had significant up-regulation. In the set of 45 down-regulated proteins, those involved in carbohydrate and lipid metabolism predominated. A STRING network analysis revealed tight interaction of proteins within the apoptosis, stress response and protein synthesis pathways. We short-listed a common set of 30 proteins that can be implicated in cellular pathology of CHIKV infection by comparing our results and results of earlier CHIKV proteomics studies. Modulation of eight proteins selected from this set was re-confirmed at transcript level. One among them, Nucleophosmin, a nuclear chaperone, showed temporal modulation and cytoplasmic aggregation upon CHIKV infection in double immunofluorescence staining and confocal microscopy. The short-listed cellular proteins will be potential candidates for targeted study of the molecular interactions of CHIKV with host cells.

Biological significance

Chikungunya remained as a neglected tropical disease till its re-emergence in 2005 in the La RéUnion islands and subsequently, in India and many parts of South East Asia. These and the epidemics that followed in subsequent years ran an explosive course leading to extreme morbidity and attributed mortality to this originally benign virus infection. Apart from classical symptoms of acute fever and debilitating polyarthralgia lasting for several weeks, a number of complications were documented. These included aphthous-like ulcers and vesiculo-bullous eruptions on the skin, hepatic involvement, central nervous system complications such as encephalopathy and encephalitis, and transplacental transmission. The disease has recently spread to the Americas with its initial documentation in the Caribbean islands. The Asian genotype of this positive-stranded RNA virus of the Alphavirus genus has been attributed in these outbreaks. However, the disease ran a similar course as the one caused by the East, Central and South African (ECSA) genotype in the other parts of the world. Studies have documented a number of mutations in the re-emerging strains of the virus that enhances mosquito adaptability and modulates virus infectivity. This might support the occurrence of fiery outbreaks in the absence of herd immunity in affected population. Several research groups work to understand the pathogenesis of chikungunya and the mechanisms of complications using cellular and animal models. A few proteomics approaches have been employed earlier to understand the protein level changes in the infected cells. Our present study, which couples a high throughput proteomic analysis and a comparative review of these earlier studies, identifies a few critical molecules as hypothetical candidates that might be important in this infection and for future study.

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High throughput expression proteomics analysis in HEK293 cells

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Identified four major cellular pathways affected in Chikungunya virus infection

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Short-listed 30 key proteins modulated by a comparative review

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Confirmed modulation of Nucleophosmin and other selected proteins upon infection

Proteomics profiling of chikungunya-infected Aedes albopictus C6/36 cells reveal important mosquito cell factors in virus replication

Chikungunya virus (CHIKV) is the only causative agent of CHIKV fever with persistent arthralgia, and in some cases may lead to neurological complications which can be highly fatal, therefore it poses severe health issues in many parts of the world. CHIKV transmission can be mediated via the Aedes albopictus mosquito; however, very little is currently known about the involvement of mosquito cellular factors during CHIKV-infection within the mosquito cells. Unravelling the neglected aspects of mosquito proteome changes in CHIKV-infected mosquito cells may increase our understanding on the differences in the host factors between arthropod and mammalian cells for successful replication of CHIKV. In this study, the CHIKV-infected C6/36 cells with differential cellular proteins expression were profiled using two-dimensional gel electrophoresis (2DE) coupled with the use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). 2DE analysis on CHIKV-infected C6/36 cells has shown 23 mosquito cellular proteins that are differentially regulated, and which are involved diverse biological pathways, such as protein folding and metabolic processes. Among those identified mosquito proteins, spermatogenesis-associated factor, enolase phosphatase e-1 and chaperonin-60kD have been found to regulate CHIKV infection. Furthermore, siRNA-mediated gene knockdown of these proteins has demonstrated the biological importance of these host proteins that mediate CHIKV infection. These findings have provided an insight to the importance of mosquito host factors in the replication of CHIKV, thus providing a potential channel for developing novel antiviral strategies against CHIKV transmission.

Chikungunya virus (CHIKV), a re-emerging mosquito-borne virus, is the main cause of CHIKV fever, persistent arthralgia and serious neurological complications which can be highly fatal; therefore, it poses serious health threats worldwide. Unraveling the underappreciated aspects of mosquito cellular factors that contribute to the replication processes of CHIKV was performed using two-dimensional gel electrophoresis (2DE) coupled with the use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The 2DE proteomics profiling of CHIKV-infected mosquito C6/36 cells has revealed twenty-three proteins that were differentially regulated upon CHIKV infection. These proteins are shown to be involved in diverse biological pathways and cellular processes. Notably, upon selected genes knockdown, spermatogenesis-associated factor, enolase phosphatase e-1 and chaperonin-60kD are found to be important during the replication processes of CHIKV. This study illustrates the importance of mosquito cellular factors in association with CHIKV infection in mosquito cells and reveals an interesting portal for developing novel antiviral strategies in CHIKV studies.