Project description:The mosquito Aedes aegypti serves as the primary vector for dengue virus (DENV), a human pathogen responsible for infecting hundreds of millions of people globally each year. Natural populations of Ae. aegypti show significant variability in their ability to become infected with DENV, which is largely governed by mosquito genetic factors. Previous studies suggest that genes encoding digestive enzymes, such as trypsins, and canonical antiviral immune genes may contribute to this variation 5-10. However, the specific causal gene variants underlying DENV susceptibility in Ae. aegypti are unknown. Here, we identify a gene encoding a cytochrome P450 (CYP4G15) whose genetic variants drive differences in DENV susceptibility in a natural Ae. aegypti population. CYP4G15 is transiently overexpressed in the midguts of DENV-resistant mosquitoes early in infection. Knockdown of CYP4G15 expression increases DENV susceptibility, while transgenic overexpression enhances resistance. A naturally occurring CYP4G15 variant with an 18-base-pair deletion in its promoter shows reduced expression and confers higher DENV susceptibility. The identification of CYP4G15 as a factor underlying DENV susceptibility in Ae. aegypti is unexpected because cytochrome P450 enzymes are typically associated with metabolism. Our finding challenges the long-standing focus on canonical immune pathways and opens new avenues for understanding antiviral defense and DENV transmission in mosquitoes.
Project description:Dengue viruses (DENV) are generally maintained in a cycle which requires horizontal transmission via their arthropod vector, Ae. Aegypti, to the vertebrate host. One important consequence of this process is the interference of these arboviruses with both invertebrate and vertebrate immune systems. While infection of vertebrates causes disease, the presence of DENV gives rise to life-long, persistent infection in mosquitoes. The results of a comparative transcriptome analysis between DENV-infected and uninfected salivary glands revealed activation of both the immune deficiency (IMD) and the Toll pathways, as well as involvement of the putative antibacterial cecropin-like peptide (AAEL000598), in controlling DENV infection in Ae. aegypti. The mature form of this peptide was found to be active against DENV and Chikungunya viruses, whereas its precursor also had a strong anti-Leishmania effect. This study is the first to establish a comparative transcriptome analysis of DENV-infected and uninfected salivary glands and demonstrates that certain DENV-induced peptides, that are part of the IMD pathway, possess broad-spectrum anti-pathogenic activity and may have therapeutic potential in human. Infectious blood meals were offered to 3-day-old, adult, female Ae. aegypti Liverpool mosquitoes using a silicone membrane feeder system (Alto et al., 2005). Human blood was combined with DENV-2 16681 to provide a blood meal titer of 5.106 plaque forming units (PFU)/ml. At different time-points after the blood meal, salivary glands were dissected in acid guanidium thiocyanate-phenol-chloroform (RNAble; Eurobio, France) or phosphate-buffered saline (PBS), and the samples were frozen at -70°C until use.
Project description:Dengue viruses (DENV) are generally maintained in a cycle which requires horizontal transmission via their arthropod vector, Ae. Aegypti, to the vertebrate host. One important consequence of this process is the interference of these arboviruses with both invertebrate and vertebrate immune systems. While infection of vertebrates causes disease, the presence of DENV gives rise to life-long, persistent infection in mosquitoes. The results of a comparative transcriptome analysis between DENV-infected and uninfected salivary glands revealed activation of both the immune deficiency (IMD) and the Toll pathways, as well as involvement of the putative antibacterial cecropin-like peptide (AAEL000598), in controlling DENV infection in Ae. aegypti. The mature form of this peptide was found to be active against DENV and Chikungunya viruses, whereas its precursor also had a strong anti-Leishmania effect. This study is the first to establish a comparative transcriptome analysis of DENV-infected and uninfected salivary glands and demonstrates that certain DENV-induced peptides, that are part of the IMD pathway, possess broad-spectrum anti-pathogenic activity and may have therapeutic potential in human.
Project description:We have generated transgenic Ae. aegypti that express a ZIKV-specific inverted repeat RNA intended to trigger the mosquito siRNA anti-viral immune pathway. To confirm that the transgene is expressed and processed, we performed small RNA sequencing on both Higgs White Eye (HWE) & anti-NS3/4A-ZIKV transgenic Ae. aegypti 24 hours post-bloodmeal
Project description:Vector-borne diseases are closely linked to the environment by the ecology of the vectors and their hosts. Elucidating these causal relationships is one of the most pressing challenges faced by researchers and public health scientists as increasing anthropogenic alternations in the environment can drive shifts in vector-borne disease dynamics. However, as one of the major environmental stressors, the impact of sublethal exposure of insecticides on vector behavior remains poorly investigated. Here, we analyzed how sublethal exposure of the promising vector-control bioinsecticide spinetoram on Aedes aegypti larvae, the latest generation of the spinosyns that have been suggested as a promising new bioinsecticide for vector control, at the larval stage of Ae. aegypti alters adult performance and susceptibility to dengue virus (DENV) infection. While spinetoram sublethal exposure leads to extended immature development time, these survivors were significantly smaller and exhibited weaker blood-feeding capacity than normal females. More importantly, surviving females presented higher DENV susceptibility than the control group after spinetoram sublethal exposure on larvae. Mechanistically, the transcriptomic analysis showed that inhibition of oxidative phosphorylation (OXPHOS) may function in stimulating DENV production in adult Ae. aegypti. In vitro study revealed that spinetoram induces apoptosis via mitochondrial reactive oxygen species (mtROS)-regulated OXPHOS dysregulation in Aag2 cells, and thereby may stimulate DENV production through the metabolic switch between OXPHOS and glycolysis. Altogether, our data demonstrate that sublethal spinetoram exposure could act as a crucial factor on life traits and vector competence in Ae. aegypti. Given that other insecticides are known to induce mitochondrial dysfunction in mosquito vectors, this research may have wider implications.
Project description:Arthropod-borne viruses (arboviruses) such as dengue virus (DENV) and Zika virus (ZIKV) pose a significant threat to global health. Novel approaches to control arbovirus spread are focused on harnessing the antiviral immune system of their main vector, the Aedes aegypti mosquito. In arthropods, genes of the Vago family are often presented as analogs of mammalian cytokines with potential antiviral functions, but the role of Vago genes upon virus infection in Ae. aegypti is largely unknown. We performed a phylogenetic analysis of the Vago gene family in Diptera that prompted us to focus on a Vago-like gene that we named VLG-1. Using CRISPR/Cas9-mediated gene editing, we generated a VLG-1 mutant line of Ae. aegypti that revealed a proviral effect of this gene upon DENV and ZIKV infection. In the absence of VLG-1, virus dissemination throughout the mosquito’s body was impaired, albeit not altering virus transmission rates. A tissue-specific transcriptome analysis revealed that the loss of VLG-1 impacted numerous biological processes potentially linked to viral replication, such as the oxidative stress response. Our results challenge the conventional understanding of Vago-like genes as antiviral factors and underscores the need for further research to elucidate the molecular mechanisms underlying mosquito-arbovirus interactions.
Project description:MicroRNAs (miRNA) have alternative forms known as isomiRs, which differ from each other by a few nucleotides. Next generation sequencing platforms facilitate identification of these isomiRs and recent discoveries regarding their functional importance have increased our understandings of the regulatory complexities of the microRNAome. Observed changes in the miRNA profiles in mosquitoes infected with flaviviruses have implicated small RNAs in the interactions between viruses and their vectors. Here we analysed the isomiR profiles of both uninfected and infected blood fed Aedes aegypti mosquitoes with a major human pathogen, Dengue virus at two time points post-infection. We found noticeable changes to the isomiR expression profile in response to infection and aging. Data analysis revealed a distinct bias towards isomiR production in the mature miRNA as opposed to the star strand. Furthermore, we noticed that only in 40% of Ae. aegypti miRNAs, the most abundant reads for each particular miRNA match the exact sequence reported in the miRbase. The isomiR expression variations between an Ae. aegypti embryonic cell line (Aag2) and whole mosquitoes demonstrated a tissue-specific pattern of isomiR production. Our results illustrated a bias for certain types of isomiRs for each miRNA. The findings presented in this study also provide evidence that isomiR production is not a random phenomenon and may be important in DENV colonisation of its vector. Examination of isomiR production rate in DENV infected and non infected mosquitoes
Project description:Background: The piRNA pathway has been shown in model organisms to be involved in silencing of transposons thereby providing genome stability. In D. melanogaster the majority of piRNAs map to these sequences. The medically important mosquito species Aedes aegypti has a large genome size, a high transposon load which includes Miniature Inverted repeat Transposable Elements (MITES) and an expansion of the piRNA biogenesis genes. Studies of transgenic lines of Ae. aegypti have indicated that introduced transposons are poorly remobilized and we sought to explore the basis of this. We wished to analyze the piRNA profile of Ae. aegypti and thereby determine if it be responsible for transposon silencing in this mosquito. Results: Estimated piRNA sequence diversity was comparable between Ae. aegypti and D. melanogaster, but surprisingly only 19% of mosquito piRNAs mapped to transposons compared to 51% for D. melanogaster. Ae. aegypti piRNA clusters made up a larger percentage of the total genome than those of D. melanogaster but did not contain significantly higher percentages of transposon derived sequences than other regions of the genome. Ae. aegypti contains a number of protein coding genes that may be sources of piRNA biogenesis with two, traffic jam and maelstrom, implicated in this process in model organisms. Several genes of viral origin were also targeted by piRNAs. Examination of six mosquito libraries that had previously been transformed with transposon derived sequence revealed that new piRNA sequences had been generated to the transformed sequences, suggesting that they may have stimulated a transposon inactivation mechanism. Conclusions: Ae. aegypti has a large piRNA complement that maps to transposons but primarily gene sequences, including many viral-derived sequences. This, together the more uniform distribution of piRNA clusters throughout its genome suggest that some aspects of the piRNA system differ between Ae. aegypti and D. melanogaster.
Project description:Background: The piRNA pathway has been shown in model organisms to be involved in silencing of transposons thereby providing genome stability. In D. melanogaster the majority of piRNAs map to these sequences. The medically important mosquito species Aedes aegypti has a large genome size, a high transposon load which includes Miniature Inverted repeat Transposable Elements (MITES) and an expansion of the piRNA biogenesis genes. Studies of transgenic lines of Ae. aegypti have indicated that introduced transposons are poorly remobilized and we sought to explore the basis of this. We wished to analyze the piRNA profile of Ae. aegypti and thereby determine if it be responsible for transposon silencing in this mosquito. Results: Estimated piRNA sequence diversity was comparable between Ae. aegypti and D. melanogaster, but surprisingly only 19% of mosquito piRNAs mapped to transposons compared to 51% for D. melanogaster. Ae. aegypti piRNA clusters made up a larger percentage of the total genome than those of D. melanogaster but did not contain significantly higher percentages of transposon derived sequences than other regions of the genome. Ae. aegypti contains a number of protein coding genes that may be sources of piRNA biogenesis with two, traffic jam and maelstrom, implicated in this process in model organisms. Several genes of viral origin were also targeted by piRNAs. Examination of six mosquito libraries that had previously been transformed with transposon derived sequence revealed that new piRNA sequences had been generated to the transformed sequences, suggesting that they may have stimulated a transposon inactivation mechanism. Conclusions: Ae. aegypti has a large piRNA complement that maps to transposons but primarily gene sequences, including many viral-derived sequences. This, together the more uniform distribution of piRNA clusters throughout its genome suggest that some aspects of the piRNA system differ between Ae. aegypti and D. melanogaster. 5 small RNA libraries were generated from total RNA of whole adult Aedes aegypti tissues, two of these libraries were sequenced twice (technical replicates). 1 small RNA library was generated from total RNA of a whole adult Drosophila melanogaster tissue.