Genomic approaches for understanding dengue: insights from the virus, vector, and host

Investigation of small molecules disrupting dengue virus assembly by inhibiting capsid protein and blocking RNA encapsulation

Dengue fever is a significant global public health concern, causing substantial morbidity and mortality worldwide. The disease can manifest in various forms, from mild fever to potentially life-threatening complications. Developing effective treatments remains a critical challenge to healthcare systems. Despite extensive research, no antiviral drugs have been approved for either the prevention or treatment of dengue. Targeting the virus during its early phase of attachment is essential to inhibit viral replication. The capsid protein plays a crucial role in the virus's structural integrity, assembly, and viral genome release. In the present study, we employed a computational approach focused on the capsid protein to identify possible potent inhibitors against the dengue virus from a library of FDA-approved drugs. We employed high-throughput virtual screening on FDA-approved drugs to identify drug molecules that could potentially combat the disease and save both cost and time. The screening process identified four drug molecules (Nordihydroguaiaretic acid, Ifenprodil tartrate, Lathyrol, and Safinamide Mesylate) based on their highest binding affinity and MM/GBSA scores. Among these, Nordihydroguaiaretic acid showed higher binding affinity than the reference molecule with - 11.66 kcal/mol. In contrast, Ifenprodil tartrate and Lathyrol showed similar results to the reference molecule, with binding energies of - 9.42 kcal/mol and - 9.29 kcal/mol, respectively. Following the screening, molecular dynamic simulations were performed to explore the molecular stability and conformational possibilities. The drug molecules were further supported by post-molecular simulation analysis. Furthermore, binding energies were also computed using the MM/GBSA approach, and the free energy landscape was used to calculate the different transition states, revealing that the drugs exhibited significant transition states. Specifically, Nordihydroguaiaretic acid and Ifenprodil tartrate displayed higher flexibility, while Lathyrol and Safinamide Mesylate showed more predictable and consistent protein folding. This significant breakthrough offers new hope against dengue, highlighting the power of computational drug discovery in identifying potent inhibitors and paving the way for novel treatment approaches.

Cryptic transmission and novel introduction of Dengue 1 and 2 genotypes in Colombia

Dengue fever remains as a public health challenge in Colombia, standing as the most prevalent infectious disease in the country. The cyclic nature of dengue epidemics, occurring approximately every 3 years, is intricately linked to meteorological events like El Niño Southern Oscillation (ENSO). Therefore, the Colombian system faces challenges in genomic surveillance. This study aimed to evaluate local dengue virus (DENV) transmission and genetic diversity in four Colombian departments with heterogeneous incidence patterns (department is first-level territorial units in Colombia). For this study, we processed 266 serum samples to identify DENV. Subsequently, we obtained 118 genome sequences by sequencing DENV genomes from serum samples of 134 patients infected with DENV-1 and DENV-2 serotypes. The predominant serotype was DENV-2 (108/143), with the Asian-American (AA) genotype (91/118) being the most prevalent one. Phylogenetic analysis revealed concurrent circulation of two lineages of both DENV-2 AA and DENV-1 V, suggesting ongoing genetic exchange with sequences from Venezuela and Cuba. The continuous migration of Venezuelan citizens into Colombia can contribute to this exchange, emphasizing the need for strengthened prevention measures in border areas. Notably, the time to most recent common ancestor analysis identified cryptic transmission of DENV-2 AA since approximately 2015, leading to the recent epidemic. This challenges the notion that major outbreaks are solely triggered by recent virus introductions, emphasizing the importance of active genomic surveillance. The study also highlighted the contrasting selection pressures on DENV-1 V and DENV-2 AA, with the latter experiencing positive selection, possibly influencing its transmissibility. The presence of a cosmopolitan genotype in Colombia, previously reported in Brazil and Peru, raises concerns about transmission routes, emphasizing the necessity for thorough DENV evolution studies. Despite limitations, the study underscores genomic epidemiology's crucial role in early detection and comprehension of DENV genotypes, recommending the use of advanced sequencing techniques as an early warning system to help prevent and control dengue outbreaks in Colombia and worldwide.

A serotype-specific and tiled amplicon multiplex PCR method for whole genome sequencing of dengue virus

Dengue fever, a mosquito-borne viral disease of significant public health concern in tropical and subtropical regions, is caused by any of the four serotypes of the dengue virus (DENV1-4). Cutting-edge technologies like next-generation sequencing (NGS) are revolutionizing virology, enabling in-depth exploration of DENV's genetic diversity. Here, we present an optimized workflow for full-genome sequencing of DENV 1-4 utilizing tiled amplicon multiplex PCR and Illumina sequencing. Our assay, sequenced on the Illumina MiSeq platform, demonstrates its ability to recover the full-length dengue genome across various viral abundances in clinical specimens with high-quality base coverage. This high quality underscores its suitability for precise examination of intra-host diversity, enriching our understanding of viral evolution and holding potential for improved diagnostic and intervention strategies in regions facing dengue outbreaks.

Accurate Recapitulation of Chikungunya Virus Complete Coding Sequence Phylogeny Using Variable Genome Regions for Genomic Surveillance

Chikungunya virus (CHIKV) is transmitted by mosquito bites and causes chikungunya fever (CHIKF). CHIKV has a single-stranded RNA genome and belongs to a single serotype with three genotypes. The Asian lineage has recently emerged in the Western Hemisphere, likely due to travel-associated introduction. Genetic variation accumulates in the CHIKV genome as the virus replicates, creating new lineages. Whole genome sequencing is ideal for studying virus evolution and spread but is expensive and complex. This study investigated whether specific, highly variable regions of the CHIKV genome could recapitulate the phylogeny obtained with a complete coding sequence (CDS). Our results revealed that concatenated highly variable regions accurately reconstructed CHIKV phylogeny, exhibiting statistically indistinguishable branch lengths and tree confidence compared to CDS. In addition, these regions adequately inferred the evolutionary relationships among CHIKV isolates from the American outbreak with similar results to the CDS. This finding suggests that highly variable regions can effectively capture the evolutionary relationships among CHIKV isolates, offering a simpler approach for future studies. This approach could be particularly valuable for large-scale surveillance efforts.

Integrated One Health strategies in Dengue

Zoonoses have rapidly spread globally, necessitating the implementation of vaccination strategies as a control measure. Emerging and re-emerging vector-borne diseases are among the major global public health concerns. Dengue, a zoonotic viral infection transmitted to humans by a vector, the Aedes mosquito, is a severe global health problem. Dengue is a serious tropical infectious disease, second only to malaria, causing around 25,000 deaths each year. The resurgence of Dengue is mainly due to climate change, demographic transitions and evolving social dynamics. The development of an effective vaccine against Dengue has proven to be a complex undertaking due to four different viral serotypes with distinct antigenic profiles. This review highlights the urgent need to address the dengue threat by exploring the application of biotechnological and -OMICS sciences.

The Development of New Primer Sets for the Amplification and Sequencing of the Envelope Gene of All Dengue Virus Serotypes

Dengue virus (DENV) poses a significant threat to global health, infecting approximately 390 million people annually. This virus comprises four serotypes capable of causing severe disease. Genetic analyses are crucial for understanding the epidemiology, evolution, and spread of DENV. Although previous studies have focused on the envelope protein-coding (E) gene, only a few primers can efficiently detect and amplify the viral genes from multiple endemic countries simultaneously. In this study, we designed degenerate primer pairs for each DENV serotype to amplify and sequence the entire E gene, using globally representative sequences for each serotype. These primers were validated using DENV isolates from various Asian countries and demonstrated broad-spectrum detection capabilities and high-quality sequences. The primers provide effective tools for genetic analysis in the regions affected by dengue, aiding strain identification and epidemiological studies during outbreaks.

Identification of an Arylnaphthalene Lignan Derivative as an Inhibitor against Dengue Virus Serotypes 1 to 4 (DENV-1 to -4) Using a Newly Developed DENV-3 Infectious Clone and Replicon

Dengue virus (DENV) is the most widespread arbovirus, causing symptoms ranging from dengue fever to severe dengue, including hemorrhagic fever and shock syndrome. Four serotypes of DENV (DENV-1 to -4) can infect humans; however, no anti-DENV drug is available. To facilitate the study of antivirals and viral pathogenesis, here we developed an infectious clone and a subgenomic replicon of DENV-3 strains for anti-DENV drug discovery by screening a synthetic compound library. The viral cDNA was amplified from a serum sample from a DENV-3-infected individual during the 2019 epidemic; however, fragments containing the prM-E-partial NS1 region could not be cloned until a DENV-3 consensus sequence with 19 synonymous substitutions was introduced to reduce putative Escherichia coli promoter activity. Transfection of the resulting cDNA clone, plasmid DV3syn, released an infectious virus titer of 2.2 × 102 focus-forming units (FFU)/mL. Through serial passages, four adaptive mutations (4M) were identified, and addition of 4M generated recombinant DV3syn_4M, which produced viral titers ranging from 1.5 × 104 to 6.7 × 104 FFU/mL and remained genetically stable in transformant bacteria. Additionally, we constructed a DENV-3 subgenomic replicon and screened an arylnaphthalene lignan library, from which C169-P1 was identified as exhibiting inhibitory effects on viral replicon. A time-of-drug addition assay revealed that C169-P1 also impeded the internalization process of cell entry. Furthermore, we demonstrated that C169-P1 inhibited the infectivity of DV3syn_4M, as well as DENV-1, DENV-2, and DENV-4, in a dose-dependent manner. This study provides an infectious clone and a replicon for the study of DENV-3 and a candidate compound for future development against DENV-1 to -4 infections. IMPORTANCE Dengue virus (DENV) is the most prevalent mosquito-transmitted virus, and there is no an anti-dengue drug. Reverse genetic systems representative of different serotype viruses are invaluable tools for the study of viral pathogenesis and antiviral drugs. Here, we developed an efficient infectious clone of a clinical DENV-3 genotype III isolate. We successfully overcame the instability of flavivirus genome-length cDNA in transformant bacteria, an unsolved issue for construction of cDNA clones of flaviviruses, and adapted this clone to efficiently produce infectious viruses following plasmid transfection of cell culture. Moreover, we constructed a DENV-3 subgenomic replicon and screened a compound library. An arylnaphthalene lignan, C169-P1, was identified as an inhibitor of virus replication and cell entry. Finally, we demonstrated that C169-P1 exhibited a broad-spectrum antiviral effect against the infections with DENV-1 to -4. The reverse genetic systems and the compound candidate described here facilitate the study of DENV and related RNA viruses.

Intrahost Genetic Diversity of Dengue Virus in Human Hosts and Mosquito Vectors under Natural Conditions Which Impact Replicative Fitness In Vitro

Dengue virus (DENV) is an arbovirus whose transmission cycle involves disparate hosts: humans and mosquitoes. The error-prone nature of viral RNA replication drives the high mutation rates, and the consequently high genetic diversity affects viral fitness over this transmission cycle. A few studies have been performed to investigate the intrahost genetic diversity between hosts, although their mosquito infections were performed artificially in the laboratory setting. Here, we performed whole-genome deep sequencing of DENV-1 (n = 11) and DENV-4 (n = 13) derived from clinical samples and field-caught mosquitoes from the houses of naturally infected patients, in order to analyze the intrahost genetic diversity of DENV between host types. Prominent differences in DENV intrahost diversity were observed in the viral population structure between DENV-1 and DENV-4, which appear to be associated with differing selection pressures. Interestingly, three single amino acid substitutions in the NS2A (K81R), NS3 (K107R), and NS5 (I563V) proteins in DENV-4 appear to be specifically acquired during infection in Ae. aegypti mosquitoes. Our in vitro study shows that the NS2A (K81R) mutant replicates similarly to the wild-type infectious clone-derived virus, while the NS3 (K107R), and NS5 (I563V) mutants have prolonged replication kinetics in the early phase in both Vero and C6/36 cells. These findings suggest that DENV is subjected to selection pressure in both mosquito and human hosts. The NS3 and NS5 genes may be specific targets of diversifying selection that play essential roles in early processing, RNA replication, and infectious particle production, and they are potentially adaptive at the population level during host switching.

Demographic characteristics, clinical symptoms, biochemical markers and probability of occurrence of severe dengue: A multicenter hospital-based study in Bangladesh

Establishing reliable early warning models for severe dengue cases is a high priority to facilitate triage in dengue-endemic areas and optimal use of limited resources. However, few studies have identified the complex interactive relationship between potential risk factors and severe dengue. This research aimed to assess the potential risk factors and detect their high-order combinative effects on severe dengue. A structured questionnaire was used to collect detailed dengue outbreak data from eight representative hospitals in Dhaka, Bangladesh, in 2019. Logistic regression and machine learning models were used to examine the complex effects of demographic characteristics, clinical symptoms, and biochemical markers on severe dengue. A total of 1,090 dengue cases (158 severe and 932 non-severe) were included in this study. Dyspnoea (Odds Ratio [OR] = 2.87, 95% Confidence Interval [CI]: 1.72 to 4.77), plasma leakage (OR = 3.61, 95% CI: 2.12 to 6.15), and hemorrhage (OR = 2.33, 95% CI: 1.46 to 3.73) were positively and significantly associated with the occurrence of severe dengue. Classification and regression tree models showed that the probability of occurrence of severe dengue cases ranged from 7% (age >12.5 years without plasma leakage) to 92.9% (age ≤12.5 years with dyspnoea and plasma leakage). The random forest model indicated that age was the most important factor in predicting severe dengue, followed by education, plasma leakage, platelet, and dyspnoea. The research provides new evidence to identify key risk factors contributing to severe dengue cases, which could be beneficial to clinical doctors to identify and predict the severity of dengue early.

A phylogenetic study of dengue virus in urban Vietnam shows long-term persistence of endemic strains

Dengue virus (DENV) causes repeated outbreaks of disease in endemic areas, with patterns of local transmission strongly influenced by seasonality, importation via human movement, immunity, and vector control efforts. An understanding of how each of these interacts to enable endemic transmission (continual circulation of local virus strains) is largely unknown. There are times of the year when no cases are reported, often for extended periods of time, perhaps wrongly implying the successful eradication of a local strain from that area. Individuals who presented at a clinic or hospital in four communes in Nha Trang, Vietnam, were initially tested for DENV antigen presence. Enrolled positive individuals then had their corresponding household members invited to participate, and those who enrolled were tested for DENV. The presence of viral nucleic acid in all samples was confirmed using quantitative polymerase chain reaction, and positive samples were then whole-genome sequenced using an amplicon and target enrichment library preparation techniques and Illumina MiSeq sequencing technology. Generated consensus genome sequences were then analysed using phylogenetic tree reconstruction to categorise sequences into clades with a common ancestor, enabling investigations of both viral clade persistence and introductions. Hypothetical introduction dates were additionally assessed using a molecular clock model that calculated the time to the most recent common ancestor (TMRCA). We obtained 511 DENV whole-genome sequences covering four serotypes and more than ten distinct viral clades. For five of these clades, we had sufficient data to show that the same viral lineage persisted for at least several months. We noted that some clades persisted longer than others during the sampling time, and by comparison with other published sequences from elsewhere in Vietnam and around the world, we saw that at least two different viral lineages were introduced into the population during the study period (April 2017-2019). Next, by inferring the TMRCA from the construction of molecular clock phylogenies, we predicted that two of the viral lineages had been present in the study population for over a decade. We observed five viral lineages co-circulating in Nha Trang from three DENV serotypes, with two likely to have remained as uninterrupted transmission chains for a decade. This suggests clade cryptic persistence in the area, even during periods of low reported incidence.

Contribution of phylogenetics to understanding the evolution and epidemiology of dengue virus

Dengue virus (DENV) is one of the most important arboviral pathogens in the tropics and subtropics, and nearly one‐third of the world's population is at risk of infection. The transmission of DENV involves a sylvatic cycle between nonhuman primates (NHP) and Aedes genus mosquitoes, and an endemic cycle between human hosts and predominantly Aedes aegypti. DENV belongs to the genus Flavivirus of the family Flaviviridae and consists of four antigenically distinct serotypes (DENV‐1‐4). Phylogenetic analyses of DENV have revealed its origin, epidemiology, and the drivers that determine its molecular evolution in nature. This review discusses how phylogenetic research has improved our understanding of DENV evolution and how it affects viral ecology and improved our ability to analyze and predict future DENV emergence.

Three highly variable genome regions of the four dengue virus serotypes can accurately recapitulate the CDS phylogeny

The circulation of the four-dengue virus (DENV) serotypes has significantly increased in recent years, accompanied by an increase in viral genetic diversity. In order to conduct disease surveillance and understand DENV evolution and its effects on virus transmission and disease, efficient and accurate methods for phylogenetic classification are required. Phylogenetic analysis of different viral genes sequences is the most used method, the envelope gene (E) being the most frequently selected target. We explored the genetic variability of the four DENV serotypes throughout their complete coding sequence (CDS) of sequences available in GenBank and used genomic regions of different variability rate to recapitulate the phylogeny obtained with the DENV CDS. Our results indicate that the use of high or low variable regions accurately recapitulate the phylogeny obtained with CDS of sequences from different DENV genotypes. However, when analyzing the phylogeny of a single genotype, highly variable regions performed better in recapitulating the distance branch length, topology, and support of the CDS phylogeny. The use of three concatenated highly variable regions was not statistically different in distance branch length and support to that obtained in CDS phylogeny.•This study demonstrated the ability of highly variable regions of the DENV genome to recapitulate the phylogeny obtained with the full coding sequence (CDS).•The use of genomic regions of high or low variability did not affect the performance in recapitulating the phylogeny obtained with CDS from different genotypes. However, when phylogeny was analyzed for sequences from a single genotype, highly variable regions performed better in recapitulating the distance branch length, topology, and support of the CDS phylogeny.•The use of concatenated highly variable genome regions represent a useful option for recapitulating genome-wide phylogenies in analyses of sequences belonging to the same DENV genotype.

Intra-Host Diversity of Dengue Virus in Mosquito Vectors

Dengue virus (DENV) is the most common arbovirus, causing a significant burden on both the economy and global healthcare systems. The virus is transmitted by Aedes species of mosquitoes as a swarm of closely related virus genomes, collectively referred to as a quasispecies. The level of genomic diversity within this quasispecies varies as DENV moves through various ecological niches within its transmission cycle. Here, the factors that influence the level of DENV quasispecies diversity during the course of infection in the mosquito vectors are reviewed.

Suppression of TGF-β/Smad2 signaling by GW788388 enhances DENV-2 clearance in macrophages

Dengue fever, caused by the dengue virus (DENV‐1, −2, −3, and −4), affects millions of people in the tropical and subtropical regions worldwide. Severe dengue is correlated with high viraemia and cytokine storm, such as high levels of transforming growth factor‐β1 (TGF‐β1) in the patient's serum. Here, the TGF‐β1 signaling was investigated in the context of in vitro viral clearance. Macrophages were infected with DENV‐2 at MOI 5 and treated with the TGF‐β receptor 1 and 2 inhibitor, GW788388. TGF‐β1 expression, signal transduction and viral load were evaluated 48 h after DENV‐2 infection by enzyme‐linked immunoassay, immunofluorescence, and RT‐qPCR assays. Total TGF‐β1 level was reduced in 15% after DENV‐2 infection, but the secretion of its biologically active form increased threefold during infection, which was followed by the phosphorylation of Smad2 protein. Phosphorylation of Smad2 was reduced by treatment with GW788388 and it was correlated with reduced cytokine production. Importantly, treatment led to a dose‐dependent reduction in viral load, ranging from 6.6 × 10⁵ RNA copies/ml in untreated cultures to 2.3 × 10³ RNA copies/ml in cultures treated with 2 ng/ml of GW788388. The anti‐TGF‐β1 antibody treatment also induced a significant reduction in viral load to 1.6 × 10³ RNA copies/ml. On the other hand, the addition of recombinant TGF‐β1 in infected cultures promoted an increase in viral load to 7.0 × 10⁶ RNA copies/ml. These results support that TGF‐β1 plays a significant role in DENV‐2 replication into macrophages and suggest that targeting TGF‐β1 may represent an alternative therapeutic strategy to be explored in dengue infection.

Gene Expression Profiling of Early Acute Febrile Stage of Dengue Infection and Its Comparative Analysis With Streptococcus pneumoniae Infection

Infectious diseases are the disorders caused by organisms such as bacteria, viruses, fungi, or parasites. Although many of them are permentantly hazardous, a number of them live in and on our bodies and they are normally harmless or even helpful. Under certain circumstances, some organisms may cause diseases and these infectious diseases may be passed directly from person to person or via intermediate vectors including insects and other animals. Dengue virus and Streptococcus pneumoniae are the critical and common sources of infectious diseases. So, it is critical to understand the gene expression profiling and their inferred functions in comparison to the normal and virus infected conditions. Here, we have analyzed the gene expression profiling for dengue hemorrhagic fever, dengue fever, and normal human dataset. Similar to it, streptococcus pneumoniae infectious data were analyzed and both the outcomes were compared. Our study leads to the conclusion that the dengue hemorrhagic fever arises in result to potential change in the gene expression pattern, and the inferred functions obviously belong to the immune system, but also there are some additional potential pathways which are critical signaling pathways. In the case of pneumoniae infection, 19 pathways were enriched, almost all these pathways are associated with the immune system and 17 of the enriched pathways were common with dengue infection except platelet activation and antigen processing and presentation. In terms of the comparative study between dengue virus and Streptococcus pneumoniae infection, we conclude that cell adhesion molecules (CAMs), MAPK signaling pathway, natural killer cell mediated cytotoxicity, regulation of actin cytoskeleton, and cytokine-cytokine receptor interaction are commonly enriched in all the three cases of dengue infection and Streptococcus pneumoniae infection, focal adhesion was enriched between classical dengue fever — dengue hemorrhagic fever, dengue hemorrhagic fever—normal samples, and SP, and antigen processing and presentation and Leukocyte transendothelial migration were enriched in classical dengue fever —normal samples, dengue hemorrhagic fever—normal samples, and Streptococcus pneumoniae infection.

The Global Trends and Regional Differences in Incidence of Dengue Infection from 1990 to 2019: An Analysis from the Global Burden of Disease Study 2019

INTRODUCTION

Dengue, as a neglected tropical disease, brings a heavy socioeconomic burden. To provide tailored global prevention strategies, we analyzed the global trends and regional differences in incidence of dengue infection from 1990 to 2019.

METHODS

We obtained data on annual dengue episodes and incidence rates, which reflected the epidemic status of dengue infection from the 2019 Global Burden of Disease (GBD) Study. The changes in dengue episodes and estimated annual percentage changes (EAPCs) of the age-standardized incidence rate (ASR) were calculated to quantify the temporal trends of dengue infection.

RESULTS

Globally, dengue ASR increased by 1.70% (95% CI 1.62%-1.78%) per year from 1990 to 2011; subsequently, it decreased by 0.41% (95% CI 0.20%-0.62%) per year from 2011 to 2019. However, the global number of dengue episodes increased steadily by 85.47% from 30.67 million in 1990 to 56.88 million in 2019. Against the global trend of decreasing ASR from 2011 to 2019, an increasing trend was reported in Oceania (EAPC 11.01, 95% CI 8.79-13.27), East Asia (EAPC 4.84, 95% CI 2.70-7.03) and Southeast Asia (EAPC 0.38, 95% CI 0.13-0.62). For socio-demographic index (SDI) regions, ASR continued to have an increasing trend in the middle (EAPC 0.26, 95% CI 0.07-0.45) and high-middle (EAPC 1.70, 95% CI 0.98-2.42) SDI regions from 2011 to 2019. In contrast to the global peak age of dengue incidence rate (10 to 25 years), the dengue incidence rate of older people (> 65 years) was higher than in other age groups in low and low-middle SDI regions. Additionally, the proportions of dengue episodes in the > 70-year-old age group increased in 2019 (using the baseline in 1990 or 2011) in most GBD regions.

CONCLUSIONS

Global dengue episodes have increased tremendously in 3 decades. Although global dengue ASR decreased in the last decade, it is still increasing in hyperendemic regions including Oceania, East Asia and Southeast Asia, and also in the middle and high-middle SDI regions. More attention should be paid to the elderly because of the higher dengue incidence rate among them in low and low-middle SDI regions and the increased proportions of dengue episodes among the elderly in most GBD regions. Therefore, more efforts should be undertaken to develop targeted prevention strategies for crucial regions and older populations.

Metabolomics applied in the study of emerging arboviruses caused by Aedes aegypti mosquitoes: A review

Arboviruses, such as chikungunya, dengue, yellow fever, and zika, caused by the bite of the Aedes aegypti mosquito, have been a frequent public health problem, with a high incidence of outbreaks in tropical and subtropical countries. These diseases are easily confused with a flu-like illness and present very similar symptoms, difficult to distinguish, and treat appropriately. The effects that these infections cause in the organism are fundamentally derived from complex metabolic processes. A prominent area of science that investigates the changes in the metabolism of complex organisms is the metabolomics. Metabolomics measures the metabolites produced or altered in biological organisms, through the use of robust analytical platforms, such as separation techniques hyphenated with mass spectrometry, combined with bioinformatics. This review article presents an overview of the basic concepts of metabolomics workflow and advances in this field, and compiles research articles that use this omic approach to study these arboviruses. In this context, the metabolomics is applied to search new therapies, understand the viral replication mechanisms, and access the host-virus interactions.

Unidentified dengue serotypes in DENV positive samples and detection of other pathogens responsible for an acute febrile illness outbreak 2016 in Cajamarca, Peru

Objective

To describe the prevalence of dengue virus serotypes, as well as other viral and bacterial pathogens that cause acute febrile illness during an outbreak in Cajamarca in 2016.

Results

Dengue virus (DENV) was the most frequent etiologic agent detected in 25.8% of samples (32/124), followed by Rickettsia spp. in 8.1% (10/124), Zika virus in 4.8% (6/124), Chikungunya virus 2.4% (3/124) and Bartonella bacilliformis 1.6% (2/124) cases. No positive cases were detected of Oropouche virus and Leptospira spp. DENV serotypes identification was only achieved in 23% of the total positive for DENV, two samples for DENV-2 and four samples for DENV-4.

During the 2016 outbreak in Cajamarca—Peru, it was observed that in a large percentage of positive samples for DENV, the infecting serotype could not be determined by conventional detection assays. This represents a problem for the national surveillance system and for public health due to its epidemiological and clinical implications. Other viral and bacterial pathogens responsible for acute febrile syndrome were less frequently identified.

Epidemiology of dengue fever in Guatemala

Dengue fever occurs worldwide and about 1% of cases progress to severe haemorrhage and shock. Dengue is endemic in Guatemala and its surveillance system could document long term trends. We analysed 17 years of country-wide dengue surveillance data in Guatemala to describe epidemiological trends from 2000 to 2016.Data from the national dengue surveillance database were analysed to describe dengue serotype frequency, seasonality, and outbreaks. We used Poisson regression models to compare the number of cases each year with subsequent years and to estimate incidence ratios within serotype adjusted by age and gender. 91,554 samples were tested. Dengue was confirmed by RT-qPCR, culture or NS1-ELISA in 7097 (7.8%) cases and was IgM ELISA-positive in 19,290 (21.1%) cases. DENV1, DENV2, DENV3, and DENV4 were detected in 2218 (39.5%), 2580 (45.9%), 591 (10.5%), and 230 (4.1%) cases. DENV1 and DENV2 were the predominant serotypes, but all serotypes caused epidemics. The largest outbreak occurred in 2010 with 1080 DENV2 cases reported. The incidence was higher among adults during epidemic years, with significant increases in 2005, 2007, and 2013 DENV1 outbreaks, the 2010 DENV2 and 2003 DENV3 outbreaks. Adults had a lower incidence immediately after epidemics, which is likely linked to increased immunity.

Dengue is the most common mosquito-borne virus, and a major cause of fever, with an estimated 390 million infections annually. Guatemala, in Central America, has had ongoing dengue transmission since the 1990s. Its national surveillance system monitors outbreaks and seasonal trends of infections to inform public health responses. We have analysed 17 years of surveillance data collected from 2000 to 2016, to describe seasonal trends, outbreak years, and the fluctuating prevalence of the four dengue serotypes. Laboratory data from 91,554 individual serum samples were included, of which 7.8% were positive for dengue. All four dengue serotypes circulate in the country, with dengue 1 and 2 being the predominant serotypes. This is important, as it increases the likelihood of dengue infections being followed by a new infection with a different serotype, which can lead to severe dengue. We also report that adults in Guatemala have a lower likelihood of infection the year after an epidemic, which might be linked to an increased immunity in the population.

Visual Detection of Dengue-1 RNA Using Gold Nanoparticle-Based Lateral Flow Biosensor

Dengue is a rapidly spreading mosquito-borne viral disease. Early diagnosis is important for clinical screening, medical management, and disease surveillance. The objective of this study was to develop a colorimetric lateral flow biosensor (LFB) for the visual detection of dengue-1 RNA using dextrin-capped gold nanoparticle (AuNP) as label. The detection was based on nucleic acid sandwich-type hybridization among AuNP-labeled DNA reporter probe, dengue-1 target RNA, and dengue-1 specific DNA capture probe immobilized on the nitrocellulose membrane. Positive test generated a red test line on the LFB strip, which enabled visual detection. The optimized biosensor has a cut-off value of 0.01 µM using synthetic dengue-1 target. Proof-of-concept application of the biosensor detected dengue-1 virus in pooled human sera with a cut-off value of 1.2 × 104 pfu/mL. The extracted viral RNA, when coupled with nucleic acid sequence-based amplification (NASBA), was detected on the LFB in 20 min. This study first demonstrates the applicability of dextrin-capped AuNP as label for lateral flow assay. The biosensor being developed provides a promising diagnostic platform for early detection of dengue infection in high-risk resource-limited areas.

Potent neutralizing antibodies elicited by dengue vaccine in rhesus macaque target diverse epitopes

There is still no safe and effective vaccine against dengue virus infection. Epidemics of dengue virus infection are increasingly a threat to human health around the world. Antibodies generated in response to dengue infection have been shown to impact disease development and effectiveness of dengue vaccine. In this study, we investigated monoclonal antibody responses to an experimental dengue vaccine in rhesus macaques. Variable regions of both heavy chain (VH) and light chain (VL) were cloned from single antibody-secreting B cells. A total of 780 monoclonal antibodies (mAbs) composed of paired VH and VL were characterized. Results show that the vaccination induces mAbs with diverse germline sequences and a wide range of binding affinities. Six potent neutralizing mAbs were identified among 130 dengue envelope protein binders. Critical amino acids for each neutralizing antibody binding to the dengue envelope protein were identified by alanine scanning of mutant libraries. Diverse epitopes were identified, including epitopes on the lateral ridge of DIII, the I-III hinge, the bc loop adjacent to the fusion loop of DII, and the β-strands and loops of DI. Significantly, one of the neutralizing mAbs has a previously unknown epitope in DII at the interface of the envelope and membrane protein and is capable of neutralizing all four dengue serotypes. Taken together, the results of this study not only provide preclinical validation for the tested experimental vaccine, but also shed light on a potential application of the rhesus macaque model for better dengue vaccine evaluation and design of vaccines and immunization strategies.

Dengue virus (DENV) is a leading cause of human illness in the tropics and subtropics, with about 40% of the world’s population living in areas at risk for infection. There are four DENV serotypes. Patients who have previously been infected by one dengue serotype may develop more severe symptoms such as bleeding and endothelial leakage upon secondary infection with another dengue serotype. This study reports the extensive cloning and analysis of 780 monoclonal antibodies (mAbs) from single B cells of rhesus macaques after immunization with an experimental dengue vaccine. We identified a panel of potent neutralizing mAbs with diverse epitopes on the DENV envelope protein. Antibodies in this panel were found to bind to the lateral ridge of DIII, the I-III hinge, the bc loop adjacent to the fusion loop of DII, and the β-strands and the loops of DI. We also isolated one mAb (d448) that can neutralize all four dengue serotypes and binds to a novel epitope at the interface of the DENV envelope and membrane proteins. Further investigation of these neutralizing monoclonal antibodies is warranted for better vaccine efficacy evaluation and vaccine design.

Applied shotgun metagenomics approach for the genetic characterization of dengue viruses

Dengue virus (DENV), an arthropod-borne virus, has rapidly spread in recent years. DENV diagnosis is performed through virus serology, isolation or molecular detection, while genotyping is usually done through Sanger sequencing of the envelope gene. This study aimed to optimize the use of shotgun metagenomics and subsequent bioinformatics analysis to detect and type DENV directly from clinical samples without targeted amplification. Additionally, presence of DENV quasispecies (intra-host variation) was revealed by detecting single nucleotide variants. Viral RNA was isolated with or without DNase-I treatment from 17 DENV (1-4) positive blood samples. cDNA libraries were generated using either a combination of the NEBNext® RNA to synthesize cDNA followed by Nextera XT DNA library preparation, or the TruSeq RNA V2 (TS) library preparation kit. Libraries were sequenced using both the MiSeq and NextSeq. Bioinformatic analysis showed complete ORFs for all samples by all approaches, but longer contigs and higher sequencing depths were obtained with the TS kit. No differences were observed between MiSeq and NextSeq sequencing. Detection of multiple DENV serotypes in a single sample was feasible. Finally, results were obtained within three days with associated reagents costs between €130-170/sample. Therefore, shotgun metagenomics is suitable for identification and typing of DENV in a clinical setting.

Molecular epidemiology of dengue, yellow fever, Zika and Chikungunya arboviruses: An update

Arboviruses are a group of viruses transmitted by arthropods. They are characterized by a wide geographic distribution, which is associated with the presence of the vector, and cause asymptomatic infections or febrile diseases in humans in both enzootic and urban cycles. Recent reports of human infections caused by viruses such as dengue, Zika, and chikungunya have raised concern regarding public health, and have led to the re-evaluation of surveillance mechanisms and measures to control the transmission of these arboviruses. Viruses such as Mayaro and Usutu are not currently responsible for a high number of symptomatic infections in humans, but should remain under epidemiological surveillance to avoid the emergence of new epidemics, as happened with Zika virus, that are associated with new or more severe symptoms. Additionally, significant variation has been observed in these viruses, giving rise to different lineages. Until recently, the emergence of new lineages has primarily been related to geographical distribution and dispersion, allowing us to ascertain the possible origins and direction of expansion of each virus type, and to make predictions regarding regions where active infections in humans are likely to occur. Therefore, this review is focused on untangling the molecular epidemiology of Dengue, Yellow fever, Zika and Chikungunya due to their recent epidemics in Latinamerica but provides an update on the geographical distribution globally of these viral variants, and outlines the need for further understanding of the genotypes/lineages assignment.

Immune responses induced by different genotypes of the disease-specific protein of Rice stripe virus in the vector insect

Persistent plant viruses circulate between host plants and vector insects, possibly leading to the genetic divergence in viral populations. We analyzed the single nucleotide polymorphisms (SNPs) of Rice stripe virus (RSV) when it incubated in the small brown planthopper and rice. Two SNPs, which lead to nonsynonymous substitutions in the disease-specific protein (SP) of RSV, produced three genotypes, i.e., GG, AA and GA. The GG type mainly existed in the early infection period of RSV in the planthoppers and was gradually substituted by the other two genotypes during viral transmission. The two SNPs did not affect the interactions of SP with rice PsbP or with RSV coat protein. The GG genotype of SP induced stronger immune responses than those of the other two genotypes in the pattern recognition molecule and immune-responsive effector pathways. These findings demonstrated the population variations of RSV during the circulation between the vector insect and host plant.

Emergence of new genotypes and lineages of dengue viruses during the 2012-15 epidemics in southern India

OBJECTIVES

To genotypically characterize dengue virus (DENV) isolates among dengue-infected children from 2012-13/2014-15 outbreaks in southern India.

METHODS

Children hospitalized with suspected dengue were tested for dengue RT-PCR targeting Capsid-preMembrane (C-prM) and Envelope (Env) regions. Following virologic confirmation (n=612), a representative selection of DENV isolates (n=99) were sequenced for C-prM, aligned using ClustalW and subjected to phylogenetic analysis by maximum-likelihood method in MEGA6.

RESULTS

In 2012-13 (n=113), DENV-3 (44, 38.9%) and DENV-2 (43, 38.1%) predominated; DENV-1 (22, 19.5%) and DENV-4 (1, 0.9%) were less common. The pattern changed in 2014-15 (n=499), when DENV-1 (329, 65.7%) predominated, followed by DENV-2 (97, 21.2%), DENV-3 (36, 6.7%) and DENV-4 (10, 2.0%). Multiple-serotype co-infections occurred in 2.7% and 5.4% in 2012-13 and 2014-15, respectively. Genotype III (GIII) of DENV-1 predominated (85.7%) in 2012-13, ceding to GI predominance (80.8%) in 2014-15. Among DENV-2, 71.9% (23/32) showed distinct clustering suggesting a new lineage, 'GIVc'. All tested DENV-4 were GIC, whose clustering pattern showed the emergence of two distinct clades.

CONCLUSIONS

New genotypic/lineage variations in DENV-1 and DENV-2 may have influenced the magnitude and severity of dengue epidemics in southern India during this period. These findings emphasize the role of active surveillance of DENV serotypes/genotypes in aiding outbreak control and vaccine studies.

Complete assembly of a dengue virus type 3 genome from a recent genotype III clade by metagenomic sequencing of serum

Background: Mosquito-borne flaviviruses, such as dengue and Japanese encephalitis virus (JEV), cause life-threatening diseases, particularly in the tropics. Methods: Here we performed unbiased metagenomic sequencing of RNA extracted from the serum of four patients and the plasma of one patient, all hospitalized at a tertiary care centre in South India with severe or prolonged febrile illness, together with the serum from one healthy control, in 2014. Results: We identified and assembled a complete dengue virus type 3 sequence from a case of severe dengue fever. We also identified a small number of JEV sequences in the serum of two adults with febrile illness, including one with severe dengue. Phylogenetic analysis revealed that the dengue sequence belonged to genotype III. It has an estimated divergence time of 13.86 years from the most highly related Indian strains. In total, 11 amino acid substitutions were predicted for this strain in the antigenic envelope protein, when compared to the parent strain used for development of the first commercial dengue vaccine.  Conclusions: We demonstrate that both genome assembly and detection of a low number of viral sequences are possible through the unbiased sequencing of clinical material. These methods may help ascertain causal agents for febrile illnesses with no known cause.

Dengue drug discovery: Progress, challenges and outlook

In the context of the only available vaccine (DENGVAXIA) that was marketed in several countries, but poses higher risks to unexposed individuals, the development of antivirals for dengue virus (DENV), whilst challenging, would bring significant benefits to public health. Here recent progress in the field of DENV drug discovery made in academic laboratories and industry is reviewed. Characteristics of an ideal DENV antiviral molecule, given the specific immunopathology provoked by this acute viral infection, are described. New chemical classes identified from biochemical, biophysical and phenotypic screens that target viral (especially NS4B) and host proteins, offer promising opportunities for further development. In particular, new methodologies ("omics") can accelerate the discovery of much awaited flavivirus specific inhibitors. Challenges and opportunities in lead identification activities as well as the path to clinical development of dengue drugs are discussed. To galvanize DENV drug discovery, collaborative public-public partnerships and open-access resources will greatly benefit both the DENV research community and DENV patients.

Impact of Dengue Virus Serotype 2 Strain Diversity on Serological Immune Responses to Dengue

Dengue is a mosquito-borne disease caused by four dengue virus serotypes (DENV1-4) that are loosely categorized by sequence commonalities and antibody recognition profiles. The highly variable envelope protein (E) that is prominently displayed on the surface of DENV is an essential component of vaccines currently under development, yet the impact of using single strains to represent each serotype in tetravalent vaccines has not been adequately studied. We synthesized chimeric E by replacing highly variable residues from a dengue virus serotype 2 vaccine strain (PUO-218) with those from 16 DENV2 lineages spanning 60 years of antigen evolution. Examining sera from human and rhesus macaques challenged with single strains of DENV2, antibody-E interactions were markedly inhibited or enhanced by residues mainly focused within a 480 Ų footprint displayed on the E backbone. The striking impact of E diversity on polyclonal immune responses suggests that frequent antigen updates may be necessary for vaccines to counter shifts in circulating strains.

Inter- and intra-host sequence diversity reveal the emergence of viral variants during an overwintering epidemic caused by dengue virus serotype 2 in southern Taiwan

Purifying selection during dengue viral infection has been suggested as the driving force of viral evolution and the higher complexity of the intra-host quasi-species is thought to offer an adaptive advantage for arboviruses as they cycle between arthropod and vertebrate hosts. However, very few studies have been performed to investigate the viral genetic changes within (intra-host) and between (inter-host) humans in a spatio-temporal scale. Viruses of different serotypes from various countries imported to Taiwan cause annual outbreaks. During 2001-2003, two consecutive outbreaks were caused by dengue virus serotype 2 (DENV-2) and resulted in a larger-scale epidemic with more severe dengue cases in the following year. Phylogenetic analyses showed that the viruses from both events were similar and related to the 2001 DENV-2 isolate from the Philippines. We comprehensively analyzed viral sequences from representative dengue patients and identified three consensus genetic variants, group Ia, Ib and II, with different spatio-temporal population dynamics. The phylodynamic analysis suggested group Ib variants, characterized by lower genetic diversity, transmission rate, and intra-host variant numbers, might play the role of maintenance variants. The residential locations among the patients infected by group Ib variants were in the outer rim of case clusters throughout the 2001-2003 period whereas group Ia and II variants were located in the centers of case clusters, suggesting that group Ib viruses might serve as "sheltered overwintering" variants in an undefined ecological niche. Further deep sequencing of the viral envelope (E) gene directly from individual patient serum samples confirmed the emergence of variants belonging to three quasi-species (group Ia, Ib, and II) and the ancestral role of the viral variants in the latter phase of the 2001 outbreak contributed to the later, larger-scale epidemic beginning in 2002. These findings enhanced our understanding of increasing epidemic severity over time in the same epidemic area. It also highlights the importance of combining phylodynamic and deep sequencing analysis as surveillance tools for detecting dynamic changes in viral variants, particularly searching for and monitoring any specific viral subpopulation. Such subpopulations might have selection advantages in both fitness and transmissibility leading to increased epidemic severity.

Molecular characterization and phylogenetic analysis of a dengue virus serotype 3 isolated from a Chinese traveler returned from Laos

BACKGROUND

Dengue virus (DENV) infection caused by international visitors has become a public health concern in China. Although sporadic imported cases of DENV have been documented in Yunnan, China since 2000, a complete genome sequence of dengue virus serotype 3 (DENV-3) imported from Laos is still not available. Here, we report the first complete genome sequence and genomic characterization of a DENV-3 strain (YNPE3) isolated from a patient returned from Laos.

METHODS

Viral isolation from the patient's serum was performed using mosquitoes C6/36 cells. Reverse transcriptase polymerase chain reaction (RT-PCR) was used for identification and serotyping of the virus. The complete sequence was determined by Sanger dideoxy sequencing. Homology analysis was implemented by NCBI-BLAST. Multiple sequence alignment was performed using MegAlign module of the Lasergene 7 software package DNASTAR. MFOLD software was used to predict the RNA secondary structure of 5' untranslated region (UTR) and 3' UTR. Phylogenetic analysis, which was based on envelope gene and complete coding sequence, was performed by Maximum-Likelihood method.

RESULTS

RT-PCR analysis confirmed that the virus belonged to dengue virus serotype 3, which was named YNPE3 strain. The full-length genome of the YNPE3 strain was 10,627 nucleotides (nts) with an open reading frame (ORF) encoding 3390 amino acids. Strain YNPE3 shared 98.6-98.8% nucleotide identity with the closely related strains isolated in India (JQ922556, KU216209, KU216208). We observed the deletion of about 40 nts in the 5' UTR and 3' UTR of strain YNPE3, and 11 nts (ACGCAGGAAGT) insertion that was present in the 3' UTR of YNPE3. Compared with prototype strain H87, abundant amino acid substitutions in the YNPE3 strain were observed. Phylogenetic analysis revealed that the YNPE3 strain belonged to genotype III of DENV-3, and that it might be closely related with genotype III strains isolated in Laos and India.

CONCLUSIONS

This is the first report of the complete genome sequence and molecular characterization of a DENV-3 isolate imported from Laos. The presented results can further promote disease surveillance, and epidemiological and evolutionary studies of the DENV-3 in Yunnan province of China.

In-silico Designing and Testing of Primers for Sanger Genome Sequencing of Dengue Virus Types of Asian Origin

Rarity in reporting whole genome sequence of Dengue virus from dengue endemic countries leaves lacunae in understanding regional pattern of virus mutation and ultimately leading to non-understanding of transmission pattern and clinical outcomes emerging at regional levels. Due to inter-serotype genomic similarity and intra-serotype genomic diversity, appropriate designing of primer pairs appears as an exhaustive exercise. Present paper reports new Dengue virus type-specific primer which may help in characterizing virus specific to Asian origin. Genomes of dengue virus serotypes of Asian region were searched and using advanced bioinformatics tools, serotype specific primers were designed and tested for their targeted amplification efficiency. 19 primers sets for DENV-1, 18 primer sets for DENV-2, 17 for DENV-3 and 18 for DENV-4 were designed. In-silico and experimental testing of the designed primers were performed on virus isolated from both clinical isolates and passaged cultures. While all 17 and 18 primer sets of DENV-3 and DENV-2 respectively yielded good quality sequencing results; in case of DENV-4, 16 out of 18 primer sets and in DENV-1, 16 out of 19 primer sets yielded good results. Average sequencing read length was 382 bases and around 82% nucleotide bases were Phred quality QV20 bases (representing an accuracy of circa one miscall every 100 bases) or higher. Results also highlighted importance of use of primer development algorithm and identified genomic regions which are conservative, yet specific for developing primers to achieve efficiency and specificity during experiments.

Understanding dengue virus evolution to support epidemic surveillance and counter-measure development

Dengue virus (DENV) causes a profound burden of morbidity and mortality, and its global burden is rising due to the co-circulation of four divergent DENV serotypes in the ecological context of globalization, travel, climate change, urbanization, and expansion of the geographic range of the Ae.aegypti and Ae.albopictus vectors. Understanding DENV evolution offers valuable opportunities to enhance surveillance and response to DENV epidemics via advances in RNA virus sequencing, bioinformatics, phylogenetic and other computational biology methods. Here we provide a scoping overview of the evolution and molecular epidemiology of DENV and the range of ways that evolutionary analyses can be applied as a public health tool against this arboviral pathogen.

Complete assembly of a dengue virus type 3 genome from a recent genotype III clade by metagenomic sequencing of serum

Background: Mosquito-borne flaviviruses, such as dengue and Japanese encephalitis virus (JEV), cause life-threatening diseases, particularly in the tropics. Methods: Here we performed unbiased metagenomic sequencing of RNA extracted from the serum of four patients and the plasma of one patient, all hospitalized at a tertiary care centre in South India with severe or prolonged febrile illness, together with the serum from one healthy control, in 2014. Results: We identified and assembled a complete dengue virus type 3 sequence from a case of severe dengue fever. We also identified a small number of JEV sequences in the serum of two adults with febrile illness, including one with severe dengue. Phylogenetic analysis revealed that the dengue sequence belonged to genotype III. It has an estimated divergence time of 13.86 years from the most highly related Indian strains. In total, 11 amino acid substitutions were predicted for this strain in the antigenic envelope protein, when compared to the parent strain used for development of the first commercial dengue vaccine.  Conclusions: We demonstrate that both genome assembly and detection of a low number of viral sequences are possible through the unbiased sequencing of clinical material. These methods may help ascertain causal agents for febrile illnesses with no known cause.

Inhibitor Bound Dengue NS2B-NS3pro Reveals Multiple Dynamic Binding Modes

Dengue virus poses a significant global health threat as the source of increasingly deleterious dengue fever, dengue hemorrhagic fever, and dengue shock syndrome. As no specific antiviral treatment exists for dengue infection, considerable effort is being applied to discover therapies and drugs for maintenance and prevention of these afflictions. The virus is primarily transmitted by mosquitoes, and infection occurs following viral endocytosis by host cells. Upon entering the cell, viral RNA is translated into a large multisubunit polyprotein which is post-translationally cleaved into mature, structural and nonstructural (NS) proteins. The viral genome encodes the enzyme to carry out cleavage of the large polyprotein, specifically the NS2B-NS3pro cofactor-protease complex-a target of high interest for drug design. One class of recently discovered NS2B-NS3pro inhibitors is the substrate-based trifluoromethyl ketone containing peptides. These compounds interact covalently with the active site Ser135 via a hemiketal adduct. A detailed picture of the intermolecular protease/inhibitor interactions of the hemiketal adduct is crucial for rational drug design. We demonstrate, through the use of protein- and ligand-detected solution-state ¹⁹F and ¹H NMR methods, an unanticipated multibinding mode behavior of a representative of this class of inhibitors to dengue NS2B-NS3pro. Our results illustrate the highly dynamic nature of both the covalently bound ligand and protease protein structure, and the need to consider these dynamics when designing future inhibitors in this class.

Working towards dengue as a vaccine-preventable disease: challenges and opportunities

INTRODUCTION

Dengue is an emerging viral disease that affects the human population around the globe. Recent advancements in dengue virus research have opened new avenues for the development of vaccines against dengue. The development of a vaccine against dengue is a challenging task because any of the four serotypes of dengue viruses can cause disease. The development of a dengue vaccine aims to provide balanced protection against all the serotypes. Several dengue vaccine candidates are in the developmental stages such as inactivated, live attenuated, recombinant subunit, and plasmid DNA vaccines. Area covered: The authors provide an overview of the progress made in the development of much needed dengue vaccines. The authors include their expert opinion and their perspectives for future developments. Expert opinion: Human trials of a live attenuated tetravalent chimeric vaccine have clearly demonstrated its potential as a dengue vaccine. Other vaccine candidate molecules such as DENVax, a recombinant chimeric vaccine andTetraVax, are at different stages of development at this time. The authors believe that the novel strategies for testing and improving the immune response of vaccine candidates in humans will eventually lead to the development of a successful dengue vaccine in future.

Dengue and Zika viruses: lessons learned from the similarities between these Aedes mosquito-vectored arboviruses

The currently spreading arbovirus epidemic is having a severe impact on human health worldwide. The two most common flaviviruses, dengue virus (DENV) and Zika virus (ZIKV), are transmitted through the same viral vector, Aedes spp. mosquitoes. Since the discovery of DENV in 1943, this virus has been reported to cause around 390 million human infections per year, approximately 500,000 of which require hospitalization and over 20,000 of which are lethal. The present DENV epidemic is primarily concentrated in Southeast Asia. ZIKV, which was discovered in 1952, is another important arthropod-borne flavivirus. The neurotropic role of ZIKV has been reported in infected newborns with microcephaly and in adults with Guillain-Barre syndrome. Despite DENV and ZIKV sharing the same viral vector, their complex pathogenic natures are poorly understood, and the infections they cause do not have specific treatments or effective vaccines. Therefore, this review will describe what is currently known about the clinical characteristics, pathogenesis mechanisms, and transmission of these two viruses. Better understanding of the interrelationships between DENV and ZIKV will provide a useful perspective for developing an effective strategy for controlling both viruses in the future.