Chikungunya Virus Strains Research Articles

Identification and genotyping of Chikungunya virus using reverse transcription polymerase chain reaction and restriction fragment length polymorphism methods

INTRODUCTION. Chikungunya virus (CHIKV) genotyping involves sequencing fractions of genes encoding E1, E2, and nsP1 proteins or the entire genome of the virus. Available reagent kits or polymerase chain reaction protocols cannot be used for CHIKV genotyping, and nucleic acid sequencing requires expensive equipment and materials, which are not always available. Therefore, it seems promising to use a simpler and more cost-effective restriction fragment length polymorphism (RFLP) method, which has not previously been used for CHIKV genotyping.AIM. This study aimed to investigate the possibility of using reverse transcription polymerase chain reaction (RT-PCR) and RFLP for CHIKV identification and genotyping.MATERIALS AND METHODS. The experimental study used RNA from CHIKV strains of four genotypes, including the Asian, West African (WAf), and East/Central/South African (ECSA) genotypes, and the Indian Ocean Lineage of the ECSA genotype (ECSA-IOL). The study used RT-PCR followed by DNA restriction and restriction fragment length analysis.RESULTS. The nsP2 gene fragment of 648 bp in length (positions 3806 to 4453) contains recognition sites for the restriction endonucleases PspEI, PvuII, and DraI. The presence or absence of these sites generates a different combination specific to each of the four CHIKV genotypes. The authors designed primers for amplification of the selected gene region and performed RTPCR and RFLP.CONCLUSIONS. The RFLP method can be used for rapid CHIKV identification and genotyping. The method provides results within a few hours and does not require high-tech equipment.

The Approved Live-Attenuated Chikungunya Virus Vaccine (IXCHIQ®) Elicits Cross-Neutralizing Antibody Breadth Extending to Multiple Arthritogenic Alphaviruses Similar to the Antibody Breadth Following Natural Infection.

The first vaccine against chikungunya virus (CHIKV) was recently licensed in the U.S., Europe, and Canada (brand IXCHIQ®, referred to as VLA1553). Other pathogenic alphaviruses co-circulate with CHIKV and major questions remain regarding the potential of IXCHIQ to confer cross-protection for populations that are exposed to them. Here, we characterized the cross-neutralizing antibody (nAb) responses against heterotypic CHIKV and additional arthritogenic alphaviruses in individuals at one month, six months, and one year post-IXCHIQ vaccination. We characterized nAbs against CHIKV strains LR2006, 181/25, and a 2021 isolate from Tocantins, Brazil, as well as O'nyong-nyong virus (ONNV), Mayaro virus (MAYV), and Ross River virus (RRV). IXCHIQ elicited 100% seroconversion to each virus, with the exception of RRV at 83.3% seroconversion of vaccinees, and cross-neutralizing antibody potency decreased with increasing genetic distance from CHIKV. We compared vaccinee responses to cross-nAbs elicited by natural CHIKV infection in individuals living in the endemic setting of Puerto Rico at 8-9 years post-infection. These data suggest that IXCHIQ efficiently and potently elicits cross-nAb breadth that extends to related alphaviruses in a manner similar to natural CHIKV infection, which may have important implications for individuals that are susceptible to alphavirus co-circulation in regions of potential vaccine rollout.

Complete genome sequence of an Indian outbreak strain of chikungunya virus.

Here, we report the complete genome sequence of an Indian strain of chikungunya virus isolated from an infected patient from Hyderabad, Andhra Pradesh, India, during a massive outbreak in 2005-2006. The genome length spans 11,811 nucleotides and has a poly(A) tail of 29 residues at the 3' end.

In Silico Drug Repurposing Uncovered the Antiviral Potential of the Antiparasitic Drug Oxibendazole Against the Chikungunya Virus.

Chikungunya virus (CHIKV) has been reported in over 120 countries and is the causative agent of Chikungunya fever. The debilitating nature of this disease, which can persist months to years after acute infection, drastically impacts the quality of life of patients. Yet, specific antivirals are lacking for the treatment of this disease, which makes the search for new drugs necessary. In this context, the nsP2 protease emerges as an attractive therapeutic target, and drug repurposing strategies have proven to be valuable. Therefore, we combined in silico and in vitro methods to identify known drugs as potential CHIKV nsP2 protease inhibitors with antiviral properties within DrugBank. Herein, we developed a hybrid virtual screening pipeline comprising pharmacophore- and target-based screening, drug-like, and pharmaceutical filtering steps. Six virtual hits were obtained, and two of them, capecitabine (CPB) and oxibendazole (OBZ), were evaluated against CHIKV replication in Vero cells. CPB did not present antiviral activity, whereas OBZ inhibited the replication of two different strains of CHIKV, namely, 181-25 (Asian genotype) and BRA/RJ/18 (clinical isolate from ECSA genotype). OBZ showed potent antiviral activity against the CHIKV BRA/RJ/18 (EC50 = 11.4 μM) with a high selectivity index (>44). Analogs of OBZ (albendazole, fenbendazole, and mebendazole) were also evaluated, but none exhibited anti-CHIKV activity, and further, their stereoelectronic features were analyzed. Additionally, we observed that OBZ acts mainly at post-entry steps. Hence, our results support further in vivo studies to investigate the antiviral potential of OBZ, which offers a new alternative to fight CHIKV infections.

High Frequencies of kdr Mutation and Chikungunya Infection in Aedes aegypti Population from Minas Gerais, Brazil.

The Chikungunya virus (CHIKV) presents global health challenges, with Brazil experiencing outbreaks since its introduction in 2014. In 2023, following a CHIKV outbreak in Minas Gerais (MG), social media was used to optimize an entomological survey aimed at identifying vectors and viral lineages and assessing insecticide resistance. Following Instagram posts, residents with suspected CHIKV infection were able to schedule mosquito aspirations. In total, 421 mosquitoes (165 Aedes aegypti and 256 Culex quinquefasciatus) were captured from 40 households in Salinas city (MG) and tested for the Dengue, Zika, and Chikungunya viruses through RT-qPCR. Twelve of 57 pools (10 Ae. aegypti and two Cx. quinquefasciatus) tested positive for CHIKV RNA. Viral RNA was also detected in the heads of nine Ae. aegypti, indicating viral dissemination but not in Cx. quinquefasciatus. Genome sequencing yielded the first near-complete genome from the 2023 outbreak, unveiling that the CHIKV strain belonged to the East/Central/South African (ECSA) genotype. Additionally, genetic analyses revealed high frequencies of kdr alleles, including in CHIKV-infected mosquitoes, suggesting resistance to pyrethroid insecticides in this Ae. aegypti population. Social media was important for guiding mosquito-capture efforts in CHIKV transmission hotspots, thus optimizing the opportunity for viral detection. These findings emphasize the urgent need for innovative vector studies and control strategies, as well as interdisciplinary approaches in public health interventions.

Chikungunya virus infection disrupts MHC-I antigen presentation via nonstructural protein 2.

Infection by chikungunya virus (CHIKV), a mosquito-borne alphavirus, causes severe polyarthralgia and polymyalgia, which can last in some people for months to years. Chronic CHIKV disease signs and symptoms are associated with the persistence of viral nucleic acid and antigen in tissues. Like humans and nonhuman primates, CHIKV infection in mice results in the development of robust adaptive antiviral immune responses. Despite this, joint tissue fibroblasts survive CHIKV infection and can support persistent viral replication, suggesting that they escape immune surveillance. Here, using a recombinant CHIKV strain encoding the fluorescent protein VENUS with an embedded CD8+ T cell epitope, SIINFEKL, we observed a marked loss of both MHC class I (MHC-I) surface expression and antigen presentation by CHIKV-infected joint tissue fibroblasts. Both in vivo and ex vivo infected joint tissue fibroblasts displayed reduced cell surface levels of H2-Kb and H2-Db MHC-I proteins while maintaining similar levels of other cell surface proteins. Mutations within the methyl transferase-like domain of the CHIKV nonstructural protein 2 (nsP2) increased MHC-I cell surface expression and antigen presentation efficiency by CHIKV-infected cells. Moreover, expression of WT nsP2 alone, but not nsP2 with mutations in the methyltransferase-like domain, resulted in decreased MHC-I antigen presentation efficiency. MHC-I surface expression and antigen presentation was rescued by replacing VENUS-SIINFEKL with SIINFEKL tethered to β2-microglobulin in the CHIKV genome, which bypasses the requirement for peptide processing and TAP-mediated peptide transport into the endoplasmic reticulum. Collectively, this work suggests that CHIKV escapes the surveillance of antiviral CD8+ T cells, in part, by nsP2-mediated disruption of MHC-I antigen presentation.

Antiviral and Virucidal Activities of Uncaria tomentosa (Cat's Claw) against the Chikungunya Virus.

Uncaria tomentosa (UT) is a medicinal plant popularly known as cat's claw belonging to the Rubiaceae family that has been reported to display antiviral and anti-inflammatory activities. The chikungunya virus (CHIKV) outbreaks constitute a Brazilian public health concern. CHIKV infection develops an abrupt onset of fever, usually accompanied by a skin rash, besides incapacitating polyarthralgia. There is no vaccine available or treatment for CHIKV infection. The present study evaluates the hydroalcoholic extract of UT bark as a potential antiviral against CHIKV. The in vitro antiviral activity of the UT extract against the Brazilian CHIKV strain was assessed using quantitative reverse transcription polymerase chain reaction, flow cytometry, and plaque assay. Results obtained demonstrated that UT inhibits CHIKV infection in a dose-dependent manner. At the non-cytotoxic concentration of 100 µg/mL, UT exhibited antiviral activity above 90% as determined by plaque reduction assay, and it reduced the viral cytopathic effect. Similarly, a significant virucidal effect of 100 µg/mL UT was observed after 24 and 48 h post-infection. This is the first report on the antiviral activity of UT against CHIKV infection, and the data presented here suggests UT as a potential antiviral to treat CHIKV infection.

Construction and Characterization of an Infectious Clone of Chikungunya Virus Strain 37997

Construction and Characterization of an Infectious Clone of Chikungunya Virus Strain 37997

Efficacy of interferon inducers against Chikungunya virus <i>in vitro</i>

Scientific relevance. To date, no specific antivirals have been approved to treat and prevent Chikungunya fever, its complications, and sequelae. Therefore, the development of therapeutic and preventive medicinal products against Chikungunya virus (CHIKV), including interferon inducers, is gaining relevance.Aim. The authors aimed to study the effectiveness of prophylactic administration of an interferon inducer against CHIKV in an in vitro model.Materials and methods. The study used two cell lines (Vero and А549), a CHIKV strain (Nika2021), and an interferon-inducing medicinal product (double-stranded RNA sodium salt) at two doses (250 μg/mL and 500 μg/mL) administered at two schedules: Prevention (4 h prior to the virus challenge) and Emergency Prevention (at the time of the virus challenge). The authors determined the CHIKV titre by its cytopathogenic effect, the CHIKV RNA content by the cycle threshold value in real-time reverse-transcription polymerase chain reaction, and the concentration of cytokines using the enzyme immunoassay method. The study monitored the changes in CHIKV biological activity, CHIKV RNA levels, and the production of interferon-alpha (IFN-α), interferon-gamma (IFN-γ), interleukin-6 (IL-6), and tumour necrosis factor-alpha (TNF-α) in cells over time. The statistical analysis of the resulting data used Microsoft Office Excel 2016 and StatTech.Results. The medicinal product at doses of 250 μg/mL and 500 μg/mL stimulated the production of both IFN-α and IFN-γ (IFN-α to a greater extent than IFN-γ) in both cell lines (in A549 to a greater extent than in Vero). The changes in CHIKV RNA levels with time corresponded to those of the virus titre. In general, CHIKV RNA levels in Vero cells were significantly higher than those in A549 cells (р<0.002 at 250 μg/mL and р<0.0005 at 500 μg/mL). The CHIKV RNA content after preventive interferon inducer administration was significantly lower than that in the control experiment (challenge without administration of the medicinal product) for both doses and both cell lines (р<0.002 for Vero cells; р<0.0003 for А549 cells). The CHIKV RNA content after interferon inducer administration as emergency prevention was significantly lower than that in the control experiment (р<0.05 for Vero cells; р<0.003 for А549 cells). The study demonstrated the efficacy of the interferon inducer against CHIKV and a higher applicability of the A549 cell line to studying antiviral activity in vitro. The authors observed the production of IL-6 and TNF-α by intact cells of both lines.Conclusions. According to the results, the studied interferon inducer has a positive antiviral effect against CHIKV in vitro, with the antiviral effect degree depending on the cell line used. This experimental study demonstrated the need to carefully select the cell line for a study in accordance with its objectives and to evaluate the production of cytokines by a monolayer of cells before stimulation with viruses and/or medicinal products.

Genetic characterization of the complete genome of a strain of Chikungunya virus circulating in Brazil

The Chikungunya virus (CHIKV) is a single-stranded positive-sense RNA virus that belongs to the Alphavirus genus of the Togaviridae family. It is primarily transmitted by Aedes aegypti and albopictus mosquitoes. Its genome encodes four non-structural proteins (NSP 1-4) and three structural proteins (C, E1, and E2). Four lineages of this virus have been identified, namely the West African, East African, Central and South African (ECSA), Asian (AL), and Indian Ocean Lineages (IOL). CHIKV is an endemic arbovirus circulating in 51 countries in the Americas. Clinical manifestations attributed to it include high fever, rash, myalgia, and episodes of arthralgia, which subsequently lead to chronic pain and disability, especially in the joints. Sequencing the complete genome of the Chikungunya virus is essential to understand its biology, evolution, and spread and to develop effective strategies for prevention, diagnosis, and treatment. This information is crucial for combating the disease and minimizing its impact on public health. For these reasons, the complete genome of the Chikungunya virus strain br33, identified in the northeastern city of Recife, in the state of Pernambuco, Brazil, was sequenced. The genome has a size of 11,601 nucleotides and contains coding regions for two polyproteins. A phylogenetic analysis indicates that the recent Brazilian strain of CHIKV belongs to the East, Central, and South African lineage (ECSA). This phylogenetic identification is important because this particular genotype has been associated with greater damage and clinical severity. Until 2016, the CHIKV virus was directly associated with travel, and its transmission was limited. Subsequently, the largest outbreak occurred in the state associated with the introduction of a new ECSA lineage, as identified in this study. It is highly likely that new CHIKV outbreaks will occur in the near future due to the abundance of competent vectors in Brazil and a susceptible population, exposing more than 11 million inhabitants to an increasing risk of infection.

Understanding the resurgence of chikungunya virus during 2020-2021 in Pune, India, based on genomic analyses: A seven year study.

A surge in chikungunya was observed during 2020-21 in Pune district of Maharashtra, India. Whole genome sequencing and phylogenetic analysis of 21 samples/sequences revealed them as Indian ocean lineage of East Central South African genotype. Two distinct sequence clusters were found to circulate during 2020-21; one with E1:K211E and E2:V264A mutations while the other had E1:I317V mutation along with E1:K211E and E2: V264A mutations. The former, the predominant cluster (n = 18), clustered with chikungunya virus (CHIKV) strains of pre 2014 period while the latter (n = 3) clustered with 2016-2018 period Indian strains. Though E1: A226V was not detected in any of the 21 sequences, several unique mutations were detected in the strains which might have played key roles in the enhanced virus transmission during the period. The study highlights parallel evolution, introduction from the neighboring regions and cocirculation of two sequence clusters of CHIKV in Pune. The complete genome data can be useful to determine how the circulating strains differ from candidate vaccines and might help to predict the protective efficacy of chikungunya vaccine candidates.

Development of a novel multi-epitope vaccine based on capsid and envelope protein against Chikungunya virus

Chikungunya virus (CHIKV), a type A virus borne by mosquitoes that can cause major clinical manifestations including rash, fever and debilitating arthritis, grown into a reemerging serious public health issue. Currently, there is no licensed therapy or vaccine available for CHIKV, although the most promising form of treatment appears to be immunotherapy. Neutralizing antibodies for CHIKV can provide high protection for all CHIKV strains, as well as other alphaviruses. Development of a protective vaccine may be an effective strategy to prevent the outbreak of CHIKV and provide protection for travelers. In this study, we designed a multi-epitope vaccine with a 543-amino-acid structure based on the E1, E2 and capsid proteins of CHIKV, including 6 CTL epitopes, 6 HTL epitopes, 12 linear B epitopes, along with the adjuvant β-defensin III. All T-cell epitopes were docked with their corresponding MHC alleles to validate their effect on inducing immune responses, and the vaccine’s sequence was proven to have acceptable physicochemical properties. Further, the developed vaccine was docked with TLR3 and TLR8, both of which play an important role in recognizing RNA viruses. Basic analyses of the docked complexes and molecular dynamic simulations revealed that the vaccine interacted strongly with TLRs. Immunological simulations indicated that the vaccine could induce both cellular and humoral immunity. Hopefully, this proposed vaccine structure can serve as a viable candidate against CHIKV infection. Communicated by Ramaswamy H. Sarma

Interactions of the nsP3 proteins of CHIKV with the human host protein NAP1 plays a significant role in viral pathogenesis – An in silico study

Non-structural protein 3 (nsP3) of Chikungunya virus (CHIKV) is known to interact with numerous mammalian host proteins during the course of its infection. Two such proteins are NAP1L1 and NAP1L4 (nucleosome assembly protein 1 like proteins 1 and 4), which are known to bind at the C-terminal domain of nsP3 and redundantly stimulate replication. However, the detailed mechanism of this pro-viral effect is not fully understood. During the last two decades, ChikV outbreak has occurred in several countries making it a major public health problem. The outbreak strain have shown a higher virulence, and carry specific point mutations in their structural and non-structural proteins, including nsP3. We considered the possibility that the presence of these mutations may cause the nsP3 of the more virulent outbreak strain to interact with the NAP1 proteins differently than that of the less virulent prototype strain. We carried out in silico studies of the interactions of NAP1L1/L4 proteins with the nsP3 proteins of three different strains of CHIKV, one of which is a highly virulent outbreak strain. The results of our structure prediction and docking studies showed that in a less virulent strain, NAP1L4 binds relatively better than NAP1L1 to the C-terminal domain of nsP3. In the more virulent strain, the difference between the bindings of these two proteins was even higher. A Molecular dynamic simulation of the docked complexes of nsP3 with the host NAP1L1 and NAP1L4 proteins for a 100 ns timeframe study over a period of 100 ns validated the reliability of the binding models and further substantiated the differences between the two complexes. Our results suggest that NAP1L4 is possibly a better target than NAP1L1 for designing antiviral drugs against CHIKV infection.

Effect of Viral Strain and Host Age on Clinical Disease and Viral Replication in Immunocompetent Mouse Models of Chikungunya Encephalomyelitis.

The alphavirus chikungunya virus (CHIKV) represents a reemerging public health threat as mosquito vectors spread and viruses acquire advantageous mutations. Although primarily arthritogenic in nature, CHIKV can produce neurological disease with long-lasting sequelae that are difficult to study in humans. We therefore evaluated immunocompetent mouse strains/stocks for their susceptibility to intracranial infection with three different CHIKV strains, the East/Central/South African (ECSA) lineage strain SL15649 and Asian lineage strains AF15561 and SM2013. In CD-1 mice, neurovirulence was age- and CHIKV strain-specific, with SM2013 inducing less severe disease than SL15649 and AF15561. In 4-6-week-old C57BL/6J mice, SL15649 induced more severe disease and increased viral brain and spinal cord titers compared to Asian lineage strains, further indicating that neurological disease severity is CHIKV-strain-dependent. Proinflammatory cytokine gene expression and CD4+ T cell infiltration in the brain were also increased with SL15649 infection, suggesting that like other encephalitic alphaviruses and with CHIKV-induced arthritis, the immune response contributes to CHIKV-induced neurological disease. Finally, this study helps overcome a current barrier in the alphavirus field by identifying both 4-6-week-old CD-1 and C57BL/6J mice as immunocompetent, neurodevelopmentally appropriate mouse models that can be used to examine CHIKV neuropathogenesis and immunopathogenesis following direct brain infection.

Replication and innate immune responses of two chikungunya virus genotypes in human monocyte-derived macrophages.

Chikungunya virus (CHIKV) is a re-emerging mosquito-borne virus, which causes epidemics of fever, joint pain and rash. There are three genotypes: West African, East/Central/South/Africa (ECSA) and Asian, with the latter two predominant globally. Genotype-specific differences in clinical presentations, virulence and immunopathology have been described. Macrophages are key cells in immune responses against CHIKV. Circulating blood monocytes enter tissue to differentiate into monocyte-derived macrophages (MDMs) in response to CHIKV infection at key replication sites such as lymphoid organs and joints. This study analyses differences in replication and induced immune mediators following infection of MDMs with Asian and ECSA CHIKV genotypes. Primary human MDMs were derived from residual blood donations. Replication of Asian (MY/06/37348) or ECSA (MY/08/065) genotype strains of CHIKV in MDMs was measured by plaque assay. Nineteen immune mediators were measured in infected cell supernatants using multiplexed immunoassay or ELISA. MY/08/065 showed significantly higher viral replication at 24 h post-infection (h p.i.) but induced significantly lower expression of proinflammatory cytokines (CCL-2, CCL-3, CCL-4, RANTES and CXCL-10) and the anti-inflammatory IL-1Ra compared to MY/06/37348. No differences were seen at later time points up to 72 h p.i. During early infection, MY/08/065 induced lower proinflammatory immune responses in MDMs. In vivo, this may lead to poorer initial control of viral infection, facilitating CHIKV replication and dissemination to other sites such as joints. This may explain the consistent past findings that the ECSA genotype is associated with greater viremia and severity of symptoms than the Asian genotype. Knowledge of CHIKV genotype-specific immunopathogenic mechanisms in human MDMs is important in understanding of clinical epidemiology, biomarkers and therapeutics in areas with co-circulation of different genotypes.

The First Genomic Characterization of the Chikungunya Virus in Saudi Arabia

BackgroundChikungunya is an arboviral infection caused by the Chikungunya virus (CHIKV) transmitted to humans by mosquitoes of Aedes spp. CHIKV has been confined to African countries and South-East Asia up to 2004, but since then, the pathogen has become more global, and its high morbidity rate has become more visible. Saudi Arabia is not an endemic region of CHIKV, and the virus’s origin is not yet fully understood. This study aimed to characterize the genome of CHIKV from samples detected in Jeddah in 2018.MethodTwenty-two sets of primers were designed to amplify near-full length genome of CHIKV. RT-PCR was conducted from clinical samples. Two samples were used for studying near complete genome sequence while the remaining samples were used to study the E1 gene. Different bioinformatics tools were utilized.ResultsPhylogenetic analysis showed that the CHIKV strains clustered with strains isolated from Kenya during 2017–2018 and belonged to ECSA genotype. E1: L136F, K211E and I317V mutations were identified in our strains. Also, E2: M74I, A76T, and V264A mutations were documented. Additionally, the capsid N79S substitution was also detected.ConclusionThe genome of CHIKV was analyzed for the first time in Saudi Arabia to better understand the origin of the CHIKV and its genetic diversity, which showed high similarity with IE—a subclade of CHIKV strains detected in Mombasa (Kenya) indicating its possible origin.

Generation of a Live-Attenuated Strain of Chikungunya Virus from an Indian Isolate for Vaccine Development.

Chikungunya virus (CHIKV) re-emergence in the last decade has resulted in explosive epidemics. Along with the classical symptoms of fever and debilitating arthralgia, there were occurrences of unusual clinical presentations such as neurovirulence and mortality. These generated a renewed global interest to develop prophylactic vaccines. Here, using the classical approach of virus attenuation, we developed an attenuated CHIKV strain (RGCB355/KL08-p75) for the purpose. Repeated passaging (75 times) of a local clinical isolate of ECSA lineage virus in U-87 MG human astrocytoma cells, an interferon-response-deficient cell line, resulted in efficient adaptation and attenuation. While experimental infection of 3-day old CHIKV-susceptible BALB/c pups with the parent strain RGCB355/KL08-p4 resulted in death of all the animals, there was 100% survival in mice infected with the attenuated p75. In adult, immunocompetent, CHIKV-non-susceptible C57BL/6 mice, inoculation with p75 induced high antibody response without any signs of disease. Both p4 and p75 strains are uniformly lethal to interferon-response-deficient AG129 mice. Passive protection studies in AG129 mice using immune serum against p75 resulted in complete survival. Whole-genome sequencing identified novel mutations that might be responsible for virus attenuation. Our results establish the usefulness of RGCB355/KL08-p75 as a strain for vaccine development against chikungunya.

Re-emergence of dengue, chikungunya, and Zika viruses in 2021 after a 10-year gap in Gabon

Mosquito-borne viral infections are a major concern in endemic areas, such as Africa. Although outbreaks have been reported throughout Africa, only a few surveillance studies have been conducted in Gabon since the outbreaks of dengue virus (DENV) and chikungunya virus (CHIKV) in 2010. Therefore, the current situation is unknown. This study aimed to investigate the presence of arboviruses, especially DENV (serotypes 1–4), CHIKV, and Zika virus (ZIKV), in Gabon, Central Africa. Between 2020 and 2021, we collected 1060 serum samples from febrile patients and screened them against viruses using reverse transcription-quantitative PCR. We detected two DENV serotypes 1 (DENV-1), one CHIKV, and one ZIKV, and subsequently analyzed the genome sequences. To determine the genetic diversity and transmission route of the viruses, phylogenetic analysis was performed using complete or partial genome sequences. The DENV-1 and CHIKV strains detected in this study were closely related to the previous Gabonese strains, whereas the recent ZIKV strain was genetically different from a strain detected in 2007 in Gabon. This study provides new genomic information on DENV-1, CHIKV, and ZIKV that were detected in Gabon and insight into the circulation of the viruses in the country and their introduction from neighboring African countries.

The origin and continuing adaptive evolution of chikungunya virus.

Chikungunya virus (CHIKV) is the responsible agent of chikungunya fever, a debilitating arthritic disease in humans. CHIKV is endemic in Africa and Asia, although transmission cycles are considerably different on these continents. Before 2004, CHIKV had received little attention, since it was only known to cause localised outbreaks in a limited region with no fatalities. However, the recent global reemergence of CHIKV has caused serious global health problems and shown its potential to become a significant viral threat in the future. Unexpectedly, the reemergence is more rapid and is geographically more extensive, especially due to increased intensity of global travel systems or failure to contain mosquito populations. Another important factor is the successful adaptation of CHIKV to a new vector, the Aedes albopictus mosquito. Ae. albopictus survives in both temperate and tropical climates, thus facilitating CHIKV expansion to non-endemic regions. The continuous spread and transmission of CHIKV pose challenges for the development of effective vaccines and specific antiviral therapies. In this review, we discuss the biology and origin of CHIKV in Africa as well as its subsequent expansion to other parts of the world. We also review the transmission cycle of CHIKV and its continuing adaptation to its mosquito vectors and vertebrate hosts. More-complete understanding of the continuous evolution of CHIKV may help in predicting the emergence of CHIKV strains with possibly greater transmission efficiency in the future.

Virological, Serological and Clinical Analysis of Chikungunya Virus Infection in Thai Patients.

From 2018 to 2020, the Chikungunya virus (CHIKV) outbreak re-emerged in Thailand with a record of more than 10,000 cases up until the end of 2020. Here, we studied acute CHIKV-infected patients who had presented to the Bangkok Hospital for Tropical Diseases from 2019 to 2020 by assessing the relationship between viral load, clinical features, and serological profile. The results from our study showed that viral load was significantly high in patients with fever, headache, and arthritis. We also determined the neutralizing antibody titer in response to the viral load in patients, and our data support the evidence that an effective neutralizing antibody response against the virus is important for control of the viral load. Moreover, the phylogenetic analysis revealed that the CHIKV strains we studied belonged to the East, Central, and Southern African (ECSA) genotype, of the Indian ocean lineage (IOL), and possessed E1-K211E and E1-I317V mutations. Thus, this study provides insight for a better understanding of CHIKV pathogenesis in acute infection, along with the genomic diversity of the current CHIKV strains circulating in Thailand.