DENVirDB is a web portal that provides the sequence information and computationally curated information of dengue viral proteins. The advent of genomic technology has increased the sequences available in the public databases. In order to create relevant concise information on Dengue Virus (DENV), the genomic sequences were collected, analysed with the bioinformatics tools and presented as DENVirDB. It provides the comprehensive information of complete genome sequences of dengue virus isolates of Southeast Asia, viz. India, Bangladesh, Sri Lanka, East Timor, Philippines, Malaysia, Papua New Guinea, Brunei and China. DENVirDB also includes the structural and non-structural protein sequences of DENV. It intends to provide the integrated information on the physicochemical properties, topology, secondary structure, domain and structural properties for each protein sequences. It contains over 99 entries in complete genome sequences and 990 entries in protein sequences, respectively. Therefore, DENVirDB could serve as a user friendly database for researchers in acquiring sequences and proteomic information in one platform.
Dengue virus type 3 genotype III (DENV-3/III) is widely distributed in most dengue-endemic regions. It emerged in Malaysia in 2008 and autochthonously spread in the midst of endemic DENV-3/I circulation. The spread, however, was limited and the virus did not cause any major outbreak. Spatiotemporal distribution study of DENV-3 over the period between 2005 and 2011 revealed that dengue cases involving DENV-3/III occurred mostly in areas without pre-existing circulating DENV-3. Neutralisation assays performed using sera of patients with the respective infection showed that the DENV-3/III viruses can be effectively neutralised by sera of patients with DENV-3 infection (50% foci reduction neutralisation titres (FRNT50) > 1300). Sera of patients with DENV-1 infection (FRNT50 ⩾ 190), but not sera of patients with DENV-2 infection (FRNT50 ⩽ 50), were also able to neutralise the virus. These findings highlight the possibility that the pre-existing homotypic DENV-3 and the cross-reacting heterotypic DENV-1 antibody responses could play a role in mitigating a major outbreak involving DENV-3/III in the Klang Valley, Malaysia.
Objective: To confirm the laboratory diagnosis of dengue bordline cases reported in Henan Province and trace its origin from molecular level in 2017. Methods: The study samples were blood samples (3-5 ml), which came from 8 suspected cases of dengue fever reported in the 2017 direct reporting system of Henan provincial infectious disease monitoring network. Meanwhile, case investigation was conducted according to National dengue fever surveillance programme. Serum were separated from blood samples and tested for Dengue NS1 antigen, IgM & IgG antibodies, and dengue RNA. According to dengue diagnosis criteria, confirmed cases were identified by testing results. Samples carried dengue RNA performed for real-time PCR genotyping and amplification of E gene. Then, the amplicons were sequenced and homological and phylogenetic analyses were constructed. Results: 8 serum samples of suspected dengue cases were collected in Henan Province, 2017. Six of them were diagnosed as dengue confirmed cases. All the dengue confirmed cases belonged to outside imported cases, 5 of them were positive by dengue RNA testing. Genotyping results showed there were 1 DENV1 case, 2 DENV2 cases and 2 DENV3 cases. A DENV2 case and a DENV3 case of this study were traced its origin successfully. The sequence of Pakistan imported DENV2 case belongs to cosmopolitan genotype, which was the most consistent with Pakistan's DENV2 KJ010186 in 2013 (identity 99.0%). The sequence of Malaysia imported DENV3 case belongs to genotype I, which was the most consistent with Singapore's DENV3 KX224276 in 2014(identity 99.0%). Conclusion: The laboratory diagnosis and molecular traceability of dengue cases in Henan Province in 2017 confirmed that all cases were imported and did not cause local epidemics.
Ancestral sylvatic dengue virus type 1, which was isolated from a monkey in 1972, was isolated from a patient with dengue fever in Malaysia. The virus is neutralized by serum of patients with endemic DENV-1 infection. Rare isolation of this virus suggests a limited spillover infection from an otherwise restricted sylvatic cycle.
Alteration in the endothelium leading to increased vascular permeability contributes to plasma leakage seen in dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). An earlier study showed that senescent endothelial cells (ECs) altered the ECs permeability. Here we investigated the susceptibility of senescing human umbilical vein endothelial cells (HUVECs) to dengue virus infection and determined if dengue virus infection induces HUVECs senescence. Our results suggest that DENV type-2 (DENV-2) foci forming unit (FFU) and extracellular virus RNA copy number were reduced by at least 35% and 85% in infection of the intermediate young and early senescent HUVECs, respectively, in comparison to infection of young HUVECs. No to low infectivity was recovered from infection of late senescent HUVECs. DENV infection also increases the percentage of HUVECs expressing senescence-associated (SA)-β-gal, cells arrested at the G2/M phase or 4N DNA content stage and cells with enlarged morphology, indicative of senescing cells. Alteration of HUVECs morphology was recorded using impedance-based real-time cell analysis system following DENV-2 infection. These results suggest that senescing HUVECs do not support DENV infection and DENV infection induces HUVECs senescence. The finding highlights the possible role of induction of senescence in DENV infection of the endothelial cells.
BACKGROUND: Early and rapid detection of dengue virus (DENV) infection during the febrile period is crucial for proper patient management and prevention of disease spread. An easy to perform and highly sensitive method is needed for routine implementation especially in the resource-limited rural healthcare settings where dengue is endemic.
METHODS: A single-tube reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assay with a set of nine primers was developed for the detection of all four DENV serotypes and their different genotypes. The sensitivity and specificity of the RT-LAMP were evaluated. The clinical applicability of RT-LAMP assay for detection of DENV RNA was assessed in a total of 305 sera of clinically-suspected dengue patients. The test results of RT-LAMP were statistically compared to those of quantitative reverse transcription-polymerase chain reaction (qRT-PCR), IgM- and IgG-capture enzyme-linked immunosorbent assays (ELISA).
RESULTS: Acute DENV infection was confirmed in 171 samples (n = 305); 43.3% (74/171) and 46.8% (80/171) of the samples were positive for DENV using RT-LAMP and qRT-PCR, respectively. The combination of RT-LAMP with the dengue IgM and IgG ELISA increased detection of acute DENV infection to 97.7% (167/171), in comparison to only 70.8% (121/171) when dengue IgM and IgG ELISA alone were used. The RT-LAMP assays showed high concordance (κ = 0.939) with the qRT-PCR. The RT-LAMP assay detected up to 10 copies of virus RNA within an hour but 100% reproducibility (12/12) was achieved with 100 copies. There was no cross reactivity of RT-LAMP with other closely related arboviruses.
CONCLUSION: The RT-LAMP assay developed in this study is sensitive, specific and simple to perform. The assay improved the detection of dengue when used in combination with serological methods.
This study investigates the effects of 2-phenyl-1-benzopyran-4-one (flavone) on DENV-2 infectivity in Vero cells. Virus adsorption and attachment and intracellular virus replication were investigated using a foci forming unit assay (FFUA) and quantitative RT-PCR, respectively. Addition of flavone (100 μg/mL) significantly increased the number of DENV-2 foci by 35.66% ± 1.52 and 49.66% ± 2.51 when added during and after virus adsorption to the Vero cells, respectively. The average foci size after 4 days of infection increased by 33% ± 2.11 and 89% ± 2.13. The DENV-2 specific RNA copy number in the flavone-treated infected cells increased by 6.41- and 23.1-fold when compared to the mock-treated infected cells. Flavone (100 μg/mL) did not promote or inhibit Vero cell proliferation. The CC₅₀ value of flavone against Vero cells was 446 µg/mL. These results suggest that flavone might enhance dengue virus replication by acting antagonistically towards flavonoids known to inhibit dengue virus replication.
Dengue viruses are mosquito-borne viruses that cause dengue fever and dengue hemorrhagic fever, both of which are globally important diseases. These viruses have evolved in a transmission cycle between human hosts and mosquito vectors in various tropical and subtropical environments. We previously isolated three strains of dengue type 1 virus (DENV1) and 14 strains of dengue type 3 virus (DENV3) during an outbreak of dengue fever and dengue hemorrhagic fever in Jakarta, Indonesia in 1988. Here, we compared the nucleotide sequences of the entire envelope protein-coding region among these strains. The isolates were 97.6-100% identical for DENV1 and 98.8-100% identical for DENV3. All DENV1 isolates were included in two different clades of genotype IV and all DENV3 isolates were included in a single clade of genotype I. For DENV1, three Yap Island strains isolated in 2004 were the only strains closely related to the present isolates; the recently circulated Indonesian strains were in different clades. Molecular clock analyses estimated that ancestors of the genotype IV strains of DENV1 have been indigenous in Indonesia since 1948. We predict that they diverged frequently around 1967 and that their offspring distributed to Southeast Asia, the Western Pacific, and Africa. For DENV3, the clade containing all the present isolates also contained strains isolated from other Indonesian regions and other countries including Malaysia, Singapore, China, and East Timor from 1985-2010. Molecular clock analyses estimated that the common ancestor of the genotype I strains of DENV3 emerged in Indonesia around 1967 and diverged frequently until 1980, and that their offspring distributed mainly in Southeast Asia. The first dengue outbreak in 1968 and subsequent outbreaks in Indonesia might have influenced the divergence and distribution of the DENV1 genotype IV strains and the DENV3 genotype I strains in many countries.
Dengue virus type 4 (DENV-4) circulates in tropical and subtropical countries from Asia and the Americas. Despite the importance of dengue virus distribution, little is known about the worldwide viral spread. Following a Bayesian phylogenetic approach we inferred the evolutionary history of 310 isolates sampled from 37 countries during the time period 1956-2008 and the spreading dynamics for genotypes I and II. The region (tropical rainforest biome) comprised by Malaysia-Thailand was the most likely ancestral area from which the serotype has originated and spread. Interestingly, cross-correlation analysis on demographic time series with the Asian sequences showed a statistically significant negative correlation that could be suggestive of competition among genotypes within the same serotype.
To isolate and identify the pathogen of Dengue fever from Shenzhen city in 2005 - 2006, and to analyze the molecular characteristics of the isolated Dengue virus strain as well as to explore its possible origin.
In this study, artificial membrane feeding technique was used to orally feed Aedes aegypti with dengue and chikungunya viruses. Virus detection was carried out by reverse transcriptase polymerase chain reaction. The study did not detect dual infection of Ae. aegypti with dengue and chikungunya virus from the same pool or from individual mosquitoes. Oral receptivity of Ae. aegypti to chikungunya virus was higher than that of dengue virus.
Indonesia is one of the biggest dengue endemic countries, and, thus, is an important place to investigate the evolution of dengue virus (DENV). We have continuously isolated DENV in Surabaya, the second biggest city in Indonesia, since 2008. We previously reported sequential changes in the predominant serotype from DENV type 2 (DENV-2) to DENV type 1 (DENV-1) in November 2008 and from DENV-1 to DENV-2 in July 2013. The predominance of DENV-2 continued in 2014, but not in 2015. We herein phylogenetically investigated DENV-2 transitions in Surabaya between 2008 and 2014 to analyze the divergence and evolution of DENV-2 concomitant with serotype shifts. All DENV-2 isolated in Surabaya were classified into the Cosmopolitan genotype, and further divided into 6 clusters. Clusters 1-3, dominated by Surabaya strains, were defined as the "Surabaya lineage". Clusters 4-6, dominated by strains from Singapore, Malaysia, and many parts of Indonesia, were the "South East Asian lineage". The most recent common ancestor of these strains existed in 1988, coinciding with the time that an Indonesian dengue outbreak took place. Cluster 1 appeared to be unique because no other DENV-2 isolate was included in this cluster. The predominance of DENV-2 in 2008 and 2013-14 were caused by cluster 1, whereas clusters 2 and 3 sporadically emerged in 2011 and 2012. The characteristic amino acids of cluster 1, E-170V and E-282Y, may be responsible for its prevalence in Surabaya. No amino acid difference was observed in the envelope region between strains in 2008 and 2013-14, suggesting that the re-emergence of DENV-2 in Surabaya was due to the loss or decrease of herd immunity in the 5-year period when DENV-2 subsided. The South East Asian lineage primarily emerged in Surabaya in 2014, probably imported from other parts of Indonesia or foreign countries.
We present the results of a laboratory-based surveillance of dengue in Taiwan in 2014. A total of 240 imported dengue cases were identified. The patients had arrived from 16 countries, and Malaysia, Indonesia, the Philippines, and China were the most frequent importing countries. Phylogenetic analyses showed that genotype I of dengue virus type 1 (DENV-1) and the cosmopolitan genotype of DENV-2 were the predominant DENV strains circulating in southeast Asia. The 2014 dengue epidemic was the largest ever to occur in Taiwan since World War II, and there were 15,492 laboratory-confirmed indigenous dengue cases. Phylogenetic analysis showed that the explosive dengue epidemic in southern Taiwan was caused by a DENV-1 strain of genotype I imported from Indonesia. There were several possible causes of this outbreak, including delayed notification of the outbreak, limited staff and resources for control measures, abnormal weather conditions, and a serious gas pipeline explosion in the dengue hot spot areas in Kaohsiung City. However, the results of this surveillance indicated that both active and passive surveillance systems should be strengthened so appropriate public health measures can be taken promptly to prevent large-scale dengue outbreaks.
Centrifugal microfluidic systems utilize a conventional spindle motor to automate parallel biochemical assays on a single microfluidic disk. The integration of complex, sequential microfluidic procedures on these platforms relies on robust valving techniques that allow for the precise control and manipulation of fluid flow. The ability of valves to consistently return to their former conditions after each actuation plays a significant role in the real-time manipulation of fluidic operations. In this paper, we introduce an active valving technique that operates based on the deflection of a latex film with the potential for real-time flow manipulation in a wide range of operational spinning speeds. The reversible thermo-pneumatic valve (RTPV) seals or reopens an inlet when a trapped air volume is heated or cooled, respectively. The RTPV is a gas-impermeable valve composed of an air chamber enclosed by a latex membrane and a specially designed liquid transition chamber that enables the efficient usage of the applied thermal energy. Inputting thermo-pneumatic (TP) energy into the air chamber deflects the membrane into the liquid transition chamber against an inlet, sealing it and thus preventing fluid flow. From this point, a centrifugal pressure higher than the induced TP pressure in the air chamber reopens the fluid pathway. The behaviour of this newly introduced reversible valving system on a microfluidic disk is studied experimentally and theoretically over a range of rotational frequencies from 700 RPM to 2500 RPM. Furthermore, adding a physical component (e.g., a hemispherical rubber element) to induce initial flow resistance shifts the operational range of rotational frequencies of the RTPV to more than 6000 RPM. An analytical solution for the cooling of a heated RTPV on a spinning disk is also presented, which highlights the need for the future development of time-programmable RTPVs. Moreover, the reversibility and gas impermeability of the RTPV in the microfluidic networks are validated on a microfluidic disk designed for performing liquid circulation. Finally, an array of RTPVs is integrated into a microfluidic cartridge to enable sequential aliquoting for the conversion of dengue virus RNA to cDNA and the preparation of PCR reaction mixtures.
Endemic/epidemic dengue viruses (DEN) that are transmitted among humans by the mosquito vectors Aedes aegypti and Aedes albopictus are hypothesized to have evolved from sylvatic DEN strains that are transmitted among nonhuman primates in West Africa and Malaysia by other Aedes mosquitoes. We tested this hypothesis with phylogenetic studies using envelope protein gene sequences of both endemic/epidemic and sylvatic strains. The basal position of sylvatic lineages of DEN-1, -2, and -4 suggested that the endemic/epidemic lineages of these three DEN serotypes evolved independently from sylvatic progenitors. Time estimates for evolution of the endemic/epidemic forms ranged from 100 to 1,500 years ago, and the evolution of endemic/epidemic forms represents relatively recent events in the history of DEN evolution. Analysis of envelope protein amino acid changes predicted to have accompanied endemic/epidemic emergence suggested a role for domain III in adaptation to new mosquito and/or human hosts.
The nucleic acid sequences of the pre-membrane/membrane and envelope protein genes of 23 geographically and temporally distinct dengue (DEN)-3 viruses were determined. This was accomplished by reverse transcriptase-PCR amplification of the structural genes followed by automated DNA sequence analysis. Comparison of nucleic acid sequences revealed that similarity among the viruses was greater than 90%. The similarity among deduced amino acids was between 95% and 100%, and in many cases identical amino acid substitutions occurred among viruses from similar geographical regions. Alignment of nucleic acid sequences followed by parsimony analysis allowed the generation of phylogenetic trees, demonstrating that geographically independent evolution of DEN-3 viruses had occurred. The DEN-3 viruses were separated into four genetically distinct subtypes. Subtype I consists of viruses from Indonesia, Malaysia, the Philippines and the South Pacific islands; subtype II consists of viruses from Thailand; subtype III consists of viruses from Sri Lanka, India, Africa and Samoa; subtype IV consists of viruses from Puerto Rico and the 1965 Tahiti virus. Phylogenetic analysis has also contributed to our understanding of the molecular epidemiology and worldwide distribution of DEN-3 viruses.