Dengue: a continuing global threat

A review on structural genomics approach applied for drug discovery against three vector-borne viral diseases: Dengue, Chikungunya and Zika

Structural genomics involves the advent of three-dimensional structures of the genome encoded proteins through various techniques available. Numerous structural genomics research groups have been developed across the globe and they contribute enormously to the identification of three-dimensional structures of various proteins. In this review, we have discussed the applications of the structural genomics approach towards the discovery of potential lead-like molecules against the genomic drug targets of three vector-borne diseases, namely, Dengue, Chikungunya and Zika. Currently, all these three diseases are associated with the most important global public health problems and significant economic burden in tropical countries. Structural genomics has accelerated the identification of novel drug targets and inhibitors for the treatment of these diseases. We start with the current development status of the drug targets and antiviral drugs against these three diseases and conclude by describing challenges that need to be addressed to overcome the shortcomings in the process of drug discovery.

A retrospective study on the socio-demographic factors and clinical parameters of dengue disease and their effects on the clinical course and recovery of the patients in a tertiary care hospital of Bangladesh

Dengue, a mosquito transmitted febrile viral disease, is a serious public health concern in Bangladesh. Despite significant number of incidences and reported deaths each year, there are inadequate number of studies relating the temporal trends of the clinical parameters as well as socio-demographic factors with the clinical course of the disease. Therefore, this study aims to associate the clinical parameters, demographic and behavioral factors of the dengue patients admitted in a tertiary care hospital in Dhaka, Bangladesh during the 2019 outbreak of dengue with the clinical course of the disease. Data were collected from the 336 confirmed dengue in-patients and analyzed using SPSS 26.0 software. Majority of the patients were male (2.2 times higher than female) who required longer time to recover compared to females (p < 0.01), urban resident (54.35%) and belonged to the age group of 18–40 years (73.33%). Dengue fever (90.77%) and dengue hemorrhagic fever (5.95%) were reported in most of the dengue patients while fever (98%) was the most frequently observed symptom. A significantly positive association was found between patient’s age and number of manifested symptoms (p = 0.013). Average duration of stay in the hospital was 4.9 days (SD = 1.652) and patient’s recovery time was positively correlated with delayed hospitalization (p < 0.01). Additionally, recovery time was negatively correlated with initial blood pressure (both systolic (p = 0.001, and diastolic (p = 0.023)) and platelet count (p = 0.003) of the patients recorded on the first day of hospitalization. Finally, a statistical model was developed which predicted that, hospital stay could be positively associated with an increasing trend of temperature, systolic blood pressure and reduced platelets count. Findings of this study may be beneficial to better understand the clinical course of the disease, identify the potential risk factors and ensure improved patient management during future dengue outbreaks.

Safety and immunogenicity of a single dose, live-attenuated 'tetravalent dengue vaccine' in healthy Indian adults; a randomized, double-blind, placebo controlled phase I/II trial

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Dengue Tetravalent Vaccine, Live-attenuated Recombinant of Panacea Biotec is a lyophilized vaccine based on novel formulation.

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Dengue Tetravalent Vaccine targets protection against dengue disease caused by all four dengue virus serotypes.

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Dengue Tetravalent Vaccine Phase I/II clinical trial is the first study conducted in an Indian population and proved to be safe and immunogenic.

Background

Dengue fever is the most prevalent mosquito-borne viral disease in the world, with 390 million dengue infections occurring every year. There is an unmet medical need to develop a safe, effective and affordable dengue vaccine against all four Dengue serotype viruses-DENV1, DENV-2, DENV-3 and DENV-4. Panacea Biotec Ltd (PBL) has developed a cell culture-derived, live-attenuated, lyophilized Tetravalent Dengue Vaccine (TDV). Here, in phase I/II study we assessed the safety and immunogenicity of single dose ‘Dengue Tetravalent Vaccine’ in healthy Indian adults.

Methods

In the study, 100 healthy adult volunteers aged 18–60 years were enrolled. The participants were allocated to TDV and placebo groups in 3:1 ratio, i.e. 75 participants to TDV group and 25 participants to the placebo group. Enrolled participants were administered a single dose of 0.5 ml of the test vaccine / placebo by subcutaneous route. Primary outcome for safety included all solicited AEs up to 21 days, unsolicited AEs up to 28 days and all AEs/serious adverse events (SAEs) till day 90 post-vaccination. For immunogenicity assessment the primary outcome was seroconversion & seropositivity rate by PRNT₅₀ to all four serotype till 90 days.

Results

Overall, 100 subjects were vaccinated out of which 8 subjects (5 subjects in vaccine group and 3 subjects in placebo group) dropped out from the study. The most commonly reported solicited local AE was pain and most common solicited systemic AE was headache and fever. No SAE was reported during the study. There was no statistically significant difference between TDV and placebo groups in terms of AEs. Of the 92 subjects who completed all scheduled visits in the study, 59 (81.9%) achieved seroconversion for DENV-1, 56 (77.8%) for DENV-2; 59 (81.9%) for DENV-3 and 57 (79.2%) for DENV-4 in TDV group. The seroconversion rate in the TDV group was statistically significant (p < 0.001) compared to placebo.

Clinical trial registration: CTRI/2017/02/007923.

A wMel Wolbachia variant in Aedes aegypti from field-collected Drosophila melanogaster with increased phenotypic stability under heat stress

Mosquito‐borne diseases remain a major cause of morbidity and mortality. Population replacement strategies involving the wMel strain of Wolbachia are being used widely to control mosquito‐borne diseases. However, these strategies may be influenced by temperature because wMel is vulnerable to heat. wMel infections in Drosophila melanogaster are genetically diverse, but few transinfections of wMel variants have been generated in Aedes aegypti. Here, we successfully transferred a wMel variant (termed wMelM) originating from a field‐collected D. melanogaster into Ae. aegypti. The new wMelM variant (clade I) is genetically distinct from the original wMel transinfection (clade III), and there are no genomic differences between wMelM in its original and transinfected host. We compared wMelM with wMel in its effects on host fitness, temperature tolerance, Wolbachia density, vector competence, cytoplasmic incompatibility and maternal transmission under heat stress in a controlled background. wMelM showed a higher heat tolerance than wMel, likely due to higher overall densities within the mosquito. Both wMel variants had minimal host fitness costs, complete cytoplasmic incompatibility and maternal transmission, and dengue virus blocking under laboratory conditions. Our results highlight phenotypic differences between Wolbachia variants and wMelM shows potential as an alternative strain in areas with strong seasonal temperature fluctuations.

Anti-viral triterpenes: a review

Triterpenes are naturally occurring derivatives biosynthesized following the isoprene rule of Ruzicka. The triterpenes have been reported to possess a wide range of therapeutic applications including anti-viral properties. In this review, the recent studies (2010-2020) concerning the anti-viral activities of triterpenes have been summarized. The structure activity relationship studies have been described as well as brief biosynthesis of these triterpenes is discussed.

Development of Novel Dengue NS1 Multiplex Lateral Flow Immunoassay to Differentiate Serotypes in Serum of Acute Phase Patients and Infected Mosquitoes

Dengue is among the most rapidly spreading arboviral disease in the world. A low-cost, easy to use point-of-care diagnostic tool for the detection and differentiation of dengue virus serotypes could improve clinical management, disease prevention, epidemiological surveillance, and outbreak monitoring, particularly in regions where multiple serotypes co-circulate. Despite widespread deployment, no commercial dengue antigen diagnostic test has proven effective in differentiating among dengue virus serotypes. In the current study, we first established mAb pairs and developed a multiplex lateral flow immunoassay for the simultaneous detection of the dengue viral NS1 antigen and identification of serotype. The proposed system, called Dengue serotype NS1 Multiplex LFIA, provides high sensitivity and specificity. In testing for JEV, ZIKV, YFV, WNV, and CHIKV, the multiplex LFIA gave no indication of cross- reactivity with cell culture supernatants of other flaviviruses or chikungunya virus. In analyzing 187 samples from patients suspected of dengue infection, the detection sensitivity for serotype D1 to D4 was 90.0%, 88.24%, 82.61%, and 83.33% and serotype specificity was 98.74%, 96.13%, 99.39%, and 97.04%, respectively. Our multiplex LFIA can also identify mono- and co-infection of different serotype of dengue viruses in mosquitoes. The proposed Multiplex LFIA provides a simple tool for the rapid detection of dengue serotypes and in the differential diagnosis of fever patients in regions where medical resources are limited and/or multiple DENVs co-circulate.

Virological Surveillance of Aedes aegypti Vectors Identifies All Four Dengue Serotypes in a Hyperendemic Region

Dengue virus (DENV) 1-4 is the etiological agent of dengue, the most important viral infection transmitted by Aedes spp mosquitoes to humans. Our goal was to identify the circulating DENV in Aedes aegypti collected in an area of Brazil where all four DENV serotypes had already been detected in humans, understand the epidemiology better, and to test the vector as a virological surveillance tool. Twenty-eight larvae pools and 174 females of Aedes aegypti were screened by reverse transcriptase quantitative polymerase chain reaction and semi-nested PCR assays. PCR products were sequenced, and phylogenetic analyses were performed. Nine larvae pools (32.1%) were positive for DENV, four (44.4%) with DENV-3, and five (55.6%) with more than one serotype. Fifteen females (8.6%) were positive for any DENV serotype. DENV-1 isolates belong to genotype V, DENV-2 to American-Asian genotype, DENV-3 to genotypes I and III, and DENV-4 to genotypes I and II. We demonstrate for the first time the co-circulation of all four DENV serotypes in larvae pools and adult Aedes aegypti in a hyperendemic area. This scenario represents a challenge for disease control and reinforces the importance of virological surveillance in the vector as a tool for predicting circulating DENV serotypes in humans.

Mathematical models for dengue fever epidemiology: A 10-year systematic review

Mathematical models have a long history in epidemiological research, and as the COVID-19 pandemic progressed, research on mathematical modeling became imperative and very influential to understand the epidemiological dynamics of disease spreading. Mathematical models describing dengue fever epidemiological dynamics are found back from 1970. Dengue fever is a viral mosquito-borne infection caused by four antigenically related but distinct serotypes (DENV-1 to DENV-4). With 2.5 billion people at risk of acquiring the infection, it is a major international public health concern. Although most of the cases are asymptomatic or mild, the disease immunological response is complex, with severe disease linked to the antibody-dependent enhancement (ADE) - a disease augmentation phenomenon where pre-existing antibodies to previous dengue infection do not neutralize but rather enhance the new infection. Here, we present a 10-year systematic review on mathematical models for dengue fever epidemiology. Specifically, we review multi-strain frameworks describing host-to-host and vector-host transmission models and within-host models describing viral replication and the respective immune response. Following a detailed literature search in standard scientific databases, different mathematical models in terms of their scope, analytical approach and structural form, including model validation and parameter estimation using empirical data, are described and analyzed. Aiming to identify a consensus on infectious diseases modeling aspects that can contribute to public health authorities for disease control, we revise the current understanding of epidemiological and immunological factors influencing the transmission dynamics of dengue. This review provide insights on general features to be considered to model aspects of real-world public health problems, such as the current epidemiological scenario we are living in.

Using amino acids co-occurrence matrices and explainability model to investigate patterns in dengue virus proteins

Background

Dengue is a common vector-borne disease in tropical countries caused by the Dengue virus. This virus may trigger a disease with several symptoms like fever, headache, nausea, vomiting, and muscle pain. Indeed, dengue illness may also present more severe and life-threatening conditions like hemorrhagic fever and dengue shock syndrome. The causes that lead hosts to develop severe infections are multifactorial and not fully understood. However, it is hypothesized that different viral genome signatures may partially contribute to the disease outcome. Therefore, it is plausible to suggest that deeper DENV genetic information analysis may bring new clues about genetic markers linked to severe illness.

Method

Pattern recognition in very long protein sequences is a challenge. To overcome this difficulty, we map protein chains onto matrix data structures that reveal patterns and allow us to classify dengue proteins associated with severe illness outcomes in human hosts. Our analysis uses co-occurrence of amino acids to build the matrices and Random Forests to classify them. We then interpret the classification model using SHAP Values to identify which amino acid co-occurrences increase the likelihood of severe outcomes.

Results

We trained ten binary classifiers, one for each dengue virus protein sequence. We assessed the classifier performance through five metrics: PR-AUC, ROC-AUC, F1-score, Precision and Recall. The highest score on all metrics corresponds to the protein E with a 95% confidence interval. We also compared the means of the classification metrics using the Tukey HSD statistical test. In four of five metrics, protein E was statistically different from proteins M, NS1, NS2A, NS2B, NS3, NS4A, NS4B and NS5, showing that E markers has a greater chance to be associated with severe dengue. Furthermore, the amino acid co-occurrence matrix highlight pairs of amino acids within Domain 1 of E protein that may be associated with the classification result.

Conclusion

We show the co-occurrence patterns of amino acids present in the protein sequences that most correlate with severe dengue. This evidence, used by the classification model and verified by statistical tests, mainly associates the E protein with the severe outcome of dengue in human hosts. In addition, we present information suggesting that patterns associated with such severe cases can be found mostly in Domain 1, inside protein E. Altogether, our results may aid in developing new treatments and being the target of debate on new theories regarding the infection caused by dengue in human hosts.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12859-022-04597-y.

[Dengue virus circulation in West Africa: An emerging public health issue]

Dengue is the most widespread arbovirosis in the world, with approximately 390 million cases per year, 96 millions of which have clinical manifestations and 25,000 deaths. In West Africa, the circulation of this virus in human populations was first reported in the 1960s in Nigeria. Clinical diagnosis of dengue in West Africa is made difficult by the existence of other diseases with similar clinical presentations. Biological diagnosis remains therefore the only alternative. This biological diagnosis requires high quality equipment and well-trained personnel, which are not always available in resource-limited countries. Thus, many cases of dengue fever are consistently reported as malaria, leading to mismanagement, which can have serious consequences on the health status of patients. It is therefore necessary to set up surveillance systems for febrile infections of unknown origin in Africa by strengthening the diagnostic capacities of national laboratories.

Murine models of dengue virus infection for novel drug discovery

INTRODUCTION

Dengue virus (DENV) is the causative agent of the most prevalent human disease transmitted by mosquitoes in tropical and subtropical regions worldwide. At present, no antiviral drug is available and the difficulties to develop highly protective vaccines against the four DENV serotypes maintain the requirement of effective options for dengue chemotherapy.

AREAS COVERED

The availability of animal models that reproduce human disease is a very valuable tool for the preclinical evaluation of potential antivirals. Here, the main murine models of dengue infection are described, including immunocompetent wild-type mice, immunocompromised mice deficient in diverse components of the interferon (IFN) pathway and humanized mice. The main findings in antiviral testing of DENV inhibitory compounds in murine models are also presented.

EXPERT OPINION

At present, there is no murine model that fully recapitulates human disease. However, immunocompromised mice deficient in IFN-α/β and -γ receptors, with their limitations, have shown to be the most suitable system for antiviral preclinical testing. In fact, the AG129 mouse model allowed the identification of celgosivir, an inhibitor of cellular glucosidases, as a promising option for DENV therapy. However, clinical trials still were not successful, emphasizing the difficulties in the transition from preclinical testing to human treatment.

Myricetin Allosterically Inhibits the Dengue NS2B-NS3 Protease by Disrupting the Active and Locking the Inactive Conformations

The dengue NS2B-NS3 protease existing in equilibrium between the active and inactive forms is essential for virus replication, thus representing a key drug target. Here, myricetin, a plant flavonoid, was characterized to noncompetitively inhibit the dengue protease. Further NMR study identified the protease residues perturbed by binding to myricetin, which were utilized to construct the myricetin-protease complexes. Strikingly, in the active form, myricetin binds to a new allosteric site (AS2) far away from the active site pocket and the allosteric site (AS1) for binding curcumin, while in the inactive form, it binds to both AS1 and AS2. To decipher the mechanism for the allosteric inhibition by myricetin, we conducted molecular dynamics simulations on different forms of dengue NS2B-NS3 proteases. Unexpectedly, the binding of myricetin to AS2 is sufficient to disrupt the active conformation by displacing the characteristic NS2B C-terminal β-hairpin from the active site pocket. By contrast, the binding of myricetin to AS1 and AS2 results in locking the inactive conformation. Therefore, myricetin represents the first small molecule, which allosterically inhibits the dengue protease by both disrupting the active conformation and locking the inactive conformation. The results enforce the notion that a global allosteric network exists in the dengue NS2B-NS3 protease, which is susceptible to allosteric inhibition by small molecules such as myricetin and curcumin. As myricetin has been extensively used as a food additive, it might be directly utilized to fight the dengue infections and as a promising starting material for further design of potent allosteric inhibitors.

In-vitro antiviral action of Eupatorium perfoliatum against dengue virus infection: Modulation of mTOR signaling and autophagy

ETHNOPHARMACOLOGICAL RELEVANCE

Dengue virus (DENV) is a re-emerging mosquito-borne flavivirus that has recently engendered large epidemics around the world. Consequently antivirals with effective anti-DENV therapeutic activity are urgently required. In the 18th century, Europeans, as well as native inhabitants of North America, were known to adapt the medicinal property of the common perennial plant Eupatorium perfoliatum L. to treat fever and infections. Previous studies have shown that Eupatorium perfoliatum L. possesses anti-inflammatory, anti-oxidative, anti-plasmodial, anti-bacterial and antiviral activities. However, to the best of our knowledge, no anti-DENV activity of E. perfoliatum L. has been investigated at the molecular level so far.

AIM OF STUDY

Here, for the first time we have attempted to study the action of E. perfoliatum extract and its few bioactive components i.e., quercetin, caffeic acid and eupafolin against wild primary clinical isolate of DENV-2 infection in an in vitro model.

MATERIALS AND METHODS

The presence of the bioactive components in the E. perfoliatum extract, were analyzed by HPLC- DAD. Then, CC₅₀ as well as IC₅₀ values of the extract and its bioactive components were measured against DENV in HepG2 cell line. After that, the antiviral activity was studied by Time of addition assay using qRT-PCR. Further, the downstream signalling action of E. perfoliatum extract, was studied by Human phosphorylation MAPK antibody array, followed by immunofluorescence microscopy. Moreover, a molecular docking analysis was done to study the binding affinity of bioactive components of E. perfoliatum extract with TIM-1 transmembrane receptor protein, which is known for viral internalization.

RESULT

We found that E. perfoliatum extract has marked antiviral activity during pre-treatment against DENV infection in HepG2 cell line. The extract also significantly reduced the DENV induced autophagy in HepG2 cell line as detected by LC3 II localization. The presence of different bioactive compounds in E. perfoliatum extract were confirmed by HPLC-DAD. In the bioactive components, in parallel to earlier studies, quercetin showed the most significant preventive action against DENV infection. Further, in molecular docking analysis also, quercetin showed the strongest binding affinity towards DENV membrane receptor TIM-1 protein.

CONCLUSION

Our findings suggests that E. perfoliatum extract has significant potential to be an anti-DENV therapeutic agent. Moreover, among the bioactive components, quercetin may have a prophylaxis role in executing the antiviral activity of E. perfoliatum extract against DENV infection.

USP14: Structure, Function, and Target Inhibition

Ubiquitin-specific protease 14 (USP14), a deubiquitinating enzyme (DUB), is associated with proteasomes and exerts a dual function in regulating protein degradation. USP14 protects protein substrates from degradation by removing ubiquitin chains from proteasome-bound substrates, whereas promotes protein degradation by activating the proteasome. Increasing evidence have shown that USP14 is involved in several canonical signaling pathways, correlating with cancer, neurodegenerative diseases, autophagy, immune responses, and viral infections. The activity of USP14 is tightly regulated to ensure its function in various cellular processes. Structural studies have demonstrated that free USP14 exists in an autoinhibited state with two surface loops, BL1 and BL2, partially hovering above and blocking the active site cleft binding to the C-terminus of ubiquitin. Hence, both proteasome-bound and phosphorylated forms of USP14 require the induction of conformational changes in the BL2 loop to activate its deubiquitinating function. Due to its intriguing roles in the stabilization of disease-causing proteins and oncology targets, USP14 has garnered widespread interest as a therapeutic target. In recent years, significant progress has been made on identifying inhibitors targeting USP14, despite the complexity and challenges in improving their selectivity and affinity for USP14. In particular, the crystal structures of USP14 complexed with IU1-series inhibitors revealed the underlying allosteric regulatory mechanism and enabled the further design of potent inhibitors. In this review, we summarize the current knowledge regarding the structure, regulation, pathophysiological function, and selective inhibition of USP14, including disease associations and inhibitor development.

Review of -omics studies on mosquito-borne viruses of the Flavivirus genus

Arboviruses are transmitted by arthropods (arthropod-borne virus) which can be mosquitoes or other hematophagous arthropods, in which their life cycle occurs before transmission to other hosts. Arboviruses such as Dengue, Zika, Saint Louis Encephalitis, West Nile, Yellow Fever, Japanese Encephalitis, Rocio and Murray Valley Encephalitis viruses are some of the arboviruses transmitted biologically among vertebrate hosts by blood-taking vectors, mainly Aedes and Culex sp., and are associated with neurological, viscerotropic, and hemorrhagic reemerging diseases, posing as significant health and socioeconomic concern, as they become more and more adaptive to new environments, to arthropods vectors and human hosts. One of the main families that include mosquito-borne viruses is Flaviviridae, and here, we review the case of the Flavivirus genus, which comprises the viruses cited above, using a variety of research approaches published in literature, including genomics, transcriptomics, proteomics, metabolomics, etc., to better understand their structures as well as virus-host interactions, which are essential for development of future antiviral therapies.

Rapid molecular assays for the detection of the four dengue viruses in infected mosquitoes

The pantropic emergence of severe dengue disease can partly be attributed to the co-circulation of different dengue viruses (DENVs) in the same geographical location. Effective monitoring for circulation of each of the four DENVs is critical to inform disease mitigation strategies. In low resource settings, this can be effectively achieved by utilizing inexpensive, rapid, sensitive and specific assays to detect viruses in mosquito populations. In this study, we developed four rapid DENV tests with direct applicability for low-resource virus surveillance in mosquitoes. The test protocols utilize a novel sample preparation step, a single-temperature isothermal amplification, and a simple lateral flow detection. Analytical sensitivity testing demonstrated tests could detect down to 1,000 copies/µL of virus-specific DENV RNA, and analytical specificity testing indicated tests were highly specific for their respective virus, and did not detect closely related flaviviruses. All four DENV tests showed excellent diagnostic specificity and sensitivity when used for detection of both individually infected mosquitoes and infected mosquitoes in pools of uninfected mosquitoes. With individually infected mosquitoes, the rapid DENV-1, -2 and -3 tests showed 100% diagnostic sensitivity (95% CI = 69% to 100%, n=8 for DENV-1; n=10 for DENV 2,3) and the DENV-4 test showed 92% diagnostic sensitivity (CI: 62% to 100%, n=12) along with 100% diagnostic specificity (CI: 48-100%) for all four tests. Testing infected mosquito pools, the rapid DENV-2, -3 and -4 tests showed 100% diagnostic sensitivity (95% CI = 69% to 100%, n=10) and the DENV-1 test showed 90% diagnostic sensitivity (55.50% to 99.75%, n=10) together with 100% diagnostic specificity (CI: 48-100%). Our tests reduce the operational time required to perform mosquito infection status surveillance testing from > two hours to only 35 minutes, and have potential to improve accessibility of mosquito screening, improving monitoring and control strategies in low-income countries most affected by dengue outbreaks.

Serological Diagnosis of Dengue

A reliable and specific diagnosis is imperative in viral diagnosis, both for clinical management and surveillance, and to ensure that early treatment and control measures are carried out. The number of days of illness is important to choose the most appropriate method to be used and for the correct interpretation of the results obtained. Specific IgM is elicited after that period, indicating an active infection and usually lasts up to 3 months. However, in DENV secondary infections, IgM levels may be significantly lower or undetectable. After 10-12 days, a lifetime specific IgG is produced. Routinely, the laboratory diagnosis of DENV infections can be performed by viral isolation and/or detection of viral nucleic acid, serological assays for the detection of specific antibodies (IgM/IgG), antigen (NS1) and the detection of viral antigens in tissues, which are suitable during certain phases of the disease. For serological diagnosis, serum, plasma, or cerebrospinal fluid (CSF) samples may be investigated. If the test is carried out a few days after collection, the specimens can be stored at 4 °C, since the immunoglobulins are stable in serum or plasma. If the storage period is extended, the material must be kept at -20 °C or -70 °C. In serology, several methods can be used to detect specific viral antigens and/or antibodies, produced by the host in response to DENV infection. Routinely, serological tests include the hemagglutination inhibition (HI) assay, the plaque reduction neutralizing test (PRNT), the gold standard assay for dengue immune response characterization, and ELISAs to detect IgM (MAC-ELISA) and IgG (IgG-ELISA).

Rapid molecular assays for the detection of the four dengue viruses in infected mosquitoes

The pantropic emergence of severe dengue disease can partly be attributed to the co-circulation of different dengue viruses (DENVs) in the same geographical location. Effective monitoring for circulation of each of the four DENVs is critical to inform disease mitigation strategies. In low resource settings, this can be effectively achieved by utilizing inexpensive, rapid, sensitive and specific assays to detect viruses in mosquito populations. In this study, we developed four rapid DENV tests with direct applicability for low-resource virus surveillance in mosquitoes. The test protocols utilize a novel sample preparation step, a single-temperature isothermal amplification, and a simple lateral flow detection. Analytical sensitivity testing demonstrated tests could detect down to 1,000 copies/µL of virus-specific DENV RNA, and analytical specificity testing indicated tests were highly specific for their respective virus, and did not detect closely related flaviviruses. All four DENV tests showed excellent diagnostic specificity and sensitivity when used for detection of both individually infected mosquitoes and infected mosquitoes in pools of uninfected mosquitoes. With individually infected mosquitoes, the rapid DENV-1, -2 and -3 tests showed 100% diagnostic sensitivity (95% CI = 69% to 100%, n=8 for DENV-1; n=10 for DENV 2,3) and the DENV-4 test showed 92% diagnostic sensitivity (CI: 62% to 100%, n=12) along with 100% diagnostic specificity (CI: 48-100%) for all four tests. Testing infected mosquito pools, the rapid DENV-2, -3 and -4 tests showed 100% diagnostic sensitivity (95% CI = 69% to 100%, n=10) and the DENV-1 test showed 90% diagnostic sensitivity (55.50% to 99.75%, n=10) together with 100% diagnostic specificity (CI: 48-100%). Our tests reduce the operational time required to perform mosquito infection status surveillance testing from > two hours to only 35 minutes, and have potential to improve accessibility of mosquito screening, improving monitoring and control strategies in low-income countries most affected by dengue outbreaks.

Transcriptional response of Wolbachia-transinfected Aedes aegypti mosquito cells to dengue virus at early stages of infection

Mosquito-borne flaviviruses are responsible for viral infections and represent a considerable public health burden. Aedes aegypti is the principal vector of dengue virus (DENV), therefore understanding the intrinsic virus-host interactions is vital, particularly in the presence of the endosymbiont Wolbachia, which blocks virus replication in mosquitoes. Here, we examined the transcriptional response of Wolbachia-transinfected Ae. aegypti Aag2 cells to DENV infection. We identified differentially expressed immune genes that play a key role in the activation of anti-viral defence such as the Toll and immune deficiency pathways. Further, genes encoding cytosine and N6-adenosine methyltransferases and SUMOylation, involved in post-transcriptional modifications, an antioxidant enzyme, and heat-shock response were up-regulated at the early stages of DENV infection and are reported here for the first time. Additionally, several long non-coding RNAs were among the differentially regulated genes. Our results provide insight into Wolbachia-transinfected Ae. aegypti's initial virus recognition and transcriptional response to DENV infection.

Perspectives Concerning Various Symptoms of SARS-CoV-2 Detected Individuals

After exposure to SARS-CoV-2, varying symptoms of COVID-19 ranging from asymptomatic symptoms to morbidity and mortality have been exhibited in each individual. SARS-CoV-2 requires various cellular molecules for penetration into a target host cell. Angiotensin-converting enzyme2 (ACE2) acts as the viral receptor molecule. After attachment, SARS-CoV-2 also requires the transmembrane protease serine-2 (TMPRSS-2) and furin molecules, which serve as co-receptors for penetration into the target cell and for subsequent replication. In the meantime, a major histocompatibility complex (MHC) is required for the induction of adaptive immune cells, especially cytotoxic T cells and helper T cells, to clear the virally infected cells. This perspective review article proposes different aspects to explain the varying symptoms of the individuals who have been exposed to SARS-CoV-2, which relates to the polymorphisms of these involved molecules.

Dengue Infection Susceptibility of Five Aedes aegypti Populations from Manaus (Brazil) after Challenge with Virus Serotypes 1–4

The successful spread and maintenance of the dengue virus (DENV) in mosquito vectors depends on their viral infection susceptibility, and parameters related to vector competence are the most valuable for measuring the risk of viral transmission by mosquitoes. These parameters may vary according to the viral serotype in circulation and in accordance with the geographic origin of the mosquito population that is being assessed. In this study, we investigated the effect of DENV serotypes (1–4) with regards to the infection susceptibility of five Brazilian Ae. aegypti populations from Manaus, the capital of the state of Amazonas, Brazil. Mosquitoes were challenged by oral infection with the DENV serotypes and then tested for the presence of the arbovirus using quantitative PCR at 14 days post-infection, which is the time point that corresponds to the extrinsic incubation period of Ae. aegypti when reared at 28 °C. Thus, we were able to determine the infection patterns for DENV-1, -2, -3 and -4 in the mosquito populations. The mosquitoes had both interpopulation and inter-serotype variation in their viral susceptibilities. All DENV serotypes showed a similar tendency to accumulate in the body in a greater amount than in the head/salivary gland (head/SG), which does not occur with other flaviviruses. For DENV-1, DENV-3, and DENV-4, the body viral load varied among populations, but the head/SG viral loads were similar. Differently for DENV-2, both body and head/SG viral loads varied among populations. As the lack of phenotypic homogeneity represents one of the most important reasons for the long-term fight against dengue incidence, we expect that this study will help us to understand the dynamics of the infection patterns that are triggered by the distinct serotypes of DENV in mosquitoes.

Impact of Cymbopogon flexuosus (Poaceae) essential oil and primary components on the eclosion and larval development of Aedes aegypti

The current study describes the effects of sub-lethal concentrations and constituent compounds (citral and geranyl acetate) of Cymbopogon flexuosus essential oil (EO) on the development of Aedes aegypti. We treated eggs with 6, 18, or 30 mg L^-1 and larvae with 3 or 6 mg L^-1 of EO and its major compounds (citral and geranyl acetate). Citral and geranyl acetate were evaluated at 18, 30, and 42 mg L^-1 and compared with commercial growth inhibitors (diflubenzuron and methoprene). We measured larval head diameter, siphon length, and larval length. Finally, we examined concentrations of molt hormone (MH) and juvenile hormone III (JH III) using high-performance liquid chromatography coupled to mass spectrometry. All geranyl acetate concentrations decreased egg hatching, while EO altered molting among larval instars and between larvae and pupae, with an increase in the larval length (3 mg L^-1: 6 ± 0.0 mm; 6 mg L^-1: 6 ± 0.7 mm) and head width (3 mg L^-1: 0.8 ± 0 mm; 6 mg L^-1: 0.8 ± 0.0 mm) compared with the control group. We did not detect chromatographic signals of MH and JH III in larvae treated with C. flexuosus EO or their major compounds. The sub-lethal concentrations C. flexuosus EO caused a similar effect to diflubenzuron, namely decreased hormone concentrations, an extended larval period, and death.

Increased Plasma Heparanase Activity and Endothelial Glycocalyx Degradation in Dengue Patients Is Associated With Plasma Leakage

Background

Endothelial hyper-permeability with plasma leakage and thrombocytopenia are predominant features of severe dengue virus infection. It is well established that heparanase, the endothelial glycocalyx degrading enzyme, plays a major role in various diseases with vascular leakage. It is yet to be elucidated whether heparanase activity plays a major role in dengue-associated plasma leakage. Moreover, the major source of heparanase secretion and activation in dengue remains elusive. Since a relatively high amount of heparanase is stored in platelets, we postulate that heparanase released by activated platelets contributes to the increased plasma heparanase activity during dengue virus infection.

Methods

Heparanase activity (plasma and urine), and heparan sulfate and syndecan-1 (plasma levels) were measured in dengue patients with thrombocytopenia in acute phase (n=30), during course of disease (n=10) and in convalescent phase (n=25). Associations with clinical parameters and plasma leakage markers were explored. Platelets from healthy donors were stimulated with dengue non-structural protein-1, DENV2 virus and thrombin to evaluate heparanase release and activity ex vivo.

Results

Heparanase activity was elevated in acute dengue and normalized during convalescence. Similarly, glycocalyx components, such as heparan sulfate and syndecan-1, were increased in acute dengue and restored during convalescence. Increased heparanase activity correlated with the endothelial dysfunction markers heparan sulfate and syndecan-1, as well as clinical markers of plasma leakage such as ascites, hematocrit concentration and gall-bladder wall thickening. Notably, platelet number inversely correlated with heparanase activity. Ex vivo incubation of platelets with thrombin and live DENV2 virus, but not dengue virus-2-derived non-structural protein 1 induced heparanase release from platelets.

Conclusion

Taken together, our findings suggest that the increase of heparanase activity in dengue patients is associated with endothelial glycocalyx degradation and plasma leakage. Furthermore, thrombin or DENV2 activated platelets may be considered as a potential source of heparanase.

Evidence of co-circulation of multiple arboviruses transmitted by Aedes species based on laboratory syndromic surveillance at a health unit in a slum of the Federal District, Brazil

Background

Vector-borne diseases, especially arboviruses transmitted by Aedes sp. mosquitos, should be a health policy priority in Brazil. Despite this urgency, there are significant limitations in the traditional surveillance system, mainly in vulnerable areas. This study aimed to investigate the circulation of dengue (DENV), Zika (ZIKV), and chikungunya viruses (CHIKV) by laboratory syndromic surveillance (LSS) in a slum area of the Federal District of Brazil, comparing the results with traditional surveillance data.

Methods

LSS for acute febrile and/or exanthematous symptoms was developed at a health unit of Cidade Estrutural, in order to identify the circulation of arboviruses transmitted by Aedes sp. mosquitos. Between June 2019 and March 2020, 131 valid participants were identified and sera tested by reverse transcription polymerase chain reaction (RT-PCR) for DENV (by serotype), ZIKV, and CHIKV acute infection and by immunoglobulin M enzyme-inked immunosorbent assay (ELISA-IgM) for DENV and CHIKV 15–21 days after symptom onset, when the participant reported no respiratory signs (cough and/or coryza). The results obtained were compared with traditional surveillance data for the study area and period.

Results

At least three DENV-1 (2.3%), four DENV-2 (3%), and one CHIKV (0.7%) cases were confirmed in the laboratory, showing evidence of hyperendemicity even though LSS had not reached the historic peak dengue fever months in the Federal District (April–May). When the results obtained here were compared with traditional surveillance, a significant discrepancy was observed, including underreporting of CHIKV infection.

Conclusions

In addition to the risks posed to the study population, the area investigated with its respective socio-environmental profile may be a potential site for spread of the virus, given the cosmopolitan presence of Aedes sp. and human mobility in the Federal District. It is also suggested that traditional epidemiological surveillance may be reporting acute viral infections other than DENV as dengue fever, while underreporting other arboviruses transmitted by Aedes sp. mosquitos in the Federal District.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-05110-9.

Tackling the global health threat of arboviruses: An appraisal of the three holistic approaches to health

Background: The rapid circulation of arboviruses in the human population has been linked with changes in climatic, environmental, and socio-economic conditions. These changes are known to alter the transmission cycles of arboviruses involving the anthropophilic vectors and thus facilitate an extensive geographical distribution of medically important arboviral diseases, thereby posing a significant health threat. Using our current understanding and assessment of relevant literature, this review aimed to understand the underlying factors promoting the spread of arboviruses and how the three most renowned interdisciplinary and holistic approaches to health such as One Health, Eco-Health, and Planetary Health can be a panacea for control of arboviruses. Methods: A comprehensive structured search of relevant databases such as Medline, PubMed, WHO, Scopus, Science Direct, DOAJ, AJOL, and Google Scholar was conducted to identify recent articles on arboviruses and holistic approaches to health using the keywords including "arboviral diseases", "arbovirus vectors", "arboviral infections", "epidemiology of arboviruses", "holistic approaches", "One Health", "Eco-Health", and "Planetary Health". Results: Changes in climatic factors like temperature, humidity, and precipitation support the growth, breeding, and fecundity of arthropod vectors transmitting the arboviral diseases. Increased human migration and urbanization due to socio-economic factors play an important role in population increase leading to the rapid geographical distribution of arthropod vectors and transmission of arboviral diseases. Medical factors like misdiagnosis and misclassification also contribute to the spread of arboviruses. Conclusion: This review highlights two important findings: First, climatic, environmental, socio-economic, and medical factors influence the constant distributions of arthropod vectors. Second, either of the three holistic approaches or a combination of any two can be adopted on arboviral disease control. Our findings underline the need for holistic approaches as the best strategy to mitigating and controlling the emerging and reemerging arboviruses.

Presenting Complaints in Acute Dengue Infection and Differences in Presenting Complaints Between Primary and Secondary Dengue Infections

Aim and objectives

To describe the presenting complaints in acute dengue infection, and identify any differences in presenting complaints between primary and secondary dengue infection patients.

Material and methods

This cross-sectional observational study was conducted at the Department of Infectious Diseases and Medicine, Holy Family Hospital, Rawalpindi, from July 2019 to December 2019 during the Dengue Rawalpindi Epidemic 2019. Presenting complaints of patients who fulfilled the inclusion criteria of the study were recorded on a proforma on their admissions and their informed consent was taken. Of these patients, 70 primary and 70 secondary dengue infection patients were randomly selected for comparison of presenting complaints. The two groups were compared using the chi-square test and a P-value of <0.05 was considered significant.

Results

Intermittent fever (88.6%), headache (85%), myalgia (87.9%), arthralgia/bone pain (75%), and retro-orbital pain (47.9%) were common in most dengue patients. Hemorrhagic manifestations, such as rash (15%), epistaxis (11.4%), gum bleeding (15%), melena (7.9%), hematemesis (6.4%), hemoptysis (5.7%), and hematuria (6.4%), were less common.

Abdominal pain was significantly more common in secondary dengue infections (50% in secondary dengue infections compared to 32.9% in primary dengue infections).

Conclusions

Fever, headache, myalgia, arthralgia/bone pains, retro-orbital pain as well as rash, epistaxis, gum bleeding, melena, hematemesis, hemoptysis, hematuria, and decreased urine output despite fluid intake are presenting complaints of dengue infection.

Patients with abdominal pain in addition to the above presenting complaints are more likely to be cases of the more serious secondary dengue infection. 

Challenges, Advances and Opportunities in Exploring Natural Products to Control Arboviral Disease Vectors

Natural products constitute an important source of molecules for product development. However, despite numerous reports of compounds and active extracts from biodiversity, poor and developing countries continue to suffer with endemic diseases caused by arboviral vectors, including dengue, Zika, chikungunya and urban yellow fever. Vector control remains the most efficient disease prevention strategy. Wide and prolonged use of insecticides has resulted in vector resistance, making the search for new chemical prototypes imperative. Considering the potential of natural products chemistry for developing natural products-based products, including insecticides, this contribution discusses the general aspects and specific characteristics involved in the development of drug leads for vector control. Throughout this work, we highlight the obstacles that need to be overcome in order for natural products compounds to be considered promising prototypes. Moreover, we analyze the bottlenecks that should be addressed, together with potential strategies, to rationalize and improve the efficiency of the drug discovery process.

Mammalian animal models for dengue virus infection: a recent overview

Dengue, a rapidly spreading mosquito-borne human viral disease caused by dengue virus (DENV), is a public health concern in tropical and subtropical areas due to its expanding geographical range. DENV can cause a wide spectrum of illnesses in humans, ranging from asymptomatic infection or mild dengue fever (DF) to life-threatening dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). Dengue is caused by four DENV serotypes; however, dengue pathogenesis is complex and poorly understood. Establishing a useful animal model that can exhibit dengue-fever-like signs similar to those in humans is essential to improve our understanding of the host response and pathogenesis of DENV. Although several animal models, including mouse models, non-human primate models, and a recently reported tree shrew model, have been investigated for DENV infection, animal models with clinical signs that are similar to those of DF in humans have not yet been established. Although animal models are essential for understanding the pathogenesis of DENV infection and for drug and vaccine development, each animal model has its own strengths and limitations. Therefore, in this review, we provide a recent overview of animal models for DENV infection and pathogenesis, focusing on studies of the antibody-dependent enhancement (ADE) effect in animal models.

Kinetic Changes of Peripheral Blood Monocyte Subsets and Expression of Co-Stimulatory Molecules during Acute Dengue Virus Infection

Monocytes, one of the main target cells for dengue virus (DENV) infection, contribute to the resolution of viremia and to pathogenesis. We performed a longitudinal study by a detailed phenotypic comparison of classical (CD14++CD16−, non-classical (CD14+CD16++) and intermediate (CD14++CD16+) monocyte subsets in blood samples from dengue fever (DF) to the severe dengue hemorrhagic fever (DHF) and healthy individuals. Various costimulatory molecules of CD40, CD80, CD86 and inducible costimulatory ligand (ICOSL) expressed on these three monocyte subsets were also analyzed. DENV-infected patients showed an increase in the frequency of intermediate monocytes and a decrease in the classical monocytes when compared to healthy individuals. Although these differences did not correlate with disease severity, changes during the early phase of infection gradually returned to normal in the defervescence phase. Moreover, decreased frequency of classical monocytes was associated with a significant up-regulation of co-stimulatory molecules CD40, CD86 and ICOSL. Kinetics of these co-stimulatory molecule-expressing classical monocytes showed different patterns throughout the sampling times of acute DENV infection. Different distribution of monocyte subsets and their co-stimulatory molecules in the peripheral blood during acute infection might exacerbate immune responses like cytokine storms and ADE, and future studies on intracellular molecular pathways utilized by these monocyte linages are warranted.

Electropolymerized-molecularly imprinted polymers (E-MIPS) as sensing elements for the detection of dengue infection

A straightforward in situ detection method for dengue infection was demonstrated through the molecular imprinting of a dengue nonstructural protein 1 (NS1) epitope into an electropolymerized molecularly imprinted polyterthiophene (E-MIP) film sensor. The key enabling step in the sensor fabrication is based on an epitope imprinting strategy, in which short peptide sequences derived from the original target molecules were employed as the main template for detection and analysis. The formation of the E-MIP sensor films was facilitated using cyclic voltammetry (CV) and monitored in situ by electrochemical quartz crystal microbalance (EC-QCM). Surface properties were analyzed using different techniques including atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and polarization modulation-infrared reflection-adsorption (PM-IRRAS). The standard calibration curve (R = 0.9830) was generated for the detection of the epitope, Ac-VHTWTEQYKFQ-NH₂, with a linear range of 0.2 to 30 μg/mL and detection limit of 0.073 μg/mL. A separate calibration curve (R = 0.9786) was obtained using spiked buffered solutions of dengue NS1 protein, which resulted in a linear range of 0.2 to 10 μg/mL and a detection limit of 0.056 μg/mL. The fabricated E-MIP sensor exhibited long-term stability, high sensitivity, and good selectivity towards the targeted molecules. These results indicated that the formation of the exact and stable cavity imprints in terms of size, shape, and functionalities was successful. In our future work, we aim to use our E-MIP sensors for NS1 detection in real-life samples such as serum and blood.

Dengue and Zika virus infection patterns vary among Aedes aegypti field populations from Belo Horizonte, a Brazilian endemic city

Dengue virus (DENV) and Zika virus (ZIKV) belong to the same viral family, the Flaviviridae. They cause recurring threats to the public health systems of tropical countries such as Brazil. The primary Brazilian vector of both viruses is the mosquito Aedes aegypti. After the mosquito ingests a blood meal from an infected person, the viruses infect and replicate in the midgut, disseminate to secondary tissues and reach the salivary gland (SG), where they are ready to be transmitted to a vertebrate host. It is thought that the intrinsic discrepancies among mosquitoes could affect their ability to deal with viral infections. This study confirms that the DENV and ZIKV infection patterns of nine Ae. aegypti field populations found in geographically separate health districts of an endemic Brazilian city vary. We analyzed the infection rate, disseminated infection, vector competence, and viral load through quantitative PCR. Mosquitoes were challenged using the membrane-feeding assay technique and were tested seven and fourteen days post-infection (early and late infection phases, respectively). The infection responses varied among the Ae. aegypti populations for both flaviviruses in the two infection phases. There was no similarity between DENV and ZIKV vector competencies or viral loads. According to the results of our study, the risk of viral transmission overtime after infection either increases or remains unaltered in ZIKV infected vectors. However, the risk may increase, decrease, or remain unaltered in DENV-infected vectors depending on the mosquito population. For both flaviviruses, the viral load persisted in the body even until the late infection phase. In contrast to DENV, the ZIKV accumulated in the SG over time in all the mosquito populations. These findings are novel and may help direct the development of control strategies to fight dengue and Zika outbreaks in endemic regions, and provide a warning about the importance of understanding mosquito responses to arboviral infections.

Dengue and Zika are neglected diseases caused by viruses transmitted to humans by mosquitoes (vector-borne diseases). The primary vector of both diseases is Aedes aegypti, a highly abundant mosquito in tropical countries and adapted to the urban habitat. The viral cycle in the vector starts when the mosquito bites an infected person and acquires the viruses through the blood meal. When the infected blood reaches the mosquito’s midgut, the viruses invade the epithelial cells and disseminate in several organs until they reach the salivary glands, enabling viral transmission to the next person. However, the mosquitoes have developed strategies to combat the viral invasion and dissemination in their body, making this journey a challenge to the viruses. Herein, we show that the mosquito responses against dengue and Zika viruses are distinct. In addition, mosquitoes from separate populations of the same city have different abilities to deal with the viruses in both cases, dengue and Zika infections. Our results show the diversity of responses that the mosquitoes may present to viral infections. These findings may better direct disease control strategies to combat dengue and Zika outbreaks in endemic regions.

Detecting dengue outbreaks in Malaysia using geospatial techniques

Dengue is a complex disease with an increasing number of infections worldwide. This study aimed to analyse spatiotemporal dengue outbreaks using geospatial techniques and examine the effects of the weather on dengue outbreaks in the Klang Valley area, Kuala Lumpur, Malaysia. Daily weather variables including rainfall, temperature (maximum and minimum) and wind speed were acquired together with the daily reported dengue cases data from 2001 to 2011 and converted into geospatial format to identify whether there was a specific pattern of the dengue outbreaks. The association between these variables and dengue outbreaks was assessed using Spearman's correlation. The result showed that dengue outbreaks consistently occurred in the study area during a 11-year study period. And that the strongest outbreaks frequently occurred in two high-rise apartment buildings located in Kuala Lumpur City centre. The results also show significant negative correlations between maximum temperature and minimum temperature on dengue outbreaks around the study area as well as in the area of the high-rise apartment buildings in Kuala Lumpur City centre.

Natural immunogenic properties of bioinformatically predicted linear B-cell epitopes of dengue envelope and pre-membrane proteins

Background

The natural antibody responses to B-cell epitopes from dengue structural proteins were assessed using immune sera from people having well-defined past dengue infections with one of the four serotypes.

Method

Based on an immune-computational analysis previously conducted, nineteen epitopes from the envelope (E) and eight epitopes from pre-membrane (prM), which were more than 50% conserved across all the four DENV serotypes, were selected. Peptides to represent these B-cell epitopes were obtained from commercially available arrays, and were subjected to enzyme linked immunosorbent assay with sera obtained from dengue seropositive healthy volunteers (DENV1 n = 12: DENV2 n = 12: DENV3 n = 12 and DENV4 n = 12), and 10 dengue seronegative healthy volunteers from Sri Lanka. The cut-off value for the positive antibody response was set by taking the mean response of a peptide to the negative sera plus three standard deviations. The peptides (N = 7) showing the broad immune responses were used to generate antibodies in three mice (Balb/c) batches. The mice antisera were then subjected to microneutralization assays against all the four DENV serotypes. An EC₅₀ viral neutralization ≥ 40 times the serum dilution was considered as neutralizing.

Results

Five of the E-peptide and two prM peptides were recognised by most individuls exposed to infections with each of the four serotypes, showing a serotype cross-reactive broad antibody response. The mice immune sera against the peptides representing the five E protein epitopes neutralized all the four DENV serotypes. Two of these five epitopes are from the Domain II, whereas one of them includes the whole bc-loop region.

Conclusion

The antibody responses of highly conserved epitopes across the serotypes, were broadly responsive with sera of all four DENV serotypes collected from individuals infected with only one DENV serotype. Weakly conserved epitopes showed rather specific antibody responses dominated by one or few serotypes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12865-021-00462-4.

Factors associated with severe dengue in Savannakhet Province, Lao People's Democratic Republic

This study aimed to describe the socio-demographic and clinical characteristics of dengue inpatients at a provincial hospital, and to identify factors associated with severe dengue. This is a retrospective study involving 402 dengue patients admitted to the Savannakhet Provincial Hospital, Lao People's Democratic Republic (Lao PDR), between January 2018 and April 2019. Socio-demographic factors, clinical signs and laboratory data on admission, final diagnosis, use of health care services before admission, admission date, and hospitalization period were collected from patient records. The number of dengue inpatients was higher in the rainy season than in the dry season. Of the 402 patients, 205 patients (51.0%) were finally diagnosed with severe dengue. Children aged <15 years had more symptoms, higher proportion of severe dengue (69.8% vs. 35.9%), and longer hospitalization (3.5 days vs. 3.0 days) than adults aged ≥15 years. In multivariable analyses, factors associated with severe dengue were nausea on admission (adjusted odds ratio=3.57, 95% CI=1.05-12.09, P=0.04) in children and persistent vomiting on admission (adjusted odds ratio=3.82, 95% CI=1.23-11.92, P=0.02) in adults. In adults, the creatinine level on admission was significantly higher in patients with a final diagnosis of severe dengue compared to the others. The proportion of severe dengue in our study was higher than that in other countries. Nausea and persistent vomiting on admission were suggested to be predictive factors for severe dengue. To reduce the incidence of severe dengue in Lao PDR, improvements in access to health care, referral system, and training of health care workers are needed.

Molecular epidemiology of dengue in a setting of low reported endemicity: Kupang, East Nusa Tenggara province, Indonesia

BACKGROUND

Most regions in Indonesia experience annual dengue epidemics. However, the province of East Nusa Tenggara has consistently reported low incidence. We conducted a dengue molecular epidemiology study in Kupang, the capital of the province.

METHODS

Dengue patients were recruited from May 2016 to September 2017. Dengue virus (DENV) screening was performed using NS1 and immunoglobulin G (IgG)/IgM detection. Serotype was determined using reverse transcription polymerase chain reaction and the envelope genes were sequenced to infer the genetic identity and phylogeny.

RESULTS

From 119 patients, dengue was confirmed in 62 (52%). Compared with official data, underreporting of dengue incidence was observed. The majority (36%) of patients were children <10 y of age. Most patients (80%) experienced mild fever. All serotypes were detected, with DENV-3 as the predominant (57%). Kupang DENV-1 isolate was classified as genotype IV, an old and endemic strain, DENV-2 as cosmopolitan, DENV-3 as genotype I and DENV-4 as genotype II. Most isolates showed relatively low evolutionary rates and are closely related with strains from Bali and Timor Leste.

CONCLUSIONS

The low dengue incidence was most likely caused by sustained local circulation of endemic viruses. This study provides information on the epidemiology of dengue in a low-endemicity setting that should help future mitigation and disease management.

Genotype-Dependent Immunogenicity of Dengue Virus Type 2 Asian I and Asian/American Genotypes in Common Marmoset (Callithrix jacchus): Discrepancy in Neutralizing and Infection-Enhancing Antibody Levels between Genotypes

Owing to genotype-specific neutralizing antibodies, analyzing differences in the immunogenic variation among dengue virus (DENV) genotypes is central to effective vaccine development. Herein, we characterized the viral kinetics and antibody response induced by DENV type 2 Asian I (AI) and Asian/American (AA) genotypes using marmosets (Callithrix jacchus) as models. Two groups of marmosets were inoculated with AI and AA genotypes, and serial plasma samples were collected. Viremia levels were determined using quantitative reverse transcription-PCR, plaque assays, and antigen enzyme-linked immunosorbent assay (ELISA). Anti-DENV immunoglobulin M and G antibodies, neutralizing antibody titer, and antibody-dependent enhancement (ADE) activity were determined using ELISA, plaque reduction neutralization test, and ADE assay, respectively. The AI genotype induced viremia for a longer duration, but the AA genotype induced higher levels of viremia. After four months, the neutralizing antibody titer induced by the AA genotype remained high, but that induced by the AI genotype waned. ADE activity toward Cosmopolitan genotypes was detected in marmosets inoculated with the AI genotype. These findings indicate discrepancies between heterologous genotypes that influence neutralizing antibodies and viremia in marmosets, a critical issue in vaccine development.

Current Trends and Limitations in Dengue Antiviral Research

Dengue is the most prevalent arthropod-borne viral disease worldwide and affects approximately 2.5 billion people living in over 100 countries. Increasing geographic expansion of Aedes aegypti mosquitoes (which transmit the virus) has made dengue a global health concern. There are currently no approved antivirals available to treat dengue, and the only approved vaccine used in some countries is limited to seropositive patients. Treatment of dengue, therefore, remains largely supportive to date; hence, research efforts are being intensified for the development of antivirals. The nonstructural proteins, 3 and 5 (NS3 and NS5), have been the major targets for dengue antiviral development due to their indispensable enzymatic and biological functions in the viral replication process. NS5 is the largest and most conserved nonstructural protein encoded by flaviviruses. Its multifunctionality makes it an attractive target for antiviral development, but research efforts have, this far, not resulted in the successful development of an antiviral targeting NS5. Increase in structural insights into the dengue NS5 protein will accelerate drug discovery efforts focused on NS5 as an antiviral target. In this review, we will give an overview of the current state of therapeutic development, with a focus on NS5 as a therapeutic target against dengue.

Molecular Characterization of Imported and Autochthonous Dengue in Northeastern Spain

Dengue is the most significant arbovirus worldwide and a public health threat to non-endemic areas in which Aedes vectors are present. Autochthonous dengue transmission has been reported in several European countries in the last decade. Infected travelers from endemic regions arriving to areas colonized by Aedes albopictus in Europe need to be monitored in surveillance and control programs. We aimed to perform molecular characterization of RT-PCR-positive dengue cases detected in Catalonia, northeastern Spain, from 2013 to 2018. The basic demographic information and the geographical regions of importation were also analyzed. One-hundred four dengue cases were studied (103 imported infections and the first autochthonous case in our region). The dengue virus strains detected were serotyped and genotyped using molecular methods, and phylogenetic analyses were conducted. All four dengue serotypes were detected in travelers, including up to 10 different genotypes, reflecting the global circulation of dengue in endemic areas. The primary travel-related case of the 2018 autochthonous transmission was not identified, but the molecular analysis revealed dengue serotype 1, genotype I of Asian origin. Our results highlight the diversity of imported dengue virus strains and the role of molecular epidemiology in supporting arbovirus surveillance programs.

DNA-Modified Plasmonic Sensor for the Direct Detection of Virus Biomarkers from the Blood

The rapid spread of viral infections demands early detection strategies to minimize proliferation of the disease. Here, we demonstrate a plasmonic biosensor to detect Dengue virus, which was chosen as a model, via its nonstructural protein NS1 biomarker. The sensor is functionalized with a synthetic single-stranded DNA oligonucleotide and provides high affinity toward NS1 protein present in the virus genome. We demonstrate the detection of NS1 protein at a concentration of 0.1-10 μg/mL in bovine blood using an on-chip microfluidic plasma separator integrated with the plasmonic sensor which covers the clinical threshold of 0.6 μg/mL of high risk of developing Dengue hemorrhagic fever. The conceptual and practical demonstration shows the translation feasibility of these microfluidic optical biosensors for early detection of a wide range of viral infections, providing a rapid clinical diagnosis of infectious diseases directly from minimally processed biological samples at point of care locations.

Modeling Dengue Immune Responses Mediated by Antibodies: A Qualitative Study

Simple Summary

With more than one-third of the world population at risk of acquiring the disease, dengue fever is a major public health problem. Caused by four antigenically distinct but related serotypes, disease severity is associated with the immunological status of the individual, seronegative or seropositive, prior to a natural dengue infection. While a primary natural dengue infection is often asymptomatic or mild, individuals experiencing a secondary dengue infection with a heterologous serotype have higher risk of developing the severe form of the disease, linked to the antibody-dependent enhancement (ADE) process. We develop a modeling framework to describe the dengue immune responses mediated by antibodies. Our model framework can describe qualitatively the dynamic of the viral load and antibodies production for scenarios of primary and secondary infections, as found in the empirical immunology literature. Studies such as the one described here serve as a baseline to further model extensions. Future refinements of our framework will be of use to evaluate the impact of imperfect dengue vaccines.

Abstract

Dengue fever is a viral mosquito-borne infection and a major international public health concern. With 2.5 billion people at risk of acquiring the infection around the world, disease severity is influenced by the immunological status of the individual, seronegative or seropositive, prior to natural infection. Caused by four antigenically related but distinct serotypes, DENV-1 to DENV-4, infection by one serotype confers life-long immunity to that serotype and a period of temporary cross-immunity (TCI) to other serotypes. The clinical response on exposure to a second serotype is complex with the so-called antibody-dependent enhancement (ADE) process, a disease augmentation phenomenon when pre-existing antibodies to previous dengue infection do not neutralize but rather enhance the new infection, used to explain the etiology of severe disease. In this paper, we present a minimalistic mathematical model framework developed to describe qualitatively the dengue immunological response mediated by antibodies. Three models are analyzed and compared: (i) primary dengue infection, (ii) secondary dengue infection with the same (homologous) dengue virus and (iii) secondary dengue infection with a different (heterologous) dengue virus. We explore the features of viral replication, antibody production and infection clearance over time. The model is developed based on body cells and free virus interactions resulting in infected cells activating antibody production. Our mathematical results are qualitatively similar to the ones described in the empiric immunology literature, providing insights into the immunopathogenesis of severe disease. Results presented here are of use for future research directions to evaluate the impact of dengue vaccines.

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.