RESUMEN
Prostaglandins (PGs) are immuno-active lipids that mediate the immune response in invertebrates and vertebrates. In insects, PGs play a role on different physiological processes such as reproduction, ion transport and regulation of cellular immunity. However, it is unclear whether PGs play a role in invertebrate's humoral immunity, and, if so, which immune signaling pathways would be modulated by PGs. Here, we show that Aedes aegypti gut microbiota and Gram-negative bacteria challenge induces prostaglandin production sensitive to an irreversible inhibitor of the vertebrate cyclooxygenase, acetylsalicylic acid (ASA). ASA treatment reduced PG synthesis and is associated with decreased expression of components of the Toll and IMD immune pathways, thereby rendering mosquitoes more susceptible to both bacterial and viral infections. We also shown that a cytosolic phospholipase (PLAc), one of the upstream regulators of PG synthesis, is induced by the microbiota in the midgut after blood feeding. The knockdown of the PLAc decreased prostaglandin production and enhanced the replication of Dengue in the midgut. We conclude that in Ae. aegypti, PGs control the amplitude of the immune response to guarantee an efficient pathogen clearance.
Asunto(s)
Aedes/virología , Virus del Dengue/fisiología , Inmunidad Humoral , Prostaglandinas/metabolismo , Aedes/inmunología , Animales , Línea Celular , Virus del Dengue/inmunología , Femenino , Regulación Enzimológica de la Expresión Génica , Interacciones Huésped-Patógeno , Fosfolipasas A2/genética , Fosfolipasas A2/metabolismo , Prostaglandinas/genéticaRESUMEN
Aedes (Stegomyia) aegypti, the principal global vector of dengue viruses, has differences in its susceptibility to dengue virus infection. We compared the global expression of genes in the midguts of Colombian Ae. aegypti dengue-susceptible (Cali-S) and dengue-refractory (Cali-MIB) field derived strains after ingesting either a sugarmeal, a bloodmeal, or a bloodmeal containing dengue virus serotype 2 (DENV-2). Microarray-based transcriptome analysis among treatments indicated a total of 4725 transcripts with differential expression between the two strains. Eleven genes were selected from different functional groups based on their significant up or down expression levels as well as reports in the literature suggesting they are associated with dengue virus elimination. We measured mRNA abundance of these 11 genes at 0, 8, 24, and 36 h postinfection using quantitative real time PCR (qPCR) to confirm the microarray results and assess any temporal patterns. Four genes were selected (Gram-negative binding protein-GNBP [AAEL009176], Niemann Pick Type-C2-NPC2 [AAEL015136], Keratinocyte lectin [AAEL009842], and Cathepsin-b [AAEL007585]) for knockdown experiments using RNA interference (RNAi) methodology to determine the phenotype (DENV-2 susceptible or refractory). Silencing GNBP, Cathepsin-b and Keratinocyte lectin reduced the percentage of mosquitoes with disseminated virus in the Cali-S strain to 8%, 20%, and 12% respectively compared with 96% in the controls. Silencing of NPC2 increased the percentage of mosquitos with disseminated virus infections in Cali-MIB to 66% compared with 35% in the controls. This study provides insight into genes that may contribute to the Cali-S susceptible and Cali-MIB refractory phenotypes in Ae. aegypti.
Asunto(s)
Aedes/genética , Virus del Dengue/inmunología , Interacciones Huésped-Patógeno/genética , Proteínas de Insectos/fisiología , Mosquitos Vectores/genética , Aedes/inmunología , Aedes/virología , Animales , Femenino , Predisposición Genética a la Enfermedad , Interacciones Huésped-Patógeno/inmunología , Mosquitos Vectores/inmunología , Mosquitos Vectores/virologíaRESUMEN
In mammals, lipid droplets (LDs) are ubiquitous organelles that modulate immune and inflammatory responses through the production of lipid mediators. In insects, it is unknown whether LDs play any role during the development of immune responses. We show that Aedes aegypti Aag2 cells - an immune responsive cell lineage - accumulates LDs when challenged with Enterobacter cloacae, Sindbis, and Dengue viruses. Microarray analysis of Aag2 challenged with E.cloacae or infected with Dengue virus revealed high transcripts levels of genes associated with lipid storage and LDs biogenesis, correlating with the increased LDs numbers in those conditions. Similarly, in mosquitoes, LDs accumulate in midgut cells in response to Serratia marcescens and Sindbis virus or when the native microbiota proliferates, following a blood meal. Also, constitutive activation of Toll and IMD pathways by knocking-down their respective negative modulators (Cactus and Caspar) increases LDs numbers in the midgut. Our results show for the first time an infection-induced LDs accumulation in response to both bacterial and viral infections in Ae. Aegypti, and we propose a role for LDs in mosquito immunity. These findings open new venues for further studies in insect immune responses associated with lipid metabolism.
Asunto(s)
Aedes , Virus del Dengue/inmunología , Enterobacter cloacae/inmunología , Gotas Lipídicas/inmunología , Metabolismo de los Lípidos/inmunología , Aedes/inmunología , Aedes/microbiología , Aedes/virología , Animales , Línea Celular , Serratia marcescens/inmunología , Virus Sindbis/inmunologíaRESUMEN
Blood-feeding mosquitoes are exposed to high levels of heme, the product of hemoglobin degradation. Heme is a pro-oxidant that influences a variety of cellular processes. We performed a global analysis of heme-regulated Aedes aegypti (yellow fever mosquito) transcriptional changes to better understand influence on mosquito physiology at the molecular level. We observed an iron- and reactive oxygen species (ROS)-independent signaling induced by heme that comprised genes related to redox metabolism. By modulating the abundance of these transcripts, heme possibly acts as a danger signaling molecule. Furthermore, heme triggered critical changes in the expression of energy metabolism and immune response genes, altering the susceptibility towards bacteria and dengue virus. These findings seem to have implications on the adaptation of mosquitoes to hematophagy and consequently on their ability to transmit diseases. Altogether, these results may also contribute to the understanding of heme cell biology in eukaryotic cells.
Asunto(s)
Virus del Dengue/patogenicidad , Aedes/virología , Animales , Hemo/metabolismo , Inmunidad/fisiología , Especies Reactivas de Oxígeno/metabolismo , Transducción de Señal/fisiologíaRESUMEN
Genetic variation among Aedes aegypti populations can greatly influence their vector competence for human pathogens such as the dengue virus (DENV). While intra-species transcriptome differences remain relatively unstudied when compared to coding sequence polymorphisms, they also affect numerous aspects of mosquito biology. Comparative molecular profiling of mosquito strain transcriptomes can therefore provide valuable insight into the regulation of vector competence. We established a panel of A. aegypti strains with varying levels of susceptibility to DENV, comprising both laboratory-maintained strains and field-derived colonies collected from geographically distinct dengue-endemic regions spanning South America, the Caribbean, and Southeast Asia. A comparative genome-wide gene expression microarray-based analysis revealed higher basal levels of numerous immunity-related gene transcripts in DENV-refractory mosquito strains than in susceptible strains, and RNA interference assays further showed different degrees of immune pathway contribution to refractoriness in different strains. By correlating transcript abundance patterns with DENV susceptibility across our panel, we also identified new candidate modulators of DENV infection in the mosquito, and we provide functional evidence for two potential DENV host factors and one potential restriction factor. Our comparative transcriptome dataset thus not only provides valuable information about immune gene regulation and usage in natural refractoriness of mosquito populations to dengue virus but also allows us to identify new molecular interactions between the virus and its mosquito vector.