Dengue: a continuing global threat

Taguchi array optimization of the reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay for sensitive and rapid detection of dengue virus serotype 2

OBJECTIVES

Serotype 2 of dengue virus (DENV-2) is the most prevalent cause of dengue fevers. In this study, the C-prM gene was used for specific detection of DENV-2 by RT-LAMP assay. The RT-LAMP assay was optimized using the Taguchi design of experiments.

RESULTS

The efficiency of the assay in such optimal conditions resulted in 100% sensitivity, 100% specificity, and 100% overall accuracy for detection of 4 copies/μL of the genome of DENV-2. In addition, the detection of 2 copies/μL of the genome of DENV-2 was feasible, although the sensitivity was 50%. Considering the importance of the specific detection of the dengue virus serotypes, the cost-effective RT-LAMP approach can be used for rapid, specific, and sensitive detection of DENV-2.

CONCLUSION

RT-LAMP, as a cost-effective method, was optimized using Taguchi array approach for specific and rapid detection of DENV-2. Such methods can facilitate the diagnosis procedure in remote regions.

Recent Insights Into the Molecular Mechanism of Toll-Like Receptor Response to Dengue Virus Infection

Dengue is the most prevalent and rapidly spreading mosquito-borne viral disease caused by dengue virus (DENV). Recently, DENV has been affecting humans within an expanding geographic range due to the warming of the earth. Innate immune responses play a significant role in antiviral defense, and Toll-like receptors (TLRs) are key regulators of innate immunity. Therefore, a detailed understanding of TLR and DENV interactions is important for devising therapeutic and preventive strategies. Several studies have indicated the ability of DENV to modulate the TLR signaling pathway and host immune response. Vaccination is considered one of the most successful medical interventions for preventing viral infections. However, only a partially protective dengue vaccine, the first licensed dengue vaccine CYD-TDV, is available in some dengue-endemic countries to protect against DENV infection. Therefore, the development of a fully protective, durable, and safe DENV vaccine is a priority for global health. Here, we demonstrate the progress made in our understanding of the host response to DENV infection, with a particular focus on TLR response and how DENV avoids the response toward establishing infection. We also discuss dengue vaccine candidates in late-stage development and the issues that must be overcome to enable their success.

Minireview: Epidemiological impact of arboviral diseases in Latin American countries, arbovirus-vector interactions and control strategies

Mosquitoes are the most crucial insects in public health due to their vector capacity and competence to transmit pathogens, including arboviruses, bacterias and parasites. Re-emerging and emerging arboviral diseases, such as yellow fever virus (YFV), dengue virus (DENV), zika virus (ZIKV), and chikungunya virus (CHIKV), constitute one of the most critical health public concerns in Latin America. These diseases present a significant incidence within the human settlements increasing morbidity and mortality events. Likewise, among the different genus of mosquito vectors of arboviruses, those of the most significant medical importance corresponds to Aedes and Culex. In Latin America, the mosquito vector species of YFV, DENV, ZIKV, and CHIKV are mainly Aedes aegypti and Ae. Albopictus. Ae. aegypti is recognized as the primary vector in urban environments, whereas Ae. albopictus, recently introduced in the Americas, is more prone to rural settings. This minireview focuses on what is known about the epidemiological impact of mosquito-borne diseases in Latin American countries, with particular emphasis on YFV, DENV, ZIKV and CHIKV, vector mosquitoes, geographic distribution, and vector-arbovirus interactions. Besides, it was analyzed how climate change and social factors have influenced the spread of arboviruses and the control strategies developed against mosquitoes in this continent.

Genetic Diversity of Dengue Virus in Clinical Specimens from Bangkok, Thailand, during 2018-2020: Co-Circulation of All Four Serotypes with Multiple Genotypes and/or Clades

Dengue is an arboviral disease highly endemic in Bangkok, Thailand. To characterize the current genetic diversity of dengue virus (DENV), we recruited patients with suspected DENV infection at the Hospital for Tropical Diseases, Bangkok, during 2018-2020. We determined complete nucleotide sequences of the DENV envelope region for 111 of 276 participant serum samples. All four DENV serotypes were detected, with the highest proportion being DENV-1. Although all DENV-1 sequences were genotype I, our DENV-1 sequences were divided into four distinct clades with different distributions in Asian countries. Two genotypes of DENV-2 were identified, Asian I and Cosmopolitan, which were further divided into two and three distinct clades, respectively. In DENV-3, in addition to the previously dominant genotype III, a cluster of 6 genotype I viruses only rarely reported in Thailand was also observed. All of the DENV-4 viruses belonged to genotype I, but they were separated into three distinct clades. These results indicated that all four serotypes of DENV with multiple genotypes and/or clades co-circulate in Bangkok. Continuous investigation of DENV is warranted to further determine the relationship between DENV within Thailand and neighboring countries in Southeast Asia and Asia.

Molecular Communications in Viral Infections Research: Modeling, Experimental Data, and Future Directions

Hundreds of millions of people worldwide are affected by viral infections each year, and yet, several of them neither have vaccines nor effective treatment during and post-infection. This challenge has been highlighted by the COVID-19 pandemic, showing how viruses can quickly spread and impact society as a whole. Novel interdisciplinary techniques must emerge to provide forward-looking strategies to combat viral infections, as well as possible future pandemics. In the past decade, an interdisciplinary area involving bioengineering, nanotechnology and information and communication technology (ICT) has been developed, known as Molecular Communications. This new emerging area uses elements of classical communication systems to molecular signalling and communication found inside and outside biological systems, characterizing the signalling processes between cells and viruses. In this paper, we provide an extensive and detailed discussion on how molecular communications can be integrated into the viral infectious diseases research, and how possible treatment and vaccines can be developed considering molecules as information carriers. We provide a literature review on molecular communications models for viral infection (intra-body and extra-body), a deep analysis on their effects on immune response, how experimental can be used by the molecular communications community, as well as open issues and future directions.

Prevalence of arbovirus antibodies in young healthy adult population in Brazil

Background

The emergence and re-emergence of infectious diseases are a cause for worldwide concern. The introduction of Zika and Chikungunya diseases in the Americas has exposed unforeseen medical and logistical challenges for public health systems. Moreover, the lack of preventive measures and vaccination against known and emerging mosquito-transmitted pathogens, and the occurrence of unanticipated clinical complications, has had an enormous social and economic impact on the affected populations. In this study, we aimed to measure the seroprevalence of endemic and emerging viral pathogens in military personnel stationed in Manaus, Amazonas state.

Methods

We measured the seropositivity of antibodies against 19 endemic and emerging viruses in a healthy military personnel group using a hemagglutination inhibition assay (HIA).

Results

Overall, DENV positivity was 60.4%, and 30.9% of the individuals reacted against ZIKV. Also, 46.6%, 54.7%, 51.3% and 48.7% individuals reacted against West Nile virus (WNV), Saint Louis encephalitis virus (SLEV), Ilheus virus (ILHV) and Rocio virus (ROCV), respectively. Individuals with high DENV HIA titer reacted more frequently with ZIKV or WNV compared to those with low HIA titers. Observed cross-reactivity between Flaviviruses varied depending on the virus serogroup. Additionally, 0.6% and 0.3% individuals were seropositive for Oropouche virus (OROV) and Catu virus (CATUV) from the family Peribunyaviridae, respectively. All samples were negative for Eastern Equine Encephalitis virus (EEEV), Western Equine Encephalomyelitis virus (WEEV), Mayaro virus (MAYV), Mucambo virus (MUCV) and CHIKV from the family Togaviridae.

Conclusions

A high proportion of individuals in our high-risk population (~ 60%) lacked antibodies against major endemic and emerging viruses, which makes them susceptible for further infections. Military personnel serving in the Amazon region could serve as sentinels to strengthen global infectious disease surveillance, particularly in remote areas.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04901-4.

Correlation of serotype-specific strain in patients with dengue virus infection with neurological manifestations and its outcome

INTRODUCTION

Neurological manifestation of dengue virus infection is a rare entity. Serotypes commonly associated with neurological manifestation are DENV-2 and DENV-3. We plan to detect the serotypes related to the neurological presentation in dengue infection and its correlation with different neurological complications and outcome.

METHODS

In this case-control study, consecutive dengue cases with different neurological manifestations were enrolled along with age and sex-matched controls (dengue patients without neurological complication). Serotyping using RT-PCR of samples of cases and controls were done. Level of correlation was analyzed with various parameters and outcomes.

RESULTS

In cases out of 33 samples, 6 sample serotypes were detected, which were composed of DENV-1 (n = 2) and DENV-2 (n = 4). In controls, DENV-1 (n = 5), DENV-2 (n = 6), and DENV-3 (n = 3) were detected. When statistically correlated, no significant association was found in cases and controls with dengue virus serotype. The frequency of serotype 2 was higher in hypokalemic paralysis cases than non-hypokalemic paralysis cases and the difference was significant (p < 0.05). The outcome was good (mRS < 3) in all the cases where serotypes were detected, but on statistical correlation, it was not found significant (p > 0.05).

CONCLUSION

DENV-1 and DENV-2 are associated with neurological manifestation of dengue infection, which is different from the existing literature, where DENV-2 and DENV-3 are reported. The detection of DENV serotype will help in predicting and best management of neurological complication. The serotype 2 of dengue virus is more commonly associated with dengue-associated hypokalemic paralysis than other neurological complication (p < 0.05). There is no significant association of serotypes with outcome or mortality.

Highly sensitive detection of dengue biomarker using streptavidin-conjugated quantum dots

A highly sensitive immunosensor using streptavidin-conjugated quantum dots (QDs/SA) was developed to detect dengue biomarker of non-structural protein 1 (NS1) at very low concentration, so that it can probe dengue infection even in the early stage. The QDs/SA were first bound to biotinylated NS1 antibody (Ab) and the QDs/SA-Ab conjugates were then used to detect the NS1 antigen (Ag) in the Ag concentration range of 1 pM to 120 nM. The formation of QDs/SA-Ab and QDs/SA-Ab-Ag conjugates was confirmed by the measurements of field emission scanning electron microscopy (FF-SEM), field emission transmission electron microscopy (FE-TEM), dynamic light scattering (DLS), and zeta-potential. Fluorescence emission spectra of QDs/SA-Ab-Ag conjugates showed that the magnitude of fluorescence quenching was linearly proportional to the NS1 Ag concentration and it nicely followed the Stern-Volmer (SV) equation in phosphate buffer solution. However, in human plasma serum solution, the fluorescence quenching behavior was negatively deviated from the SV equation presumably due to interference by the serum component biomolecules, and it was well explained by the Lehrer equation. These results suggest that the current approach is promising because it is highly sensitive, fast, simple, and convenient, and thus it has a potential of application for point-of-care.

Laboratory Findings in Patients with Probable Dengue Diagnosis from an Endemic Area in Colombia in 2018

As demonstrated with the novel coronavirus pandemic, rapid and accurate diagnosis is key to determine the clinical characteristic of a disease and to improve vaccine development. Once the infected person is identified, hematological findings may be used to predict disease outcome and offer the correct treatment. Rapid and accurate diagnosis and clinical parameters are pivotal to track infections during clinical trials and set protection status. This is also applicable for re-emerging diseases like dengue fever, which causes outbreaks in Asia and Latin America every 4 to 5 years. Some areas in the US are also endemic for the transmission of dengue virus (DENV), the causal agent of dengue fever. However, significant number of DENV infections in rural areas are diagnosed solely by clinical and hematological findings because of the lack of availability of ELISA or PCR-based tests or the infrastructure to implement them in the near future. Rapid diagnostic tests (RDT) are a less sensitive, yet they represent a timely way of detecting DENV infections. The purpose of this study was to determine whether there is an association between hematological findings and the probability for an NS1-based DENV RDT to detect the DENV NS1 antigen. We also aimed to describe the hematological parameters that are associated with the diagnosis through each test.

Aptamers isolated against mosquito-borne pathogens

Mosquito-borne diseases are a major threat to public health. The shortcomings of diagnostic tools, especially those that are antibody-based, have been blamed in part for the rising annual morbidity and mortality caused by these diseases. Antibodies harbor a number of disadvantages that can be clearly addressed by aptamers as the more promising molecular recognition elements. Aptamers are defined as single-stranded DNA or RNA oligonucleotides generated by SELEX that exhibit high binding affinity and specificity against a wide variety of target molecules based on their unique structural conformations. A number of aptamers were developed against mosquito-borne pathogens such as Dengue virus, Zika virus, Chikungunya virus, Plasmodium parasite, Francisella tularensis, Japanese encephalitis virus, Venezuelan equine encephalitis virus, Rift Valley fever virus and Yellow fever virus. Intrigued by these achievements, we carry out a comprehensive overview of the aptamers developed against these mosquito-borne infectious agents. Characteristics of the aptamers and their roles in diagnostic, therapeutic as well as other applications are emphasized.

The key amino acids of E protein involved in early flavivirus infection: viral entry

Flaviviruses are enveloped viruses that infect multiple hosts. Envelope proteins are the outermost proteins in the structure of flaviviruses and mediate viral infection. Studies indicate that flaviviruses mainly use envelope proteins to bind to cell attachment receptors and endocytic receptors for the entry step. Here, we present current findings regarding key envelope protein amino acids that participate in the flavivirus early infection process. Among these sites, most are located in special positions of the protein structure, such as the α-helix in the stem region and the hinge region between domains I and II, motifs that potentially affect the interaction between different domains. Some of these sites are located in positions involved in conformational changes in envelope proteins. In summary, we summarize and discuss the key envelope protein residues that affect the entry process of flaviviruses, including the process of their discovery and the mechanisms that affect early infection.

Efficacy profile of the CYD-TDV dengue vaccine revealed by Bayesian survival analysis of individual-level phase III data

Background:

Sanofi-Pasteur’s CYD-TDV is the only licensed dengue vaccine. Two phase three trials showed higher efficacy in seropositive than seronegative recipients. Hospital follow-up revealed increased hospitalisation in 2–5- year-old vaccinees, where serostatus and age effects were unresolved.

Methods:

We fit a survival model to individual-level data from both trials, including year 1 of hospital follow-up. We determine efficacy by age, serostatus, serotype and severity, and examine efficacy duration and vaccine action mechanism.

Results:

Our modelling indicates that vaccine-induced immunity is long-lived in seropositive recipients, and therefore that vaccinating seropositives gives higher protection than two natural infections. Long-term increased hospitalisation risk outweighs short-lived immunity in seronegatives. Independently of serostatus, transient immunity increases with age, and is highest against serotype 4. Benefit is higher in seropositives, and risk enhancement is greater in seronegatives, against hospitalised disease than against febrile disease.

Conclusions:

Our results support vaccinating seropositives only. Rapid diagnostic tests would enable viable ‘screen-then-vaccinate’ programs. Since CYD-TDV acts as a silent infection, long-term safety of other vaccine candidates must be closely monitored.

Funding:

Bill & Melinda Gates Foundation, National Institute for Health Research, UK Medical Research Council, Wellcome Trust, Royal Society.

Clinical trial number:

NCT01373281 and NCT01374516.

Risk predictors of progression to severe disease during the febrile phase of dengue: a systematic review and meta-analysis

BACKGROUND

The ability to accurately predict early progression of dengue to severe disease is crucial for patient triage and clinical management. Previous systematic reviews and meta-analyses have found significant heterogeneity in predictors of severe disease due to large variation in these factors during the time course of the illness. We aimed to identify factors associated with progression to severe dengue disease that are detectable specifically in the febrile phase.

METHODS

We did a systematic review and meta-analysis to identify predictors identifiable during the febrile phase associated with progression to severe disease defined according to WHO criteria. Eight medical databases were searched for studies published from Jan 1, 1997, to Jan 31, 2020. Original clinical studies in English assessing the association of factors detected during the febrile phase with progression to severe dengue were selected and assessed by three reviewers, with discrepancies resolved by consensus. Meta-analyses were done using random-effects models to estimate pooled effect sizes. Only predictors reported in at least four studies were included in the meta-analyses. Heterogeneity was assessed using the Cochrane Q and I2 statistics, and publication bias was assessed by Egger's test. We did subgroup analyses of studies with children and adults. The study is registered with PROSPERO, CRD42018093363.

FINDINGS

Of 6643 studies identified, 150 articles were included in the systematic review, and 122 articles comprising 25 potential predictors were included in the meta-analyses. Female patients had a higher risk of severe dengue than male patients in the main analysis (2674 [16·2%] of 16 481 vs 3052 [10·5%] of 29 142; odds ratio [OR] 1·13 [95% CI 1·01-1·26) but not in the subgroup analysis of studies with children. Pre-existing comorbidities associated with severe disease were diabetes (135 [31·3%] of 431 with vs 868 [16·0%] of 5421 without; crude OR 4·38 [2·58-7·43]), hypertension (240 [35·0%] of 685 vs 763 [20·6%] of 3695; 2·19 [1·36-3·53]), renal disease (44 [45·8%] of 96 vs 271 [16·0%] of 1690; 4·67 [2·21-9·88]), and cardiovascular disease (nine [23·1%] of 39 vs 155 [8·6%] of 1793; 2·79 [1·04-7·50]). Clinical features during the febrile phase associated with progression to severe disease were vomiting (329 [13·5%] of 2432 with vs 258 [6·8%] of 3797 without; 2·25 [1·87-2·71]), abdominal pain and tenderness (321 [17·7%] of 1814 vs 435 [8·1%] of 5357; 1·92 [1·35-2·74]), spontaneous or mucosal bleeding (147 [17·9%] of 822 vs 676 [10·8%] of 6235; 1·57 [1·13-2·19]), and the presence of clinical fluid accumulation (40 [42·1%] of 95 vs 212 [14·9%] of 1425; 4·61 [2·29-9·26]). During the first 4 days of illness, platelet count was lower (standardised mean difference -0·34 [95% CI -0·54 to -0·15]), serum albumin was lower (-0·5 [-0·86 to -0·15]), and aminotransferase concentrations were higher (aspartate aminotransferase [AST] 1·06 [0·54 to 1·57] and alanine aminotransferase [ALT] 0·73 [0·36 to 1·09]) among individuals who progressed to severe disease. Dengue virus serotype 2 was associated with severe disease in children. Secondary infections (vs primary infections) were also associated with severe disease (1682 [11·8%] of 14 252 with vs 507 [5·2%] of 9660 without; OR 2·26 [95% CI 1·65-3·09]). Although the included studies had a moderate to high risk of bias in terms of study confounding, the risk of bias was low to moderate in other domains. Heterogeneity of the pooled results varied from low to high on different factors.

INTERPRETATION

This analysis supports monitoring of the warning signs described in the 2009 WHO guidelines on dengue. In addition, testing for infecting serotype and monitoring platelet count and serum albumin, AST, and ALT concentrations during the febrile phase of illness could improve the early prediction of severe dengue.

FUNDING

Wellcome Trust, National Institute for Health Research, Collaborative Project to Increase Production of Rural Doctors, and Royal Thai Government.

Transcriptional Response of Wolbachia to Dengue Virus Infection in Cells of the Mosquito Aedes aegypti

Aedes aegypti transmits one of the most significant mosquito-borne viruses, dengue virus (DENV). The absence of effective vaccines and clinical treatments and the emergence of insecticide resistance in A. aegypti necessitate novel vector control strategies. A new approach uses the endosymbiotic bacterium Wolbachia pipientis to reduce the spread of arboviruses. However, the Wolbachia-mediated antiviral mechanism is not well understood. To shed light on this mechanism, we investigated an unexplored aspect of Wolbachia-virus-mosquito interaction. We used RNA sequencing to examine the transcriptional response of Wolbachia to DENV infection in A. aegypti Aag2 cells transinfected with the wAlbB strain of Wolbachia. Our results suggest that genes encoding an endoribonuclease (RNase HI), a regulator of sigma 70-dependent gene transcription (6S RNA), essential cellular, transmembrane, and stress response functions and primary type I and IV secretion systems were upregulated, while a number of transport and binding proteins of Wolbachia, ribosome structure, and elongation factor-associated genes were downregulated due to DENV infection. Furthermore, bacterial retrotransposon, transposable, and phage-related elements were found among the up- and downregulated genes. We show that Wolbachia elicits a transcriptional response to virus infection and identify differentially expressed Wolbachia genes mostly at the early stages of virus infection. These findings highlight Wolbachia's ability to alter its gene expression in response to DENV infection of the host cell. IMPORTANCE Aedes aegypti is a vector of several pathogenic viruses, including dengue, Zika, chikungunya, and yellow fever viruses, which are of importance to human health. Wolbachia is an endosymbiotic bacterium currently used in transinfected mosquitoes to suppress replication and transmission of dengue viruses. However, the mechanism of Wolbachia-mediated virus inhibition is not fully understood. While several studies have shown mosquitoes' transcriptional responses to dengue virus infection, none have investigated these responses in Wolbachia, which may provide clues to the inhibition mechanism. Our results suggest changes in the expression of a number of functionally important Wolbachia genes upon dengue virus infection, including those involved in stress responses, providing insights into the endosymbiont's reaction to virus infection.

The atypical lymphocyte count: a novel predictive factor for severe thrombocytopenia related to dengue

BACKGROUND

Early identification of patients at risk of severe dengue disease (DD) is critical to guide its management. We evaluated whether the atypical lymphocyte count (ALC), generated from the Sysmex automated full blood count analyzer, is predictive of severe thrombocytopenia secondary to Dengue infection.

METHODS

We prospectively collected data on patients admitted with DD between December 2017 and October 2018. ALC data were extracted from the Sysmex XS500i analyzer from day 1 to day 7 of admission. Clinical data were obtained from patients' medical records.

RESULTS

We enrolled 256 patients with DD. A negative correlation between ALC on admission and platelet count on day 5 to day 7 (Spearmen's correlation; day 5:-0.485, day 6:-0.428 and day 7:-0.344) (p=0.001) was observed. Based on receiver operator characteristic curve analysis, we found that an ALC of >0.5x103/L had 90% sensitivity and 70% specificity for severe thrombocytopenia (platelet count <50x109/L) on day 5. The positive and negative predictive values were 74.4 and 91.2%, respectively (power 84.7).

CONCLUSIONS

We propose that ALC on admission may be a novel negative predictive factor for severe thrombocytopenia on day 5 to day 7 of DD. Further studies are required to validate our findings and evaluate whether ALC is predictive of other complications of DD.

Dengue epidemic in Malaysia: urban versus rural comparison of dengue immunoglobulin G seroprevalence among Malaysian adults aged 35-74 years

BACKGROUND

A periodic serosurvey of dengue seroprevalence is vital to determine the prevalence of dengue in countries where this disease is endemic. This study aimed to determine the prevalence of dengue immunoglobulin G (IgG) seropositivity among healthy Malaysian adults living in urban and rural areas.

METHODS

A total of 2598 serum samples (1417 urban samples, 1181 rural samples) were randomly collected from adults ages 35-74 y. The presence of the dengue IgG antibody and neutralising antibodies to dengue virus (DENV) 1-4 was determined using enzyme-linked immunosorbent assay and the plaque reduction neutralisation test assay, respectively.

RESULTS

The prevalence of dengue IgG seropositivity was 85.39% in urban areas and 83.48% in rural areas. The seropositivity increased with every 10-y increase in age. Ethnicity was associated with dengue seropositivity in urban areas but not in rural areas. The factors associated with dengue seropositivity were sex and working outdoors. In dengue IgG-positive serum samples, 98.39% of the samples had neutralising antibodies against DENV3, but only 70.97% of them had neutralising antibodies against DENV4.

CONCLUSION

The high seroprevalence of dengue found in urban and rural areas suggests that both urban and rural communities are vital for establishing and sustaining DENV transmission in Malaysia.

Dengue Detection: Advances in Diagnostic Tools from Conventional Technology to Point of Care

The dengue virus (DENV) is a vector-borne flavivirus that infects around 390 million individuals each year with 2.5 billion being in danger. Having access to testing is paramount in preventing future infections and receiving adequate treatment. Currently, there are numerous conventional methods for DENV testing, such as NS1 based antigen testing, IgM/IgG antibody testing, and Polymerase Chain Reaction (PCR). In addition, novel methods are emerging that can cut both cost and time. Such methods can be effective in rural and low-income areas throughout the world. In this paper, we discuss the structural evolution of the virus followed by a comprehensive review of current dengue detection strategies and methods that are being developed or commercialized. We also discuss the state of art biosensing technologies, evaluated their performance and outline strategies to address challenges posed by the disease. Further, we outline future guidelines for the improved usage of diagnostic tools during recurrence or future outbreaks of DENV.

Potential role of vector-mediated natural selection in dengue virus genotype/lineage replacements in two epidemiologically contrasted settings

Dengue virus (DENV) evolutionary dynamics are characterized by frequent DENV genotype/lineage replacements, potentially associated with changes in disease severity and human immunity. New Caledonia (NC) and Cambodia, two contrasted epidemiological settings, respectively experienced a DENV-1 genotype IV to I replacement in 2012 and a DENV-1 genotype I lineage 3–4 replacement in 2005–2007, both followed by a massive dengue outbreak. However, their underlying evolutionary drivers have not been elucidated. Here, we tested the hypothesis that these genotype/lineage switches reflected a higher transmission fitness of the replacing DENV genotype/lineage in the mosquito vector using in vivo competition experiments. For this purpose, field-derived Aedes aegypti from NC and Cambodia were orally challenged with epidemiologically relevant pairs of four DENV-1 genotype I and IV strains from NC or four DENV-1 genotype I lineage 3 and 4 strains from Cambodia, respectively. The relative transmission fitness of each DENV-1 genotype/lineage was measured by quantitative RT–PCR for infection, dissemination, and transmission rates. Results showed a clear transmission fitness advantage of the replacing DENV-1 genotype I from NC within the vector. A similar but more subtle pattern was observed for the DENV-1 lineage 4 replacement in Cambodia. Our results support the hypothesis that vector-driven selection contributed to the DENV-1 genotype/lineage replacements in these two contrasted epidemiological settings, and reinforce the idea that natural selection taking place within the mosquito vector plays an important role in DENV short-term evolutionary dynamics.

Modeling the Relationship Between Antibody-Dependent Enhancement and Disease Severity in Secondary Dengue Infection

Sequential infections with different dengue serotypes (DENV-1, 4) significantly increase the risk of a severe disease outcome (fever, shock, and hemorrhagic disorders). Two hypotheses have been proposed to explain the severity of the disease: (1) antibody-dependent enhancement (ADE) and (2) original T cell antigenic sin. In this work, we explored the first hypothesis through mathematical modeling. The proposed model reproduces the dynamic of susceptible and infected target cells and dengue virus in scenarios of infection-neutralizing and infection-enhancing antibody competition induced by two distinct serotypes of the dengue virus during secondary infection. The enhancement and neutralization functions are derived from basic concepts of chemical reactions and used to mimic binding to the virus by two distinct populations of antibodies. The analytic study of the model showed the existence of two equilibriums: a disease-free equilibrium and an endemic one. Using the concept of the basic reproduction number [Formula: see text], we performed the asymptotic stability analysis for the two equilibriums. To measure the severity of the disease, we considered the maximum value of infected cells as well as the time when this maximum is reached. We observed that it corresponds to the time when the maximum enhancing activity for the infection occurs. This critical time was calculated from the model to be a few days after the occurrence of the infection, which corresponds to what is observed in the literature. Finally, using as output [Formula: see text], we were able to rank the contribution of each parameter of the model. In particular, we highlighted that the cross-reactive antibody responses may be responsible for the disease enhancement during secondary heterologous dengue infection.

A novel approach for synthesis of silver nanoparticles using Pila virens shell and its mosquito larvicidal activity

Mosquito act as a vector for variety of deadly diseases. In this study, larvicide activity was investigated in relation to Aedes aegypti (A. aegypti) and Culex quinquefasciatus (C. quinquefasciatus) of synthesised silver nanoparticles (AgNPs) of the Pila virens (P.virens) shell extract. The characterization techniques UV-vis spectral, Fourier transforms infrared spectroscopy (FTIR),High Resonance Scanning electron microscope (HR-SEM) analysis, X-ray diffraction studies (XRD), High Resonance-Transmission electron microscopy (HR-TEM) used to characterize biosynthesized AgNPs. UV-vis, absorption showed peaks of 450 nm for the biosynthesised AgNPs, SEM observed spherical shaped particles of 25.9-28.9 nm in size and the XRD pattern shows the synthesized AgNPs fcc structure. FTIR investigation shown that the esters, carboxylic acid and ether as functional groups have been intricate in the reduction of metal ions. The larvicidal efficacy of synthesized AgNPs towards a larvae of A. aegypti LC50and LC90 value of (37.87 and 132.86 ppm) and C. quinquefasciatus was (14.70 and 28.96 ppm) respectively. The synthesized AgNPs of P. virens confirmed highest mortality towards larvae of and A. aegypti and C. quinquefasciatus.

Dengue Virus Induces the Expression and Release of Endocan from Endothelial Cells by an NS1-TLR4-Dependent Mechanism

A common hallmark of dengue infections is the dysfunction of the vascular endothelium induced by different biological mechanisms. In this paper, we studied the role of recombinant NS1 proteins representing the four dengue serotypes, and their role in promoting the expression and release of endocan, which is a highly specific biomarker of endothelial cell activation. We evaluated mRNA expression and the levels of endocan protein in vitro following the stimulation of HUVEC and HMEC-1 cell lines with recombinant NS1 proteins. NS1 proteins increase endocan mRNA expression 48 h post-activation in both endothelial cell lines. Endocan mRNA expression levels were higher in HUVEC and HMEC-1 cells stimulated with NS1 proteins than in non-stimulated cells (p < 0.05). A two-fold to three-fold increase in endocan protein release was observed after the stimulation of HUVECs or HMEC-1 cells with NS1 proteins compared with that in non-stimulated cells (p < 0.05). The blockade of Toll-like receptor 4 (TLR-4) signaling on HMEC-1 cells with an antagonistic antibody prevented NS1-dependent endocan production. Dengue-infected patients showed elevated serum endocan levels (≥30 ng/mL) during early dengue infection. High endocan serum levels were associated with laboratory abnormalities, such as lymphopenia and thrombocytopenia, and are associated with the presence of NS1 in the serum.

Brivanib alaninate inhibited dengue virus proliferation through VEGFR2/AMPK pathway

Dengue virus (DENV) is the most prevalent arthropod-borne viral disease of humans and has a major impact on global public health. There is no clinically approved drugs for DENV infection. Since intracellular VEGFR2 is increased in DENV infected patients, we thus hypothesized that VEGFR2 participated DENV proliferation and its inhibitors could be served as antivirals against DENV. Actually our results showed that VEGFR2 was induced by DENV infection. Also the agonist of VEGFR2, VEGF-A, promoted DENV proliferation. Therefore, we screened the inhibitors of VEGFR2 and found that brivanib alaninate (brivanib) showed the best anti-DENV ability with the lowest cellular cytotoxicity. Mechanically, our results indicated VEGFR2 directly interacted with PTP1B to dephosphorylate AMPK to provide lipid environment for viral replication. However, this effect could be inhibited by brivanib, which significantly reversed the reduction of AMPK phosphorylation caused by DENV infection, thus improving the cellular lipid environment. Moreover, the antiviral effect of brivanib could be reversed by AMPK inhibitor, Compound C. In addition, oral administration of brivianib (20-50 mg/kg/day) clearly improved the survival rate of DENV2 infection, and this effect was abolished in accompanied with Compound C (10mg/kg/day). Collectively, our study disclosed the mechanism of VEGFR2 in DENV2 and evaluated the antiviral ability of brivanib, which deserved more attention for clinical usage in DENV infection.

Immunological and Pathological Landscape of Dengue Serotypes 1-4 Infections in Immune-Competent Mice

Dengue virus (DENV), a Flavivirus, causes a broad spectrum of disease in humans with key clinical signs including thrombocytopenia, vascular leakage and hemorrhaging. A major obstacle to understanding DENV immunity has been the lack of a validated immune-competent mouse model. Here, we report the infection profiles of human clinical isolates of DENV serotypes 1-4 in an immune-competent mouse model. We detected replicating DENV in the peritoneal cells, liver and the spleen that was generally resolved within 2 weeks. The DENV target cell types for infection were monocytes/macrophages, dendritic cells, endothelial cells, and we identified a novel DENV cellular target, fibroblast reticular cells of the spleen. We observed gross pathologies in the spleen and liver that are consistent with dengue disease, including hemorrhaging as well as transcriptional patterns suggesting that antiviral responses and tissue damage were induced. Key clinical blood parameters that define human DENV disease such as hemoconcentration, leukopenia and reduced number of platelets were also observed. Thus, immune-competent mice sustain replicating infection and experience signs, such as hemorrhaging, that define DENV disease in humans. This study thoroughly characterizes DENV1-4 infection in immune-competent mice and confirms the wild-type mouse model as a valid and reproducible system for investigating the mechanisms of DENV pathogenesis.

Dengue in parts of the Guinea Savannah region of Nigeria and the risk of increased transmission

BACKGROUND

Dengue virus (DENV) is spreading to parts of the world where it had not been previously reported. Increased international travel has led to intercontinental importation of dengue by visitors returning from countries in sub-Saharan Africa. Although dengue is well documented in the rain forest region of Nigeria, there is a dearth of information in the Guinea Savannah region, which is a major transit point for local and international visitors in the most populous nation in Africa. We provide preliminary evidence of dengue activity in the Guinea Savannah and highlight the risk factors.

METHODS

Blood was collected from a cross-section of 200 patients attending four hospitals in Anyigba, Kogi State. Anti-dengue antibody was identified using DENV immunoglobulin G (IgG) immunoassays. Questionnaires were used to obtain sociodemographic variables and risk factors. Data were analysed with SPSS version 16.0 for Windows.

RESULTS

Forty-two (20.5%) participants had anti-DENV IgG antibodies. Persons within the 45-59 y age group were more seropositive, with a rate of 35%. Males were more seropositive compared with females. Marriage, formal education, involvement in business activities and the presence of grasses around homes were associated with higher IgG seropositivity. The presence of open water containers around human dwellings and a lack of mosquito net use are predisposing factors.

CONCLUSIONS

This study identified past exposure to DENV among people in Anyigba, located in the Guinea Savannah region. Proper diagnosis of febrile episodes is required to improve case management and curtail off-target treatment. The high rate of previous exposure of patients to dengue indicates the need to strengthen vector control and dengue surveillance programs.

Dengue virus infection induces inflammation and oxidative stress on the heart

OBJECTIVE

Dengue fever is one of the most important arboviral diseases in the world, and its severe forms are characterised by a broad spectrum of systemic and cardiovascular hallmarks. However, much remains to be elucidated regarding the pathogenesis triggered by Dengue virus (DENV) in the heart. Herein, we evaluated the cardiac outcomes unleashed by DENV infection and the possible mechanisms associated with these effects.

METHODS

A model of an adapted DENV-3 strain was used to infect male BALB/c mice to assess haemodynamic measurements and the functional, electrophysiological, inflammatory and oxidative parameters in the heart.

RESULTS

DENV-3 infection resulted in increased systemic inflammation and vascular permeability with consequent reduction of systolic blood pressure and increase in heart rate. These changes were accompanied by a decrease in the cardiac output and stroke volume, with a reduction trend in the left ventricular end-systolic and end-diastolic diameters and volumes. Also, there was a reduction trend in the calcium current density in the ventricular cardiomyocytes of DENV-3 infected mice. Indeed, DENV-3 infection led to leucocyte infiltration and production of inflammatory mediators in the heart, causing pericarditis and myocarditis. Moreover, increased reactive oxygen species generation and lipoperoxidation were also verified in the cardiac tissue of DENV-3 infected mice.

CONCLUSIONS

DENV-3 infection induced a marked cardiac dysfunction, which may be associated with inflammation, oxidative stress and electrophysiological changes in the heart. These findings provide new cardiac insights into the mechanisms involved in the pathogenesis triggered by DENV, contributing to the research of new therapeutic targets for clinical practice.

Electrochemical aptasensor for NS1 detection: Towards a fast dengue biosensor

Dengue is one of the most commonly neglected tropical diseases transmitted by Aedes aegypti infected with Dengue virus. This virus belongs to the gender Flavivirus and produces a non-structural protein 1 (NS1), which is an important biomarker found at high levels in blood in early disease stage. Therefore, this study focused on the development of an electrochemical biosensor for NS1 detection using DNA aptamers. Gold electrodes were co-immobilized with specific aptamers and 6-mercapto-1-hexanol (MCH) to obtain a self-assembled monolayer. The molar ratio between aptamers and MCH was optimized and the platform characterized by electrochemical impedance spectroscopy and atomic force microscopy. Bovine serum albumin was added in NS1 solution to stabilize it and block the surface to avoid non-specific interactions. The biosensor performance was tested with NS1 protein serotype 4 (in phosphate saline buffer and human serum) and with a solution of serotype 1 in human serum. The results showed a sensitivity of 2.9%, 2.7% and 1.7% per decade, respectively, and low limit of detection (0.05, 0.022 and 0.025 ng/mL). The platform was also tested with Envelope protein as negative control. Furthermore, the aptamer sensor was able to detect NS1 in clinical range and it is a promising candidate for a new class for miniaturized point-of-care device for different Dengue serotypes.

Effects of Ascogregarina culicis (Eugregarinorida: Lecudinidae) on Mosquito Size and Dengue Virus Infection in Aedes aegypti (Diptera: Culicidae)

Dengue virus infection, transmitted via mosquito bites, poses a substantial risk to global public health. Studies suggest that the mosquito's microbial community can profoundly influence vector-borne pathogen transmissions, including dengue virus. Ascogregarina culicis (Ross) of the phylum Apicomplexa is among the most common parasites of Aedes aegypti (Linnaeus), the principal vector of dengue. Despite a high prevalence worldwide, including in the areas where dengue is endemic, the impact of A. culicis on Ae. aegypti vector competence for dengue virus is unknown. This study aimed to investigate the effects of A. culicis infection on mosquito size and fitness, as measured by wing length, and the susceptibility to dengue virus infection in Ae. aegypti. Our results showed that there was no statistically significant difference in wing lengths between Ae. aegypti infected and not infected with A. culicis. Furthermore, A. culicis infection did not significantly affect dengue virus infection or disseminated infection rate. However, there was a significant association between shorter wings and higher dengue virus infection rate, whereby a 0.1-mm increase in wing length decreased the odds of the mosquito being infected by 32%. Thus, based on our result, A. culicis infection does not influence the body size and dengue virus infection in Ae. aegypti. This study helps to shed light on a common but neglected eukaryotic mosquito parasite.

A Fatal Case of Dengue-Associated Hemophagocytic Lymphohistiocytosis and Retroperitoneal Hematoma in a Patient With Autoimmune Hemolytic Anemia

Hemophagocytic lymphohistiocytosis (HLH) is a rare but potentially life-threatening complication of dengue infection which necessitates early diagnosis and treatment to improve patient outcomes. Severe dengue infection complicated by HLH may require interventions such as systemic corticosteroids, intravenous immunoglobulin, or chemotherapy. Here, we report a case of concurrent dengue-induced HLH and flare of underlying autoimmune hemolytic anemia (AIHA). The disease was refractory to treatment including corticosteroids and intravenous immunoglobulin. The course of illness was later complicated by dengue shock syndrome, severe liver dysfunction, and a large retroperitoneal hematoma. Unfortunately, the patient succumbed on day 10 of illness.

A chimeric dengue virus vaccine candidate delivered by high density microarray patches protects against infection in mice

Dengue viruses (DENV) cause an estimated 390 million infections globally. With no dengue-specific therapeutic treatment currently available, vaccination is the most promising strategy for its control. A wide range of DENV vaccines are in development, with one having already been licensed, albeit with limited distribution. We investigated the immunogenicity and protective efficacy of a chimeric virus vaccine candidate based on the insect-specific flavivirus, Binjari virus (BinJV), displaying the structural prM/E proteins of DENV (BinJ/DENV2-prME). In this study, we immunized AG129 mice with BinJ/DENV2-prME via a needle-free, high-density microarray patch (HD-MAP) delivery system. Immunization with a single, 1 µg dose of BinJ/DENV2-prME delivered via the HD-MAPs resulted in enhanced kinetics of neutralizing antibody induction when compared to needle delivery and complete protection against mortality upon virus challenge in the AG129 DENV mouse model.

Contributions of Ubiquitin and Ubiquitination to Flaviviral Antagonism of Type I IFN

Flaviviruses implement a broad range of antagonism strategies against the host antiviral response. A pivotal component of the early host response is production and signaling of type I interferon (IFN-I). Ubiquitin, a prevalent cellular protein-modifying molecule, is heavily involved in the cellular regulation of this and other immune response pathways. Viruses use ubiquitin and ubiquitin machinery to antagonize various steps of these pathways through diverse mechanisms. Here, we highlight ways in which flaviviruses use or inhibit ubiquitin to antagonize the antiviral IFN-I response.

Molecular investigation of the dengue outbreak in Karnataka, South India, reveals co-circulation of all four dengue virus serotypes

The growing incidence of dengue outbreaks in the state of Karnataka prompted us to study the circulating dengue virus (DENV) and their proportion among the suspected cases of dengue patients during the disease outbreak at Mysuru district of Southern India. The presence of the DENV in a patient's serum sample was identified by RT-PCR using previously published primer pairs targeting CprM gene. DENV serotyping was carried out by semi-nested multiplex PCR using serotype-specific primers and nucleotide sequencing. Three hundred fifty-five samples of serum from suspected dengue cases were collected, and 203 samples (57.18%) were found positives. In 2016, DENV-4 (97.87%) was found to be the most dominant DENV serotype either alone or as co-infection, followed by DENV-2 (8.51%) and DENV-3 (4.25%). In 47 positive cases, co-infection with more than one serotype was detected in 4 cases (8.51%). The analysis of the dengue cases in 2017, DENV-4 was dominating serotype (33.97%), followed by the emergence of DENV-2 (32.05%), DENV-3 (25.64%), and DENV-1 (25.00%). Our study also reports the circulation of all four DENV serotypes in the Mysuru district of Southern India, with concurrent infections rate of 16.66% in 2017. The present study provides information regarding the genetic variation among the circulating DENV serotype in an Indian state of Karnataka. The need for the studying genetic diversity of DENV will be useful during the continuous monitoring for disease burden as well as the development of appropriate prophylactic measures to control the spread of dengue infection.

Comparable Accuracies of Nonstructural Protein 1- and Envelope Protein-Based Enzyme-Linked Immunosorbent Assays in Detecting Anti-Dengue Immunoglobulin G Antibodies

Background: Dengue virus (DENV) infection remains a global public health concern. Enzyme-linked immunosorbent assays (ELISAs), which detect antibodies targeting the envelope (E) protein of DENV, serve as the front-line serological test for presumptive dengue diagnosis. Very few studies have determined the serostatus by detecting antibodies targeting the nonstructural protein 1 (NS1), which can function as diagnostic biomarkers to distinguish natural immunity from vaccine-induced immunity. Methods: We used community-acquired human serum specimens, with the serostatus confirmed by focus reduction microneutralization test (FRμNT), to evaluate the diagnostic performances of two NS1-based ELISA methods, namely, immunoglobulin G antibody-capture ELISA (NS1 GAC–ELISA) and indirect NS1 IgG ELISA, and compared the results with an E-based virus-like particle (VLP) GAC–ELISA. Results: NS1-based methods had comparable accuracies as VLP GAC–ELISA. Although the sensitivity in detecting anti-NS1 IgM was poor, indirect NS1 IgG ELISA showed similar limits of detection (~1–2 ng/mL) as NS1 GAC–ELISA in detecting anti-NS1 IgG. Combining the results from two or more tests as a composite reference standard can determine the DENV serostatus with a specificity reaching 100%. Conclusion: NS1-based ELISAs have comparable accuracies as VLP GAC–ELISA in determining dengue serostatus, which could effectively assist clinicians during assessments of vaccine eligibility.

Full-genome sequencing and analysis of DENV-3 serotype isolated from Yemen

BACKGROUND

Dengue virus causes the dengue fever as well as hemorrhagic fever in tropical and sub-tropical countries. It is now endemic in most parts of the South East Asia. Full-genome information of dengue virus 3 is not available from Yemen.

METHODS

In this study, the dengue virus 3 was detected by diagnostic tools like serology and RT-PCR in the samples isolated from a patient in Yemen. The full-genome was sequenced, and the identity, phylogenetic relationship and recombination analysis was performed by using BioEdit, MEGA X and RDP4 softwares.

RESULTS

The full-genome of the Yemen isolate was found to be 10,643 nt long with 3390 amino acids. The Yemen dengue virus 3 isolate showed the sequence similarity (98.5-92.4%) with dengue virus 3 isolates from China, Pakistan, India and Bangladesh respectively. The significant non-synonymous substitutions of amino acid in Yemen isolate were observed with selected isolates. The phylogenetic tree of Yemen isolate formed a unique clade within genotype III and sub-clade into lineage III. The Dengue virus isolate from Jeddah formed separated cluster with lineage IV.

CONCLUSIONS

This reveals the unique genetic variability among DENV-3 serotypes from Jeddah and earlier reported isolates from other regions.

Beyond Basicity: Discovery of Nonbasic DENV-2 Protease Inhibitors with Potent Activity in Cell Culture

The viral serine protease NS2B-NS3 is one of the promising targets for drug discovery against dengue virus and other flaviviruses. The molecular recognition preferences of the protease favor basic, positively charged moieties as substrates and inhibitors, which leads to pharmacokinetic liabilities and off-target interactions with host proteases such as thrombin. We here present the results of efforts that were aimed specifically at the discovery and development of noncharged, small-molecular inhibitors of the flaviviral proteases. A key factor in the discovery of these compounds was a cellular reporter gene assay for the dengue protease, the DENV2proHeLa system. Extensive structure-activity relationship explorations resulted in novel benzamide derivatives with submicromolar activities in viral replication assays (EC₅₀ 0.24 μM), selectivity against off-target proteases, and negligible cytotoxicity. This structural class has increased drug-likeness compared to most of the previously published active-site-directed flaviviral protease inhibitors and includes promising candidates for further preclinical development.

Dengue Virus and Vaccines: How Can DNA Immunization Contribute to This Challenge?

Dengue infections still have a tremendous impact on public health systems in most countries in tropical and subtropical regions. The disease is systemic and dynamic with broad range of manifestations, varying from mild symptoms to severe dengue (Dengue Hemorrhagic Fever and Dengue Shock Syndrome). The only licensed tetravalent dengue vaccine, Dengvaxia, is a chimeric yellow fever virus with prM and E genes from the different dengue serotypes. However, recent results indicated that seronegative individuals became more susceptible to develop severe dengue when infected after vaccination, and now WHO recommends vaccination only to dengue seropositive people. One possibility to explain these data is the lack of robust T-cell responses and antibody-dependent enhancement of virus replication in vaccinated people. On the other hand, DNA vaccines are excellent inducers of T-cell responses in experimental animals and it can also elicit antibody production. Clinical trials with DNA vaccines have improved and shown promising results regarding the use of this approach for human vaccination. Therefore, in this paper we review preclinical and clinical tests with DNA vaccines against the dengue virus. Most of the studies are based on the E protein since this antigen is the main target for neutralizing antibody production. Yet, there are other reports with DNA vaccines based on non-structural dengue proteins with protective results, as well. Combining structural and non-structural genes may be a solution for inducing immune responses aging in different infection moments. Furthermore, DNA immunizations are also a very good approach in combining strategies for vaccines against dengue, in heterologous prime/boost regimen or even administering different vaccines at the same time, in order to induce efficient humoral and cellular immune responses.

Probability of consolidation constrains novel serotype emergence in dengue fever virus

Since their first sequencing 40 years ago, Dengue virus (DENV) genotypes have shown extreme coherence regarding the serotype class they encode. Considering that DENV is a ribonucleic acid (RNA) virus with a high mutation rate, this behavior is intriguing. Here, we explore the effect of various parameters on likelihood of new serotype emergence. In order to determine the time scales of such an event, we used a Timed Markov Transmission Model to explore the influences of sylvatic versus peri-urban transmission, viral mutation rate, and vertical transmission on the probabilities of novel serotype emergence. We found that around 1 000 years are required for a new serotype to emerge, consistent with phylogenetic analysis of extant dengue serotypes. Furthermore, we show that likelihood of establishing chains of mosquito-human-mosquito infection, known as consolidation, is the primary factor which constrains novel serotype emergence. Our work illustrates the restrictions on and provides a mechanistic explanation for the low probability of novel dengue virus serotype emergence and the low number of observed DENV serotypes.

Repurposing of approved drug molecules for viral infectious diseases: a molecular modelling approach

The identification of new viral drugs has become a task of paramount significance due to the frequent occurrence of viral infections and especially during the current pandemic. Despite the recent advancements, the development of antiviral drugs has not made parallel progress. Reduction of time frame and cost of the drug development process is the major advantage of drug repurposing. Therefore, in this study, a drug repurposing strategy using molecular modelling techniques, i.e. biological activity prediction, virtual screening, and molecular dynamics simulation was employed to find promising repurposing candidates for viral infectious diseases. The biological activities of non-redundant (4171) drug molecules were predicted using PASS analysis, and 1401 drug molecules were selected which showed antiviral activities in the analysis. These drug molecules were subjected to virtual screening against the selected non-structural viral proteins. A series of filters, i.e. top 10 drug molecules based on binding affinity, mean value of binding affinity, visual inspection of protein-drug complexes, and number of H-bond between protein and drug molecules were used to narrow down the drug molecules. Molecular dynamics simulation analysis was carried out to validate the intrinsic atomic interactions and binding conformations of protein-drug complexes. The binding free energies of drug molecules were assessed by employing MMPBSA analysis. Finally, nine drug molecules were prioritized, as promising repurposing candidates with the potential to inhibit the selected non-structural viral proteins.Communicated by Ramaswamy H. Sarma.

Systemic dengue infection associated with a new dengue virus type 2 introduction in Brazil - a case report

BACKGROUND

Dengue infection is caused by an arbovirus with a wide range of presentations, varying from asymptomatic disease to unspecific febrile illness and haemorrhagic syndrome with shock, which can evolve to death. In Brazil, the virus circulates since the 1980s with many introductions of new serotypes, genotypes, and lineages since then. Here we report a fatal case of dengue associated with a Dengue virus (DENV) lineage not detected in the country until now.

CASE PRESENTATION

The patient, a 58-year-old man arrived at the hospital complaining of fever and severe abdominal pain due to intense gallbladder edema, mimicking acute abdomen. After 48 h of hospital admission, he evolved to refractory shock and death. DENV RNA was detected in all tissues collected (heart, lung, brain, kidney, spleen, pancreas, liver, and testis). Viral sequencing has shown that the virus belongs to serotype 2, American/Asian genotype, in a new clade, which has never been identified in Brazil before. The virus was phylogenetically related to isolates from central America [Puerto Rico (2005-2007), Martinique (2005), and Guadeloupe (2006)], most likely arriving in Brazil from Puerto Rico.

CONCLUSION

In summary, this was the first fatal documented case with systemic dengue infection associated with the new introduction of Dengue type 2 virus in Brazil during the 2019 outbreak.

Outbreak of severe dengue associated with DENV-3 in the city of Manado, North Sulawesi, Indonesia

BACKGROUND

In early 2019, an outbreak of severe dengue was reported in Manado, North Sulawesi Province, Indonesia. This epidemic raised public concern and recorded the highest number of cases in the last 10 years. This study aimed to determine the clinical spectrum, disease aetiology and virological characteristics associated with this outbreak of severe dengue.

METHODS

Dengue was diagnosed using non-structural protein 1 detection, reverse transcription polymerase chain reaction and immunoglobulin (Ig)G/IgM serology. Envelope gene sequencing was conducted to determine the phylogeny of the dengue virus (DENV).

RESULTS

In total, 146 patients with a median age of 8 years (interquartile range IQR 5-11 years) were recruited. Most patients experienced expanded dengue syndrome, characterized by severe organ involvement including liver enlargement, stomach ache and coagulation problems. During the outbreak, DENV-3 was the dominant serotype (75.9%). Smaller numbers of DENV-1, -2 and -4 were also detected. Phylogenetically, the dominant DENV-3 strains were grouped in multiple clusters and were related to other Indonesian strains, suggesting the emergence of heterogenous local viruses.

CONCLUSION

The occurrence of an outbreak of severe dengue in Manado was confirmed, and DENV-3 was found to be the dominant serotype during the outbreak. This study shows the benefits of virological surveillance in understanding the aetiological agents responsible for outbreaks of severe dengue.

A case of dengue fever that should be considered as imported infectious disease with digestive symptoms

Patients with dengue fever usually present with fever and rash, but non-specific symptoms such as headache, myalgia, arthralgia, and digestive symptoms are sometimes seen. We report a case of dengue fever with digestive symptoms in a patient who traveled to Indonesia. A 35-year-old man presented with fever, diarrhea, headache, and arthralgia. He later developed generalized rash. Dengue fever was clinically suspected from the travel history and confirmed by laboratory tests. He tested positive for anti-dengue virus antibodies, so dengue fever was diagnosed. Dengue fever should be included in the differential diagnosis of patients with digestive symptoms after returning to Japan.

Diagnostic Performance of a Magnetic Field-Enhanced Agglutination Readout in Detecting Either Viral Genomes or Host Antibodies in Arbovirus Infection

Arbovirus diagnostics on blood from donors and travelers returning from endemic areas is increasingly important for better patient management and epidemiological surveillance. We developed a flexible approach based on a magnetic field-enhanced agglutination (MFEA) readout to detect either genomes or host-derived antibodies. Dengue viruses (DENVs) were selected as models. For genome detection, a pan-flavivirus amplification was performed before capture of biotinylated amplicons between magnetic nanoparticles (MNPs) grafted with DENV probes and anti-biotin antibodies. Magnetization cycles accelerated this chaining process to within 5 min while simple turbidimetry measured the signal. This molecular MFEA readout was evaluated on 43 DENV RNA(+) and 32 DENV RNA(−) samples previously screened by real-time RT-PCR. The sensitivity and the specificity were 88.37% (95% CI, 78.76%–97.95%) and 96.87% (95% CI, 90.84%–100%), respectively. For anti-DENV antibody detection, 103 plasma samples from donors were first screened using ELISA assays. An immunological MFEA readout was then performed by adding MNPs grafted with viral antigens to the samples. Anti-DENV antibodies were detected with a sensitivity and specificity of 90.62% (95% CI, 83.50%–97.76%) and 97.44% (95% CI, 92.48%–100%), respectively. This adaptable approach offers flexibility to platforms dedicated to the screening of emerging infections.

Dengue Virus Non-Structural Protein 5 as a Versatile, Multi-Functional Effector in Host-Pathogen Interactions

Dengue is emerging as one of the most prevalent mosquito-borne viral diseases of humans. The 11kb RNA genome of the dengue virus encodes three structural proteins (envelope, pre-membrane, capsid) and seven non-structural proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5), all of which are translated as a single polyprotein that is subsequently cleaved by viral and host cellular proteases at specific sites. Non-structural protein 5 (NS5) is the largest of the non-structural proteins, functioning as both an RNA-dependent RNA polymerase (RdRp) that replicates the viral RNA and an RNA methyltransferase enzyme (MTase) that protects the viral genome by RNA capping, facilitating polyprotein translation. Within the human host, NS5 interacts with several proteins such as those in the JAK-STAT pathway, thereby interfering with anti-viral interferon signalling. This mini-review presents annotated, consolidated lists of known and potential NS5 interactors in the human host as determined by experimental and computational approaches respectively. The most significant protein interactors and the biological pathways they participate in are also highlighted and their implications discussed, along with the specific serotype of dengue virus as appropriate. This information can potentially stimulate and inform further research efforts towards providing an integrative understanding of the mechanisms by which NS5 manipulates the human-virus interface in general and the innate and adaptive immune responses in particular.

Differential effects of larval and adult nutrition on female survival, fecundity, and size of the yellow fever mosquito, Aedes aegypti

Background

The yellow fever mosquito, Aedes aegypti, is the principal vector of medically-important infectious viruses that cause severe illness such as dengue fever, yellow fever and Zika. The transmission potential of mosquitoes for these arboviruses is largely shaped by their life history traits, such as size, survival and fecundity. These life history traits, to some degree, depend on environmental conditions, such as larval and adult nutrition (e.g., nectar availability). Both these types of nutrition are known to affect the energetic reserves and life history traits of adults, but whether and how nutrition obtained during larval and adult stages have an interactive influence on mosquito life history traits remains largely unknown.

Results

Here, we experimentally manipulated mosquito diets to create two nutritional levels at larval and adult stages, that is, a high or low amount of larval food (HL or LL) during larval stage, and a good and poor adult food (GA or PA, represents normal or weak concentration of sucrose) during adult stage. We then compared the size, survival and fecundity of female mosquitoes reared from these nutritional regimes. We found that larval and adult nutrition affected size and survival, respectively, without interactions, while both larval and adult nutrition influenced fecundity. There was a positive relationship between fecundity and size. In addition, this positive relationship was not affected by nutrition.

Conclusions

These findings highlight how larval and adult nutrition differentially influence female mosquito life history traits, suggesting that studies evaluating nutritional effects on vectorial capacity traits should account for environmental variation across life stages.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12983-021-00395-z.

Metal Ions Induce Liquid Condensate Formation by the F Domain of Aedes aegypti Ecdysteroid Receptor. New Perspectives of Nuclear Receptor Studies

The superfamily of nuclear receptors (NRs), composed of ligand-activated transcription factors, is responsible for gene expression as a reaction to physiological and environmental changes. Transcriptional machinery may require phase separation to fulfil its role. Although NRs have a similar canonical structure, their C-terminal domains (F domains) are considered the least conserved and known regions. This article focuses on the peculiar molecular properties of the intrinsically disordered F domain of the ecdysteroid receptor from the Aedes aegypti mosquito (AaFEcR), the vector of the world's most devastating human diseases such as dengue and Zika. The His-Pro-rich segment of AaFEcR was recently shown to form the unique poly-proline helix II (PPII) in the presence of Cu²⁺. Here, using widefield microscopy of fluorescently labeled AaFEcR, Zn²⁺- and Cu²⁺-induced liquid-liquid phase separation (LLPS) was observed for the first time for the members of NRs. The perspectives of this finding on future research on the F domain are discussed, especially in relation to other NR members.

Top Down Computational Approach: A Vaccine Development Step to Find Novel Superantigenic HLA Binding Epitopes from Dengue Virus Proteome

Dengue virus (DENV) is a major mosquito vector based human pathogenic flavivirus which is causing major threat worldwide, yet the availability of therapeutic treatment and several vaccines, still called for advance treatment and vaccine development. The present top down computational approach is a vaccine development step to find novel super antigenic HLA binding epitopes from DENV proteome. The approach used sequence based screening to find complete conserve and high population coverage, common epitopes among all DENV serotype. Propred and Immune Epitope Data Base were used for sequence based screening with recommended parameters. Among top 29 identified epitopes, five structural protein epitopes viz. ³³LQGRGPLKL⁴¹, ²⁴⁹VVVLGSQEG²⁵⁷, ¹⁷²LVGIVTLYL¹⁸⁰, ¹⁴⁶MKILIGVVI¹⁵⁴, ⁷²YIIVGVEPG⁸⁰ and one nonstructural protein epitope ¹⁸LKNDIPMTG²⁶ were showed high conserve nature and high population coverage from complete DENV proteome. Further structure based study involving docking and molecular dynamic simulation to confirm stable behavior of HLA allele–peptide complex to give potent cell mediated immune response. Docking of epitope ⁷²YIIVGVEPG⁸⁰–DRB1 0401 allele and epitope ³³LQGRGPLKL⁴¹–B*5101 allele complexes showed the best binding energy of − 7.71 and − 7.20 kcal/mol, respectively and stable binding pattern over the time window during molecular dynamic simulation. This computational approach resulted novel epitopes which can be used in the design and development of short epitope based vaccines as well as diagnosis tools for dengue infection.

Population bottlenecks and founder effects: implications for mosquito-borne arboviral emergence

Transmission of arthropod-borne viruses (arboviruses) involves infection and replication in both arthropod vectors and vertebrate hosts. Nearly all arboviruses are RNA viruses with high mutation frequencies, which leaves them vulnerable to genetic drift and fitness losses owing to population bottlenecks during vector infection, dissemination from the midgut to the salivary glands and transmission to the vertebrate host. However, despite these bottlenecks, they seem to avoid fitness declines that can result from Muller's ratchet. In addition, founder effects that occur during the geographic introductions of human-amplified arboviruses, including chikungunya virus and Zika virus, can affect epidemic and endemic circulation, as well as virulence. In this Review, we discuss the role of genetic drift following population bottlenecks and founder effects in arboviral evolution and spread, and the emergence of human disease.

Antiviral Activity of 7-Substituted 7-Deazapurine Ribonucleosides, Monophosphate Prodrugs, and Triphoshates against Emerging RNA Viruses

A series of 7-deazaadenine ribonucleosides bearing alkyl, alkenyl, alkynyl, aryl, or hetaryl groups at position 7 as well as their 5'-O-triphosphates and two types of monophosphate prodrugs (phosphoramidates and S-acylthioethanol esters) were prepared and tested for antiviral activity against selected RNA viruses (Dengue, Zika, tick-borne encephalitis, West Nile, and SARS-CoV-2). The modified triphosphates inhibited the viral RNA-dependent RNA polymerases at micromolar concentrations through the incorporation of the modified nucleotide and stopping a further extension of the RNA chain. 7-Deazaadenosine nucleosides bearing ethynyl or small hetaryl groups at position 7 showed (sub)micromolar antiviral activities but significant cytotoxicity, whereas the nucleosides bearing bulkier heterocycles were still active but less toxic. Unexpectedly, the monophosphate prodrugs were similarly or less active than the corresponding nucleosides in the in vitro antiviral assays, although the bis(S-acylthioethanol) prodrug 14h was transported to the Huh7 cells and efficiently released the nucleoside monophosphate.