The first confirmed outbreak of chikungunya reported in Timor-Leste, 2024.

Abstract: Timor-Leste is a mountainous, half-island nation with a population of 1.3 million, which shares a land border with Indonesia and is 550 km from Darwin, Australia. Since independence in 2002, Timor-Leste has achieved significant development; however, high levels of poverty remain. Chikungunya virus (CHIKV) is endemic in over 100 countries in Africa, Asia, Europe and in the Americas. It is transmitted by the bite of infected Aedes aegypti or Ae. albopictus mosquitoes, which are present in Timor-Leste and which contribute to annual rainy-season dengue virus (DENV) outbreaks. Symptomatic people typically suffer from acute onset of fever, usually accompanied by severe arthritis or arthralgia. Joint pain can be debilitating for several days, and may sometimes last for weeks, months or years. Unlike DENV infection which has significant mortality, most people recover completely. Between 2002 and 2023, there were 26 cases of CHIKV notified in Australia who acquired their infection in Timor-Leste; however, laboratory testing capability for CHIKV in Timor-Leste only became available in 2021 using polymerase chain reaction (PCR). The first locally diagnosed case was notified in November 2023. In January 2024, an outbreak of CHIKV was recognised in Timor-Leste for the first time, with 195 outbreak cases reported during 1-31 January 2024; all were PCR positive. There were no cases hospitalised, and no deaths. The median age of cases was 17 years (range 1-76 years); 51% were males. Cases were reported across the country; most (88/195) were from Dili, although the highest incidence was seen in the neighbouring municipality of Ermera (monthly incidence rate of 58.8 cases per 100,000 population). This first reported outbreak of CHIKV in Timor-Leste highlights the need for improved mosquito-borne illness control and response strategies, including minimising breeding sites and promoting early presentation for treatment and differential diagnosis from DENV, and consideration of the deployment of Wolbachia-infected mosquitoes, particularly as they have shown to reduce the transmission of CHIKV, DENV and Zika virus, all of which pose threats in Timor-Leste.

A case series of post-infectious chikungunya myeloradiculoneuropathy.

Chikungunya fever is an arboviral illness caused by chikungunya virus (CHIKV) and transmitted by the bite of Aedes aegypti and Aedes albopictus. It is an RNA virus belonging to the genus Alphavirus and family Togaviridae. We present a case series of three patients with chikungunya illness developing para/post-infectious myeloradiculoneuropathy.These patients developed neurological symptoms in the form of bilateral lower limb weakness with sensory and bowel involvement after the recovery from the initial acute episode of chikungunya fever. Clinical examination findings suggested myeloradiculoneuropathy with normal Magnetic Resonance Imaging of the Spine, with the nerve conduction study showing sensorimotor axonal polyneuropathy. All the patients were treated with 1 g of methylprednisolone once a day for five days, and case 2 was given intravenous immunoglobulin also. In the follow-up, cases 1 and 2 showed complete recovery without recurrence, and case 3 did not show improvement at one month.

Cryptic circulation of chikungunya virus in São Jose do Rio Preto, Brazil, 2015-2019.

BACKGROUND: Chikungunya virus (CHIKV) has spread across Brazil with varying incidence rates depending on the affected areas. Due to cocirculation of arboviruses and overlapping disease symptoms, CHIKV infection may be underdiagnosed. To understand the lack of CHIKV epidemics in São José do Rio Preto (SJdRP), São Paulo (SP), Brazil, we evaluated viral circulation by investigating anti-CHIKV IgG seroconversion in a prospective study of asymptomatic individuals and detecting anti-CHIKV IgM in individuals suspected of dengue infection, as well as CHIKV presence in Aedes mosquitoes. The opportunity to assess two different groups (symptomatic and asymptomatic) exposed at the same geographic region aimed to broaden the possibility of identifying the viral circulation, which had been previously considered absent. METHODOLOGY/PRINCIPAL FINDINGS: Based on a prospective population study model and demographic characteristics (sex and age), we analyzed the anti-CHIKV IgG seroconversion rate in 341 subjects by ELISA over four years. The seroprevalence increased from 0.35% in the first year to 2.3% after 3 years of follow-up. Additionally, we investigated 497 samples from a blood panel collected from dengue-suspected individuals during the 2019 dengue outbreak in SJdRP. In total, 4.4% were positive for anti-CHIKV IgM, and 8.6% were positive for IgG. To exclude alphavirus cross-reactivity, we evaluated the presence of anti-Mayaro virus (MAYV) IgG by ELISA, and the positivity rate was 0.3% in the population study and 0.8% in the blood panel samples. In CHIKV and MAYV plaque reduction neutralization tests (PRNTs), the positivity rate for CHIKV-neutralizing antibodies in these ELISA-positive samples was 46.7%, while no MAYV-neutralizing antibodies were detected. Genomic sequencing and phylogenetic analysis revealed CHIKV genotype ECSA in São José do Rio Preto, SP. Finally, mosquitoes collected to complement human surveillance revealed CHIKV positivity of 2.76% of A. aegypti and 9.09% of A. albopictus (although it was far less abundant than A. aegypti) by RT-qPCR. CONCLUSIONS/SIGNIFICANCE: Our data suggest cryptic CHIKV circulation in SJdRP detected by continual active surveillance. These low levels, but increasing, of viral circulation highlight the possibility of CHIKV outbreaks, as there is a large naïve population. Improved knowledge of the epidemiological situation might aid in outbreaks prevention.

Genomic and eco-epidemiological investigations in Uruguay reveal local Chikungunya virus transmission dynamics during its expansion across the Americas in 2023.

Uruguay experienced its first Chikungunya virus outbreak in 2023, resulting in a significant burden to its healthcare system. We conducted analysis based on real-time genomic surveillance (30 novel whole genomes) to offer timely insights into recent local transmission dynamics and eco-epidemiological factors behind its emergence and spread in the country.

Pathophysiology of chikungunya virus infection associated with fatal outcomes.

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that causes acute, subacute, and chronic human arthritogenic diseases and, in rare instances, can lead to neurological complications and death. Here, we combined epidemiological, virological, histopathological, cytokine, molecular dynamics, metabolomic, proteomic, and genomic analyses to investigate viral and host factors that contribute to chikungunya-associated (CHIK) death. Our results indicate that CHIK deaths are associated with multi-organ infection, central nervous system damage, and elevated serum levels of pro-inflammatory cytokines and chemokines compared with survivors. The histopathologic, metabolite, and proteomic signatures of CHIK deaths reveal hemodynamic disorders and dysregulated immune responses. The CHIKV East-Central-South-African lineage infecting our study population causes both fatal and survival cases. Additionally, CHIKV infection impairs the integrity of the blood-brain barrier, as evidenced by an increase in permeability and altered tight junction protein expression. Overall, our findings improve the understanding of CHIK pathophysiology and the causes of fatal infections.

Molecular characterization of Chikungunya virus recovered from patients in the Maranhão state, Brazil.

BACKGROUND: Chikungunya virus (CHIKV) is an arbovirus from the Togaviridae family which has four genotypes: West African (WA), East/Central/South African (ECSA) and Asian/Caribbean lineage (AL) and Indian Ocean Lineage (IOL). The ECSA genotype was first registered in Brazil in Feira de Santana and spread to all Brazilian regions. This study reports the characterization of CHIKV isolates recovered from sera samples of fifty patients from seventeen cities in Maranhão, a state from Brazilian northeast region and part of the Legal Amazon area. METHODS AND RESULTS: Primers were developed to amplify the partial regions coding structural proteins (E1, E3, E2, 6 K, and Capsid C). The consensus sequences have 2871 bp, covering approximately 24% of the genome. The isolates were highly similar (> 99%) to the ECSA isolate from Feira de Santana (BHI3734/H804698), presenting 30 non-synonymous mutations in E1 (5.95%), 18 in E2 (4.46%), and 1 in E3 (3.03%), taking the BHI3734/H804698 isolate as standard. Although the mutations described have not previously been related to increased infectivity or transmissibility of CHIKV, in silico analysis showed changes in physicochemical characteristics, antigenicity, and B cell epitopes of E1 and E2. CONCLUSIONS: These findings demonstrate the importance of molecular approaches for monitoring the viral adaptations undergone by CHIKV and its geographic distribution.

N6-methyladenosine modification is not a general trait of viral RNA genomes.

Despite the nuclear localization of the m6A machinery, the genomes of multiple exclusively-cytoplasmic RNA viruses, such as chikungunya (CHIKV) and dengue (DENV), are reported to be extensively m6A-modified. However, these findings are mostly based on m6A-Seq, an antibody-dependent technique with a high rate of false positives. Here, we address the presence of m6A in CHIKV and DENV RNAs. For this, we combine m6A-Seq and the antibody-independent SELECT and nanopore direct RNA sequencing techniques with functional, molecular, and mutagenesis studies. Following this comprehensive analysis, we find no evidence of m6A modification in CHIKV or DENV transcripts. Furthermore, depletion of key components of the host m6A machinery does not affect CHIKV or DENV infection. Moreover, CHIKV or DENV infection has no effect on the m6A machinery's localization. Our results challenge the prevailing notion that m6A modification is a general feature of cytoplasmic RNA viruses and underscore the importance of validating RNA modifications with orthogonal approaches.

Clinical description of dengue and chikungunya virus infections amongst acute febrile patients in a malaria endemic area of Mfou, the Centre region of Cameroon.

This study aims to determine the frequency and clinical manifestations of dengue and chikungunya viral infections in the district hospital of Mfou, Centre region of Cameroon where malaria is endemic. Blood samples were collected from suspected cases and tested for Plasmodium parasites and for the molecular detection of viral RNAs (dengue, zika and chikungunya viruses) using TRIOPLEX qPCR. A total of 108 patients were clinically suspected among which 25 % were male and 50 % were less than 15.5 years old. Of these 14.8 % (16/108) and 2.8 % (3/108) had acute dengue and chikungunya fevers respectively. Co-infection with malaria was reported in 56.3 % (9/16) of Dengue cases and 33.3 % (1/3) of chikungunya cases. Clinical profiling further revealed that nausea and vomiting show a significant difference in dengue infected individuals to those of non-infected individuals (P = 0.027). The presence of dengue fever and chikungunya fever and the absence of specific clinical manifestations highlight the need to strengthen surveillance of acute febrile infections for a better estimation of the burden of arboviruses.

Crosstalk between CD64+MHCII+ macrophages and CD4+ T cells drives joint pathology during chikungunya.

Communications between immune cells are essential to ensure appropriate coordination of their activities. Here, we observed the infiltration of activated macrophages into the joint-footpads of chikungunya virus (CHIKV)-infected animals. Large numbers of CD64+MHCII+ and CD64+MHCII- macrophages were present in the joint-footpad, preceded by the recruitment of their CD11b+Ly6C+ inflammatory monocyte precursors. Recruitment and differentiation of these myeloid subsets were dependent on CD4+ T cells and GM-CSF. Transcriptomic and gene ontology analyses of CD64+MHCII+ and CD64+MHCII- macrophages revealed 89 differentially expressed genes, including genes involved in T cell proliferation and differentiation pathways. Depletion of phagocytes, including CD64+MHCII+ macrophages, from CHIKV-infected mice reduced disease pathology, demonstrating that these cells play a pro-inflammatory role in CHIKV infection. Together, these results highlight the synergistic dynamics of immune cell crosstalk in driving CHIKV immunopathogenesis. This study provides new insights in the disease mechanism and offers opportunities for development of novel anti-CHIKV therapeutics.

Detection of Chikungunya Virus RNA in Oral Fluid and Urine: An Alternative Approach to Diagnosis?

To evaluate whether oral fluids (OF) and urine can serve as alternative, non-invasive samples to diagnose chikungunya virus (CHIKV) infection via RT-qPCR, we employed the same RNA extraction and RT-qPCR protocols on paired serum, OF and urine samples collected from 51 patients with chikungunya during the acute phase of the illness. Chikungunya patients were confirmed through RT-qPCR in acute-phase sera (N = 19), IgM seroconversion between acute- and convalescent-phase sera (N = 12), or IgM detection in acute-phase sera (N = 20). The controls included paired serum, OF and urine samples from patients with non-arbovirus acute febrile illness (N = 28) and RT-PCR-confirmed dengue (N = 16). Nine (47%) of the patients with positive RT-qPCR for CHIKV in sera and two (17%) of those with CHIKV infection confirmed solely via IgM seroconversion had OF positive for CHIKV in RT-qPCR. One (5%) patient with CHIKV infection confirmed via serum RT-qPCR was positive in the RT-qPCR performed on urine. None of the negative control group samples were positive. Although OF may serve as an alternative sample for diagnosing acute chikungunya in specific settings, a negative result cannot rule out an infection. Further research is needed to investigate whether OF and urine collected later in the disease course when serum becomes RT-qPCR-negative may be helpful in CHIKV diagnosis and surveillance, as well as to determine whether urine and OF pose any risk of CHIKV transmission.

Attenuation of neurovirulence of chikungunya virus by a single amino acid mutation in viral E2 envelope protein.

BACKGROUND: Chikungunya virus (CHIKV) has reemerged as a major public health concern, causing chikungunya fever with increasing cases and neurological complications. METHODS: In the present study, we investigated a low-passage human isolate of the East/ Central/South African (ECSA) lineage of CHIKV strain LK(EH)CH6708, which exhibited a mix of small and large viral plaques. The small and large plaque variants were isolated and designated as CHIKV-SP and CHIKV-BP, respectively. CHIKV-SP and CHIKV-BP were characterized in vitro and in vivo to compare their virus production and virulence. Additionally, whole viral genome analysis and reverse genetics were employed to identify genomic virulence factors. RESULTS: CHIKV-SP demonstrated lower virus production in mammalian cells and attenuated virulence in a murine model. On the other hand, CHIKV-BP induced higher pro-inflammatory cytokine levels, compromised the integrity of the blood-brain barrier, and led to astrocyte infection in mouse brains. Furthermore, the CHIKV-SP variant had limited transmission potential in Aedes albopictus mosquitoes, likely due to restricted dissemination. Whole viral genome analysis revealed multiple genetic mutations in the CHIKV-SP variant, including a Glycine (G) to Arginine (R) mutation at position 55 in the viral E2 glycoprotein. Reverse genetics experiments confirmed that the E2-G55R mutation alone was sufficient to reduce virus production in vitro and virulence in mice. CONCLUSIONS: These findings highlight the attenuating effects of the E2-G55R mutation on CHIKV pathogenicity and neurovirulence and emphasize the importance of monitoring this mutation in natural infections.

Capsid protein mediated evasion of IRAK1-dependent signalling is essential to Sindbis virus neuroinvasion and virulence in mice.

ABSTRACTAlphaviruses are arthropod-borne, single-stranded positive-sense RNA viruses that are recognized as rapidly emerging pathogens. Despite being exquisitely sensitive to the effects of the innate immune response alphaviruses can readily replicate, disseminate, and induce pathogenesis in immunologically competent hosts. Nonetheless, how alphaviruses evade the induction of an innate immune response prior to viral gene expression, or in non-permissive infections, is unknown. Previously we reported the identification of a novel host/pathogen interaction between the viral Capsid (CP) protein and the host IRAK1 protein. The CP/IRAK1 interaction was determined to negatively impact IRAK1-dependent PAMP detection in vitro, however, the precise importance of the CP/IRAK1 interaction to alphaviral infection remained unknown. Here we detail the identification of the CP/IRAK1 interaction determinants of the Sindbis virus (SINV) CP protein and examine the importance of the interaction to alphaviral infection and pathogenesis in vivo using an interaction deficient mutant of the model neurotropic strain of SINV. Importantly, these interaction determinants are highly conserved across multiple Old-World alphaviruses, including Ross River virus (RRV), Mayaro virus (MAYV), Chikungunya virus (CHIKV), and Semliki Forest virus (SFV). In the absence of a functional CP/IRAK1 interaction, SINV replication is significantly restricted and fails to disseminate from the primary site of inoculation due to the induction of a robust type-I Interferon response. Altogether these data indicate that the evasion of IRAK1-dependent signalling is critical to overcoming the host innate immune response and the in vivo data presented here demonstrate the importance of the CP/IRAK1 interaction to neurovirulence and pathogenesis.

Chikungunya virus antepartum transmission and abnormal infant outcomes in a cohort of pregnant women in Nigeria.

OBJECTIVES: Chikungunya virus (CHIKV), a reemerging global public health concern, which causes acute febrile illness, rash, and arthralgia and may affect both mothers and infants during pregnancy. Mother-to-child transmission (MTCT) of CHIKV in Africa remains understudied. METHODS: Our cohort study screened 1006 pregnant women with a Zika/dengue/CHIKV rapid test at two clinics in Nigeria between 2019 and 2022. Women who tested positive for the rapid test were followed through their pregnancy and their infants were observed for 6 months, with a subset tested by reverse transcription-polymerase chain reaction (RT-PCR) and neutralization, to investigate seropositivity rates and MTCT of CHIKV. RESULTS: Of the 1006, 119 tested positive for CHIKV immunoglobulin (Ig)M, of which 36 underwent detailed laboratory tests. While none of the IgM reactive samples were RT-PCR positive, 14 symptomatic pregnant women were confirmed by CHIKV neutralization test. Twelve babies were followed with eight normal and four abnormal outcomes, including stillbirth, cleft lip/palate with microcephaly, preterm delivery, polydactyly with sepsis, and jaundice. CHIKV IgM testing identified three possible antepartum transmissions. CONCLUSION: In Nigeria, we found significant CHIKV infection in pregnancy and possible CHIKV antepartum transmission associated with birth abnormalities.

Advancing Chikungunya Diagnosis: A Cost-Effective and Rapid Visual employing Loop-mediated isothermal reaction.

The diagnosis of Chikungunya (CHIKV), along with the simultaneous monitoring of virus circulation in the population or vectors, is essential for global health. Although effective diagnostic methods for CHIKV, such as RT-qPCR, exist, their utilization is constrained by high costs. With the aim of contributing to the field of diagnostics, we have developed a diagnostic assay using isothermal amplification technology with visually interpretable results. This test can detect the virus within a maximum timeframe of 30 minutes. The detection limit of RT-LAMP CHIKV was found to be 66 copies of RNA molecules (Ct ≅ 31.28), and no cross-reactivity with other arboviruses was observed. During test validation, our assay demonstrated a sensitivity of 80.43%, specificity of 100%, and an overall accuracy of 88.89%. By utilizing more cost-effective reagents and equipment compared to RT-qPCR, this test holds the potential for broader application and enhanced accessibility, particularly in point-of-care settings.

Molecular detection of dengue and chikungunya viruses in surveillance of wild-caught Aedes mosquitoes in Punjab, North India.

BACKGROUND: Dengue (DENV), Zika (ZIKV) and chikungunya (CHIKV) viruses are transmitted mainly by Aedes mosquitoes and are responsible for a significant global healthcare burden. The current study aimed to detect arboviruses in the Aedes mosquitoes in close proximity of patients during the transmission season. METHODS: Both immature and adult mosquitoes were collected from in and around the patients' houses. Mosquito pools were homogenized and extracted RNA was subjected to reverse transcription polymerase chain reaction for arboviral detection. Transovarian transmission (TOT) was assessed by screening F0 adults. Mosquito positivity was correlated with the aetiological agents identified in patients. RESULTS: Of 46 pools, 19 consisted of wild Aedes, with arboviral positivity in 53% (10/19) of pools. Among wild A. aegypti pools, positivity of DENV mono-infection, CHIKV mono-infection and DENV+CHIKV co-infection was noted in four, two and three pools, respectively. One wild pool of Aedes albopictus was positive for DENV-1. Similarly, A. aegypti F0 (adult Aedes developed from immatures) pools showed 59.2% (16/27) positivity for arboviruses. F0 Aedes showed positivity in three, six and seven pools for DENV-2, CHIKV and DENV+CHIKV, respectively, suggestive of TOT. DENV serotypes and CHIKV from 24 patients' serum samples were matched with strains isolated from Aedes and correlation was observed in four instances. CONCLUSIONS: The study detected DENV and CHIKV from wild-caught Aedes and found evidence of DENV and CHIKV TOT in F0 adults.

The Chikungunya virus: A reemerging cause of acute febrile illness in the high jungle of northern Peru.

BACKGROUND: The Chikungunya virus (CHIKV) is an emerging arthropod-borne virus (arbovirus) that causes undifferentiated acute febrile illness. Cases of CHIKV may be under-reported in Peru, given the various difficulties in diagnosing it, such as lack of diagnostic tests in remote areas, the passive nature of epidemiological surveillance, and co-circulation of other arthropod-borne pathogens. Therefore, a study was conducted in the high jungle of northern Peru to determine the prevalence of CHIKV among febrile patients and describe their clinical characteristics. METHODS: A cross-sectional study was conducted in the province of Jaen, Cajamarca, located in the high jungle of northern Peru. Patients attending primary healthcare centers within Cajamarca's Regional Health Directorate were enrolled. The study took place from June 2020 through June 2021. Patients were eligible if they sought outpatient healthcare for a clinical diagnosis of acute febrile illness (AFI). Serum samples were collected from all patients, and the diagnosis of CHIKV was determined using real-time RT-PCR, as well as the detection of IgM antibodies by ELISA. A logistic regression model was employed to identify the risk factors for CHIKV, and the odds ratios (ORs) were calculated, along with their corresponding 95% confidence intervals (95% CI). RESULTS: A total of 1 047 patients with AFI were included during the study period. CHIKV was identified in 130 patients of 1 047 (12.4%). Among the CHIKV positive cases, 84 of 130 (64.6%) were diagnosed by RT-PCR, 42 of 130 (32.3%) by IgM ELISA detection, and 4 of 130 (3.1%) by both assays. The majority of patients with CHIKV infection fell within the 18-39 years age group (50.0%), followed by the 40-59 years age group (23.9%) and those with 60 years or older (10.8%). The most common clinical symptoms observed in patients with CHIKV infection were headache (85.4%), myalgias (72.3%), and arthralgias (64.6%). The highest number of positive CHIKV cases occurred in May (23.1%), followed by March (20.0%) and February (13.8%) of 2021. CONCLUSION: The study reports a considerable frequency of CHIKV infections among patients with AFI from the high jungle of northern Peru. These findings highlight the importance of recognizing CHIKV as an ongoing pathogen with continuous transmission in various areas of Peru. It is crucial to enhance epidemiological surveillance by implementing reliable diagnostic techniques, as the clinical symptoms of CHIKV infection can be nonspecific.

Rapid On-Site Detection of Arboviruses by a Direct RT-qPCR Assay.

Arthropod-borne diseases currently constitute a source of major health concerns worldwide. They account for about 50% of global infectious diseases and cause nearly 700,000 deaths every year. Their rapid increase and spread constitute a huge challenge for public health, highlighting the need for early detection during epidemics, to curtail the virus spread, and to enhance outbreak management. Here, we compared a standard quantitative polymerase chain reaction (RT-qPCR) and a direct RT-qPCR assay for the detection of Zika (ZIKV), Chikungunya (CHIKV), and Rift Valley Fever (RVFV) viruses from experimentally infected-mosquitoes. The direct RT-qPCR could be completed within 1.5 h and required 1 µL of viral supernatant from homogenized mosquito body pools. Results showed that the direct RT-qPCR can detect 85.71%, 89%, and 100% of CHIKV, RVFV, and ZIKV samples by direct amplifications compared to the standard method. The use of 1:10 diluted supernatant is suggested for CHIKV and RVFV direct RT-qPCR. Despite a slight drop in sensitivity for direct PCR, our technique is more affordable, less time-consuming, and provides a better option for qualitative field diagnosis during outbreak management. It represents an alternative when extraction and purification steps are not possible because of insufficient sample volume or biosecurity issues.

Evaluation of renal markers and liver enzymes in patients infected with the Chikungunya virus.

Chikungunya virus (CHIKV) is an arbovirus (Togaviridae family, Alphavirus genus) that was first identified in 1953 in Tanzania. In 2014, the Asian and East/Central/South/African (ECSA) genotypes were identified in Brazil, although the genotype that spread the most in the following years across the Brazilian territory was the ECSA. The clinical symptoms associated with the infection caused by CHIKV include mainly fever, myalgia, headache, and arthralgia. In infections caused by other arboviruses (such as the ones caused by Dengue and West Nile viruses), changes in biochemical markers are often observed. This study aims to evaluate the biochemical markers profile of kidney and liver injury in acute patients infected with CHIKV. Two groups of correlations were found between the variables analyzed, namely, one between liver enzymes (r = 0.91), and another for kidney markers (r = 0.54-0.66). A significant elevation in the percentage of altered creatinine in CHIKV-infected patients was observed, followed by uric acid and AST. Altogether, in 8 different comparisons, it was possible to observe statistically significant differences between the levels of the markers when compared to the manifestation of symptoms (presence and absence). These noticeable changes in marker measurements could potentially be connected to the range of clinical symptoms seen in the disease.

The RNA helicase DDX39A binds a conserved structure in chikungunya virus RNA to control infection.

Alphaviruses are a large group of re-emerging arthropod-borne RNA viruses. The compact viral RNA genomes harbor diverse structures that facilitate replication. These structures can be recognized by antiviral cellular RNA-binding proteins, including DExD-box (DDX) helicases, that bind viral RNAs to control infection. The full spectrum of antiviral DDXs and the structures that are recognized remain unclear. Genetic screening identified DDX39A as antiviral against the alphavirus chikungunya virus (CHIKV) and other medically relevant alphaviruses. Upon infection, the predominantly nuclear DDX39A accumulates in the cytoplasm inhibiting alphavirus replication, independent of the canonical interferon pathway. Biochemically, DDX39A binds to CHIKV genomic RNA, interacting with the 5' conserved sequence element (5'CSE), which is essential for the antiviral activity of DDX39A. Altogether, DDX39A relocalization and binding to a conserved structural element in the alphavirus genomic RNA attenuates infection, revealing a previously unknown layer to the cellular control of infection.

The Evil DExH/D: Chikungunya virus runs but cannot hide from DDX39A.

In this issue, Tapescu et al.1 identify DDX39A as a novel antiviral protein that acts on conserved features of alphavirus RNA to limit infection in an IFN-independent manner.