Chikungunya: epidemiology

Does Nutrient Availability and Larval Competition Alter Chikungunya Virus Infection in the Mosquito Aedes albopictus?

Aedes albopictus is a mosquito that has spread rapidly in the United States and is considered an important vector for arbovirus transmission to humans in several countries. Larval interactions and environmental conditions can influence mosquitoes and their ability to transmit pathogens as adults. We investigated whether intraspecific larval competition among Ae. albopictus mosquitoes from Florida, combined with varying food availability, affects vector competence for Chikungunya virus (CHIKV). We reared larvae under four competition treatment densities and two food levels. Measurements were taken for larval development duration, survival rate, and female wing length. Mosquitoes from each treatment group were orally challenged with CHIKV. Our results showed that development time was longer for both female and male Ae. albopictus under high-competition conditions and appeared as the most important factor, followed by survivorship. Survival rates were highest under low-density conditions compared to those reared under high-density conditions. Mosquitoes reared with a low amount of food had the lowest survivorship and longest development times compared to those provided with high food levels. Our results also showed susceptibility infection and disseminated infection of CHIKV was influenced by an interaction of density and food availability. Mosquitoes from the high-food, high-density treatment group exhibited lower CHIKV infection and dissemination rates compared to other treatment combinations. These findings highlight the role of larval competition and nutritional stress during immature stages in shaping adult mosquito traits, with important epidemiological implications for CHIKV transmission.

Pathogenesis and clinical management of arboviral diseases

Arboviral diseases are viral infections transmitted to humans through the bites of arthropods, such as mosquitoes, often causing a variety of pathologies associated with high levels of morbidity and mortality. Over the past decades, these infections have proven to be a significant challenge to health systems worldwide, particularly following the considerable geographic expansion of the dengue virus (DENV) and its most recent outbreak in Latin America as well as the difficult-to-control outbreaks of yellow fever virus (YFV), chikungunya virus (CHIKV), and Zika virus (ZIKV), leaving behind a substantial portion of the population with complications related to these infections. Currently, the world is experiencing a period of intense globalization, which, combined with global warming, directly contributes to wider dissemination of arbovirus vectors across the globe. Consequently, all continents remain on high alert for potential new outbreaks. Thus, this review aims to provide a comprehensive understanding of the pathogenesis of the four main arboviruses today (DENV, ZIKV, YFV, and CHIKV) discussing their viral characteristics, immune responses, and mechanisms of viral evasion, as well as important clinical aspects for patient management. This includes associated symptoms, laboratory tests, treatments, existing or developing vaccines and the main associated complications, thus integrating a broad historical, scientific and clinical approach.

Spatial-temporal distribution of chikungunya virus in Brazil: a review on the circulating viral genotypes and Aedes (Stegomyia) albopictus as a potential vector

Chikungunya virus (CHIKV) is mainly transmitted by the invasive mosquito Aedes (Stegomyia) aegypti in tropical and subtropical regions worldwide. However, genetic adaptations of the virus to the peri domestic mosquito vector Aedes (Stegomyia) albopictus has resulted in enhanced vector competence and associated epidemics and may contribute to further geographic expansion of CHIKV. However, evidence-based data on the relative role of Ae. albopictus in CHIKV transmission dynamics are scarce, especially in regions where Ae. aegypti is the main vector, such as in Brazil. Here, we review the CHIKV genotypes circulating in Brazil, spatial and temporal distribution of Chikungunya cases in Brazil, and susceptibility to infection and transmission (i.e., vector competence) of Ae. albopictus for CHIKV to better understand its relative contribution to the virus transmission dynamics.

Chikungunya virus vaccine: a decade of progress solving epidemiological dilemma, emerging concepts, and immunological interventions

Chikungunya virus (CHIKV), a single-stranded RNA virus transmitted by Aedes mosquitoes, poses a significant global health threat, with severe complications observed in vulnerable populations. The only licensed vaccine, IXCHIQ, approved by the US FDA, is insufficient to address the growing disease burden, particularly in endemic regions lacking herd immunity. Monoclonal antibodies (mAbs), explicitly targeting structural proteins E1/E2, demonstrate promise in passive transfer studies, with mouse and human-derived mAbs showing protective efficacy. This article explores various vaccine candidates, including live attenuated, killed, nucleic acid-based (DNA/RNA), virus-like particle, chimeric, subunit, and adenovirus vectored vaccines. RNA vaccines have emerged as promising candidates due to their rapid response capabilities and enhanced safety profile. This review underscores the importance of the E1 and E2 proteins as immunogens, emphasizing their antigenic potential. Several vaccine candidates, such as CHIKV/IRES, measles vector (MV-CHIK), synthetic DNA-encoded antibodies, and mRNA-lipid nanoparticle vaccines, demonstrate encouraging preclinical and clinical results. In addition to identifying potential molecular targets for antiviral therapy, the study looks into the roles played by Toll-like receptors, RIG-I, and NOD-like receptors in the immune response to CHIKV. It also offers insights into novel tactics and promising vaccine candidates. This article discusses potential antiviral targets, the significance of E1 and E2 proteins, monoclonal antibodies, and RNA vaccines as prospective Chikungunya virus vaccine candidates.

The Mechanism of Action of L-Tyrosine Derivatives against Chikungunya Virus Infection In Vitro Depends on Structural Changes

Although the disease caused by chikungunya virus (CHIKV) is of great interest to public health organizations around the world, there are still no authorized antivirals for its treatment. Previously, dihalogenated anti-CHIKV compounds derived from L-tyrosine (dH-Y) were identified as being effective against in vitro infection by this virus, so the objective of this study was to determine the mechanisms of its antiviral action. Six dH-Y compounds (C1 to C6) dihalogenated with bromine or chlorine and modified in their amino groups were evaluated by different in vitro antiviral strategies and in silico tools. When the cells were exposed before infection, all compounds decreased the expression of viral proteins; only C4, C5 and C6 inhibited the genome; and C1, C2 and C3 inhibited infectious viral particles (IVPs). Furthermore, C1 and C3 reduce adhesion, while C2 and C3 reduce internalization, which could be related to the in silico interaction with the fusion peptide of the E1 viral protein. Only C3, C4, C5 and C6 inhibited IVPs when the cells were exposed after infection, and their effect occurred in late stages after viral translation and replication, such as assembly, and not during budding. In summary, the structural changes of these compounds determine their mechanism of action. Additionally, C3 was the only compound that inhibited CHIKV infection at different stages of the replicative cycle, making it a compound of interest for conversion as a potential drug.

West Nile virus in Mexico: Why vectors matter for explaining the current absence of epidemics

Since 2002, West Nile Virus (WNV) has been reported in 18 states in Mexico, either by PCR or serological testing. However, it is believed that the virus is present in more states. Only four states (out of 32) have reported confirmed human cases, and one state has serological evidence. In the country, WNV is present in mainly horses and birds, but its presence extends to crocodiles, felines, canines, swines, donkeys, caprines, antilopes, cattle, bats, and camelids. Positive mosquito species include Aedes and Culex spp. Different hypotheses have been proposed to explain the absence of WNV epidemics in Latin America. Since some regions of Mexico and the United States share ecological and climatic conditions, these hypotheses may not be sufficient to account for the absence of WNV outbreaks or epidemics. This paper discusses the proposed ideas and attempts to contextualize them for Mexico, particularly for the U.S.-Mexico border, where WNV infections have been reported in humans, horses, and mosquitoes. We propose that integration of urban ecology and entomology knowledge is needed to better understand the absence of WN cases in Mexico.

Insulin reduces the transmission potential of chikungunya virus and activates the toll pathway in Aedes aegypti mosquitoes

Chikungunya virus (CHIKV) is an alphavirus that has re-emerged globally over the last two decades and has the potential to become endemic in the United States due to the presence of competent mosquito vectors, Aedes aegypti and Aedes albopictus. CHIK disease is characterised by fever, rash, and joint pain, and causes chronic debilitating joint pain and swelling in >50% of infected individuals. Given the disease severity caused by CHIKV and the global presence of vectors to facilitate its spread, strategies to reduce viral transmission are desperately needed; however, the human biological factors driving CHIKV transmission are poorly understood. Towards that end, we have previously shown that mosquitoes fed on alphavirus-infected obese mice have reduced infection and transmission rates compared to those fed on infected lean mice despite similar viremia in lean and obese mice. One of the many host factors that increase in obese hosts is insulin, which was previously shown to impact the infection of mosquitoes by several flaviviruses. However, insulin's impact on alphavirus infection of live mosquitoes is unknown and whether insulin influences mosquito-borne virus transmission has not been tested. To test this, we exposed A. aegypti mosquitoes to bloodmeals with CHIKV in the presence or absence of physiologically relevant levels of insulin and found that insulin significantly lowered both infection and transmission rates. RNA sequencing analysis on mosquito midguts isolated at 1-day-post-infectious-bloodmeal (dpbm) showed enrichment in genes in the Toll immune pathway in the presence of insulin, which was validated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). We then sought to determine if the Toll pathway plays a role in CHIKV infection of Ae. aegypti mosquitoes; therefore, we knocked down Myd88, a critical immune adaptor molecule for the Toll pathway, in live mosquitoes, and found increased CHIKV infection compared to the mock knockdown control group. Overall, these data demonstrate that insulin reduces CHIKV transmission by Ae. aegypti and activates the Toll pathway in mosquitoes, suggesting that conditions resulting in higher serum insulin concentrations may reduce alphavirus transmission. Finally, these studies suggest that strategies to activate insulin or Toll signalling in mosquitoes may be an effective control strategy against medically relevant alphaviruses.

Joint Involvement Can Predict Chikungunya in a Dengue Syndemic Setting in India

Dengue and chikungunya have been endemic in India but have the tendency to cause periodic epidemics, often together, wherein they are termed 'syndemic'. Such a syndemic was observed in 2016 in India which resulted in a further scarcity of already resource-poor specific diagnostic infrastructure even in many urban conglomerates. A cross-sectional study was thus conducted, on 978 fever patients that consulted the ICMR-NIMR fever clinic, New Delhi, in September 2016, with an objective to identify symptom/s that could predict chikungunya with certainty. The overall aim was to rationally channelize the most clinically suitable patients for the required specific diagnosis of chikungunya. Based on their clinical profile, febrile patients attending NIMR's clinic, appropriate laboratory tests and their association analyses were performed. Bivariate analysis on 34 clinical parameters revealed that joint pain, joint swelling, rashes, red spots, weakness, itching, loss of taste, red eyes, and bleeding gums were found to be statistically significantly associated predictors of chikungunya as compared to dengue. While, in multivariate analysis, only four symptoms (joint pain in elbows, joint swelling, itching and bleeding gums) were found in statistically significant association with chikungunya. Hence, based on the results, a clinician may preferably channelize febrile patients with one or more of these four symptoms for chikungunya-specific diagnosis and divert the rest for dengue lab diagnosis in a dengue-chikungunya syndemic setting.

Model-based estimates of chikungunya epidemiological parameters and outbreak risk from varied data types

Assessing the factors responsible for differences in outbreak severity for the same pathogen is a challenging task, since outbreak data are often incomplete and may vary in type across outbreaks (e.g., daily case counts, serology, cases per household). We propose that outbreaks described with varied data types can be directly compared by using those data to estimate a common set of epidemiological parameters. To demonstrate this for chikungunya virus (CHIKV), we developed a realistic model of CHIKV transmission, along with a Bayesian inference method that accommodates any type of outbreak data that can be simulated. The inference method makes use of the fact that all data types arise from the same transmission process, which is simulated by the model. We applied these tools to data from three real-world outbreaks of CHIKV in Italy, Cambodia, and Bangladesh to estimate nine model parameters. We found that these populations differed in several parameters, including pre-existing immunity and house-to-house differences in mosquito activity. These differences resulted in posterior predictions of local CHIKV transmission risk that varied nearly fourfold: 16% in Italy, 28% in Cambodia, and 62% in Bangladesh. Our inference method and model can be applied to improve understanding of the epidemiology of CHIKV and other pathogens for which outbreaks are described with varied data types.

Protein Profiling of Aedes aegypti Treated with Streptomyces sp. KSF103 Ethyl Acetate Extract Reveals Potential Insecticidal Targets and Metabolic Pathways

The insecticidal activity of Streptomyces sp. KSF103 ethyl acetate (EA) extract against mosquitoes is known; however, the underlying mechanism behind this activity remains elusive. In this study, liquid chromatography with tandem mass spectrometry (LC-MS/MS) was employed to investigate changes in the protein profile of Aedes aegypti larvae and adults treated with lethal concentrations of 50 (LC50) EA extract. By comparing the treated and untreated mosquitoes, this study aimed to identify proteins or pathways that exhibit alterations, potentially serving as targets for future insecticide development. Treatment with a lethal concentration of EA extract upregulated 15 proteins in larvae, while in adults, 16 proteins were upregulated, and two proteins were downregulated. These proteins were associated with metabolism, protein regulation/degradation, energy production, cellular organization and structure, enzyme activity, and catalysis, as well as calcium ion transport and homeostasis. Notably, ATP synthase, fructose-bisphosphate aldolase (FBA), and ATP citrate synthase were significantly expressed in both groups. Gene ontology analysis indicated a focus on energy metabolic processes. Molecular docking revealed a strong interaction between dodemorph, selagine (compounds from the EA extract), and FBA, suggesting FBA as a potential protein target for insecticide development. Further studies such as Western blot and transcriptomic analyses are warranted to validate the findings.

Genomic Characterization of Mosquito Isolates of Chikungunya Virus (Outbreak Strains 2022) Using Next-Generation Sequencing

Background: A massive outbreak of dengue-like illness was reported from Pune district of Maharashtra, India during May-June 2022. Isolation and characterization of the etiological agent at genomic level for possible mutations that led to higher transmissibility is the topic of the study. Methods: Entomological investigations were carried out by ICMR-National Institute of Virology (Pune, India); Aedes aegypti mosquitoes were collected and processed for virus detection by molecular techniques. Positive mosquito pools were processed for virus isolation in cell culture. Sanger sequencing and whole-genome sequencing (WGS) using Oxford Nanopore Technology platform were used for genomic characterization. Results: Reverse transcriptase RT-PCR and qRT-PCR analysis detected chikungunya virus (CHIKV) in mosquito samples. Six CHIKV isolates were obtained. WGS revealed four nonsynonymous mutations in the structural polyprotein region, and five in the nonstructural polyprotein encoding region when compared with Yawat-2000 and Shivane-2016 strains. Sixty-four nucleotide changes in the nonstructural polyprotein region and 35 in the structural polyprotein region were detected. One isolate had an exclusive amino acid change, T1123I, in the nsP2 (protease) region. Conclusion: Abundant Ae. aegypti breeding and detection of CHIKV RNA in mosquitoes confirmed it as a chikungunya outbreak. Novel mutations detected in the epidemic strain warrants investigations to address their role in disease severity, transmission, and fitness.

Enhancing the therapeutic activity of hyperimmune IgG against chikungunya virus using FcγRIIIa affinity chromatography

Introduction

Chikungunya virus (CHIKV) is a re-emerging mosquito transmitted alphavirus of global concern. Neutralizing antibodies and antibody Fc-effector functions have been shown to reduce CHIKV disease and infection in animals. However, the ability to improve the therapeutic activity of CHIKV-specific polyclonal IgG by enhancing Fc-effector functions through modulation of IgG subclass and glycoforms remains unknown. Here, we evaluated the protective efficacy of CHIKV-immune IgG enriched for binding to Fc-gamma receptor IIIa (FcγRIIIa) to select for IgG with enhanced Fc effector functions.

Methods

Total IgG was isolated from CHIKV-immune convalescent donors with and without additional purification by FcγRIIIa affinity chromatography. The enriched IgG was characterized in biophysical and biological assays and assessed for therapeutic efficacy during CHIKV infection in mice.

Results

FcγRIIIa-column purification enriched for afucosylated IgG glycoforms. In vitro characterization showed the enriched CHIKV-immune IgG had enhanced human FcγRIIIa and mouse FcγRIV affinity and FcγR-mediated effector function without reducing virus neutralization in cellular assays. When administered as post-exposure therapy in mice, CHIKV-immune IgG enriched in afucosylated glycoforms promoted reduction in viral load.

Discussion

Our study provides evidence that, in mice, increasing Fc engagement of FcγRs on effector cells, by leveraging FcγRIIIa-affinity chromatography, enhanced the antiviral activity of CHIKV-immune IgG and reveals a path to produce more effective therapeutics against these and potentially other emerging viruses.

Infection with chikungunya virus confers heterotypic cross-neutralizing antibodies and memory B-cells against other arthritogenic alphaviruses predominantly through the B domain of the E2 glycoprotein

Infections with Chikungunya virus, a mosquito-borne alphavirus, cause an acute febrile syndrome often followed by chronic arthritis that persists for months to years post-infection. Neutralizing antibodies are the primary immune correlate of protection elicited by infection, and the major goal of vaccinations in development. Using convalescent blood samples collected from both endemic and non-endemic human subjects at multiple timepoints following suspected or confirmed chikungunya infection, we identified antibodies with broad neutralizing properties against other alphaviruses within the Semliki Forest complex. Cross-neutralization generally did not extend to the Venezuelan Equine Encephalitis virus (VEEV) complex, although some subjects had low levels of VEEV-neutralizing antibodies. This suggests that broadly neutralizing antibodies elicited following natural infection are largely complex restricted. In addition to serology, we also performed memory B-cell analysis, finding chikungunya-specific memory B-cells in all subjects in this study as remotely as 24 years post-infection. We functionally assessed the ability of memory B-cell derived antibodies to bind to chikungunya virus, and related Mayaro virus, as well as the highly conserved B domain of the E2 glycoprotein thought to contribute to cross-reactivity between related Old-World alphaviruses. To specifically assess the role of the E2 B domain in cross-neutralization, we depleted Mayaro and Chikungunya virus E2 B domain specific antibodies from convalescent sera, finding E2B depletion significantly decreases Mayaro virus specific cross-neutralizing antibody titers with no significant effect on chikungunya virus neutralization, indicating that the E2 B domain is a key target of cross-neutralizing and potentially cross-protective neutralizing antibodies.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Understanding the Biology and Immune Pathogenesis of Chikungunya Virus Infection for Diagnostic and Vaccine Development

Chikungunya virus, the causative agent of chikungunya fever, is generally characterized by the sudden onset of symptoms, including fever, rash, myalgia, and headache. In some patients, acute chikungunya virus infection progresses to severe and chronic arthralgia that persists for years. Chikungunya infection is more commonly identified in tropical and subtropical regions. However, recent expansions and epidemics in the temperate regions have raised concerns about the future public health impact of chikungunya diseases. Several underlying factors have likely contributed to the recent re-emergence of chikungunya infection, including urbanization, human travel, viral adaptation to mosquito vectors, lack of effective control measures, and the spread of mosquito vectors to new regions. However, the true burden of chikungunya disease is most likely to be underestimated, particularly in developing countries, due to the lack of standard diagnostic assays and clinical manifestations overlapping with those of other endemic viral infections in the regions. Additionally, there have been no chikungunya vaccines available to prevent the infection. Thus, it is important to update our understanding of the immunopathogenesis of chikungunya infection, its clinical manifestations, the diagnosis, and the development of chikungunya vaccines.

Abundance of Phasi-Charoen-like virus in Aedes aegypti mosquito populations in different states of India

Mosquitoes are known to harbor a large number of insect specific viruses (ISV) in addition to viruses of public health importance. These ISVs are highly species specific and are non-pathogenic to humans or domestic animals. However, there is a potential threat of these ISVs evolving into human pathogens by genome alterations. Some ISVs are known to modulate replication of pathogenic viruses by altering the susceptibility of vector mosquitoes to pathogenic viruses, thereby either inhibiting or enhancing transmission of the latter. In the present study, we report predominance of Phasi Charoen-like virus (PCLV, Family: Phenuviridae) contributing to >60% of the total reads in Aedes aegypti mosquitoes collected from Pune district of Maharashtra state using next generation sequencing based metagenomic analysis of viromes. Similar results were also obtained with mosquitoes from Assam, Tamil Nadu and Karnataka states of India. Comparison of Pune mosquito sequences with PCLV Rio (Brazil) isolate showed 98.90%, 99.027% and 98.88% homologies in the S, M and L segments respectively indicating less genetic heterogeneity of PCLV. The study also demonstrated occurrence of transovarial transmission as seen by detection of PCLV in eggs, larvae, pupae and male mosquitoes. Ae. aegypti mosquitoes collected from Pune also showed a large number of reads for viruses belonging to Baculoviridae, Rhabdoviridae, Genomoviridae and Bunyaviridae families. The role of PCLV in the replication of dengue and chikungunya virus is yet not clear. It warrants further studies to know the significance of PCLV and other ISVs on the replication and transmission of Ae. aegypti borne pathogenic viruses, especially in the absence of prophylactics or therapeutics.

Exposure of Egyptian Rousette Bats (Rousettus aegyptiacus) and a Little Free-Tailed Bat (Chaerephon pumilus) to Alphaviruses in Uganda

The reservoir for zoonotic o'nyong-nyong virus (ONNV) has remained unknown since this virus was first recognized in Uganda in 1959. Building on existing evidence for mosquito blood-feeding on various frugivorous bat species in Uganda, and seroprevalence for arboviruses among bats in Uganda, we sought to assess if serum samples collected from bats in Uganda demonstrated evidence of exposure to ONNV or the closely related zoonotic chikungunya virus (CHIKV). In total, 652 serum samples collected from six bat species were tested by plaque reduction neutralization test (PRNT) for neutralizing antibodies against ONNV and CHIKV. Forty out of 303 (13.2%) Egyptian rousettes from Maramagambo Forest and 1/13 (8%) little free-tailed bats from Banga Nakiwogo, Entebbe contained neutralizing antibodies against ONNV. In addition, 2/303 (0.7%) of these Egyptian rousettes contained neutralizing antibodies to CHIKV, and 8/303 (2.6%) contained neutralizing antibodies that were nonspecifically reactive to alphaviruses. These data support the interepidemic circulation of ONNV and CHIKV in Uganda, although Egyptian rousette bats are unlikely to serve as reservoirs for these viruses given the inconsistent occurrence of antibody-positive bats.

Chikungunya Vaccine Candidates: Current Landscape and Future Prospects

Chikungunya virus (CHIKV) is an alphavirus that has spread globally in the last twenty years. Although mortality is rather low, infection can result in debilitating arthralgia that can persist for years. Unfortunately, no treatments or preventive vaccines are currently licensed against CHIKV infections. However, a large range of promising preclinical and clinical vaccine candidates have been developed during recent years. This review will give an introduction into the biology of CHIKV and the immune responses that are induced by infection, and will summarize CHIKV vaccine development.

Parálisis facial aislada posterior a infección por virus de chikunguña: un nuevo diagnóstico diferencial

En las últimas décadas, se ha incrementado el reporte de manifestaciones neurológicas asociadas con la infección por el virus de chikunguña. Se informa el caso de un adulto joven previamente sano que presentó parálisis facial izquierda aislada después de una infección reciente por el virus de chikunguña en el trópico colombiano. Se describen aspectos importantes de la fisiopatología del virus y su tropismo por el sistema nervioso central y periférico, y se sugiere considerar este virus en el diagnóstico diferencial de la parálisis facial en pacientes con infección confirmada por el virus de chikunguña en regiones tropicales endémicas o en aquellos con antecedente de viajes recientes a dichas regiones.

Progressive Course of Chronic Tick-Borne Encephalitis Manifesting as Amyotrophic Lateral Sclerosis-like Syndrome 35 Years after the Acute Disease

The chronic form of tick-borne encephalitis (TBE) is understudied and seems to be linked exclusively to Siberian and Far Eastern TBE virus (TBEV) subtypes. There are limited clinical descriptions demonstrating that chronic TBE can resemble an amyotrophic lateral sclerosis (ALS)-like disease. Here, we present a description of a clinical case of progressive chronic TBEV infection with a relapse 35 years after the initial acute infection following a tick bite. The disease manifested as an ALS-like syndrome with bulbar signs, progressive muscle weakness and atrophy, decreased reflexes, and eventual respiratory failure and death. There is no clear differentiation between chronic TBE and postencephalitic syndrome described in European sources. The reactivation of TBEV infection was supported by the presence of anti-TBEV antibodies in serum and antibodies to E protein and to the nonstructural protein NS1 in the CSF. These findings support the diagnosis of a relapse of chronic TBE in this patient.

Ocular Manifestations of Chikungunya Infection: A Systematic Review

The Chikungunya virus (CHIKV) can cause long lasting symptoms and manifestations. However, there is little information on which ocular ones are most frequent following infection. We performed a systematic review (registered in the International Prospective Register of Systematic Reviews; no CRD42020171928) to establish the most frequent ocular manifestations of CHIKV infection and their associations with gender and age. Articles published until September 2020 were selected from PubMed, Scielo, Cochrane and Scopus databases. Only studies with CHIKV-infected patients and eye alterations were included. Reviews, descriptive studies, or those not investigating the human ocular manifestations of CHIKV, those with patients with other diseases and infections, abstracts and studies without relevant data were excluded. Twenty-five studies were selected for inclusion. Their risk of bias was evaluated by a modified Newcastle-Ottawa scale. The most frequent ocular symptoms of CHIKV infection included ocular pain, inflammation and reduced visual acuity, whilst conjunctivitis and optic neuritis were the most common manifestations of the disease. These occurred mostly in individuals of 42 ± 9.5 years of age and woman. The few available reports on CHIKV-induced eye manifestations highlight the need for further research in the field to gather more substantial evidence linking CHIKV infection, the eye and age/gender. Nonetheless, the data emphasizes that ocular alterations are meaningful occurrences of CHIKV infection which can substantially affect quality of life.

Expression, Purification, and Refolding of Chikungunya Virus Full-Length Envelope E2 Protein along with B-Cell and T-Cell Epitope Analyses Using Immuno-Informatics Approaches

Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus, which causes severe illness in humans and is responsible for epidemic outbreaks in Africa, Asia, North and South America, and Europe. Despite its increased global prevalence, no licensed vaccines are available to date for treating or preventing CHIKV infection. The envelope E2 protein is one of the promising subunit vaccine candidates against CHIKV. In this study, we describe successful cloning, expression, and purification of CHIKV E2 full-length (E2-FL) and truncated (E2-ΔC and E2-ΔNC) proteins in the Escherichia coli expression system. The recombinant E2 proteins were purified from inclusion bodies using Ni-NTA chromatography. Further, we describe a detailed refolding procedure for obtaining the CHIKV E2-FL protein in native conformation, which was confirmed using circular dichroism and Fourier transform infrared spectroscopy. BALB/c mice immunized with the three different E2 proteins exhibited increased E2-specific antibody titers compared to sham-immunized controls, suggesting induction of strong humoral immune response. On analyzing the E2-specific antibody response generated in immunized mice, the CHIKV E2-FL protein was observed to be the most immunogenic among the three different CHIKV E2 antigens used in the study. Our B-cell and T-cell epitope mapping results indicate that the presence of specific immunogenic peptides located in the N-terminal and C-terminal regions of the CHIKV E2-FL protein may contribute to its increased immunogenicity, compared to truncated CHIKV E2 proteins. In summary, our study provides a detailed protocol for expressing, purifying, and refolding of the CHIKV E2-FL protein and provides an understanding of its immunogenic epitopes, which can be exploited for the development of novel multiepitope-based anti-CHIKV vaccine strategies.

Chikungunya viruses containing the A226V mutation detected retrospectively in Cameroon form a new geographical subclade

BACKGROUND

Chikungunya virus (CHIKV) is a re-emerging arbovirus associated with sporadic outbreaks in Cameroon since 2006. Viral whole genomes were generated to analyze the origins of evolutionary lineages, the potential of emergence/re-emergence, and to infer transmission dynamics of recent Cameroon CHIKV outbreak strains.

METHODS

Samples collected between 2016 and 2019 during CHIKV outbreaks in Cameroon were screened for CHIKV using reverse transcription PCR (RT-PCR), followed by whole genome sequencing of positive samples.

RESULTS

Three coding-complete CHIKV genomes were obtained from samples, which belong to an emerging sub-lineage of the East/Central/South African genotype and formed a monophyletic taxon with previous Central African strains. This clade, which we have named the new Central African clade, appears to be evolving at 3.0 × 10^-4 nucleotide substitutions per site per year (95% highest posterior density (HPD) interval of 1.94 × 10^-4 to 4.1 × 10^-4). Notably, mutations in the envelope proteins (E1-A226V, E2-L210Q, and E2-I211T), which are known to enhance CHIKV adaptability and infectious potential in Aedes albopictus, were present in all strains and mapped to established high-density Ae. albopictus populations.

CONCLUSIONS

These new CHIKV strains constitute a conserved genomic pool of an emerging sub-lineage, reflecting a putative vector host adaptation to Ae. albopictus, which has practically displaced Aedes aegypti from select regions of Cameroon.

Chikungunya in Guerrero, Mexico, 2019 and Evidence of Gross Underreporting in the Region

The local public health authorities reported nine cases of chikungunya in Mexico in 2019, none of which occurred in Guerrero, a coastal state in the southwest. To test the hypothesis that chikungunya is grossly underreported in Mexico, acute sera were collected from 639 febrile patients from low-income households in Guerrero in 2019 and serologically assayed for chikungunya virus (CHIKV). Analysis of the sera by plaque reduction neutralization test revealed that 181 (28.3%) patients were seropositive for CHIKV. To identify patients with acute CHIKV infections, a subset of sera samples were tested for CHIKV-specific IgM by ELISA. Sera samples from 21 of 189 (11.1%) patients were positive. These patients met the chikungunya case definition established by the WHO. In conclusion, we provide evidence that CHIKV remains an important public health problem in Mexico and that the true number of cases is severely underestimated.

Potential geographic distribution of the tiger mosquito Aedes albopictus (Skuse, 1894) (Diptera: Culicidae) in current and future conditions for Colombia

In Colombia, little is known on the distribution of the Asian mosquito Aedes albopictus, main vector of dengue, chikungunya, and Zika in Asia and Oceania. Therefore, this work sought to estimate its current and future potential geographic distribution under the Representative Concentration Paths (RCP) 2.6 and 8.5 emission scenarios by 2050 and 2070, using ecological niche models. For this, predictions were made in MaxEnt, employing occurrences of A. albopictus from their native area and South America and bioclimatic variables of these places. We found that, from their invasion of Colombia to the most recent years, A. albopictus is present in 47% of the country, in peri-urban (20%), rural (23%), and urban (57%) areas between 0 and 1800 m, with Antioquia and Valle del Cauca being the departments with most of the records. Our ecological niche modelling for the currently suggests that A. albopictus is distributed in 96% of the Colombian continental surface up to 3000 m (p < 0.001) putting at risk at least 48 million of people that could be infected by the arboviruses that this species transmits. Additionally, by 2050 and 2070, under RCP 2.6 scenario, its distribution could cover to nearly 90% of continental extension up to 3100 m (≈55 million of people at risk), while under RCP 8.5 scenario, it could decrease below 60% of continental extension, but expand upward to 3200 m (< 38 million of people at risk). These results suggest that, currently in Colombia, A. albopictus is found throughout the country and climate change could diminish eventually its area of distribution, but increase its altitudinal range. In Colombia, surveillance and vector control programs must focus their attention on this vector to avoid complications in the national public health setting.

Deep learning identification for citizen science surveillance of tiger mosquitoes

Global monitoring of disease vectors is undoubtedly becoming an urgent need as the human population rises and becomes increasingly mobile, international commercial exchanges increase, and climate change expands the habitats of many vector species. Traditional surveillance of mosquitoes, vectors of many diseases, relies on catches, which requires regular manual inspection and reporting, and dedicated personnel, making large-scale monitoring difficult and expensive. New approaches are solving the problem of scalability by relying on smartphones and the Internet to enable novel community-based and digital observatories, where people can upload pictures of mosquitoes whenever they encounter them. An example is the Mosquito Alert citizen science system, which includes a dedicated mobile phone app through which geotagged images are collected. This system provides a viable option for monitoring the spread of various mosquito species across the globe, although it is partly limited by the quality of the citizen scientists’ photos. To make the system useful for public health agencies, and to give feedback to the volunteering citizens, the submitted images are inspected and labeled by entomology experts. Although citizen-based data collection can greatly broaden disease-vector monitoring scales, manual inspection of each image is not an easily scalable option in the long run, and the system could be improved through automation. Based on Mosquito Alert’s curated database of expert-validated mosquito photos, we trained a deep learning model to find tiger mosquitoes (Aedes albopictus), a species that is responsible for spreading chikungunya, dengue, and Zika among other diseases. The highly accurate 0.96 area under the receiver operating characteristic curve score promises not only a helpful pre-selector for the expert validation process but also an automated classifier giving quick feedback to the app participants, which may help to keep them motivated. In the paper, we also explored the possibilities of using the model to improve future data collection quality as a feedback loop.

Arbovirus Rash in the Febrile Returning Traveler as a Diagnostic Clue

Purpose of Review

This review aims to describe briefly the general information of arboviruses dengue, Zika, and chikungunya infections and emphasize the clinical manifestations of each, to help identify and make a quick diagnosis of each.

Recent Findings

The most relevant advances in the study of these arboviruses' infections have been in the epidemiological distribution, mainly due to international travel, migration, and climate change; in the clinical manifestations of these diseases, the development of clinical decision-making software, which can help improve the management and outcomes of these patients; and in the prevention of this disease.

Summary

Although arboviruses infections constitute a clinical challenge for the attending physician in the scope of a febrile returning traveler, a thorough clinical history and exam can help to aid diagnostic reasoning. The characteristics of the rash are a very helpful clue in the evaluation of these patients. Currently, there are clinical decision aid tools that help to get the diagnosis more quickly.

Laboratory surveillance of chikungunya in Madhya Pradesh, India (2016-2017)

Background & objectives:

Chikungunya (CHIK) is a neglected, re-emerging arboviral disease. Limited information on CHIK-confirmed cases during interepidemic period is available from India. This surveillance study was conducted in Madhya Pradesh (MP), India, during the years 2016-2017, to provide information about CHIK cases.

Methods:

Blood samples collected from patients suspected having CHIK were tested by immunoglobulin (Ig) IgM ELISA or real time reverse transcription-polymerase chain reaction (rRT-PCR) for the detection of CHIK virus (CHIKV)-specific IgM antibodies or viral RNA, respectively. Partial envelope-1 gene sequencing was done. Clinical and demographic data were collected and analyzed.

Results:

Of the 4019 samples tested, 494 (12.2%) were found positive for CHIKV infection. The positivity was detected in both rural and urban areas. The mean age of CHIK-positive cases was 33.12±18.25 yr. Headache and joint pain were the most prominent symptoms, 34.6 per cent (171/494) of the CHIK cases required hospitalization and six patients with CHIKV infection died. The East/Central/South African genotype of CHIKV was found to be circulating in the study area.

Interpretation & conclusions:

Our study recorded a higher CHIK positivity during 2016-2017 in comparison to earlier reports from MP, India. A high proportion of CHIK cases required hospitalization and deaths were also reported, which indicated the severity of the disease in the study area. In-depth molecular analysis of the virus and other risk factors is essential to understand the trends in disease severity.

Occurrence of 4 Dengue Virus Serotypes and Chikungunya Virus in Kilombero Valley, Tanzania, During the Dengue Outbreak in 2018

BACKGROUND

Dengue and Chikungunya viruses can cause large-scale epidemics, with attack rates of up to 80%. In Tanzania, there have been repeated outbreaks of dengue fever, the most recent in 2018 and 2019, mostly affecting the coastal areas. Despite the importance of these viruses, there is limited knowledge on the epidemiology of dengue (DENV) and Chikungunya (CHIKV) in Tanzania. This study was conducted to investigate the prevalence of DENV and CHIKV in Kilombero Valley, Tanzania.

METHODS

A cross-sectional study was conducted at Kibaoni Health Center in Kilombero Valley, Southeastern Tanzania, in the rainy and dry seasons of 2018. Febrile patients of any age and gender were enrolled from the outpatient department. Blood samples were taken and screened for DENV and CHIKV viral RNA by real-time reverse transcription polymerase chain reaction assays.

RESULTS

Overall, 294 patients were recruited. Most were females (65%), and one-third of patients were aged 14-25 years. DENV and CHIKV were detected in 29 (9.9%) and 3 (1.0%) patients, respectively. DENV was detected across all age groups during both the dry and rainy seasons. Although all 4 DENV serotypes were detected, serotypes 1 and 3 dominated and were present in 14 patients (42.4%) each. Additionally, the study showed DENV-1 and DENV-3 co-infections.

CONCLUSIONS

This study reveals the co-circulation of all 4 DENV serotypes and CHIKV in Kilombero. Importantly, we report the first occurrence of DENV-4 in Tanzania. Unlike previous DENV outbreaks caused by DENV-2, the 2018 outbreak was dominated by DENV-1 and DENV-3. The occurrence of all serotypes suggests the possibility of severe clinical outcomes in future DENV epidemics in Tanzania.

Approach to acute febrile illness during the COVID-19 pandemic

Coronavirus disease 2019 (COVID-19) is a febrile respiratory illness that has spread rampantly across the globe and has emerged as one of the biggest pandemics of all time. Besides the direct effects of COVID-19 on mortality, collateral impacts on diagnosis and management of acute febrile illnesses (AFI) is a matter of great concern. The overlap in presentation, shunting of available resources and infection control precautions in patients with suspected COVID-19 result in a significant delay in diagnoses and management of AFI. This review highlights the challenges in the management of acute febrile illness during COVID pandemic and possible solutions for the same.

Surveillance of Culicine Mosquitoes in Six Villages of Taita-Taveta County, Kenya, With Host Determinations From Blood-Fed Females

Culicine mosquitoes are vectors of human disease-causing pathogens like filarial worms and several arthropod-borne viruses (arboviruses). Currently, there has been an increase in emerging and re-emerging vector-borne diseases along coastal Kenya, which has been of major concern in public health. This study aimed at determining culicine mosquito species abundance, diversity and their host feeding preferences in Taita-Taveta County, Coastal Kenya. Entomological sampling was done during the long-wet season (March and May) and long dry season (June to October) 2016-2018. Mosquito sampling was done using CDC light traps and Backpack aspiration for indoor and outdoor environments. All culicine mosquitoes collected were identified morphologically and categorized according to their physiological status. Blood fed culicine mosquitoes were tested for bloodmeal sources using ELISA. In total, 3,278 culicine mosquitoes were collected, of which 738 (22.5 %) were found indoors and 2,540, (77.5 %) outdoors. The mosquitoes consisted of 18 species belonging to four genera: Aedes (7), Culex (8), Mansonia (2), and Coquillettidia (1). Overall, there was high mosquito species diversity (H) in outdoors (H = 2.4339) than in indoors (H = 2.2523), whereas even distribution (EH) was higher in indoors (EH = 0.9064) than outdoors (EH = 0.8266). Majorly the bloodmeals identified were from multiple host sources with (51.6%), single hosts (41.3%), and unidentified (7.2%). This study has demonstrated a high diversity of culicine mosquitoes with relaxed feeding tendencies. These mosquitoes are contributing to mosquito biting nuisance and the likelihood of exposure of populations to diseases of public health.

Superinfection Exclusion in Mosquitoes and Its Potential as an Arbovirus Control Strategy

The continuing emergence of arbovirus disease outbreaks around the world, despite the use of vector control strategies, warrants the development of new strategies to reduce arbovirus transmission. Superinfection exclusion, a phenomenon whereby a primary virus infection prevents the replication of a second closely related virus, has potential to control arbovirus disease emergence and outbreaks. This phenomenon has been observed for many years in plants, insects and mammalian cells. In this review, we discuss the significance of identifying novel vector control strategies, summarize studies exploring arbovirus superinfection exclusion and consider the potential for this phenomenon to be the basis for novel arbovirus control strategies.

Role of MicroRNAs in Bone Pathology during Chikungunya Virus Infection

Chikungunya virus (CHIKV) is an alphavirus, transmitted by mosquitoes, which causes Chikungunya fever with symptoms of fever, rash, headache, and joint pain. In about 30%-40% of cases, the infection leads to polyarthritis and polyarthralgia. Presently, there are no treatment strategies or vaccine for Chikungunya fever. Moreover, the mechanism of CHIKV induced bone pathology is not fully understood. The modulation of host machinery is known to be essential in establishing viral pathogenesis. MicroRNAs (miRNAs) are small non-coding RNAs that regulate major cellular functions by modulating gene expression. Fascinatingly, recent reports have indicated the role of miRNAs in regulating bone homeostasis and altered expression of miRNAs in bone-related pathological diseases. In this review, we summarize the altered expression of miRNAs during CHIKV pathogenesis and the possible role of miRNAs during bone homeostasis in the context of CHIKV infection. A holistic understanding of the different signaling pathways targeted by miRNAs during bone remodeling and during CHIKV-induced bone pathology may lead to identification of useful biomarkers or therapeutics.

A cross-reactive antibody protects against Ross River virus musculoskeletal disease despite rapid neutralization escape in mice

Arthritogenic alphaviruses cause debilitating musculoskeletal disease and historically have circulated in distinct regions. With the global spread of chikungunya virus (CHIKV), there now is more geographic overlap, which could result in heterologous immunity affecting natural infection or vaccination. Here, we evaluated the capacity of a cross-reactive anti-CHIKV monoclonal antibody (CHK-265) to protect against disease caused by the distantly related alphavirus, Ross River virus (RRV). Although CHK-265 only moderately neutralizes RRV infection in cell culture, it limited clinical disease in mice independently of Fc effector function activity. Despite this protective phenotype, RRV escaped from CHK-265 neutralization in vivo, with resistant variants retaining pathogenic potential. Near the inoculation site, CHK-265 reduced viral burden in a type I interferon signaling-dependent manner and limited immune cell infiltration into musculoskeletal tissue. In a parallel set of experiments, purified human CHIKV immune IgG also weakly neutralized RRV, yet when transferred to mice, resulted in improved clinical outcome during RRV infection despite the emergence of resistant viruses. Overall, this study suggests that weakly cross-neutralizing antibodies can protect against heterologous alphavirus disease, even if neutralization escape occurs, through an early viral control program that tempers inflammation.

The induction of broadly neutralizing antibodies is a goal of many antiviral vaccine programs. In this study, we show that cross-reactive monoclonal and polyclonal antibodies developed after CHIKV infection or immunization with relatively weak cross-neutralizing activity can protect against RRV-induced musculoskeletal disease in mice. Even though RRV rapidly escaped from neutralization, antibody therapy reduced inflammation in musculoskeletal tissues and decreased viral burden near the site of infection in a manner that required type I interferon signaling. These studies in mice show that broadly reactive antibodies with limited neutralizing activity still can confer protection against heterologous alphaviruses.

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

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

Chikungunya Virus: An Emergent Arbovirus to the South American Continent and a Continuous Threat to the World

Chikungunya virus (CHIKV) is an arthropod-borne virus (arbovirus) of epidemic concern, transmitted by Aedes ssp. mosquitoes, and is the etiologic agent of a febrile and incapacitating arthritogenic illness responsible for millions of human cases worldwide. After major outbreaks starting in 2004, CHIKV spread to subtropical areas and western hemisphere coming from sub-Saharan Africa, South East Asia, and the Indian subcontinent. Even though CHIKV disease is self-limiting and non-lethal, more than 30% of the infected individuals will develop chronic disease with persistent severe joint pain, tenosynovitis, and incapacitating polyarthralgia that can last for months to years, negatively impacting an individual's quality of life and socioeconomic productivity. The lack of specific drugs or licensed vaccines to treat or prevent CHIKV disease associated with the global presence of the mosquito vector in tropical and temperate areas, representing a possibility for CHIKV to continually spread to different territories, make this virus an agent of public health burden. In South America, where Dengue virus is endemic and Zika virus was recently introduced, the impact of the expansion of CHIKV infections, and co-infection with other arboviruses, still needs to be estimated. In Brazil, the recent spread of the East/Central/South Africa (ECSA) and Asian genotypes of CHIKV was accompanied by a high morbidity rate and acute cases of abnormal disease presentation and severe neuropathies, which is an atypical outcome for this infection. In this review, we will discuss what is currently known about CHIKV epidemics, clinical manifestations of the human disease, the basic concepts and recent findings in the mechanisms underlying virus-host interaction, and CHIKV-induced chronic disease for both in vitro and in vivo models of infection. We aim to stimulate scientific debate on how the characterization of replication, host-cell interactions, and the pathogenic potential of the new epidemic viral strains can contribute as potential developments in the virology field and shed light on strategies for disease control.

Current Efforts in the Development of Vaccines for the Prevention of Zika and Chikungunya Virus Infections

Arboviruses represent major challenges to public health, particularly in tropical, and subtropical regions, and a substantial risk to other parts of the world as respective vectors extend their habitats. In recent years, two viruses transmitted by Aedes mosquitoes, Chikungunya and Zika virus, have gathered increased interest. After decades of regionally constrained outbreaks, both viruses have recently caused explosive outbreaks on an unprecedented scale, causing immense suffering and massive economic burdens in affected regions. Chikungunya virus causes an acute febrile illness that often transitions into a chronic manifestation characterized by debilitating arthralgia and/or arthritis in a substantial subset of infected individuals. Zika infection frequently presents as a mild influenza-like illness, often subclinical, but can cause severe complications such as congenital malformations in pregnancy and neurological disorders, including Guillain-Barré syndrome. With no specific treatments or vaccines available, vector control remains the most effective measure to manage spread of these diseases. Given that both viruses cause antibody responses that confer long-term, possibly lifelong protection and that such responses are cross-protective against the various circulating genetic lineages, the development of Zika and Chikungunya vaccines represents a promising route for disease control. In this review we provide a brief overview on Zika and Chikungunya viruses, the etiology and epidemiology of the illnesses they cause and the host immune response against them, before summarizing past and current efforts to develop vaccines to alleviate the burden caused by these emerging diseases. The development of the urgently needed vaccines is hampered by several factors including the unpredictable epidemiology, feasibility of rapid clinical trial implementation during outbreaks and regulatory pathways. We will give an overview of the current developments.

Optimal therapeutic activity of monoclonal antibodies against chikungunya virus requires Fc-FcγR interaction on monocytes

Chikungunya virus (CHIKV) is an emerging mosquito-borne virus that has caused explosive outbreaks worldwide. Although neutralizing monoclonal antibodies (mAbs) against CHIKV inhibit infection in animals, the contribution of Fc effector functions to protection remains unknown. Here, we evaluated the activity of therapeutic mAbs that had or lacked the ability to engage complement and Fcγ receptors (FcγR). When administered as post-exposure therapy in mice, the Fc effector functions of mAbs promoted virus clearance from infected cells and reduced joint swelling-results that were corroborated in antibody-treated transgenic animals lacking activating FcγR. The control of CHIKV infection by antibody-FcγR engagement was associated with an accelerated influx of monocytes. A series of immune cell depletions revealed that therapeutic mAbs required monocytes for efficient clearance of CHIKV infection. Overall, our study suggests that in mice, FcγR expression on monocytes is required for optimal therapeutic activity of antibodies against CHIKV and likely other related viruses.

Pre-existing chikungunya virus neutralizing antibodies correlate with risk of symptomatic infection and subclinical seroconversion in a Philippine cohort

BACKGROUND

A longitudinal cohort study performed in Cebu City, Philippines found that the presence of pre-existing chikungunya virus (CHIKV) neutralizing antibodies (NAb) was associated with a decreased risk of symptomatic CHIKV infection. However, the relationship between pre-existing NAb and the risk of subclinical seroconversion has not been well described.

METHODS

Data were analyzed from a longitudinal cohort aged 6 months to 83 years who underwent active fever surveillance in Cebu City, Philippines from 2012 to 2014. Participants with a history of fever underwent acute and 3-week convalescent visits with blood collection, and annual visits at baseline, 12 months, and 24 months. Symptomatic CHIKV infections were detected by PCR of acute illness sera. Subclinical seroconversion was defined as a ≥8-fold rise in 80% plaque reduction neutralization test (PRNT80) titer between annual visits without intervening symptomatic infection.

RESULTS

Among 854 participants who completed the 12-month visit (year 1) and 765 who completed the 24-month visit (year 2), 25 symptomatic CHIKV infections and 104 subclinical seroconversions occurred among 615 individuals with no detectable pre-year NAb in year 1 and 444 in year 2, while no symptomatic infections and one subclinical seroconversion occurred in those with a pre-year PRNT80 titer ≥1:10. Pre-year PRNT80 titer ≥1:10 was associated with zero relative risk of symptomatic CHIKV infection and 0.018 risk of subclinical seroconversion.

CONCLUSIONS

The presence of detectable pre-existing CHIKV NAb correlated with a decreased risk of both symptomatic CHIKV infection and subclinical seroconversion. These findings support the potential use of CHIKV NAb titer as a surrogate endpoint of protection from infection for vaccine development.

Differential susceptibility & replication potential of Vero E6, BHK-21, RD, A-549, C6/36 cells & Aedes aegypti mosquitoes to three strains of chikungunya virus

Background & objectives

Chikungunya virus (CHIKV), a mosquito-borne arthritogenic virus causes infections ranging from febrile illness to debilitating polyarthralgia in humans. Re-emergence of the virus has affected millions of people in Africa and Asia since 2004. During the outbreak, a new lineage of the virus has evolved as an adaptation for enhanced replication and transmission by Aedes albopictus mosquito. A study was designed to compare the susceptibility of four vertebrate cell lines, namely Vero E6 (African green monkey kidney), BHK-21 (Baby hamster kidney), RD (human rhabdomyosarcoma), A-549 (human alveolar basal epithelial cell) and C6/36 (Ae. albopictus) to Asian genotype and two lineages of East, Central and South African (E1:A226 and E1:A226V) of CHIKV.

Methods

One-step growth kinetics of different CHIKV strains was carried out in the above five cell lines to determine the growth kinetics and virus yield. Virus titre was determined by 50 per cent tissue culture infectious dose assay and titres were calculated by the Reed and Muench formula. Growth and virus yield of the three strains in Ae. aegypti mosquitoes was studied by intrathoracic inoculation and virus titration in Vero E6 cell line.

Results

Virus titration showed Vero E6, C6/36 and BHK-21 cell lines are high virus yielding with all the three lineages while RD and A-549 yielded low virus titres. C6/36 cell line was the most sensitive and yielded the maximum titre. Ae. aegypti mosquitoes, when inoculated with high titre virus, yielded an almost equal growth with the three strains while rapid growth of E1:A226V and Asian strain was observed with 1 log virus.

Interpretation & conclusions

C6/36 cell line was found to be the most sensitive and high yielding for CHIKV irrespective of lineages while Vero E6 and BHK-21 cell lines yielded high titres and may find application for vaccine/diagnostic development. Infection of Ae. aegypti mosquitoes with the three CHIKV strains gave almost identical pattern of growth.

Neutrophil Extracellular Traps Effectively Control Acute Chikungunya Virus Infection

The Chikungunya virus (CHIKV) is a re-emerging arbovirus, in which its infection causes a febrile illness also commonly associated with severe joint pain and myalgia. Although the immune response to CHIKV has been studied, a better understanding of the virus-host interaction mechanisms may lead to more effective therapeutic interventions. In this context, neutrophil extracellular traps (NETs) have been described as a key mediator involved in the control of many pathogens, including several bacteria and viruses, but no reports of this important protective mechanism were documented during CHIKV infection. Here we demonstrate that the experimental infection of mouse-isolated neutrophils with CHIKV resulted in NETosis (NETs release) through a mechanism dependent on TLR7 activation and reactive oxygen species generation. In vitro, mouse-isolated neutrophils stimulated with phorbol 12-myristate 13-acetate release NETs that once incubated with CHIKV, resulting in further virus capture and neutralization. In vivo, NETs inhibition by the treatment of the mice with DNase resulted in the enhanced susceptibility of IFNAR^−/− mice to CHIKV experimental acute infection. Lastly, by accessing the levels of MPO-DNA complex on the acutely CHIKV-infected patients, we found a correlation between the levels of NETs and the viral load in the blood, suggesting that NETs are also released in natural human infection cases. Altogether our findings characterize NETosis as a contributing natural process to control CHIKV acute infection, presenting an antiviral effect that helps to control systemic virus levels.

Viral Febrile Illnesses and Emerging Pathogens

Emerging or emerged diseases and viral pathogens are responsible historically and currently for large epidemics, global pandemics, and significant morbidity and mortality. Our civilization will continue to face the emergence of new pathogens and viruses: viruses will continue to evolve and adapt to new environments at a high rate; our population continues to grow through birth rate, land development, and migration; climate change will continue to increase the vector burden and spread and change the migratory pattern of animals; and our societal mobility will continue to increase through rapid transportation. The clinical evaluation of the febrile patient with a potential emerging viral pathogen involves documenting the likelihood for an infection by a detailed travel history, calculation of an incubation time by exposure, and an understanding of the disease progression though the clinical illness, which drives the differential diagnosis and the type of diagnostics ordered. Ultimately, the proper identification and diagnosis of a patient with a viral febrile illness due to an emerging pathogen will elicit the appropriate precautions to protect health care providers and communities, deliver appropriate therapeutic interventions, and initiate a targeted public health response.

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The majority of emerging diseases are caused by viruses, with many that are transmitted by insect vectors or are zoonotic.

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RNA viruses in particular have high mutation rates and can evolve rapidly in new and changing environments. This, in combination with societal factors, climate change, and rapid travel, has increased the number of epidemics from emerging pathogens in the last several decades.

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Understanding the travel history, incubation time of potential viruses, and the clinical presentation by illness day is essential in making the right diagnosis and identifying the infecting virus.

Clearance of Chikungunya Virus Infection in Lymphoid Tissues Is Promoted by Treatment with an Agonistic Anti-CD137 Antibody

CD137, a member of the tumor necrosis factor receptor superfamily of cell surface proteins, acts as a costimulatory receptor on T cells, natural killer cells, B cell subsets, and some dendritic cells. Agonistic anti-CD137 monoclonal antibody (MAb) therapy has been combined with other chemotherapeutic agents in human cancer trials. Based on its ability to promote tumor clearance, we hypothesized that anti-CD137 MAb might activate immune responses and resolve chronic viral infections. We evaluated anti-CD137 MAb therapy in a mouse infection model of chikungunya virus (CHIKV), an alphavirus that causes chronic polyarthritis in humans and is associated with reservoirs of CHIKV RNA that are not cleared efficiently by adaptive immune responses. Analysis of viral tropism revealed that CHIKV RNA was present preferentially in splenic B cells and follicular dendritic cells during the persistent phase of infection, and animals lacking B cells did not develop persistent CHIKV infection in lymphoid tissue. Anti-CD137 MAb treatment resulted in T cell-dependent clearance of CHIKV RNA in lymphoid tissue, although this effect was not observed in musculoskeletal tissue. The clearance of CHIKV RNA from lymphoid tissue by anti-CD137 MAb was associated with reductions in the numbers of germinal center B cells and follicular dendritic cells. Similar results were observed with anti-CD137 MAb treatment of mice infected with Mayaro virus, a related arthritogenic alphavirus. Thus, anti-CD137 MAb treatment promotes resolution of chronic alphavirus infection in lymphoid tissues by reducing the numbers of target cells for infection and persistence.IMPORTANCE Although CHIKV causes persistent infection in lymphoid and musculoskeletal tissues in multiple animals, the basis for this is poorly understood, which has hampered pharmacological efforts to promote viral clearance. Here, we evaluated the therapeutic effects on persistent CHIKV infection of an agonistic anti-CD137 MAb that can activate T cell and natural killer cell responses to clear tumors. We show that treatment with anti-CD137 MAb promotes the clearance of persistent alphavirus RNA from lymphoid but not musculoskeletal tissues. This occurs because anti-CD137 MAb-triggered T cells reduce the numbers of target germinal center B cells and follicular dendritic cells, which are the primary reservoirs for CHIKV in the spleen and lymph nodes. Our studies help to elucidate the basis for CHIKV persistence and begin to provide strategies that can clear long-term cellular reservoirs of infection.

Amyotrophic Lateral Sclerosis-like Syndrome after Chikungunya

Amyotrophic lateral sclerosis (ALS)-like syndrome refers to a group of conditions whose outcome is similar to that of amyotrophic lateral sclerosis, but with different characteristics in the initial phase and response to therapy. The involvement of an earlier age group, the subacute course, and the stabilization or improvement of the clinical condition during the treatment are most important. There is still no evidence of an association between amyotrophic lateral sclerosis-like syndrome and chikungunya (CHK) infection in the literature. This report was intended to review this syndrome and present a case that occurred after the epidemic of CHK in Pernambuco in 2016. CHK is a fast-onset febrile illness characterized by intense asthenia, arthralgia, myalgia, headache, and skin rash. Reports range from encephalitis, optic neuritis, myeloradiculitis to Guillain-Barré syndrome, generating drastic sequelae such as mental deficiency, blindness, and persistent paralysis. This is the first case report of a possible association of ALS-like syndrome and chikungunya infection. CHK infection may cause ALS-like syndrome. There is a need for further research in this field to develop therapies for neurological complications such as that of CHK.

Plant-Derived Essential Oils; Their Larvicidal Properties and Potential Application for Control of Mosquito-Borne Diseases

Mosquito-borne diseases are currently considered as important threats to human health in subtropical and tropical regions. Resistance to synthetic larvicides in different species of mosquitoes, as well as environmental pollution, are the most common adverse effects of excessive use of such agents. Plant-derived essential oils (EOs) with various chemical entities have a lower chance of developing resistance. So far, no proper classification based on lethal concentration at 50% (LC₅₀) has been made for the larvicidal activity of EOs against different species of Aedes, Anopheles and Culex mosquitoes. To better understand the problem, a summary of the most common mosquito-borne diseases have been made. Related articles were gathered, and required information such as scientific name, used part(s) of plant, target species and LC₅₀ values were extracted. 411 LC₅₀ values were found about the larvicidal activity of EOs against different species of mosquitoes. Depending on the obtained results in each species, LC₅₀ values were summarized as follows: 24 EOs with LC₅₀ < 10 µg/mL, 149 EOs with LC₅₀ in range of 10- 50 µg/mL, 143 EOs having LC₅₀ within 50- 100 µg/mL and 95 EOs showing LC₅₀ > 100 µg/mL. EOs of Callitris glaucophylla and Piper betle against Ae. aegypti, Tagetes minuta against An. gambiae, and Cananga odorata against Cx. quinquefasciatus and An. dirus having LC₅₀ of ~ 1 µg/mL were potentially comparable to synthetic larvicides. It appears that these plants could be considered as candidates for botanical larvicides.

Assessment of Immunogenicity and Neutralisation Efficacy of Viral-Vectored Vaccines Against Chikungunya Virus

Chikungunya virus (CHIKV) has caused extensive outbreaks in several countries within the Americas, Asia, Oceanic/Pacific Islands, and Europe. In humans, CHIKV infections cause a debilitating disease with acute febrile illness and long-term polyarthralgia. Acute and chronic symptoms impose a major economic burden to health systems and contribute to poverty in affected countries. An efficacious vaccine would be an important step towards decreasing the disease burden caused by CHIKV infection. Despite no licensed vaccine is yet available for CHIKV, there is strong evidence of effective asymptomatic viral clearance due to neutralising antibodies against the viral structural proteins. We have designed viral-vectored vaccines to express the structural proteins of CHIKV, using the replication-deficient chimpanzee adenoviral platform, ChAdOx1. Expression of the CHIKV antigens results in the formation of chikungunya virus-like particles. Our vaccines induce high frequencies of anti-chikungunya specific T-cell responses as well as high titres of anti-CHIKV E2 antibodies with high capacity for in vitro neutralisation. Our results indicate the potential for further clinical development of the ChAdOx1 vaccine platform in CHIKV vaccinology.

Zika Virus: Relevance to the State of Hawai'i

Zika virus (ZIKV) is spread among human populations primarily through the bite of Aedes mosquitoes. While most ZIKV infections are asymptomatic or cause self-limited symptoms, the major concerns are its association with Guillain-Barré Syndrome and fetal microcephaly together with other birth defects, known as congenital Zika syndrome (CZS). This article reviews the confirmed Zika cases in the continental United States (U.S.) and Hawai'i thus far, as well as literature of Zika research relevant to Hawai'i. The first case of CZS within the U.S. was reported in Hawai'i, highlighting the unique position of Hawai'i for emerging and re-emerging infectious diseases. Recent studies of the Zika outbreak in Florida demonstrate the key role of Ae. aegypti mosquito in transmission; continuous and proactive vector surveillance in Hawai'i is warranted. Additionally, an updated interim pregnancy guidance for pregnant women with possible ZIKV exposure was summarized. Due to recent decline of ZIKV transmission in the Americas, the risk of ZIKV importation to Hawai'i has been greatly reduced. However, given the presence of Aedes mosquitoes, climate condition, and status of Hawai'i as a travel destination and foreign import market, public health officials and healthcare providers should remain vigilant for a potential outbreak of mosquito-borne diseases in the future.

Chikungunya in Infants and Children: Is Pathogenesis Increasing?

Chikungunya virus (CHIKV) was first extensively described in children during outbreaks in India and South Asia during the mid-1960s. Prior to the 2005 emergence of CHIKV on Reunion Island, CHIKV infection was usually described as a dengue-like illness with arthralgia in Africa and febrile hemorrhagic disease in Asia. Soon after the 2005 emergence, severe CNS consequences from vertical and perinatal transmission were described and as CHIKV continued to emerge in new areas over the next 10 years, severe manifestation of infection and sequelae were increasingly reported in infants and neonates. The following review describes the global reemergence and the syndromes of Chikungunya fever (CHIKF) in infants and children. The various manifestations of CHIKF are described and connected to the viral lineage that was documented in the area at the time the disease was described. The data show that certain manifestations of CHIKF occur with specific viral lineages and genetic motifs, which suggests that severe manifestations of CHIKF in the very young may be associated with the emergence of new viral lineages.

Spectrum of neurological complications in chikungunya fever: experience at a tertiary care centre and review of literature

Chikungunya (CHIK) has re-emerged as a potential neurotropic virus, with outbreaks recently being reported from many parts of India. The present study was conducted to study the spectrum and outcome of neurological complications in patients of CHIK during the 2016 outbreak in Delhi. A total of 42 cases seropositive for IgM CHIK antibodies by MAC-ELISA and developing neurological complications were enrolled. The male:female ratio was 1:2 (age range = 18-90 years). The neurological manifestations observed were encephalitis (n = 12), bulbar palsy (n = 3), acute disseminated encephalomyelitis (n = 1), cerebellitis (n = 1), myelopathy (n = 1), radiculoneuropathy (n = 3), carpal tunnel syndrome (n = 9) and tremors (n = 1). Ten patients reported worsening of pre-existing neuropathic symptoms of diabetic peripheral neuropathy (n = 4) and carpal tunnel syndrome (n = 6). One patient had aggravation of myasthenia gravis leading to respiratory failure. The majority of patients (n = 32) showed a good outcome; ten had a poor prognosis, out of which four died, all from the encephalitis group, particularly the elderly with co-morbidities.

Long-term survival and clinical forms in the acute phase of Chikungunya virus infection in older Caribbeans

OBJECTIVE

To investigate whether the long-term survival in elderly patients with prior Chikungunya virus infection (CVI) is associated with the clinical form presented in the acute phase, as defined by the WHO classification.

METHODS

Retrospective cohort study performed in Martinique University Hospitals. Patients who attended the emergency department for suspected CVI, and who had a positive biological diagnosis of CVI by reverse transcription-polymerase chain reaction on a plasma sample between 10 January and 31 December 2014 were eligible for inclusion. Time-to-death was the primary outcome. The independent relationship between clinical forms and time-to-death was analysed using a Cox model.

RESULTS

In total, 268 patients were included. Mean age was 80 ± 8 years, 53% were women. Median length of follow-up was 28 months (range: 0-39). During follow-up, 53 (19.8%) patients died. Median survival time was 13.2 months (range: 0-33.6). At the end of follow-up, death rates were 4.6% for acute clinical cases, 19.0% for atypical cases, 19.2% for severe acute cases and 23.5% for unclassifiable cases. By multivariable analysis, the clinical form of CVI at admission was found to be independently associated with long-term survival (atypical form: HR = 2.38; 95% CI = 2.15-2.62; severe acute form: HR = 2.40; 95% CI = 2.17-2.64; unclassifiable form: HR = 2.28; 95% CI = 2.06-2.51).

CONCLUSION

The clinical form at presentation with CVI has a significant impact on long-term survival. Management of CVI patients should be tailored according to their clinical form at admission.