Midgut transcriptomic responses to dengue and chikungunya viruses in the vectors Aedes albopictus and Aedes malayensis

Dengue (DENV) and chikungunya (CHIKV) viruses are among the most preponderant arboviruses. Although primarily transmitted through the bite of Aedes aegypti mosquitoes, Aedes albopictus and Aedes malayensis are competent vectors and have an impact on arbovirus epidemiology. Here, to fill the gap in our understanding of the molecular interactions between secondary vectors and arboviruses, we used transcriptomics to profile the whole-genome responses of A. albopictus to CHIKV and of A. malayensis to CHIKV and DENV at 1 and 4 days post-infection (dpi) in midguts. In A. albopictus, 1793 and 339 genes were significantly regulated by CHIKV at 1 and 4 dpi, respectively. In A. malayensis, 943 and 222 genes upon CHIKV infection, and 74 and 69 genes upon DENV infection were significantly regulated at 1 and 4 dpi, respectively. We reported 81 genes that were consistently differentially regulated in all the CHIKV-infected conditions, identifying a CHIKV-induced signature. We identified expressed immune genes in both mosquito species, using a de novo assembled midgut transcriptome for A. malayensis, and described the immune architectures. We found the JNK pathway activated in all conditions, generalizing its antiviral function to Aedines. Our comprehensive study provides insight into arbovirus transmission by multiple Aedes vectors

Comment les flavivirus nous assaisonnent pour appâter les moustiques

International audienc

A New Role of the Mosquito Complement-like Cascade in Male Fertility in Anopheles gambiae

International audienceThioester-containing protein 1 (TEP1) is a key immune factor that determines mosquito resistance to a wide range of pathogens, including malaria parasites. Here we report a new allele-specific function of TEP1 in male fertility. We demonstrate that during spermatogenesis TEP1 binds to and removes damaged cells through the same complement-like cascade that kills malaria parasites in the mosquito midgut. Further, higher fertility rates are mediated by an allele that renders the mosquito susceptible to Plasmodium. By elucidating the molecular and genetic mechanisms underlying TEP1 function in spermatogenesis, our study suggests that pleiotropic antagonism between reproduction and immunity may shape resistance of mosquito populations to malaria parasites

Flaviviruses produce a subgenomic flaviviral RNA that enhances mosquito transmission

Mosquito-borne flaviviruses (MBFVs) are a global public health burden. MBFVs have several unique 3UTR structures that inhibit the host RNA decay machinery to produce subgenomic flaviviral RNAs (sfRNAs). Number of sfRNA species and their relative quantities are dependent on the 3UTR tertiary structures and can vary between tissues. Two recent in vivo studies demonstrated that sfRNA enhances mosquito transmission, resulting in increased infection rate of saliva. Transmission efficiency is determined by the immune response. First evidence points to sfRNA interference with the Toll and RNAi immune pathways. However, a more complex picture that includes flexibility in sfRNA production and interaction with immune-related proteins remains to be explored

RNA: Jack of All Trades and Master of All

Noncoding RNAs have regulatory capabilities that evolution harnesses to fulfill diverse functions. Lee et al. show that a noncoding RNA from Epstein-Barr virus recruits a host transcription factor to silence virus gene expression and propose that it does this through base-pairing with nascent viral transcripts

Highly efficient vertical transmission for Zika virus in Aedes aegypti after long extrinsic incubation time

While the Zika virus (ZIKV) 2014-2017 pandemic has subsided, there remains active transmission. Apart from horizontal transmission to humans, the main vector Aedes aegypti can transmit the virus vertically from mother to offspring. Large variation in vertical transmission (VT) efficiency between studies indicates the influence of parameters, which remain to be characterized. To determine the roles of extrinsic incubation time and gonotrophic cycle, we deployed an experimental design that quantifies ZIKV in individual progeny and larvae. We observed an early infection of ovaries that exponentially progressed. We quantified VT rate, filial infection rate, and viral load per infected larvae at 10 days post oral infection (d.p.i.) on the second gonotrophic cycle and at 17 d.p.i. on the second and third gonotrophic cycle. As compared to previous reports that studied pooled samples, we detected a relatively high VT efficiency from 1.79% at 10 d.p.i. and second gonotrophic cycle to 66% at 17 d.p.i. and second gonotrophic cycle. At 17 d.p.i., viral load largely varied and averaged around 800 genomic RNA (gRNA) copies. Longer incubation time and fewer gonotrophic cycles promoted VT. These results shed light on the mechanism of VT, how environmental conditions favor VT, and whether VT can maintain ZIKV circulation

Lipid Interactions Between Flaviviruses and Mosquito Vectors

International audienceMosquito-borne flaviviruses, such as dengue (DENV), Zika (ZIKV), yellow fever (YFV), West Nile (WNV), and Japanese encephalitis (JEV) viruses, threaten a large part of the human populations. In absence of therapeutics and effective vaccines against each flaviviruses, targeting viral metabolic requirements in mosquitoes may hold the key to new intervention strategies. Development of metabolomics in the last decade opened a new field of research: mosquito metabolomics. It is now clear that flaviviruses rely on mosquito lipids, especially phospholipids, for their cellular cycle and propagation. Here, we review the biosyntheses of, biochemical properties of and flaviviral interactions with mosquito phospholipids. Phospholipids are structural lipids with a polar headgroup and apolar acyl chains, enabling the formation of lipid bilayer that form plasma- and endomembranes. Phospholipids are mostly synthesized through the de novo pathway and remodeling cycle. Variations in headgroup and acyl chains influence phospholipid physicochemical properties and consequently the membrane behavior. Flaviviruses interact with cellular membranes at every step of their cellular cycle. Recent evidence demonstrates that flaviviruses reconfigure the phospholipidome in mosquitoes by regulating phospholipid syntheses to increase virus multiplication. Identifying the phospholipids involved and understanding how flaviviruses regulate these in mosquitoes is required to design new interventions

Effect of radiation on TEP1-mediated removal of damaged sperm.

<p>A <i>DSX</i> transgenic line expressing <i>GFP</i> (green) under the <i>β-tubulin</i> promoter was used. Nuclei were colored with DAPI (blue). (A,B) 3-d-old virgin males that emerged from irradiated pupae were mated with 3-d-old virgin females, and the number of (A) laid eggs and the (B) larval hatching rates per female were gauged. Means ± standard error of the mean (SEM) are plotted for <i>n</i> ≥ 25. (C) The proportion of testes with TEP1-positive spermatogonia in irradiated males (40 Gy), <i>n</i> ≥ 30. (D,E) Radiation (40 Gy) reduces the size of the spermatogonial compartment (white dotted line) in 1- and 3-d-old males. (F,G) Colocalization of TEP1 (red) and TUNEL (white) signals in (F–F”) spermatogonia and (G–G”) the GSC in irradiated 1-d-old males. (H) Occurrence of TEP1 in spermatogonia of irradiated (40 Gy) males (<i>DSX)</i> injected with <i>dsTEP1</i>, <i>dsLRIM1</i>, <i>dsHPX2</i>, and <i>dsLacZ</i> (control). Males depleted for <i>TEP1</i> (<i>7b</i> line) served as positive controls. The proportion of testes with TEP1 signal was gauged 2 d later. Mean ± standard error (SE) is shown; N, number of testes. (i) Accumulation of TUNEL-positive spermatogonia after irradiation in the testes of control and TEP1-depleted males (progeny of reciprocal crosses between <i>7b</i> and <i>DSX</i>) was examined 1 and 3 d after emergence. Each dot represents one testis. Significant differences (<i>p</i> < 0.05, χ² test) are shown by an asterisk and by characters above the corresponding values. Data used to make this figure can be found in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002255#pbio.1002255.s001" target="_blank">S1 Data</a>.</p

Effect of radiation and TEP1 depletion on male fertility.

<p>Pupae were irradiated (40 Gy), and the resulting 3-d-old males were mated with 3-d-old females. The mean ± SEM of laid eggs and the proportions of hatched larvae are plotted. N, number of oviposited females. (A) After irradiation, TEP1 depletion (<i>7b</i> line) decreases hatching rates as compared to controls (<i>T4</i> line). (B) The proportion of testes with apoptotic cells was examined by TUNEL staining in irradiated <i>TEP1-</i>homozygous (<i>S1</i>/<i>S1</i>, <i>S2</i>/<i>S2</i>, or <i>R1</i>/<i>R1</i>) 1-d-old males. Each dot represents one testis. (C) Irradiated <i>TEP1</i>-homozygous (<i>S1</i>/<i>S1</i>, <i>S2</i>/<i>S2</i>, or <i>R1</i>/<i>R1</i>) 3-d-old males were mated with <i>TEP1*S1/S1</i> females. (D) <i>TEP1</i> expression was silenced in the males of F₁ reciprocal crosses between <i>7b</i> and each of the <i>TEP1</i>-homozygogus lines. Irradiated F₁ 3-d-old males were mated with <i>TEP1*S1/S1</i>-homozygogus females. The results of two-way analysis of variance (ANOVA) tests are shown in tables below the corresponding graphs. Post hoc Tukey’s test: * <i>p</i> < 0.05; ** <i>p</i> < 0.01; *** <i>p</i> < 0.001. Data used to make this figure can be found in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002255#pbio.1002255.s001" target="_blank">S1 Data</a>.</p