Therapeutics and vaccines against chikungunya virus

Unveiling Actin Cytoskeleton Role in Mediating Chikungunya-Associated Arthritis: An Integrative Proteome-Metabolome Study

Background: Chikungunya is a zoonotic disease caused by the Chikungunya virus (CHIKV), primarily transmitted to humans through infected Aedes mosquitoes. The infection is characterized by symptoms such as high fever, musculoskeletal pain, polyarthritis, and a rash, which can lead to severe complications such as encephalitis, meningitis, and even fatalities. While many disease manifestations resemble those of other viral infections, chronic arthritis caused by CHIKV is unique, and its molecular mechanisms remain ill-defined. Materials and Methods: Proteomics data from both cellular and patient levels of CHIKV infection were curated from PubMed and screened using inclusion and exclusion criteria. Patient serum proteomics data obtained from PRIDE underwent reanalysis using Proteome Discoverer 2.2. Enrichment and protein-protein interaction network analysis were conducted on differentially expressed proteins from both serum and cellular datasets. Metabolite data from CHIKV-infected patients were further retrieved, and their protein binding partners were identified using BindingDB. The protein-metabolite interaction pathway was further developed using MetaboAnalyst. Results: The proteomics data analysis revealed differential expression of proteins involved in critical host mechanisms, such as cholesterol metabolism and mRNA splicing, during CHIKV infection. Consistent upregulation of two actin cytoskeleton proteins, TAGLN2 and PFN1, was noted in both serum and cellular datasets, and their upregulations are associated with arthritis. Furthermore, alterations in purine metabolism were observed in the integrative proteome-metabolome analysis, correlating with cytoskeletal remodelling. Conclusion: Collectively, this integrative view sheds light on the involvement of actin cytoskeleton remodeling proteins and purine metabolic pathways in the development of arthritis during CHIKV infection.

Dual pattern recognition receptor ligands CL401, CL413, and CL429 as adjuvants for inactivated chikungunya virus

Chikungunya virus (CHIKV) is responsible for incapacitating joint pains and is a significant health hazard in many countries. Though a definite need for a CHIKV vaccine is felt, long disappearance of CHIKV from circulation in humans has been a concern for vaccine development. Use of two separate pattern recognition receptor ligands has been shown to enhance immune response to the administered antigen. In addition, intradermal delivery of vaccine tends to mimic the natural mode of CHIKV infection. Therefore, in this study, we explored whether intradermal and intramuscular immunization with inactivated CHIKV (I-CHIKV) supplemented with dual pattern-recognition receptor ligands, CL401, CL413, and CL429, is an effective approach to enhancing antibody response to CHIKV. Our in vivo data show that I-CHIKV supplemented with these chimeric PRR ligands induces enhanced neutralizing antibody response after intradermal delivery, but is less efficient after intramuscular immunization. These results suggest that intradermal delivery of I-CHIKV with chimeric adjuvants is a possible way to elicited a better antibody response.

Evaluation of monophosphoryl lipid A as an adjuvanted for inactivated chikungunya virus

Currently there is no clinically approved chikungunya virus (CHIKV) vaccine for immunization. Though definite need is felt, long disappearance of CHIKV has been a concern. Inactivated CHIKV (I-CHIKV) is an attractive antigen to develop effective vaccines within a short period of time. However, highly purified inactivated CHIKV do not contain necessary triggers for induction of robust antibody response. Monophosphoryl lipid A (MPLA) is a TLR4 ligand which is expressed on immune cells and is known to enhance immune response. Additionally, route of delivery also plays a critical role in modulating the immune response. Thus, antigen, adjuvant and route of delivery might modulate immune response if combined. Therefore in this study, we explored the immunogenicity of inactivated CHIKV-MPLA combination in mice after administration by intradermal or intramuscular route. Long term immune response study was also conducted by varying the antigen concentration and keeping the adjuvant concentration constant. Our study showed that the CHIKV-MPLA combination induced higher binding antibodies as well as neutralizing antibody titers as compared to unadjuvanted CHIKV. No difference in antibody titers was observed after delivery by either of the routes. However, difference in IFNγ and IL4 profiles was observed when a supernatant from stimulated splenocytes was analyzed. Taken together, these data show that both routes could be used for administration of the I-CHIKV-MPLA combination.

Effectiveness of CHIKV vaccine VLA1553 demonstrated by passive transfer of human sera

Chikungunya virus (CHIKV) is a reemerging mosquito-borne alphavirus responsible for numerous outbreaks. Chikungunya can cause debilitating acute and chronic disease. Thus, the development of a safe and effective CHIKV vaccine is an urgent global health priority. This study evaluated the effectiveness of the live-attenuated CHIKV vaccine VLA1553 against WT CHIKV infection by using passive transfer of sera from vaccinated volunteers to nonhuman primates (NHP) subsequently exposed to WT CHIKV and established a serological surrogate of protection. We demonstrated that human VLA1553 sera transferred to NHPs conferred complete protection from CHIKV viremia and fever after challenge with homologous WT CHIKV. In addition, serum transfer protected animals from other CHIKV-associated clinical symptoms and from CHIKV persistence in tissue. Based on this passive transfer study, a 50% micro–plaque reduction neutralization test titer of ≥ 150 was determined as a surrogate of protection, which was supported by analysis of samples from a seroepidemiological study. In conclusion, considering the unfeasibility of an efficacy trial due to the unpredictability and explosive, rapidly moving nature of chikungunya outbreaks, the definition of a surrogate of protection for VLA1553 is an important step toward vaccine licensure to reduce the medical burden caused by chikungunya.

Interferon Alpha, but Not Interferon Beta, Acts Early To Control Chronic Chikungunya Virus Pathogenesis

Chikungunya virus (CHIKV) is an arthritogenic alphavirus that causes both debilitating acute and chronic disease. Previous work has shown that type I interferons (IFNs) play a critical role in limiting CHIKV pathogenesis and that interferon alpha (IFN-α) and interferon beta (IFN-β) control acute CHIKV infection by distinct mechanisms. However, the role of type I IFNs, especially specific subtypes, during chronic CHIKV disease is unclear. To address this gap in knowledge, we evaluated chronic CHIKV pathogenesis in mice lacking IFN-α or IFN-β. We found that IFN-α was the dominant subtype that controls chronic disease. Despite detecting a varying type I IFN response throughout the course of disease, IFN-α acts within the first few days of infection to control the levels of persistent CHIKV RNA. In addition, using a novel CHIKV-3'-Cre tdTomato reporter system that fate maps CHIKV-infected cells, we showed that IFN-α limits the number of cells that survive CHIKV at sites of dissemination, particularly dermal fibroblasts and immune cells. Though myofibers play a significant role in CHIKV disease, they were not impacted by the loss of IFN-α. Our studies highlight that IFN-α and IFN-β play divergent roles during chronic CHIKV disease through events that occur early in infection and that not all cell types are equally dependent on type I IFNs for restricting viral persistence. IMPORTANCE Chikungunya virus (CHIKV) is a reemerging global pathogen with no effective vaccine or antiviral treatment for acute or chronic disease, and the mechanisms underlying chronic disease manifestations remain poorly defined. The significance of our research is in defining IFN-α, but not IFN-β, as an important host regulator of chronic CHIKV pathogenesis that acts within the first 48 hours of infection to limit persistent viral RNA and the number of cells that survive CHIKV infection 1 month post-infection. Loss of IFN-α had a greater impact on immune cells and dermal fibroblasts than myofibers, highlighting the need to delineate cell-specific responses to type I IFNs. Altogether, our work demonstrates that very early events of acute CHIKV infection influence chronic disease. Continued efforts to delineate early host-pathogen interactions may help stratify patients who are at risk for developing chronic CHIKV symptoms and identify therapeutics that may prevent progression to chronic disease altogether.

Macrodomain Binding Compound MRS 2578 Inhibits Alphavirus Replication

Alphaviruses are positive-strand RNA viruses causing febrile disease. Macrodomain-containing proteins, involved in ADP-ribose-mediated signaling, are encoded by both host cells and several virus groups, including alphaviruses. In this study, compound MRS 2578 that targets the human ADP-ribose glycohydrolase MacroD1 inhibited Semliki Forest virus production as well as viral RNA replication and replicase protein expression. The inhibitor was similarly active in alphavirus trans-replication systems, indicating that it targets the viral RNA replication stage.

Semliki Forest Virus Chimeras with Functional Replicase Modules from Related Alphaviruses Survive by Adaptive Mutations in Functionally Important Hot Spots

Alphaviruses (family Togaviridae) include both human pathogens such as chikungunya virus (CHIKV) and Sindbis virus (SINV) and model viruses such as Semliki Forest virus (SFV). The alphavirus positive-strand RNA genome is translated into nonstructural (ns) polyprotein(s) that are precursors for four nonstructural proteins (nsPs). The three-dimensional structures of nsP2 and the N-terminal 2/3 of nsP3 reveal that these proteins consist of several domains. Cleavage of the ns-polyprotein is performed by the strictly regulated protease activity of the nsP2 region. Processing results in the formation of a replicase complex that can be considered a network of functional modules. These modules work cooperatively and should perform the same task for each alphavirus. To investigate functional interactions between replicase components, we generated chimeras using the SFV genome as a backbone. The functional modules corresponding to different parts of nsP2 and nsP3 were swapped with their counterparts from CHIKV and SINV. Although some chimeras were nonfunctional, viruses harboring the CHIKV N-terminal domain of nsP2 or any domain of nsP3 were viable. Viruses harboring the protease part of nsP2, the full-length nsP2 of CHIKV, or the nsP3 macrodomain of SINV required adaptive mutations for functionality. Seven mutations that considerably improved the infectivity of the corresponding chimeric genomes affected functionally important hot spots recurrently highlighted in previous alphavirus studies. These data indicate that alphaviruses utilize a rather limited set of strategies to survive and adapt. Furthermore, functional analysis revealed that the disturbance of processing was the main defect resulting from chimeric alterations within the ns-polyprotein. IMPORTANCE Alphaviruses cause debilitating symptoms and have caused massive outbreaks. There are currently no approved antivirals or vaccines for treating these infections. Understanding the functions of alphavirus replicase proteins (nsPs) provides valuable information for both antiviral drug and vaccine development. The nsPs of all alphaviruses consist of similar functional modules; however, to what extent these are independent in functionality and thus interchangeable among homologous viruses is largely unknown. Homologous domain swapping was used to study the functioning of modules from nsP2 and nsP3 of other alphaviruses in the context of Semliki Forest virus. Most of the introduced substitutions resulted in defects in the processing of replicase precursors that were typically compensated by adaptive mutations that mapped to determinants of polyprotein processing. Understanding the principles of virus survival strategies and identifying hot spot mutations that permit virus adaptation highlight a route to the rapid development of attenuated viruses as potential live vaccine candidates.

1,3-Thiazolbenzamide Derivatives as Chikungunya Virus nsP2 Protease Inhibitors

Chikungunya fever results from an infection with Chikungunya virus (CHIKV, genus Alphavirus) that is prevalent in tropical regions and is spreading fast to temperate climates with documented outbreaks in Europe and the Americas. Currently, there are no available vaccines or antiviral drugs for prevention or treatment of Chikungunya fever. The nonstructural proteins (nsPs) of CHIKV responsible for virus replication are promising targets for the development of new antivirals. This study was attempted to find out new potential inhibitors of CHIKV nsP2 protease using the ligand-based drug design. Two compounds 10 and 10c, identified by molecular docking, showed antiviral activity against CHIKV with IC₅₀ of 13.1 and 8.3 μM, respectively. Both compounds demonstrated the ability to inhibit the activity of nsP2 in a cell-free assay, and the impact of compound 10 on virus replication was confirmed by western blot. The molecular dynamics study of the interactions of compounds 10 and 10c with CHIKV nsP2 showed that a possible mechanism of action of these compounds is the blocking of the active site and the catalytic dyad of nsP2.

Seroreactivity to Chikungunya and West Nile Viruses in Rwandan Blood Donors

Introduction: Chikungunya virus (CHIKV) and West Nile virus (WNV) have previously been reported from several African countries, including those bordering Rwanda where they may have originated. However, there have been no serosurveillance reports from Rwanda regarding these two viral pathogens. In this article, we present the first study of immunoglobulin G (IgG) seroreactivity of CHIKV and WNV in Rwandan blood donor samples. Methods: Blood donors from Rwanda (n = 874) and Sweden (n = 199) were tested for IgG reactivity against CHIKV, using an in-house enzyme-linked immunosorbent assay with the E1 envelope protein fused with p62 as antigen, and against WNV using a commercial kit. Data on mosquito distribution were obtained from the 2012 assessment of yellow fever virus circulation in Rwanda. Results: Seroreactivity to CHIKV was high in Rwanda (63.0%), when compared with Swedish donors, where only 8.5% were IgG positive. However, a cross-reactivity to O'nyong'nyong virus in neutralization test was noted in Rwandan donors. No significant difference in WNV seroreactivity was found (10.4% for Rwandan and 14.1% for Swedish donors). The relatively high seroreactivity to WNV among Swedish donors could partly be explained by cross-reactivity with tick-borne encephalitis virus prevalent in Sweden. Donors from the Eastern Province of Rwanda had the highest IgG reactivity to the two investigated viruses (86.7% for CHIKV and 33.3% for WNV). Five genera of mosquitoes were found in Rwanda where Culex was the most common (82.5%). The vector of CHIKV, Aedes, accounted for 9.6% of mosquitoes and this species was most commonly found in the Eastern Province. Conclusions: Our results showed high seroreactivity to CHIKV in Rwandan donors. The highest IgG reactivity to CHIKV, and to WNV, was found in the Eastern Province, the area reporting the highest number of mosquito vectors for these two viruses. Infection control by eliminating mosquito-breeding sites in population-dense areas is recommended, especially in eastern Rwanda.

Chikungunya as a paradigm for emerging viral diseases: Evaluating disease impact and hurdles to vaccine development

Chikungunya fever (CHIKF) is an emerging infectious disease caused by an alphavirus transmitted by Aedes spp. mosquitoes. Because mosquito control programs are not highly efficient for outbreak containment, vaccines are essential to reduce the burden of disease. Although no licensed vaccine against CHIKF is yet available, many highly promising candidates are undergoing preclinical studies, and a few of them have been tested in human trials of phase 1 or 2. Here, we review recent findings regarding the need for a CHIKF vaccine and provide an update on vaccines nearing or having entered clinical trials. We also address needs to tackle bottlenecks to vaccine development—including scientific and financial barriers—and to accelerate the development of vaccines; several actions should be taken: (i) design efficacy trials to be conducted during the course of outbreaks; (ii) evaluate the opportunity for adopting the “animal rule”for demonstration of efficacy for regulatory purposes; (iii) strengthen the collective commitment of nations, international organizations, potential donors and industry; (iv) stimulate public and/or private partnerships to invest in vaccine development and licensure; and (v) identify potential markets for an effective and safe CHIKF vaccine.

Broad-spectrum monoclonal antibodies against chikungunya virus structural proteins: Promising candidates for antibody-based rapid diagnostic test development

In response to the aggressive global spread of the mosquito-borne chikungunya virus (CHIKV), an accurate and accessible diagnostic tool is of high importance. CHIKV, an arthritogenic alphavirus, comprises three genotypes: East/Central/South African (ECSA), West African (WA), and Asian. A previous rapid immunochromatographic (IC) test detecting CHIKV E1 protein showed promising performance for detection of the ECSA genotype. Unfortunately, this kit exhibited lower capacity for detection of the Asian genotype, currently in circulation in the Americas, reflecting the low avidity of one of the monoclonal antibodies (mAbs) in this IC kit for the E1 protein of the Asian-genotype because of a variant amino acid sequence. To address this shortcoming, we set out to generate a new panel of broad-spectrum mouse anti-CHIKV mAbs using hybridoma technology. We report here the successful generation of mouse anti-CHIKV mAbs targeting CHIKV E1 and capsid proteins. These mAbs possessed broad reactivity to all three CHIKV genotypes, while most of the mAbs lacked cross-reactivity towards Sindbis, dengue, and Zika viruses. Two of the mAbs also lacked cross-reactivity towards other alphaviruses, including O'nyong-nyong, Ross River, Mayaro, Western Equine Encephalitis, Eastern Equine Encephalitis, and Venezuelan Equine Encephalitis viruses. In addition, another two mAbs cross-reacted weakly only with most closely related O'nyong-nyong virus. Effective diagnosis is one of the keys to disease control but to date, no antibody-based rapid IC platform for CHIKV is commercially available. Thus, the application of the mAbs characterized here in the rapid diagnostic IC kit for CHIKV detection is expected to be of great value for clinical diagnosis and surveillance purposes.

Selection and characterization of protective anti-chikungunya virus single domain antibodies

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that causes an arthralgia febrile illness that has affected millions of people on three continents. Previously, neutralizing monoclonal antibodies that have prophylactic and therapeutic activity were found to remove virus in joint tissues, thereby reducing the severity of symptoms in mice and non-human primates. In this study, we sought to develop thermostable small recombinant antibodies against CHIKV for future diagnostic, prophylactic and therapeutic applications. To develop these single domain antibodies (sdAb) a CHIKV immune library was constructed by displaying the consortium of variable heavy domains (VHH) amplified from peripheral white blood cells isolated from llamas immunized with CHIKV virus-like particles (VLPs). Five anti-CHIKV sdAb isolated using bio-panning were evaluated for their affinity and thermal stability. Their ability to detect CHIKV VLPs was demonstrated in both MagPlex- and ELISA- based assays. Finally, the ability of two sdAb, CC3 and CA6, to inhibit CHIKV infection were tested using a plaque reduction and neutralization test (PRNT), yielding PRNT₅₀ values of 0.6 and 45.6 nM, respectively.

Recent development in the strategies projected for chikungunya vaccine in humans

The unprecedented epidemic spread of chikungunya worldwide illustrates the critical need for potent vaccines and therapeutic interventions. The morbidity and mortality associated with this arboviral infection has become a major public health problem in many countries across different continents. Increasing public–private partnerships have opened new avenues in research and development of vaccines. This review mainly focuses on the recent advances in patented approaches for chikungunya vaccine development and the forthcoming challenges.

Defining a correlate of protection for chikungunya virus vaccines

Chikungunya virus infection causes a debilitating febrile illness that in many affected individuals is associated with long-term sequelae that can persist for months or years. Over the past decade a large number of candidate vaccines have been developed, several of which have now entered clinical trials. The rapid and sporadic nature of chikungunya outbreaks poses challenges for planning of large clinical efficacy trials suggesting that licensure of chikungunya vaccines may utilize non-traditional approval pathways based on identification of immunological endpoint(s) predictive of clinical benefit. This report reviews the current status of nonclinical and clinical testing and potential challenges for defining a suitable surrogate or correlate of protection.

A Chikungunya Virus trans-Replicase System Reveals the Importance of Delayed Nonstructural Polyprotein Processing for Efficient Replication Complex Formation in Mosquito Cells

Chikungunya virus (CHIKV) is a medically important alphavirus that is transmitted by Aedes aegypti and Aedes albopictus mosquitoes. The viral replicase complex consists of four nonstructural proteins (nsPs) expressed as a polyprotein precursor and encompasses all enzymatic activities required for viral RNA replication. nsPs interact with host components of which most are still poorly understood, especially in mosquitos. A CHIKV trans-replicase system that allows the uncoupling of RNA replication and nsP expression was adapted to mosquito cells and subsequently used for analysis of universal and host-specific effects of 17 different nonstructural polyprotein (ns-polyprotein) mutations. It was found that mutations blocking nsP enzymatic activities as well as insertions of enhanced green fluorescent protein (EGFP) into different nsPs had similar effects on trans-replicase activity regardless of the host (i.e., mammalian or mosquito). Mutations that slow down or accelerate ns-polyprotein processing generally had no effect or reduced trans-replicase activity in mammalian cells, while in mosquito cells most of them increased trans-replicase activity prominently. Increased RNA replication in mosquito cells was counteracted by an antiviral RNA interference (RNAi) response. Substitution of the W258 residue in the membrane binding peptide of nsP1 resulted in a temperature-sensitive defect, in the context of both the trans-replicase and infectious CHIKV. The defect was compensated for by secondary mutations selected during passaging of mutant CHIKV. These findings demonstrate the value of alphavirus trans-replicase systems for studies of viral RNA replication and virus-host interactions.IMPORTANCE Chikungunya virus is an important mosquito-transmitted human pathogen. This virus actively replicates in mosquitoes, but the underlying molecular mechanisms and interactions of viral and host components are poorly understood. This is partly due to the lack of reliable systems for functional analysis of viral nonstructural polyproteins (ns-polyproteins) and nonstructural proteins (nsPs) in mosquito cells. Adaption of a CHIKV trans-replicase system allowed study of the effects of mutations in the ns-polyprotein on RNA replication in cells derived from mammalian and mosquito hosts. We found that a slowdown of ns-polyprotein processing facilitates replication complex formation and/or functioning in mosquito cells and that this process is antagonized by the natural RNAi defense system present in mosquito cells. The mosquito-adapted CHIKV trans-replicase system represents a valuable tool to study alphavirus-mosquito interactions at the molecular level and to develop advanced antiviral strategies.

Areas with High Hazard Potential for Autochthonous Transmission of Aedes albopictus-Associated Arboviruses in Germany

The intensity and extent of transmission of arboviruses such as dengue, chikungunya, and Zika virus have increased markedly over the last decades. Autochthonous transmission of dengue and chikungunya by Aedes albopictus has been recorded in Southern Europe where the invasive mosquito was already established and viraemic travelers had imported the virus. Ae. albopictus populations are spreading northward into Germany. Here, we model the current and future climatically suitable regions for Ae. albopictus establishment in Germany, using climate data of spatially high resolution. To highlight areas where vectors and viraemic travellers are most likely to come into contact, reported dengue and chikungunya incidences are integrated at the county level. German cities with the highest likelihood of autochthonous transmission of Aedes albopictus-borne arboviruses are currently located in the western parts of the country: Freiburg im Breisgau, Speyer, and Karlsruhe, affecting about 0.5 million people. In addition, 8.8 million people live in regions considered to show elevated hazard potential assuming further spread of the mosquito: Baden-Württemberg (Upper Rhine, Lake Constance regions), southern parts of Hesse, and North Rhine-Westphalia (Lower Rhine). Overall, a more targeted and thus cost-efficient implementation of vector control measures and health surveillance will be supported by the detailed maps provided here.

Paradoxical Effect of Chloroquine Treatment in Enhancing Chikungunya Virus Infection

Since 2005, Chikungunya virus (CHIKV) re-emerged and caused numerous outbreaks in the world, and finally, was introduced into the Americas in 2013. The lack of CHIKV-specific therapies has led to the use of non-specific drugs. Chloroquine, which is commonly used to treat febrile illnesses in the tropics, has been shown to inhibit CHIKV replication in vitro. To assess the in vivo effect of chloroquine, two complementary studies were performed: (i) a prophylactic study in a non-human primate model (NHP); and (ii) a curative study "CuraChik", which was performed during the Reunion Island outbreak in 2006 in a human cohort. Clinical, biological, and immunological data were compared between treated and placebo groups. Acute CHIKV infection was exacerbated in NHPs treated with prophylactic administration of chloroquine. These NHPs displayed a higher viremia and slower viral clearance (p < 0.003). Magnitude of viremia was correlated to the type I IFN response (Rho = 0.8, p < 0.001) and severe lymphopenia (Rho = 0.8, p < 0.0001), while treatment led to a delay in both CHIKV-specific cellular and IgM responses (p < 0.02 and p = 0.04, respectively). In humans, chloroquine treatment did not affect viremia or clinical parameters during the acute stage of the disease (D1 to D14), but affected the levels of C-reactive Protein (CRP), IFNα, IL-6, and MCP1 over time (D1 to D16). Importantly, no positive effect could be detected on prevalence of persistent arthralgia at Day 300. Although inhibitory in vitro, chloroquine as a prophylactic treatment in NHPs enhances CHIKV replication and delays cellular and humoral response. In patients, curative chloroquine treatment during the acute phase decreases the levels of key cytokines, and thus may delay adaptive immune responses, as observed in NHPs, without any suppressive effect on peripheral viral load.

Chikungunya vaccines in development

Chikungunya virus has become a global health threat, spreading to the industrial world of Europe and the Americas; no treatment or prophylactic vaccine is available. Since the late 1960s much effort has been put into the development of a vaccine, and several heterogeneous strategies have already been explored. Only two candidates have recently qualified to enter clinical phase II trials, a chikungunya virus-like particle-based vaccine and a recombinant live attenuated measles virus-vectored vaccine.

This review focuses on the current status of vaccine development against chikungunya virus in humans and discusses the diversity of immunization strategies, results of recent human trials and promising vaccine candidates.

Antiviral treatment efficiently inhibits chikungunya virus infection in the joints of mice during the acute but not during the chronic phase of the infection

Favipiravir (T-705) is a broad spectrum antiviral which has been approved in Japan for the treatment of severe influenza virus infections. We reported earlier that favipiravir inhibits the in vitro replication of CHIKV and protects against disease progression in CHIKV-infected immunodeficient mice. We here explored whether favipiravir is also able to inhibit CHIKV replication in the joints of mice either when treatment is initiated during the acute or during the chronic phase of the infection. To this end, C57BL/6J mice were infected with CHIKV in the left hind footpad and treatment with favipiravir (300 mg/kg/day, orally) was either given from day 0 to day 3 post-infection (p.i.) or from day 49 to day 55 p.i. In the untreated mice, viral RNA was still detectable in the joints up to 98 days p.i., yet no infectious viral particles were observed in these tissues. The 4 days treatment during the acute phase of the infection resulted in complete inhibition of systemic viral spread. As a consequence, no viral RNA was detected in the non-inoculated feet in contrast to the situation in the untreated control mice. When treatment was initiated at day 49 p.i., no significant reduction in viral RNA levels in joints were noted as compared to the untreated control. Interestingly, when attempting to amplify by RT-PCR material corresponding to virus genome from the chronic phase samples, some parts of the genome, such as the viral polymerase gene could not be amplified. Collectively, these results suggest that the viral RNA detected in the joints during the chronic phase is likely defective, which also explains the lack of effect of a viral replication inhibitor.

Regulatory considerations in development of vaccines to prevent disease caused by Chikungunya virus

Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus. Chikungunya disease (CHIK) in humans is characterized by sudden onset of high fever, cutaneous rash, myalgia and debilitating polyarthralgia. Until recently the virus was considered endemic to only Africa and Asia, but since 2004 CHIK has spread to previously non-endemic regions, including Europe and the Americas, thereby emerging as a global health threat. Although a variety of CHIKV vaccine candidates have been tested in animals, and a few have advanced to human clinical trials, no licensed vaccine is currently available for prevention of disease. In this article, we review recent efforts in CHIKV vaccine development and discuss regulatory considerations for CHIKV vaccine licensure under U.S. FDA regulations. Several licensure pathways are available, and the most appropriate licensure pathway for a CHIK vaccine will depend on the type of evidence that can be generated to demonstrate the vaccine's effectiveness. If "traditional approval" following demonstration of direct benefit in adequate and well-controlled clinical disease endpoint studies is not possible, the Accelerated Approval and Animal Rule pathways are potential alternatives. In terms of vaccine safety, the potential for vaccine associated arthralgia and antibody-dependent enhancement of infectivity and disease severity are important issues that should be addressed in both pre-clinical and clinical studies. CHIK vaccine developers are encouraged to communicate with the FDA during all stages of vaccine development.

Immunopathology of Chikungunya Virus Infection: Lessons Learned from Patients and Animal Models

Chikungunya virus (CHIKV) is an arthropod-borne alphavirus that causes acute and chronic arthritis. The virus reemerged in the Indian Ocean islands in 2005-2006 and is responsible for outbreaks in the Caribbean islands and the Americas since late 2013. Despite the wealth of research over the past 10 years, there are no commercially available antiviral drugs or vaccines. Treatment usually involves analgesics, anti-inflammatory drugs, and supportive care. Most studies have been focused on understanding the pathogenesis of CHIKV infection through clinical observation and with animal models. In this review, the clinical manifestations of CHIKV that define the disease and the use of relevant animal models, from mice to nonhuman primates, are discussed. Understanding key cellular factors in CHIKV infection and the interplay with the immune system will aid in the development of preventive and therapeutic approaches to combat this painful viral disease in humans.

Antiviral activity of [1,2,3]triazolo[4,5-d]pyrimidin-7(6H)-ones against chikungunya virus targeting the viral capping nsP1

Chikungunya virus (CHIKV) is a re-emerging alphavirus transmitted to humans by Aedes mosquitoes. Since 2005, CHIKV has been spreading worldwide resulting in epidemics in Africa, the Indian Ocean islands, Asia and more recently in the Americas. CHIKV is thus considered as a global health concern. There is no specific vaccine or drug available for the treatment of this incapacitating viral infection. We previously identified 3-aryl-[1,2,3]triazolo[4,5-d]pyrimidin-7(6H)-ones as selective inhibitors of CHIKV replication and proposed the viral capping enzyme nsP1 as a target. This work describes the synthesis of novel series of related compounds carrying at the aryl moiety a methylketone and related oximes combined with an ethyl or an ethyl-mimic at 5-position of the triazolopyrimidinone. These compounds have shown antiviral activity against different CHIKV isolates in the very low μM range based on both virus yield reduction and virus-induced cell-killing inhibition assays. Moreover, these antivirals inhibit the in vitro guanylylation of alphavirus nsP1, as determined by Western blot using an anti-cap antibody. Thus, the data obtained seem to indicate that the anti-CHIKV activity might be related to the inhibition of this crucial step in the viral RNA capping machinery.

How Chikungunya Virus Virology Affects Its Epidemiology and Transmission: Implications for Influencing Public Health

Chikungunya virus has been causing a series of ongoing epidemics around the globe for the past 12 years. During that time, estimates indicate that >4 million cases occurred worldwide. Despite the magnitude of these outbreaks and the broad interest in understanding the virus and disease, significant gaps still exist in our knowledge base. An in-depth understanding of the basic virological elements that can affect the epidemiology of the agent is critical for future development of control and treatment products. This work describes how knowledge of various viral genetic and structural elements has begun to advance the development of vaccines and therapeutics and suggests that further knowledge is needed to provide additional options.

Monoclonal Antibodies as Prophylactic and Therapeutic Agents Against Chikungunya Virus

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that is responsible for considerable epidemics worldwide and recently emerged in the Americas in 2013. CHIKV may cause long-lasting arthralgia after acute infection. With currently no licensed vaccines or antivirals, the design of effective therapies to prevent or treat CHIKV infection is of utmost importance and will be facilitated by increased understanding of the dynamics of chikungunya. In this article, monoclonal antibodies against CHIKV as viable prophylactic and therapeutic agents will be discussed.

Attenuated and vectored vaccines protect nonhuman primates against Chikungunya virus

Chikungunya virus (CHIKV) is rapidly spreading across the globe, and millions are infected. Morbidity due to this virus is a serious threat to public health, but at present, there is no vaccine against this debilitating disease. We have recently developed a number of vaccine candidates, and here we have evaluated 3 of them in a nonhuman primate model. A single immunization with an attenuated strain of CHIKV (Δ5nsP3), a homologous prime-boost immunization with a DNA-launched RNA replicon encoding CHIKV envelope proteins (DREP-E), and a DREP-E prime followed by a recombinant modified vaccinia virus Ankara encoding CHIKV capsid and envelope (MVA-CE) boost all induced protection against WT CHIKV infection. The attenuated Δ5nsP3 virus proved to be safe and did not show any clinical signs typically associated with WT CHIKV infections such as fever, skin rash, lymphopenia, or joint swelling. These vaccines are based on an East/Central/South African strain of Indian Ocean lineage, but they also generated neutralizing antibodies against an isolate of the Asian genotype that now is rapidly spreading across the Americas. These results form the basis for clinical development of an efficacious CHIKV vaccine that generates both humoral and cellular immunity with long-term immunological memory.

Obatoclax Inhibits Alphavirus Membrane Fusion by Neutralizing the Acidic Environment of Endocytic Compartments

As new pathogenic viruses continue to emerge, it is paramount to have intervention strategies that target a common denominator in these pathogens. The fusion of viral and cellular membranes during viral entry is one such process that is used by many pathogenic viruses, including chikungunya virus, West Nile virus, and influenza virus. Obatoclax, a small-molecule antagonist of the Bcl-2 family of proteins, was previously determined to have activity against influenza A virus and also Sindbis virus. Here, we report it to be active against alphaviruses, like chikungunya virus (50% effective concentration [EC₅₀] = 0.03 μM) and Semliki Forest virus (SFV; EC₅₀ = 0.11 μM). Obatoclax inhibited viral entry processes in an SFV temperature-sensitive mutant entry assay. A neutral red retention assay revealed that obatoclax induces the rapid neutralization of the acidic environment of endolysosomal vesicles and thereby most likely inhibits viral fusion. Characterization of escape mutants revealed that the L369I mutation in the SFV E1 fusion protein was sufficient to confer partial resistance against obatoclax. Other inhibitors that target the Bcl-2 family of antiapoptotic proteins inhibited neither viral entry nor endolysosomal acidification, suggesting that the antiviral mechanism of obatoclax does not depend on its anticancer targets. Obatoclax inhibited the growth of flaviviruses, like Zika virus, West Nile virus, and yellow fever virus, which require low pH for fusion, but not that of pH-independent picornaviruses, like coxsackievirus A9, echovirus 6, and echovirus 7. In conclusion, obatoclax is a novel inhibitor of endosomal acidification that prevents viral fusion and that could be pursued as a potential broad-spectrum antiviral candidate.

A Review of Chikungunya Virus-induced Arthralgia: Clinical Manifestations, Therapeutics, and Pathogenesis

Background:

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that circulates predominantly in tropical and subtropical regions, potentially affecting over 1 billion people. Recently, an outbreak began in the western hemisphere and has resulted in over 1.8 million reported suspected cases. Infection often results in severe fever, rash and debilitating polyarthralgia lasting weeks to months. Additionally, the current literature reports that CHIKV can result in a severe chronic arthralgia and/or arthritis that can last months to years following the initial infection.

Objective:

The purpose of this review is to evaluate the literature and summarize the current state of knowledge regarding CHIKV-associated disease, including clinical presentation, diagnosis, risk factors for development of severe disease, treatment, and pathogenesis in human patients. Additionally, recommendations are presented regarding avenues for clinical research to help further elucidate the pathogenesis of joint disease associated with CHIKV infection.

Conclusion:

While there is an association between initial CHIKV infection and acute disease, a causal relationship with development of chronic arthralgia has not been established at this time. Potential causes of chronic CHIKV-induced arthritis have been postulated, including viral persistence, induction of autoimmune disease, and exacerbation of pre-existing joint disease. While there are numerous reports of chronic CHIKV-associated arthralgia and/or arthritis, there is currently no evidence of a definitive link between initial infection and development of chronic disease. Additional, prospective clinical research on CHIKV-associated disease is necessary to further determine the potential role of virus and development of chronic joint disease.

Design and Validation of Novel Chikungunya Virus Protease Inhibitors

Chikungunya virus (CHIKV; genus Alphavirus) is the causative agent of chikungunya fever. CHIKV replication can be inhibited by some broad-spectrum antiviral compounds; in contrast, there is very little information about compounds specifically inhibiting the enzymatic activities of CHIKV replication proteins. These proteins are translated in the form of a nonstructural (ns) P1234 polyprotein precursor from the CHIKV positive-strand RNA genome. Active forms of replicase enzymes are generated using the autoproteolytic activity of nsP2. The available three-dimensional (3D) structure of nsP2 protease has made it a target for in silico drug design; however, there is thus far little evidence that the designed compounds indeed inhibit the protease activity of nsP2 and/or suppress CHIKV replication. In this study, a set of 12 compounds, predicted to interact with the active center of nsP2 protease, was designed using target-based modeling. The majority of these compounds were shown to inhibit the ability of nsP2 to process recombinant protein and synthetic peptide substrates. Furthermore, all compounds found to be active in these cell-free assays also suppressed CHIKV replication in cell culture, the 50% effective concentration (EC₅₀) of the most potent inhibitor being ∼1.5 μM. Analysis of stereoisomers of one compound revealed that inhibition of both the nsP2 protease activity and CHIKV replication depended on the conformation of the inhibitor. Combining the data obtained from different assays also indicates that some of the analyzed compounds may suppress CHIKV replication using more than one mechanism.

Vaccines against chikungunya, Zika and other emerging Aedes mosquito-borne viruses: unblocking existing bottlenecks

The emergence of Aedes mosquito-borne viral diseases is a global public health challenge. Since mosquito control programs are not highly efficient for outbreak containment, vaccines are essential to limit disease burden. Besides yellow fever vaccines, a vaccine against dengue is now available, while research on vaccines against Zika has just started. Several vaccine candidates against chikungunya are undergoing preclinical studies, and few of them have been tested in Phase II trials. To overcome hurdles and speed-up the development of vaccines against these viral diseases, several actions should be planned: first, the ‘animal rule’ could be considered for regulatory purposes; second, public–private partnership should be stimulated; third, countries, international organizations and donors commitment should be strengthened, and potential markets identified.

The Antiviral Alkaloid Berberine Reduces Chikungunya Virus-Induced Mitogen-Activated Protein Kinase Signaling

Chikungunya virus (CHIKV) has infected millions of people in the tropical and subtropical regions since its reemergence in the last decade. We recently identified the nontoxic plant alkaloid berberine as an antiviral substance against CHIKV in a high-throughput screen. Here, we show that berberine is effective in multiple cell types against a variety of CHIKV strains, also at a high multiplicity of infection, consolidating the potential of berberine as an antiviral drug. We excluded any effect of this compound on virus entry or on the activity of the viral replicase. A human phosphokinase array revealed that CHIKV infection specifically activated the major mitogen-activated protein kinase (MAPK) signaling pathways extracellular signal-related kinase (ERK), p38 and c-Jun NH2-terminal kinase (JNK). Upon treatment with berberine, this virus-induced MAPK activation was markedly reduced. Subsequent analyses with specific inhibitors of these kinases indicated that the ERK and JNK signaling cascades are important for the generation of progeny virions. In contrast to specific MAPK inhibitors, berberine lowered virus-induced activation of all major MAPK pathways and resulted in a stronger reduction in viral titers. Further, we assessed the in vivo efficacy of berberine in a mouse model and measured a significant reduction of CHIKV-induced inflammatory disease. In summary, we demonstrate the efficacy of berberine as a drug against CHIKV and highlight the importance of the MAPK signaling pathways in the alphavirus infectious cycle.

IMPORTANCE

Chikungunya virus (CHIKV) is a mosquito-borne virus that causes severe and persistent muscle and joint pain and has recently spread to the Americas. No licensed drug exists to counter this virus. In this study, we report that the alkaloid berberine is antiviral against different CHIKV strains and in multiple human cell lines. We demonstrate that berberine collectively reduced the virus-induced activation of cellular mitogen-activated protein kinase signaling. The relevance of these signaling cascades in the viral life cycle was emphasized by specific inhibitors of these kinase pathways, which decreased the production of progeny virions. Berberine significantly reduced CHIKV-induced inflammatory disease in a mouse model, demonstrating efficacy of the drug in vivo Overall, this work makes a strong case for pursuing berberine as a potential anti-CHIKV therapeutic compound and for exploring the MAPK signaling pathways as antiviral targets against alphavirus infections.

Chikungunya Virus Infection: An Update on Joint Manifestations and Management

The advent of sophisticated diagnostics has enabled the discovery of previously unknown arthropod-borne viruses like Chikungunya. This infection has become increasingly prevalent in the last 10 years across the Indian Ocean and has been brought to media attention by a recent outbreak in the Caribbean. The outbreak has been aided by a drastic rise in air travel, allowing infected individuals to transport the virus to previously unaffected regions. In addition, a recently documented viral mutation has allowed its transmission by the Aedes albopictus mosquito, therefore facilitating outbreaks in Southern Europe and the USA. The duration and extent of the arthritis seen peri- and post infection has become a topic of academic interest. Although published data are largely observational, there has been a definite increase in original research focusing on this. Symptoms can persist for years, particularly in older patients with pre-existing medical conditions. The etiology is still not fully understood, but viral persistence and immune activation within synovial fluid have been shown in mouse models. There have been no prospective clinical trials of treatment in humans; however, animal trials are in process. The mainstay of treatment remains anti-inflammatories and steroids where necessary. The clinical presentation seems to mimic common rheumatological conditions like rheumatoid arthritis; therefore recent recommendations suggest the use disease-modifying agents as a common practice for the specific syndrome. This review uses recent published data and draws on our own clinical experience to provide an overview of joint complications of Chikungunya infection.

Advancing vector biology research: a community survey for future directions, research applications and infrastructure requirements

Vector-borne pathogens impact public health, animal production, and animal welfare. Research on arthropod vectors such as mosquitoes, ticks, sandflies, and midges which transmit pathogens to humans and economically important animals is crucial for development of new control measures that target transmission by the vector. While insecticides are an important part of this arsenal, appearance of resistance mechanisms is increasingly common. Novel tools for genetic manipulation of vectors, use of Wolbachia endosymbiotic bacteria, and other biological control mechanisms to prevent pathogen transmission have led to promising new intervention strategies, adding to strong interest in vector biology and genetics as well as vector-pathogen interactions. Vector research is therefore at a crucial juncture, and strategic decisions on future research directions and research infrastructure investment should be informed by the research community. A survey initiated by the European Horizon 2020 INFRAVEC-2 consortium set out to canvass priorities in the vector biology research community and to determine key activities that are needed for researchers to efficiently study vectors, vector-pathogen interactions, as well as access the structures and services that allow such activities to be carried out. We summarize the most important findings of the survey which in particular reflect the priorities of researchers in European countries, and which will be of use to stakeholders that include researchers, government, and research organizations.

A Virus-Like Particle Vaccine Elicits Broad Neutralizing Antibody Responses in Humans to All Chikungunya Virus Genotypes

Chikungunya virus (CHIKV) is an alphavirus that has emerged as a global health burden. There are 3 CHIKV genotypes: Asian, West African, and Eastern/Central/South African. No licensed CHIKV vaccine is available, and whether the antibody response elicited by one genotype can neutralize heterologous genotypes is unclear. We assessed neutralizing antibody (NAb) responses of volunteers in a phase 1 study of a CHIKV vaccine against 9 viral strains representing all 3 genotypes. Minimal differences in vaccine-elicited NAb responses were observed among genotypes, suggesting that vaccination with a single CHIKV strain can elicit cross-protective NAbs against all 3 genotypes.

Comparative analysis of the anti-chikungunya virus activity of novel bryostatin analogs confirms the existence of a PKC-independent mechanism

Previously, we reported that salicylate-based analogs of bryostatin protect cells from chikungunya virus (CHIKV)-induced cell death. Interestingly, 'capping' the hydroxyl group at C26 of a lead bryostatin analog, a position known to be crucial for binding to and modulation of protein kinase C (PKC), did not abrogate the anti-CHIKV activity of the scaffold, putatively indicating the involvement of a pathway independent of PKC. The work detailed in this study demonstrates that salicylate-derived analog 1 and two capped analogs (2 and 3) are not merely cytoprotective compounds, but act as selective and specific inhibitors of CHIKV replication. Further, a detailed comparative analysis of the effect of the non-capped versus the two capped analogs revealed that compound 1 acts both at early and late stages in the chikungunya virus replication cycle, while the capped analogs only interfere with a later stage process. Co-dosing with the PKC inhibitors sotrastaurin and Gö6976 counteracts the antiviral activity of compound 1 without affecting that of capped analogs 2 and 3, providing further evidence that the latter elicit their anti-CHIKV activity independently of PKC. Remarkably, treatment of CHIKV-infected cells with a combination of compound 1 and a capped analog resulted in a pronounced synergistic antiviral effect. Thus, these salicylate-based bryostatin analogs can inhibit CHIKV replication through a novel, yet still elusive, non-PKC dependent pathway.

Expression and Characterization of Yeast Derived Chikungunya Virus Like Particles (CHIK-VLPs) and Its Evaluation as a Potential Vaccine Candidate

Chikungunya virus (CHIKV) has emerged as a global health concern due to its recent spread in both old and new world. So far, no CHIKV specific drug or vaccine is licensed for human use. In this study, we report production of Chikungunya virus like particles (CHIK-VLPs) using novel yeast expression system (Pichia pastoris) and its evaluation as vaccine candidate. The gene encoding structural polyprotein of CHIKV from a recent epidemic strain was cloned into yeast expression system. The multicopy integrants were processed for expression of CHIK-VLPs. The VLPs were purified and confirmed through electron microscopic analysis for their morphological identity with CHIKV. The in vitro and in vivo evaluation of CHIK-VLPs as vaccine candidate was determined in Balb/c mice. Induction of both humoral and cellular immune response was observed with different doses of CHIK-VLPs. The humoral immune response was studied through different techniques like enzyme linked immunosorbent assay, IgG Isotyping and plaque reduction neutralization test. CHIK-VLPs were found to elicit high titer of antibodies that are able to recognize native CHIKV. Higher level of IgG2a and IgG1 subtypes was identified suggestive of balanced Th1/Th2 response. Both in vitro and in vivo neutralization activity of CHIK-VLPs antibodies was observed even with low concentration, which shows its high specificity and neutralizing activity against two different CHIKV strains. Neonatal mice receiving anti-CHIK-VLPs antibodies were protected from CHIKV challenge. Induction of cellular immune response was confirmed through higher level of TNF-α, IL-10 and substantial level of IL-2, IL-4 and IFN-γ indicating a balanced response. This is the first report, where CHIK-VLPs has been expressed by Pichia pastoris and evaluated for neutralizing activity against CHIKV. These promising results indicate the utility of CHIK-VLPs as a promising vaccine candidate against emerging CHIKV.

Chikungunya virus (CHIKV) has emerged in many parts of tropics in last decade. The absence of an approved vaccine or antiviral drug for CHIKV makes it one of the important public health challenges. Though attempt to develop a CHIKV vaccine was initiated in 1980s, however it has not succeeded so far. The Virus like particles (VLPs) are now explored as promising vaccine candidate against many viruses viz. HBV, HPV etc. In this study, we report the production of CHIK-VLPs using novel yeast expression system (Pichia pastoris) and its evaluation as vaccine candidate. These CHIK-VLPs share morphological identity to native CHIKV. The results indicate that CHIK-VLPs induced both cell mediated as well as humoral response in a balanced manner, which fulfils its criteria as a potent immunogen. Further, antibodies generated against CHIK-VLPs demonstrated efficient in vitro and in vivo neutralization activity, as evaluated through plaque reduction in Vero cells and protection in CHIKV infected neonatal mice respectively using two different CHIKV strains, which makes it a promising vaccine candidate. The yeast expressed CHIK-VLPs has high potential for development of an effective vaccine candidate against CHIKV during epidemic situations.

Ophthalmologic aspects of chikungunya infection

Chikungunya fever, a viral disease epidemic in some parts of the world is newly introduced in the Americas. This is of considerable international concern, with a growing incidence owing to developing urbanization, tourism, and trade. Ocular manifestations of chikungunya fever are not frequent, but of great relevance. Common manifestations include conjunctivitis, optic neuritis, iridocyclitis, episcleritis, retinitis and uveitis. Diagnostic and monitoring investigations would include optical coherence tomography, fundus fluorescein and indocyanine green angiography, visual field analysis, and electrophysiologic tests. There have been no prospective, randomized therapeutic trials, and it is unclear if the disease is self-limiting or if treatment is actually beneficial. Prognosis varies, ranging from full resolution to permanent vision loss despite intervention.

[Emerging viral infections and hepatotropic virus]

Environmental degradation, population movements and urban agglomerations have broken down the borders for infectious diseases. The expansion of microorganisms has entered an increasing area of transmission vectors. The lack of immunity of the population leads to an increased risk of spreading infectious diseases. Furthermore, the decline in vaccination rates in developed countries and socio-economic difficulties in large regions has meant that diseases in the process of eradication have re-emerged. That is why health care workers must be trained to avoid delaying in diagnosis and to accelerate the implementation of public health measures. A great deal of education and health prevention should fall under the responsibilities of travellers who move around different regions.

Chikungunya virus pathogenesis and immunity

Chikungunya virus (CHIKV) is an arbovirus associated with acute and chronic arthralgia that re-emerged in the Indian Ocean islands in 2005-2006 and is currently responsible for the ongoing outbreaks in the Caribbean islands and the Americas. We describe here the acute and chronic clinical manifestations of CHIKV in patients that define the disease. We also review the various animal models that have been developed to study CHIKV infection and pathology and further strengthened the understanding of the cellular and molecular mechanisms of CHIKV infection and immunity. A complete understanding of the immunopathogenesis of CHIKV infection will help develop the needed preventive and therapeutic approaches to combat this arbovirosis.

Updates on chikungunya epidemiology, clinical disease, and diagnostics

Chikungunya virus (CHIKV) is an Aedes-borne alphavirus, historically found in Africa and Asia, where it caused sporadic outbreaks. In 2004, CHIKV reemerged in East Africa and spread globally to cause epidemics, including, for the first time, autochthonous transmission in Europe, the Middle East, and Oceania. The epidemic strains were of the East/Central/South African genotype. Strains of the Asian genotype of CHIKV continued to cause outbreaks in Asia and spread to Oceania and, in 2013, to the Americas. Acute disease, mainly comprising fever, rash, and arthralgia, was previously regarded as self-limiting; however, there is growing evidence of severe but rare manifestations, such as neurological disease. Furthermore, CHIKV appears to cause a significant burden of long-term morbidity due to persistent arthralgia. Diagnostic assays have advanced greatly in recent years, although there remains a need for simple, accurate, and affordable tests for the developing countries where CHIKV is most prevalent. This review focuses on recent important work on the epidemiology, clinical disease and diagnostics of CHIKV.

Computational Approach Towards Exploring Potential Anti-Chikungunya Activity of Selected Flavonoids

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that causes chikungunya infection in humans. Despite the widespread distribution of CHIKV, no antiviral medication or vaccine is available against this virus. Therefore, it is crucial to find an effective compound to combat CHIKV. We aimed to predict the possible interactions between non-structural protein 3 (nsP) of CHIKV as one of the most important viral elements in CHIKV intracellular replication and 3 potential flavonoids using a computational approach. The 3-dimensional structure of nsP3 was retrieved from the Protein Data Bank, prepared and, using AutoDock Vina, docked with baicalin, naringenin and quercetagetin as ligands. The first-rated ligand with the strongest binding affinity towards the targeted protein was determined based on the minimum binding energy. Further analysis was conducted to identify both the active site of the protein that reacts with the tested ligands and all of the existing intermolecular bonds. Compared to the other ligands, baicalin was identified as the most potential inhibitor of viral activity by showing the best binding affinity (-9.8 kcal/mol). Baicalin can be considered a good candidate for further evaluation as a potentially efficient antiviral against CHIKV.

Molecular determinants of alphavirus neuropathogenesis in mice

Alphaviruses are enveloped viruses with a positive-stranded RNA genome, of the family Togaviridae. In mammals and birds they are mosquito-transmitted and are of veterinary and medical importance. They cause primarily two types of disease: encephalitis and polyarthritis. Here we review attempts to understand the molecular basis of encephalitis and virulence for the central nervous system (CNS) in mouse models. Sindbis virus (SINV) was the first virus to be studied in this way. Other viruses analysed are Semliki Forest virus (SFV), Venezuelan equine encephalitis virus, Eastern equine encephalitis virus and Western equine encephalitis virus. Neurovirulence was found to be associated with damage to neurons in the CNS. It mapped mainly to the E2 region of the genome, and to the nsP3 gene. Also, avirulent natural isolates of both SINV and SFV have been found to have more rapid cleavage of nonstructural proteins due to mutations in the nsP1-nsP2 cleavage site. Immune-mediated demyelination for avirulent SFV has been shown to be associated with infection of oligodendrocytes. For Chikungunya virus, an emerging alphavirus that uncommonly causes encephalitis, analysis of the molecular basis of CNS pathogenicity is beginning. Experiments on SINV and SFV have indicated that virulence may be related to the resistance of virulent virus to interferon action. Although the E2 protein may be involved in tropism for neurons and passage across the blood-brain barrier, the role of the nsP3 protein during infection of neurons is unknown. More information in these areas may help to further explain the neurovirulence of alphaviruses.

Status of research and development of vaccines for chikungunya

Chikungunya virus (CHIKV) is an arthritogenic alphavirus that during the last decade has significantly expanded its geographical range and caused large outbreaks of human disease around the world. Although mortality rates associated with CHIKV outbreaks are low, acute and chronic illnesses caused by CHIKV represent a significant burden of disease largely affecting low and middle income countries. This report summarizes the current status of vaccine development for CHIKV.

Versatile Trans-Replication Systems for Chikungunya Virus Allow Functional Analysis and Tagging of Every Replicase Protein

Chikungunya virus (CHIKV; genus Alphavirus, family Togaviridae) has recently caused several major outbreaks affecting millions of people. There are no licensed vaccines or antivirals, and the knowledge of the molecular biology of CHIKV, crucial for development of efficient antiviral strategies, remains fragmentary. CHIKV has a 12 kb positive-strand RNA genome, which is translated to yield a nonstructural (ns) or replicase polyprotein. CHIKV structural proteins are expressed from a subgenomic RNA synthesized in infected cells. Here we have developed CHIKV trans-replication systems, where replicase expression and RNA replication are uncoupled. Bacteriophage T7 RNA polymerase or cellular RNA polymerase II were used for production of mRNAs for CHIKV ns polyprotein and template RNAs, which are recognized by CHIKV replicase and encode for reporter proteins. CHIKV replicase efficiently amplified such RNA templates and synthesized large amounts of subgenomic RNA in several cell lines. This system was used to create tagged versions of ns proteins including nsP1 fused with enhanced green fluorescent protein and nsP4 with an immunological tag. Analysis of these constructs and a matching set of replicon vectors revealed that the replicases containing tagged ns proteins were functional and maintained their subcellular localizations. When cells were co-transfected with constructs expressing template RNA and wild type or tagged versions of CHIKV replicases, formation of characteristic replicase complexes (spherules) was observed. Analysis of mutations associated with noncytotoxic phenotype in CHIKV replicons showed that a low level of RNA replication is not a pre-requisite for reduced cytotoxicity. The CHIKV trans-replicase does not suffer from genetic instability and represents an efficient, sensitive and reliable tool for studies of different aspects of CHIKV RNA replication process.

Assessing Chikungunya risk in a metropolitan area of Argentina through satellite images and mathematical models

BACKGROUND

Chikungunya fever is a viral disease that recently invaded the American continent. In America, it is transmitted mainly by the mosquito Aedes aegypti, but Aedes albopictus is the main vector in other regions of the world. This work estimates the risk of disease emergence and the corresponding population at risk for the case of a naive population in the metropolitan area of Buenos Aires, the capital city of Argentina.

METHODS

A classic metapopulation epidemiological model, that considers human and mosquito populations, was extended in order to include different environmental signals. First, the vital rates of the mosquitoes were affected by local temperature. Second, habitat availability estimated from satellite images was used to determine the carrying capacity for local mosquito populations. Disease invasion was proposed to occur at different moments of the year. For each scenario, Monte Carlo simulations were used to estimate the risk of disease invasion and the population at risk.

RESULTS

The risk of a Chikungunya outbreak displays strong temporal (seasonal) patterns as well as spatial variability at the level of neighborhoods in the study area. According to the model, Summer and Fall display high risk for a Chikungunya invasion. The population at risk displays less variation over the year underlying the importance of preventive actions.

CONCLUSIONS

The ability of mapping habitat quality for vector-borne diseases allows developing risk analysis at scales that are easily manageable for public health officers. For this location, the correlation of disease risk with the season of the year and the habitat availability could provide information to develop efficient control strategies. This also underlines the importance of involving the whole community when developing control measures for Chikungunya fever and other recently invading vector-borne diseases such as Zika fever.

Chikungunya: epidemiology

Chikungunya virus is a mosquito-borne alphavirus that causes fever and debilitating joint pains in humans. Joint pains may last months or years. It is vectored primarily by the tropical and sub-tropical mosquito, Aedes aegypti, but is also found to be transmitted by Aedes albopictus, a mosquito species that can also be found in more temperate climates. In recent years, the virus has risen from relative obscurity to become a global public health menace affecting millions of persons throughout the tropical and sub-tropical world and, as such, has also become a frequent cause of travel-associated febrile illness. In this review, we discuss our current understanding of the biological and sociological underpinnings of its emergence and its future global outlook.

Discovery of berberine, abamectin and ivermectin as antivirals against chikungunya and other alphaviruses

Chikungunya virus (CHIKV) is an arthritogenic arbovirus of the Alphavirus genus, which has infected millions of people after its re-emergence in the last decade. In this study, a BHK cell line containing a stable CHIKV replicon with a luciferase reporter was used in a high-throughput platform to screen approximately 3000 compounds. Following initial validation, 25 compounds were chosen as primary hits for secondary validation with wild type and reporter CHIKV infection, which identified three promising compounds. Abamectin (EC50 = 1.5 μM) and ivermectin (EC50 = 0.6 μM) are fermentation products generated by a soil dwelling actinomycete, Streptomyces avermitilis, whereas berberine (EC50 = 1.8 μM) is a plant-derived isoquinoline alkaloid. They inhibited CHIKV replication in a dose-dependent manner and had broad antiviral activity against other alphaviruses--Semliki Forest virus and Sindbis virus. Abamectin and ivermectin were also active against yellow fever virus, a flavivirus. These compounds caused reduced synthesis of CHIKV genomic and antigenomic viral RNA as well as downregulation of viral protein expression. Time of addition experiments also suggested that they act on the replication phase of the viral infectious cycle.