Yellow Fever Virus Research Articles

Comparative Analysis of Human Hepatic Lesions in Dengue, Yellow Fever, and Chikungunya: Revisiting Histopathological Changes in the Light of Modern Knowledge of Cell Pathology.

Arboviruses, such as yellow fever virus (YFV), dengue virus (DENV), and chikungunya virus (CHIKV), present wide global dissemination and a pathogenic profile developed in infected individuals, from non-specific clinical conditions to severe forms, characterised by the promotion of significant lesions in different organs of the harbourer, culminating in multiple organ dysfunction. An analytical cross-sectional study was carried out via the histopathological analysis of 70 samples of liver patients, collected between 2000 and 2017, with confirmed laboratory diagnoses, who died due to infection and complications due to yellow fever (YF), dengue fever (DF), and chikungunya fever (CF), to characterise, quantify, and compare the patterns of histopathological alterations in the liver between the samples. Of the histopathological findings in the human liver samples, there was a significant difference between the control and infection groups, with a predominance of alterations in the midzonal area of the three cases analysed. Hepatic involvement in cases of YF showed a greater intensity of histopathological changes. Among the alterations evaluated, cell swelling, microvesicular steatosis, and apoptosis were classified according to the degree of tissue damage from severe to very severe. Pathological abnormalities associated with YFV, DENV, and CHIKV infections showed a predominance of changes in the midzonal area. We also noted that, among the arboviruses studied, liver involvement in cases of YFV infection was more intense.

Tetrahydroquinazoline N-oxide derivatives inhibit reproduction of tick-borne and mosquito-borne flaviviruses.

Tick-borne encephalitis virus (TBEV), yellow fever virus (YFV), and West Nile virus (WNV) are flaviviruses causing emerging arthropod-borne infections of a great public health concern. Clinically approved drugs are not available to complement or replace the existing vaccines, which do not provide sufficient coverage. Thus, the discovery and characterization of new antiflaviviral chemotypes would advance studies in this field. In this study, a series of tetrahydroquinazoline N-oxides was synthesized, and the antiviral activity of the compounds was assessed against TBEV, YFV, and WNV using the plaque reduction assay along with the cytotoxicity to the corresponding cell lines (porcine embryo kidney and Vero). Most of the studied compounds were active against TBEV (EC50 2 to 33 μM) and WNV (EC50 0.15 to 34 μM) and a few also demonstrated inhibitory activity against YFV (EC50 0.18 to 41 μM). To investigate the potential mechanism of action of the synthesized compounds, time-of-addition (TOA) experiments and virus yield reduction assays were performed for TBEV. The TOA studies suggested that the antiviral activity of the compounds should affect the early stages of the viral replication cycle after cell entry. Compounds with tetrahydroquinazoline N-oxide scaffold show a broad spectrum of activity against flaviviruses and represent a promising chemotype for antiviral drug discovery.

Naive phenotype antigen-specific CD4 +T cells persist in the memory repertoire after vaccination

Abstract Immunization leads to activation and differentiation of antigen-specific T cells, resulting in the development of immunological memory. However, how the human immune repertoire changes after vaccination remains incompletely understood. Here, we used the live attenuated yellow fever virus (YFV) vaccine or the SARS-CoV-2 mRNA vaccine as models to track post-vaccine kinetics in healthy donors. We quantified and characterized 36 distinct YFV-specific T cell populations and 25 SARS-CoV-2-specific populations by direct ex vivo peptide-MHC tetramer staining. Unexpectedly, we found naïve-phenotype vaccine-specific T cells reappearing after vaccination. On average, 20% of T cells retained a naive phenotype by CD45RO and CCR7 staining although each population had previously expanded after vaccination. A subset of naïve-like T cells expressed other differentiation markers consistent with T memory stem cells (TSCM), but some naïve-like T cells were negative for all memory markers tested. These naïve-phenotype T cells were able to respond to antigens and showed an increased expression of a recent thymic immigrant marker CD31. In conclusion, our results provided the surprising finding that the post-exposure T cell repertoire contains naïve antigen-specific T cells. We plan to test the possibility that the thymus continues to add new T cells into the adult immune repertoire in future experiments. NIH (R01 AI134879) NIH (R01 AO66358)

Vertical Distribution of Oviposition and Temporal Segregation of Arbovirus Vector Mosquitoes (Diptera: Culicidae) in a Fragment of the Atlantic Forest, State of Rio de Janeiro, Brazil.

Culicid species, which include potential vectors of yellow fever, are diverse and abundant, with species commonly co-occurring in certain sites. Studying these species can provide important insights into their vector potential and, consequently, epizootic cycles of arboviruses carried about by these vectors. Here, we evaluated the vertical distribution and temporal segregation of mosquito oviposition with emphasis on arbovirus vectors in a fragment of the Atlantic Forest in Casimiro de Abreu, Rio de Janeiro, Brazil. Two sampling points were selected: Fazenda Três Montes and the Reserva Natural de Propriedade Privada Morro Grande. Collections were carried out at two sites using 10 ovitraps installed on the vegetation cover at different heights (0, 2, 4, 6, and 8 m above ground level) and monitored monthly from July 2018 to December 2020. The hypotheses of temporal and vertical stratification were tested through a PERMANOVA, and the relationship of each species with the vertical distribution was evaluated individually through a correlation analysis. We collected a total of 3075 eggs, including four species of medical importance: Haemagogus leucocelaenus (n = 1513), Haemagogus janthinomys (n = 16), Aedes albopictus (n = 1097), and Aedes terrens (n = 449). We found that Hg. leucocelaenus had a positive relationship with height, exhibiting behavior that appears to benefit from higher heights. The abundance of Ae. terrens seemed to follow Hg. leucocelaenus, although we did not find a relationship with height for the former species. On the other hand, Ae. albopictus exhibited a negative relationship with height, becoming absent or outnumbered at higher strata. Our study site has already presented evidence of recent transmission of the wild yellow fever virus, supporting the need to carefully monitor the emergence of febrile diseases among residents in the surrounding areas and the local population.

Latest Advances in Arbovirus Diagnostics.

Arboviruses are a diverse family of vector-borne pathogens that include members of the Flaviviridae, Togaviridae, Phenuviridae, Peribunyaviridae, Reoviridae, Asfarviridae, Rhabdoviridae, Orthomyxoviridae and Poxviridae families. It is thought that new world arboviruses such as yellow fever virus emerged in the 16th century due to the slave trade from Africa to America. Severe disease-causing viruses in humans include Japanese encephalitis virus (JEV), yellow fever virus (YFV), dengue virus (DENV), West Nile virus (WNV), Zika virus (ZIKV), Crimean-Congo hemorrhagic fever virus (CCHFV), severe fever with thrombocytopenia syndrome virus (SFTSV) and Rift Valley fever virus (RVFV). Numerous methods have been developed to detect the presence of these pathogens in clinical samples, including enzyme-linked immunosorbent assays (ELISAs), lateral flow assays (LFAs) and reverse transcriptase-polymerase chain reaction (RT-PCR). Most of these assays are performed in centralized laboratories due to the need for specialized equipment, such as PCR thermal cyclers and dedicated infrastructure. More recently, molecular methods have been developed which can be performed at a constant temperature, termed isothermal amplification, negating the need for expensive thermal cycling equipment. In most cases, isothermal amplification can now be carried out in as little as 5-20 min. These methods can potentially be used as inexpensive point of care (POC) tests and in-field deployable applications, thus decentralizing the molecular diagnosis of arboviral disease. This review focuses on the latest developments in isothermal amplification technology and detection techniques that have been applied to arboviral diagnostics and highlights future applications of these new technologies.

Fusing an agent-based model of mosquito population dynamics with a statistical reconstruction of spatio-temporal abundance patterns.

The mosquito Aedes aegypti is the vector of a number of medically-important viruses, including dengue virus, yellow fever virus, chikungunya virus, and Zika virus, and as such vector control is a key approach to managing the diseases they cause. Understanding the impact of vector control on these diseases is aided by first understanding its impact on Ae. aegypti population dynamics. A number of detail-rich models have been developed to couple the dynamics of the immature and adult stages of Ae. aegypti. The numerous assumptions of these models enable them to realistically characterize impacts of mosquito control, but they also constrain the ability of such models to reproduce empirical patterns that do not conform to the models' behavior. In contrast, statistical models afford sufficient flexibility to extract nuanced signals from noisy data, yet they have limited ability to make predictions about impacts of mosquito control on disease caused by pathogens that the mosquitoes transmit without extensive data on mosquitoes and disease. Here, we demonstrate how the differing strengths of mechanistic realism and statistical flexibility can be fused into a single model. Our analysis utilizes data from 176,352 household-level Ae. aegypti aspirator collections conducted during 1999-2011 in Iquitos, Peru. The key step in our approach is to calibrate a single parameter of the model to spatio-temporal abundance patterns predicted by a generalized additive model (GAM). In effect, this calibrated parameter absorbs residual variation in the abundance time-series not captured by other features of the mechanistic model. We then used this calibrated parameter and the literature-derived parameters in the agent-based model to explore Ae. aegypti population dynamics and the impact of insecticide spraying to kill adult mosquitoes. The baseline abundance predicted by the agent-based model closely matched that predicted by the GAM. Following spraying, the agent-based model predicted that mosquito abundance rebounds within about two months, commensurate with recent experimental data from Iquitos. Our approach was able to accurately reproduce abundance patterns in Iquitos and produce a realistic response to adulticide spraying, while retaining sufficient flexibility to be applied across a range of settings.

Where boundaries become bridges: Mosquito community composition, key vectors, and environmental associations at forest edges in the central Brazilian Amazon.

Risk of spillover and spillback of mosquito-borne viruses in the neotropics, including yellow fever, dengue, Zika (Flaviviridae: Flavivirus), chikungunya, and Mayaro (Togaviridae: Alphavirus) viruses, is highest at ecotones where humans, monkeys, and mosquitoes coexist. With a view to identifying potential bridge vectors, we investigated changes in mosquito community composition and environmental variables at ground level at distances of 0, 500, 1000, and 2000 m from the edge of a rainforest reserve bordering the city of Manaus in the central Brazilian Amazon. During two rainy seasons in 2019 and 2020, we sampled 9,467 mosquitoes at 244 unique sites using BG-Sentinel traps, hand-nets, and Prokopack aspirators. Species richness and diversity were generally higher at 0 m and 500 m than at 1000 m and 2000 m, while mosquito community composition changed considerably between the forest edge and 500 m before stabilizing by 1000 m. Shifts in environmental variables mainly occurred between the edge and 500 m, and the occurrence of key taxa (Aedes albopictus, Ae. scapularis, Limatus durhamii, Psorophora amazonica, Haemagogus, and Sabethes) was associated with one or more of these variables. Sites where Ae. aegypti and Ae. albopictus were detected had significantly higher surrounding mean NDBI (Normalized Difference Built-up Index) values than sites where they were not detected, while the opposite was true for Sabethes mosquitoes. Our findings suggest that major changes in mosquito communities and environmental variables occur within 500 m of the forest edge, where there is high risk for contact with both urban and sylvatic vectors. By 1000 m, conditions stabilize, species diversity decreases, and forest mosquitoes predominate. Environmental variables associated with the occurrence of key taxa may be leveraged to characterize suitable habitat and refine risk models for pathogen spillover and spillback.

Rapid viral metagenomics using SMART-9N amplification and nanopore sequencing.

Emerging and re-emerging viruses are a global health concern. Genome sequencing as an approach for monitoring circulating viruses is currently hampered by complex and expensive methods. Untargeted, metagenomic nanopore sequencing can provide genomic information to identify pathogens, prepare for or even prevent outbreaks. SMART (Switching Mechanism at the 5' end of RNA Template) is a popular approach for RNA-Seq but most current methods rely on oligo-dT priming to target polyadenylated mRNA molecules. We have developed two random primed SMART-Seq approaches, a sequencing agnostic approach 'SMART-9N' and a version compatible rapid adapters available from Oxford Nanopore Technologies 'Rapid SMART-9N'. The methods were developed using viral isolates, clinical samples, and compared to a gold-standard amplicon-based method. From a Zika virus isolate the SMART-9N approach recovered 10kb of the 10.8kb RNA genome in a single nanopore read. We also obtained full genome coverage at a high depth coverage using the Rapid SMART-9N, which takes only 10 minutes and costs up to 45% less than other methods. We found the limits of detection of these methods to be 6 focus forming units (FFU)/mL with 99.02% and 87.58% genome coverage for SMART-9N and Rapid SMART-9N respectively. Yellow fever virus plasma samples and SARS-CoV-2 nasopharyngeal samples previously confirmed by RT-qPCR with a broad range of Ct-values were selected for validation. Both methods produced greater genome coverage when compared to the multiplex PCR approach and we obtained the longest single read of this study (18.5 kb) with a SARS-CoV-2 clinical sample, 60% of the virus genome using the Rapid SMART-9N method. This work demonstrates that SMART-9N and Rapid SMART-9N are sensitive, low input, and long-read compatible alternatives for RNA virus detection and genome sequencing and Rapid SMART-9N improves the cost, time, and complexity of laboratory work.

Vector Competence of Aedes albopictus for Yellow Fever Virus: Risk of Reemergence of Urban Yellow Fever in Brazil.

The risk of the emergence and reemergence of zoonoses is high in regions that are under the strong influence of anthropogenic actions, as they contribute to the risk of vector disease transmission. Yellow fever (YF) is among the main pathogenic arboviral diseases in the world, and the Culicidae Aedes albopictus has been proposed as having the potential to transmit the yellow fever virus (YFV). This mosquito inhabits both urban and wild environments, and under experimental conditions, it has been shown to be susceptible to infection by YFV. In this study, the vector competence of the mosquito Ae. albopictus for the YFV was investigated. Female Ae. albopictus were exposed to non-human primates (NHP) of the genus Callithrix infected with YFV via a needle inoculation. Subsequently, on the 14th and 21st days post-infection, the legs, heads, thorax/abdomen and saliva of the arthropods were collected and analyzed by viral isolation and molecular analysis techniques to verify the infection, dissemination and transmission. The presence of YFV was detected in the saliva samples through viral isolation and in the head, thorax/abdomen and legs both by viral isolation and by molecular detection. The susceptibility of Ae. albopictus to YFV confers a potential risk of reemergence of urban YF in Brazil.

CMPK2 restricts Zika virus replication by inhibiting viral translation.

Flaviviruses continue to emerge as global health threats. There are currently no Food and Drug Administration (FDA) approved antiviral treatments for flaviviral infections. Therefore, there is a pressing need to identify host and viral factors that can be targeted for effective therapeutic intervention. Type I interferon (IFN-I) production in response to microbial products is one of the host's first line of defense against invading pathogens. Cytidine/uridine monophosphate kinase 2 (CMPK2) is a type I interferon-stimulated gene (ISG) that exerts antiviral effects. However, the molecular mechanism by which CMPK2 inhibits viral replication is unclear. Here, we report that CMPK2 expression restricts Zika virus (ZIKV) replication by specifically inhibiting viral translation and that IFN-I- induced CMPK2 contributes significantly to the overall antiviral response against ZIKV. We demonstrate that expression of CMPK2 results in a significant decrease in the replication of other pathogenic flaviviruses including dengue virus (DENV-2), Kunjin virus (KUNV) and yellow fever virus (YFV). Importantly, we determine that the N-terminal domain (NTD) of CMPK2, which lacks kinase activity, is sufficient to restrict viral translation. Thus, its kinase function is not required for CMPK2's antiviral activity. Furthermore, we identify seven conserved cysteine residues within the NTD as critical for CMPK2 antiviral activity. Thus, these residues may form an unknown functional site in the NTD of CMPK2 contributing to its antiviral function. Finally, we show that mitochondrial localization of CMPK2 is required for its antiviral effects. Given its broad antiviral activity against flaviviruses, CMPK2 is a promising potential pan-flavivirus inhibitor.

Characterizing the Wolbachia infection in field-collected Culicidae mosquitoes from Hainan Province, China

BackgroundMosquitoes are vectors of many pathogens, such as malaria, dengue virus, yellow fever virus, filaria and Japanese encephalitis virus. Wolbachia are capable of inducing a wide range of reproductive abnormalities in their hosts, such as cytoplasmic incompatibility. Wolbachia has been proposed as a tool to modify mosquitoes that are resistant to pathogen infection as an alternative vector control strategy. This study aimed to determine natural Wolbachia infections in different mosquito species across Hainan Province, China.MethodsAdult mosquitoes were collected using light traps, human landing catches and aspirators in five areas in Hainan Province from May 2020 to November 2021. Species were identified based on morphological characteristics, species-specific PCR and DNA barcoding of cox1 assays. Molecular classification of species and phylogenetic analyses of Wolbachia infections were conducted based on the sequences from PCR products of cox1, wsp, 16S rRNA and FtsZ gene segments.ResultsA total of 413 female adult mosquitoes representing 15 species were identified molecularly and analyzed. Four mosquito species (Aedes albopictus, Culex quinquefasciatus, Armigeres subalbatus and Culex gelidus) were positive for Wolbachia infection. The overall Wolbachia infection rate for all mosquitoes tested in this study was 36.1% but varied among species. Wolbachia types A, B and mixed infections of A × B were detected in Ae. albopictus mosquitoes. A total of five wsp haplotypes, six FtsZ haplotypes and six 16S rRNA haplotypes were detected from Wolbachia infections. Phylogenetic tree analysis of wsp sequences classified them into three groups (type A, B and C) of Wolbachia strains compared to two groups each for FtsZ and 16S rRNA sequences. A novel type C Wolbachia strain was detected in Cx. gelidus by both single locus wsp gene and the combination of three genes.ConclusionOur study revealed the prevalence and distribution of Wolbachia in mosquitoes from Hainan Province, China. Knowledge of the prevalence and diversity of Wolbachia strains in local mosquito populations will provide part of the baseline information required for current and future Wolbachia-based vector control approaches to be conducted in Hainan Province.Graphical

Specialized cis-Acting RNA Elements Balance Genome Cyclization to Ensure Efficient Replication of Yellow Fever Virus.

Genome cyclization is essential for viral RNA (vRNA) replication of the vertebrate-infecting flaviviruses, and yet its regulatory mechanisms are not fully understood. Yellow fever virus (YFV) is a notorious pathogenic flavivirus. Here, we demonstrated that a group of cis-acting RNA elements in YFV balance genome cyclization to govern efficient vRNA replication. It was shown that the downstream of the 5'-cyclization sequence hairpin (DCS-HP) is conserved in the YFV clade and is important for efficient YFV propagation. By using two different replicon systems, we found that the function of the DCS-HP is determined primarily by its secondary structure and, to a lesser extent, by its base-pair composition. By combining in vitro RNA binding and chemical probing assays, we found that the DCS-HP orchestrates the balance of genome cyclization through two different mechanisms, as follows: the DCS-HP assists the correct folding of the 5' end in a linear vRNA to promote genome cyclization, and it also limits the overstabilization of the circular form through a potential crowding effect, which is influenced by the size and shape of the DCS-HP structure. We also provided evidence that an A-rich sequence downstream of the DCS-HP enhances vRNA replication and contributes to the regulation of genome cyclization. Interestingly, diversified regulatory mechanisms of genome cyclization, involving both the downstream of the 5'-cyclization sequence (CS) and the upstream of the 3'-CS elements, were identified among different subgroups of the mosquito-borne flaviviruses. In summary, our work highlighted how YFV precisely controls the balance of genome cyclization to ensure viral replication. IMPORTANCE Yellow fever virus (YFV), the prototype of the Flavivirus genus, can cause devastating yellow fever disease. Although it is preventable by vaccination, there are still tens of thousands of yellow fever cases per year, and no approved antiviral medicine is available. However, the understandings about the regulatory mechanisms of YFV replication are obscure. In this study, by a combination of bioinformatics, reverse genetics, and biochemical approaches, it was shown that the downstream of the 5'-cyclization sequence hairpin (DCS-HP) promotes efficient YFV replication by modulating the conformational balance of viral RNA. Interestingly, we found specialized combinations for the downstream of the 5'-cyclization sequence (CS) and upstream of the 3'-CS elements in different groups of the mosquito-borne flaviviruses. Moreover, possible evolutionary relationships among the various downstream of the 5'-CS elements were implied. This work highlighted the complexity of RNA-based regulatory mechanisms in the flaviviruses and will facilitate the design of RNA structure-targeted antiviral therapies.

Durability of neutralizing antibodies against yellow fever virus after vaccination in healthy adults.

In accordance with the World Health Organization, one dose of yellow fever vaccine may guarantee protection lifelong in healthy adults. However, relatively little information is still available from ad hoc studies. We evaluated the persistence of neutralizing antibodies, which are considered to be an immune correlate of protection, in a large number of military personnel vaccinated up to 47years before. Overall, 322 individuals were studied. The median time from vaccination to blood collection for neutralizing antibody evaluation was 9years, ranging from <1 to 47years. Of the 322 participants, 319 had neutralizing antibodies (99.1%). The highest median PRNT50 value was observed in those vaccinated ≤1year before (median PRNT50=320). In conclusion, our study confirms on a larger scale that, in healthy adults, neutralizing antibodies may persist as long as 47years after a single yellow fever vaccines dose.

Performance assessment and validation of a plaque reduction neutralization test (PRNT) in support to yellow fever diagnostic and vaccine clinical trials.

Yellow fever (YF) virus is a mosquito-borne virus belonging to the Flaviviridae family that circulates in tropical and subtropical areas of Africa and South America. Despite the availability of an effective vaccine, YF remains a threat to travelers, residents of endemic areas, and unvaccinated populations. YF vaccination and natural infection both induce the production of neutralizing antibodies. Serological diagnostic methods detecting YF virus-specific antibodies demonstrate high levels of cross-reactivities with other flaviviruses. To date, the plaque reduction neutralization test (PRNT) is the most specific serological test for the differentiation of flavivirus infections and is considered the reference method for detecting YF neutralizingantibodies and assessing the protective immune response following vaccination. In this study, we developed and validated a YF PRNT. We optimized different parameters including cell concentration and virus-serum neutralization time period and then assessed the intra- and inter-assay precisions, dilutability, specificity, and lower limit of quantification (LLOQ) using international standard YF serum, sera from vaccinees and human specimens collected through YF surveillance. The YF PRNT has shown good robustness and 100% of intra-assay precision, 95.6% of inter-assay precision, 100% of specificity, 100% of LLOQ, and 95.3% of dilutability. The test is, therefore, suitable for use in the YF diagnostic as well as evaluation of the YF vaccine neutralizing antibody response and risk assessment studies.

The protein disulfide isomerase inhibitor 3-methyltoxoflavin inhibits Chikungunya virus.

Chikungunya virus (CHIKV) is the etiological agent of chikungunya fever, a (re)emerging arbovirus infection, that causes severe and often persistent arthritis, as well as representing a serious health concern worldwide for which no antivirals are currently available. Despite efforts over the last decade to identify and optimize new inhibitors or to reposition existing drugs, no compound has progressed to clinical trials for CHIKV and current prophylaxis is based on vector control, which has shown limited success in containing the virus. Our efforts to rectify this situation were initiated by screening 36 compounds using a replicon system and ultimately identified the natural product derivative 3-methyltoxoflavin with activity against CHIKV using a cell-based assay (EC50 200nM, SI=17 in Huh-7 cells). We have additionally screened 3-methyltoxoflavin against a panel of 17 viruses and showed that it only additionally demonstrated inhibition of the yellow fever virus (EC50 370nM, SI=3.2 in Huh-7 cells). We have also showed that 3-methyltoxoflavin has excellent in vitro human and mouse microsomal metabolic stability, good solubility and high Caco-2 permeability and it is not likely to be a P-glycoprotein substrate. In summary, we demonstrate that 3-methyltoxoflavin has activity against CHIKV, good in vitro absorption, distribution, metabolism and excretion (ADME) properties as well as good calculated physicochemical properties and may represent a valuable starting point for future optimization to develop inhibitors for this and other related viruses.

Characterization of "Off-Target" Immune Modulation Induced by Live Attenuated Yellow Fever Vaccine.

Live attenuated vaccines alter immune functions and are associated with beneficial outcomes. We previously demonstrated that live attenuated yellow fever virus (YFV) vaccine (LA-YF-Vax) dampens T-cell receptor (TCR) signaling in vitro via an RNA-based mechanism. We examined study participants before and after LA-YF-Vax to assess TCR-mediated functions in vivo. Serum samples and peripheral blood mononuclear cells (PBMCs) were obtained before and after LA-YF-Vax (with or without additional vaccines) or quadrivalent influenza vaccine. TCR-mediated activation was determined by interleukin 2 release or phosphorylation of the lymphocyte-specific Src kinase. TCR-regulating phosphatase (protein tyrosine phosphatase receptor type E [PTPRE]) expression was also measured. Compared with prevaccination findings, LA-YF-Vax recipient PBMCs demonstrated transient reduction in interleukin 2 release after TCR stimulation and PTPRE levels, unlike in control participants who received quadrivalent influenza vaccine. YFV was detected in 8 of 14 participants after LA-YF-Vax. After incubation of healthy donor PBMCs in serum-derived extracellular vesicles prepared from LA-YF-Vax recipients, TCR signaling and PTPRE levels were reduced after vaccination, even in participants without detectable YFV RNA. LA-YF-Vax reduces TCR functions and PTPRE levels after vaccination. Extracellular vesicles from serum recapitulated this effect in healthy cells. This likely contributes to the reduced immunogenicity for heterologous vaccines after LA-YF-Vax administration. Identification of specific immune mechanisms related to vaccines should contribute to understanding of the "off-target," beneficial effects of live vaccines.

Therapeutic neutralizing monoclonal antibody administration protects against lethal yellow fever virus infection.

Yellow fever virus (YFV) is a reemerging global health threat, driven by several factors, including increased spread of the mosquito vector and rapid urbanization. Although a prophylactic vaccine exists, vaccine hesitancy, supply deficits, and distribution difficulties leave specific populations at risk of severe YFV disease, as evidenced by recent outbreaks in South America. To establish a treatment for patients with severe YFV infection, we tested 37 YFV-specific monoclonal antibodies isolated from vaccinated humans and identified two capable of potently neutralizing multiple pathogenic primary YFV isolates. Using both hamster and nonhuman primate models of lethal YFV infection, we demonstrate that a single administration of either of these two potently neutralizing antibodies during acute infection fully controlled viremia and prevented severe disease and death in treated animals. Given the potential severity of YFV-induced disease, our results show that these antibodies could be effective in saving lives and fill a much-needed void in managing YFV cases during outbreaks.

Differences in gene expression in field populations of Wolbachia-infected Aedes aegypti mosquitoes with varying release histories in northern Australia.

Aedes aegypti is the principal mosquito vector of dengue, yellow fever, Zika and chikungunya viruses. The wMel strain of the endosymbiotic bacteria Wolbachia pipientis was introduced into the vector as a novel biocontrol strategy to stop transmission of these viruses. Mosquitoes with Wolbachia have been released in the field in Northern Queensland, Australia since 2011, at various locations and over several years, with populations remaining stably infected. Wolbachia infection is known to alter gene expression in its mosquito host, but whether (and how) this changes over the long-term in the context of field releases remains unknown. We sampled mosquitoes from Wolbachia-infected populations with three different release histories along a time gradient and performed RNA-seq to investigate gene expression changes in the insect host. We observed a significant impact on gene expression in Wolbachia-infected mosquitoes versus uninfected controls. Fewer genes had significantly upregulated expression in mosquitoes from the older releases (512 and 486 from the 2011 and 2013/14 release years, respectively) versus the more recent releases (1154 from the 2017 release year). Nonetheless, a fundamental signature of Wolbachia infection on host gene expression was observed across all releases, comprising upregulation of immunity (e.g. leucine-rich repeats, CLIPs) and metabolism (e.g. lipid metabolism, iron transport) genes. There was limited downregulation of gene expression in mosquitoes from the older releases (84 and 71 genes from the 2011 and 2013/14 release years, respectively), but significantly more in the most recent release (509 from the 2017 release year). Our findings indicate that at > 8 years post-introgression into field populations, Wolbachia continues to profoundly impact expression of host genes, such as those involved in insect immune response and metabolism. If Wolbachia-mediated virus blocking is underpinned by these differential gene expression changes, our results suggest it may remain stable long-term.

The Threat of Impending Pandemics: A Proactive Approach.

The incessant occurrence of devastating health-related events, either on a large scale, such as pandemics, or in a local community in the form of sporadic outbreaks due to infectious agents, warrants a rapid, target-oriented, well-organized response team to combat the demonic consequences. While the world has been recovering from the clutches of the recent disastrous COVID-19 pandemic, the struggles against novel emerging and re-emerging pathogens such as monkeypox (mpox), newer evolving strains of influenza, Ebola, Zika, and the yellow fever virus continue to date. Therefore, a multisectoral, intercontinental, collaborative, interdisciplinary, and highly dedicated approach should always be implemented to achieve optimal health and avert future threats.

Synthetic Curcumin Analogues Present Antiflavivirus Activity In Vitro with Potential Multiflavivirus Activity from a Thiazolylhydrazone Moiety

Arboviral diseases caused by flaviviruses, such as dengue, are a continuing threat and major concern worldwide, with over three billion people estimated to be living with the risk of dengue virus (DENV) infections. There are thus far no antiviral drugs available for treatment, and limited or no vaccines are available. Curcumin and seven synthetic analogues were evaluated for their antiviral activity against dengue virus serotype 2, yellow fever virus and Zika virus, as well as for their cytotoxicity in Vero cells, both by employing MTT assays. Compounds 6 and 7, which present a thiazolylhydrazone moiety, showed moderate activity against all three flaviviruses, with selectivity index (SI) values up to 4.45. In addition, the envelope protein (E) was predicted as the potential target inhibited by both compounds, supported by molecular docking and dynamics simulation analysis. We hope that this data can contribute to the development of new curcumin antiviral analogues in the near future and can help in the search for new promising compounds as potential therapeutic agents to treat flaviviruses infections.