Search Results (1,234)

Flaviviruses, encompassing notable pathogens, like Dengue, Zika, West Nile, and tick-borne encephalitis viruses, elicit complex cellular stress responses, involving pathways such as the unfolded protein response (UPR), integrated stress response (ISR), apoptosis, autophagy, and the antiviral immune response. These pathways regulate cell fate by either promoting survival to counteract virus-induced damage or triggering cell death programs under prolonged and irreparable stress. Therefore, the primary aim of flavivirus-induced cellular responses is to protect cells and hinder viral propagation. Despite cellular defenses, flaviviruses have evolved various subversion strategies, mainly involving viral proteins, which enable successful infections even when cellular responses are activated. While these cellular pathways were previously perceived as separate entities, recent studies suggest interplay and dynamic shifts among these stress response pathways, underscoring the need for further investigation in this area. In this review, we explore the key pathways activated during flavivirus infections, examine mechanisms of viral subversion, and delve into the synergy of these pathways, thereby elucidating the impact on the progression of infection. A deeper understanding of these interactions will guide future efforts to define how cellular stress responses shape flavivirus infection and leverage this knowledge toward the development of targeted antiviral strategies. Full article

The inherent genomic plasticity of RNA viruses, particularly influenza viruses and SARS-CoV-2, poses a major obstacle to the establishment of durable herd immunity. This challenge is further compounded by immune imprinting, whereby prior antigenic exposures bias subsequent responses toward previously encountered epitopes at the expense of effective recognition of antigenically drifted variants. In this review, we delineate the mechanistic basis of immune imprinting, with emphasis on the competitive dominance of cross-reactive memory B cells (MBCs). We discuss how the rapid “back-boosting” of these pre-existing clones can limit de novo priming of naïve B cells—through epitope masking and competition for antigen and T follicular helper cell support—thereby diverting germinal center selection and affinity maturation away from variant-specific de novo epitopes and promoting viral immune escape. To address this challenge, this article further reviews the characteristics of immune imprinting responses in influenza viruses, coronaviruses, and dengue virus, as well as corresponding countermeasures, providing a theoretical basis and new avenues for intervention to address immune imprinting induced by rapidly mutating RNA viruses. Full article

Dengue fever represents a significant public health challenge in Saudi Arabia, yet comprehensive molecular characterization of circulating serotypes remains limited. This study combines epidemiological and phylogenetic analyses to understand dengue virus (DENV) dynamics in the Kingdom. A systematic review and meta-analysis of dengue epidemiological data from Saudi Arabia (1992–2026) was the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. All available DENV envelope (E) gene sequences from Saudi human cases (1992–2023) were retrieved from GenBank and Global Initiative on Sharing All Influenza Data (GISAID). Phylogenetic trees were constructed using maximum likelihood with 1000 bootstrap replicates and best-fit models. Selection pressure was analyzed using SLAC, FEL, FUBAR, and MEME methods, while glycosylation sites were predicted with NetNGlyc and NetOGlyc. The pooled seroprevalence from 25 studies (n = 32,393) was 40.71% (95% CI: 26.96–56.10%). DENV-2 predominated (80.25%), followed by DENV-1 and DENV-3, with DENV-4 remaining rare (0.42%). Males (67–78%) and adults aged 25–44 years were most affected. Phylogenetic analysis of 50 Saudi isolates showed DENV-1 strains clustered within American–African (1994) and Asian (2004–2011) genotypes, all DENV-2 within the Cosmopolitan genotype, and all DENV-3 within Genotype III (bootstrap support 99–100%). Selection pressure analysis indicated pervasive positive selection in DENV-2, episodic selection across serotypes, and strong purifying selection in the E gene. Several amino acid substitutions with potential functional importance were identified. No DENV-4 E gene sequences from Saudi Arabia are publicly available. Dengue in western Saudi Arabia is characterized by DENV-2 predominance, co-circulation of three serotypes, and multiple introductions. The absence of DENV-4 sequences highlights critical surveillance gaps. Sustained molecular surveillance, expanded genomic sequencing, and data sharing are essential for effective prevention and vaccine preparedness. Full article

Secondary dengue infections are often linked to more severe clinical outcomes, yet pre-existing antibodies may exert either protective or pathogenic effects. To evaluate the role of acute-phase dengue antibodies in pediatric dengue, we analyzed clinical and laboratory features, viremia, and antibody profiles in children infected with DENV-1. We conducted a retrospective study of patients under 18 years diagnosed with DENV-1 in Salta, Argentina. Viremia was quantified by real-time RT-PCR; acute-phase IgG antibodies (within 7 days from symptom onset) against DENV, DENV-1, and DENV-NS1 were measured by immunoassays, and neutralizing antibodies by plaque reduction neutralization tests. Among 151 patients (median age 12 years), 62% presented dengue with warning signs and one case progressed to severe dengue. Viremia was higher in probable primary infections than in probable secondary infections and did not correlate with disease severity. Probable secondary infections were characterized by acute-phase antibody profiles that did not associate with DENV viremia. Age-stratified analyses revealed that adolescents exhibited higher viremia levels than younger children in probable primary infections, while viremia levels were comparable across age groups in probable secondary infections. Furthermore, children younger than 10 years displayed acute-phase antibody levels similar to those of adolescents. In adolescents with probable secondary infections, anti-DENV and anti-DENV-1 IgG were inversely correlated with platelet counts, whereas neutralizing and anti-DENV-NS1 antibodies showed no association. Collectively, these findings indicate that probable secondary DENV infections in our pediatric cohort were characterized by acute-phase antibodies that were not associated with viremia control, and that in adolescents, anti-DENV and anti-DENV-1 IgG antibodies likely associated with platelet depletion. These results highlight important implications for vaccine design, underscoring the need for vaccines that elicit strong neutralizing responses while minimizing cross-reactivity and the risk of antibody dependent enhancement. Full article

Climate change is reshaping the epidemiology of vector-borne diseases in Europe by altering the ecological conditions that determine vector survival, seasonal activity and pathogen transmission. Rising temperatures, milder winters, prolonged warm seasons and changing precipitation patterns are increasing the suitability of parts of Europe for competent mosquito, tick and sandfly vectors. These changes, combined with human mobility and land-use change, increase the probability that imported pathogens encounter permissive conditions for local transmission. This Opinion article examines autochthonous vector-borne disease transmission in Europe, using dengue as a sentinel example of a wider climate-sensitive transition. We discuss how imported viraemic cases, established competent vectors, vector–host contact and delayed clinical recognition can converge to enable local outbreaks. Beyond dengue, we consider West Nile virus, chikungunya, tick-borne encephalitis, leishmaniasis and Crimean–Congo haemorrhagic fever as examples of a broader and increasingly heterogeneous European risk landscape. We argue that the public-health impact of this transition is shaped not only by vector expansion, but also by gaps in surveillance integration, diagnostic readiness, workforce preparedness and One Health coordination. Strengthening climate-informed surveillance, rapid laboratory capacity, frontline clinical awareness and cross-sectoral response systems will be essential to prevent repeated introductions from becoming sustained public-health challenges. Full article

Dengue virus (DENV), which comprises four antigenically distinct serotypes (DENV-1 to DENV-4), remains a major global public health concern and continues to expand geographically; however, the structural features of the viral genome remain incompletely understood. Although G-quadruplexes (G4s) have previously been reported in coding regions of DENV, their presence within the 3′ untranslated region (3′ UTR) has not been experimentally characterized. Here, we focused on selected guanine-rich motifs within the 3′ UTRs of DENV-1 to DENV-4 and investigated their ability to form RNA G4 structures. Using bioinformatic analysis, we identified comparable G-rich regions in the 3′ UTRs of the four serotypes, with serotype-dependent differences in conservation. We then examined the propensity of the selected putative quadruplex-forming sequences (PQSs) to adopt G4 structures using circular dichroism spectroscopy, UV melting analysis, ¹H NMR spectroscopy, ligand-binding analysis, and reverse transcription stop (RT-stop) assays. Our results provided in vitro evidence that the 3′ UTR oligonucleotides from DENV-1 to DENV-4 are capable of forming ligand-responsive G4 structures, with serotype-dependent differences in conservation, stability, and conformational homogeneity. In addition, reverse transcription (RT)-stop analysis revealed ligand-dependent arrest at the corresponding PQS sites in the presence of the G4 ligand 6OTD, which stabilizes G4 structures. These findings suggest the DENV 3′ UTR as an additional source of ligand-responsive RNA G4-forming elements and support future studies on their possible roles in DENV RNA regulation. Full article

Airports are strategic targets for wastewater-based epidemiology because they concentrate highly mobile populations and may provide early signals of pathogen circulation. However, metagenomic investigations of airport wastewater remain limited, particularly in South America. Here, we present one of the first hybrid-capture target-enriched metagenomic investigations of airport wastewater in Brazil, integrating the detection of human-associated viruses and bacteriophage-derived host signatures to evaluate airports as sentinel surveillance sites. Seven untreated wastewater samples collected from a major Brazilian airport between December 2021 and March 2023 were concentrated, subjected to nucleic acid extraction, and analyzed using hybrid-capture target-enriched next-generation sequencing. Taxonomic analysis identified 615 viral and bacteriophage-associated taxa, including 440 viruses and 175 bacteriophages. Among the viral fraction, 21 human-associated viral taxa representing eight viral families were selected for detailed analysis. Norovirus GII was detected in all samples, while Mamastrovirus 1 and JC polyomavirus were detected in six of seven samples. SARS-CoV-2 and dengue virus type 1 were simultaneously detected in the March, 2023 sample. The bacteriophage fraction comprised 47 host-associated phage groups, with Streptococcus-associated phages predominating across samples. These findings demonstrate that airport wastewater can capture diverse human viral and bacteriophage-derived signatures associated with population mobility, supporting its application in environmental genomic surveillance and early-warning systems for emerging and circulating pathogens. Full article

Dengue is the most common vector-borne viral disease worldwide, posing an increasing global health threat. Despite its high burden, no approved antiviral treatments or widely applicable vaccines exist, and patient management remains limited to supportive care, underscoring the urgent need for antiviral development. The NS5 protein is a prime antiviral target, owing to its crucial role in viral replication, high conservation across dengue virus (DENV) serotypes and lack of a human orthologue. We conducted a comprehensive sequence-to-structure analysis to identify conserved druggable regions within NS5, integrating large-scale sequence analysis with structural characterization across all four DENV serotypes. We identified four highly promising Consensus Druggable Pockets within the NS5 dimer—CDP1d, CDP3d, CDP5d and CDP12d—that overlap functionally critical regions, alongside 149 new potential hot spot residues. Domain-specific analysis revealed that MTase offers more densely conserved targets, whereas RdRp provides broader druggable surfaces, revealing complementary features for pharmacological modulation. Several identified pockets spatially overlap known inhibitor binding sites, and preliminary docking analyses support their capacity to accommodate small molecules, reinforcing their therapeutic relevance as candidate targets. Collectively, these findings provide a robust framework for the rational design of pan-serotype anti-DENV NS5 antivirals with an enhanced barrier to resistance. Full article

Dengue virus (DENV) and chikungunya virus (CHIKV) co-circulate in many regions and present with overlapping clinical features, which complicate accurate diagnosis and disease management. This study develops an integrative transcriptomic framework to identify robust host gene signatures that distinguish between dengue, chikungunya, and healthy states. Publicly available RNA sequencing (RNA-seq) datasets derived from human blood samples were analyzed using a cross-validation design to ensure robustness and prevent information leakage. Differential expression analysis was performed independently within each dataset using the Generalized Linear Models with Quasi-Likelihood F-tests and Magnitude–Altitude Scoring (GLMQL-MAS) framework, followed by Cross-Magnitude–Altitude Scoring (Cross-MAS) integration to identify shared and virus-specific gene signatures. A strict consensus approach across folds was applied to derive reproducible gene sets. These signatures were used for dimensionality reduction and multinomial logistic regression to evaluate classification performance. A small subset of selected genes showed strong discriminative performance within the cross-validation framework, with test balanced accuracy reaching 0.97, which improved upon models using all genes. Biologically, both infections exhibited a shared antiviral response characterized by interferon signaling and innate immune activation. However, distinct virus-specific patterns were identified. Dengue infection was associated with cell-cycle and DNA replication pathways, while chikungunya infection showed stronger enrichment of inflammatory and immune signaling pathways, including NF-kappaB and Toll-like receptor signaling. Overall, this study provides a cross-validation-based framework for integrative transcriptomic analysis and identifies compact, reproducible host-response signatures with strong discriminative signals in the analyzed cohorts. These signatures require validation in larger independent cohorts before any clinical or diagnostic application. Full article

Background/Objectives: Mosquitoes, including Culex quinquefasciatus and Aedes aegypti, are important vectors of dengue fever, Zika virus, West Nile virus, Japanese encephalitis virus, Eastern equine encephalitis virus, etc. Biological control has always been urgent in mosquito prevention due to resistance developing to synthetic insecticides and environmental toxicity by insecticides. Methods: The leaf essential oil of Mosla. chinensis was isolated, and major components were identified via GC-MS, followed by olfactory behavior assays to evaluate its repellent activity against C. quinquefasciatus. Additionally, the odorant-binding protein 1 and odorant-binding protein 2 (CquiOBP1-2) genes were prokaryotically expressed, and their fluorescence competitive binding activities with the active components of essential oils were examined. Results: The bioassays indicated this essential oil greatly repels C. quinquefasciatus, which will significantly protect people against vector-borne diseases. In the fluorescence competitive binding experiments, the CquiOBP1-2 proteins exhibit great binding capacities to volatile components, including Citronellal, Citronellol, Geraniol, Limonene and Isopulegol. Furthermore, the behavioral experimental results also indicate that the mixture of these five ligand compounds has an obvious repellent effect on mosquitoes, highlighting that they may be applied as potential mosquito repellent agents. Moreover, molecular docking and site-directed mutation analysis further confirm Phe123 and Gln77 are both key amino acid residues of CquiOBP1-2 proteins involved in the olfactory recognition of repellent ligand compounds from M. chinensis essential oil. Conclusions: The behavioral experimental verification and the exploration of olfactory molecular mechanisms are helpful to promote the biological control of plant essential oils in mosquito pests. Full article

Gastrointestinal symptoms (GI) (abdominal pain, vomiting, and diarrhea) during the febrile phase of dengue (less than 5 days from fever onset) might indicate prominent innate immune responses. Serum and feces samples from cases with GI symptoms versus those without GI symptoms (n = 20 per group) were analyzed. From these, only the neutrophil extracellular traps (NETs), serum fibroblast growth factor (FGF) 21, and fecal microbiome analyses, but not the routine parameters, endotoxemia, or serum cytokines, were higher in the GI cases than in the non-GI cases. From the in vitro experiments, both lipopolysaccharide (LPS) and the dengue virus (DENV) upregulated the FGF receptor 1 (FGFR1) and cytokines in hepatocytes (HepG2) and THP-1-differentiated macrophages. Meanwhile, LPS and DENV induced NETs in isolated neutrophils from healthy volunteers. Only the starvation protocol, but not LPS or DENV, enhanced supernatant FGF-21 from hepatocytes. Incubation of recombinant FGF-21 in LPS + DENV-activated cells (hepatocytes, macrophages, and neutrophils) attenuated inflammation, as determined by supernatant cytokines and NETs. Hence, abdominal symptoms in dengue during the febrile phase indicate prominent innate immune responses, as detected by NETs and FGF-21 (an acute-phase protein), implying significant hepatic stress with a possible counteracting anti-inflammation. Full article

Dengue Virus (DENV) circulates as four antigenically distinct serotypes whose dominance fluctuates over time in many endemic regions, a phenomenon known as serotype shift that is frequently associated with large outbreaks and increased disease severity. This review, through a synthesis of epidemiological, virological, immunological, entomological, and environmental evidence, observes that serotype shift likely arises from the interaction of multiple determinants rather than solely from viral evolution, with population immunity playing a central role. The accumulation of serotype-specific herd immunity, together with short-lived cross-protection and Antibody-Dependent Enhancement (ADE), reshapes population susceptibility and creates ecological space for heterologous serotypes with higher transmission potential. The synthesis of global dengue studies indicates that these immune dynamics interact with viral genetic diversity, vector competence, climate variability, and human factors such as demography, socioeconomic status, population density and mobility to drive cyclical and sometimes abrupt changes in serotype dominance. Notably, the review indicates that serotype changes often precede or coincide with more clinical severity and patterns of outbreaks, with direct implications for the process of forecasting outbreaks, vaccine performance, and preparedness to respond with appropriate health measures. On the whole, this review confirms the opinion that the change of dengue serotype occurrence becomes a consequence of interconnected biological and ecological processes involved in the transmission of dengue serotype shifts in hyperendemic areas. Full article

Dengue virus infection remains a significant public health challenge in endemic regions, with growing evidence of autochthonous transmission in Europe. Assessing serological exposure in high-risk populations such as military personnel deployed to endemic areas is essential to quantify exposure risk and support operational decision-making, particularly regarding pre-deployment counselling and risks associated with secondary infection. We conducted a cross-sectional study involving 1355 members of the Italian Armed Forces, measuring anti-dengue IgG antibodies by ELISA and collecting data on deployment history and exposure risk. Overall, IgG seropositivity was 8.12%, with significantly higher prevalence among individuals reporting travel or deployment to endemic regions (24.71%) compared with non-exposed personnel (4.27%). Seropositivity increased with age and correlated with a CDC-derived cumulative dengue risk score (Spearman’s ρ = 0.299, p < 0.0001). A multivariable logistic regression model including age and exposure risk achieved an AUC of 0.75, while machine-learning models provided complementary predictive assessment, with random forest reaching an AUC of 0.79. These findings indicate substantial anti-dengue IgG seropositivity compatible with previous dengue exposure among Italian military personnel, particularly those deployed to endemic settings. The study highlights the need for targeted surveillance and risk-based preventive strategies, and supports the use of exposure-based models to improve epidemiological assessment and inform vaccination strategies in mobile populations. Full article

Background/Objectives: Arboviral diseases transmitted by Aedes mosquitoes, including Dengue (DENV), Zika (ZIKV), and Chikungunya (CHIKV), represent a major public health challenge in tropical regions. Their clinical similarity complicates differential diagnosis, particularly in settings of viral co-circulation, and may lead to underdiagnosis. The objective was to detect acute dengue infection and assess serological evidence of Chikungunya and Zika virus exposure among patients with acute febrile syndrome and clinical suspicion of dengue in the department of Córdoba, Colombia. Methods: A prospective descriptive study was conducted between 2023 and 2024 in healthcare institutions in Montería and Sahagún. Serum samples were analyzed by ELISA to detect DENV NS1 antigen, anti-CHIKV IgM, and anti-ZIKV IgG antibodies. Sociodemographic, clinical, and laboratory variables were described, and the association between prior ZIKV infection and dengue severity was assessed. Results: Ninety patients were included. Isolated laboratory marker detection was observed for DENV NS1 antigen in 36.7% (33/90), anti-ZIKV IgG in 30.0% (27/90), and anti-CHIKV IgM in 2.2% (2/90); combined arboviral markers were identified in 22.2% (20/90), and 8.9% (8/90) had no detectable markers. Among NS1-confirmed dengue cases (n = 47), 61.7% (29/47) were classified as dengue with warning signs. Anti-ZIKV IgG detection was not associated with dengue clinical classification (p = 0.989), although platelet counts were lower in IgG-positive cases (p = 0.037). Conclusions: The findings support laboratory-supported diagnosis and integrated acute febrile illness surveillance in Córdoba, including locally adapted vector control, in a setting of arbovirus co-circulation with overlapping laboratory markers. Full article

Dengue is an arboviral disease of global significance caused by Orthoflavivirus denguei (DENV), which has four antigenically distinct serotypes. The envelope (E) protein plays a critical role in viral entry and eliciting immune responses. This study aimed to compare the biochemical and immunological properties of the E protein across the four DENV serotypes using in silico approaches. E protein reference sequences were retrieved from RefSeq and analyzed with various bioinformatics tools. Sequence alignment revealed identities ranging from 63.08% to 77.69%. Biochemical analysis showed minimal variation in molecular weight and isoelectric point; however, the net charge of DENV-3 E protein was notably lower. Secondary structure predictions indicated a predominance of alpha-helices in DENVs-1/2, while DENVs-3/4 featured more beta-sheets. Post-translational modification analysis revealed mostly casein kinase II phosphorylation sites across all serotypes, with DENV-4 uniquely presenting also tyrosine kinase sites. Amino acids W231/D341 in DENV-1, Q86 in DENVs-2/4, and D87/D339 in DENV-3 showed maximum antigenicity scores in B cell recognition, while the human leukocyte antigen (HLA) alleles B*08:01/B*39:01 and DRB4*01:01, recognized by T cells, presented the highest number of predicted epitopes for the different DENV serotypes. Conservation analysis showed that the major antigenic regions highlighted in this study are highly conserved among contemporary DENV isolates despite the genetic variability observed within each serotype. These findings suggest that subtle structural differences in the E protein may contribute to distinct immunogenic profiles, highlighting candidate regions for future investigation. Full article