Genetic Adaptation by Dengue Virus Serotype 2 to Enhance Infection of Aedes aegypti Mosquito Midguts

Dengue virus surveillance in Nepal yields the first on-site whole genome sequences of isolates from the 2022 outbreak

BACKGROUND

The 4 serotypes of dengue virus (DENV1-4) can each cause potentially deadly dengue disease, and are spreading globally from tropical and subtropical areas to more temperate ones. Nepal provides a microcosm of this global phenomenon, having met each of these grim benchmarks. To better understand DENV transmission dynamics and spread into new areas, we chose to study dengue in Nepal and, in so doing, to build the onsite infrastructure needed to manage future, larger studies.

METHODS AND RESULTS

During the 2022 dengue season, we enrolled 384 patients presenting at a hospital in Kathmandu with dengue-like symptoms; 79% of the study participants had active or recent DENV infection (NS1 antigen and IgM). To identify circulating serotypes, we screened serum from 50 of the NS1+ participants by RT-PCR and identified DENV1, 2, and 3 - with DENV1 and 3 codominant. We also performed whole-genome sequencing of DENV, for the first time in Nepal, using our new on-site capacity. Sequencing analysis demonstrated the DENV1 and 3 genomes clustered with sequences reported from India in 2019, and the DENV2 genome clustered with a sequence reported from China in 2018.

CONCLUSION

These findings highlight DENV's geographic expansion from neighboring countries, identify China and India as the likely origin of the 2022 DENV cases in Nepal, and demonstrate the feasibility of building onsite capacity for more rapid genomic surveillance of circulating DENV. These ongoing efforts promise to protect populations in Nepal and beyond by informing the development and deployment of DENV drugs and vaccines in real time.

Evolutionary patterns and heterogeneity of dengue virus serotypes in Pakistan

A comprehensive and systematic examination of dengue virus (DENV) evolution is essential in Pakistan, where the virus poses a significant public health challenge due to its ability to adapt and evolve. To shed light on the intricate evolutionary patterns of all four DENV serotypes, we analyzed complete genome sequences (n = 43) and Envelope (E) gene sequences (n = 44) of all four DENV serotypes collected in Pakistan from 1994 to 2023, providing a holistic view of their genetic evolution. Our findings revealed that all four serotypes of DENV co-circulate in Pakistan with a close evolutionary relationship between DENV-1 and DENV-3. Among the genetically distinct serotypes DENV-2 and DENV-4, DENV-4 stands out as the most genetically different, while DENV-2 exhibits greater complexity due to the presence of multiple genotypes and the possibility of temporal fluctuations in genotype prevalence. Selective pressure analysis of the Envelope (E) gene revealed heterogeneity among sequences (n = 44), highlighting 46 codons in the genome experiencing selective pressure, characterized by a bias toward balancing selection, indicating genetic stability of the virus. Furthermore, our study suggested an intriguing evolutionary shift of DENV-4 toward the DENV-2 clade, potentially influenced by antibodies with cross-reactivity to multiple serotypes, providing a critical insight into the complex factors, shaping DENV evolution and contributing to the emergence of new serotypes.

Dengue Virus Surveillance in Nepal Yields the First On-Site Whole Genome Sequences of Isolates from the 2022 Outbreak

Background

The 4 serotypes of dengue virus (DENV1-4) can each cause potentially deadly dengue disease, and are spreading globally from tropical and subtropical areas to more temperate ones. Nepal provides a microcosm of this global phenomenon, having met each of these grim benchmarks. To better understand DENV transmission dynamics and spread into new areas, we chose to study dengue in Nepal and, in so doing, to build the onsite infrastructure needed to manage future, larger studies.

Methods and Results

During the 2022 dengue season, we enrolled 384 patients presenting at a hospital in Kathmandu with dengue-like symptoms; 79% of the study participants had active or recent DENV infection (NS1 antigen and IgM). To identify circulating serotypes, we screened serum from 50 of the NS1 + participants by RT-PCR and identified DENV1, 2, and 3 - with DENV1 and 3 codominant. We also performed whole-genome sequencing of DENV, for the first time in Nepal, using our new on-site capacity. Sequencing analysis demonstrated the DENV1 and 3 genomes clustered with sequences reported from India in 2019, and the DENV2 genome clustered with a sequence reported from China in 2018.

Conclusion

These findings highlight DENV's geographic expansion from neighboring countries, identify China and India as the likely origin of the 2022 DENV cases in Nepal, and demonstrate the feasibility of building onsite capacity for more rapid genomic surveillance of circulating DENV. These ongoing efforts promise to protect populations in Nepal and beyond by informing the development and deployment of DENV drugs and vaccines in real time.

A perspective on the worst ever dengue outbreak 2023 in Bangladesh: What makes this old enemy so deadly, and how can we combat it?

Background and Aims

Bangladesh has been going through outbreaks of dengue fever cases every year since 2000. Yet this year's (2023) episode of dengue fever has crossed every line concerning fatality. Symptoms of the fever range from high fever, headaches, and muscle aches to deadly dengue hemorrhagic fever (DHF). The present review aims to assess the current pathogenicity and associated risk factors of recent dengue outbreaks in Bangladesh.

Methods

To perform this review work, we extracted relevant information from published articles available in PubMed, Scopus, and Google Scholar. We used dengue virus, dengue fever, and dengue outbreaks as keywords while searching for information.

Results

This Aedes mosquito-transmitted viral fever is more common in Bangladesh because of the tropical nature and immense burden of populations, resulting in convenient conditions for the reproduction of the vector. The rapid genetic transformation of this RNA virus and the resistance of its vector against insecticides have intensified the situation. The number of hospitalized patients has increased, and the case fatality rate has risen to 0.47%. Inadequate mosquito control measures, plenty of vector breeding sites, and a lack of public awareness have worsened the situation. Routine spraying of effective insecticides in high-risk zones, regular inspection of potential mosquito breeding sites, and public awareness campaigns are the keys to limiting the spread of this virus. Also, the availability of detection kits, improved hospital settings, and trained health professionals are mandatory to keep disease fatalities under control.

Conclusion

Dengue fever is a preventable disease. The successful development of a competent vaccine is now a prime need for preventing any future upsurge of the disease. Also, we recommend public awareness, vector control activities, and global collaboration to prevent spread.

Mosquito E-20-Monooxygenase Gene Knockout Increases Dengue Virus Replication in Aedes aegypti Cells

E-20-monooxygenase (E20MO) is an enzymatic product of the shade (shd) locus (cytochrome p450, E20MO). Initially discovered in Drosophila, E20MO facilitates the conversion of ecdysone (E) into 20-hydroxyecdysone (20E) and is crucial for oogenesis. Prior research has implicated 20E in growth, development, and insecticide resistance. However, little attention has been given to the association between the E20MO gene and DENV2 infection. The transcriptome of Ae. aegypti cells (Aag2 cells) infected with DENV2 revealed the presence of the E20MO gene. The subsequent quantification of E20MO gene expression levels in Aag2 cells post-DENV infection was carried out. A CRISPR/Cas9 system was utilized to create an E20MO gene knockout cell line (KO), which was then subjected to DENV infection. Analyses of DENV2 copies in KO and wild-type (WT) cells were conducted at different days post-infection (dpi). Plasmids containing E20MO were constructed and transfected into KO cells, with pre- and post-transfection viral copy comparisons. Gene expression levels of E20MO increased after DENV infection. Subsequently, a successful generation of an E20MO gene knockout cell line and the verification of code-shifting mutations at both DNA and RNA levels were achieved. Furthermore, significantly elevated DENV2 RNA copies were observed in the mid-infection phase for the KO cell line. Viral RNA copies were lower in cells transfected with plasmids containing E20MO, compared to KO cells. Through knockout and plasmid complementation experiments in Aag2 cells, the role of E20MO in controlling DENV2 replication was demonstrated. These findings contribute to our understanding of the intricate biological interactions between mosquitoes and arboviruses.

Role of endoplasmic reticulum stress-related unfolded protein response and its implications in dengue virus infection for biomarker development

Dengue virus (DENV) causes debilitating disease in humans, which varies at different rates in host cells, such as monocytes, macrophages, dendritic cells, Langerhans cells, and other cell types. Such heterogeneity in DENV infection in cells could be attributed to a range of factors, including host cell immune response, anti-viral cellular proteins, and virus mediated cellular autophagy. This review delineates an important feature of every cell, the unfolded protein response (UPR) that is attributed to the accumulation of several viral and unfolded/misfolded proteins, such as in DENV infection. UPR is a normal process to counteract endoplasmic reticulum (ER) stress that leads to cell autophagy; though the phenomenon is markedly upregulated during DENV infection. This could be attributed to the uncontrolled activation of the key UPR signaling pathways: inositol-requiring transmembrane kinase/endoribonuclease 1 (IRE1), protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), and activating transcription factor-6 (ATF6), which promote cell autophagy under normal and diseased conditions through the downstream regulation of apoptosis promoting factors such as X-box binding protein (XBP1), GADD34, and ATF-6. Because DENV can modulate these signaling cascades, by promoting dysregulated cell autophagy, the ER stress mediated UPR pathways and the inherent agents could play an important role in delineating the severity of dengue infection with a potential for developing DENV targeted therapeutics.