Wolbachia endosymbionts in Drosophila regulate the resistance to Zika virus infection in a sex dependent manner

Drosophila melanogaster has been used extensively for dissecting the genetic and functional bases of host innate antiviral immunity and virus-induced pathology. Previous studies have shown that the presence of Wolbachia endosymbionts in D. melanogaster confers resistance to infection by certain viral pathogens. Zika virus is an important vector-borne pathogen that has recently expanded its range due to the wide geographical distribution of the mosquito vector. Here, we describe the effect of Wolbachia on the immune response of D. melanogaster adult flies following Zika virus infection. First, we show that the presence of Wolbachia endosymbionts promotes the longevity of uninfected D. melanogaster wild type adults and increases the survival response of flies following Zika virus injection. We find that the latter effect is more pronounced in females rather than in males. Then, we show that the presence of Wolbachia regulates Zika virus replication during Zika virus infection of female flies. In addition, we demonstrate that the antimicrobial peptide-encoding gene Drosocin and the sole Jun N-terminal kinase-specific MAPK phosphatase Puckered are upregulated in female adult flies, whereas the immune and stress response gene TotM is upregulated in male individuals. Finally, we find that the activity of RNA interference and Toll signaling remain unaffected in Zika virus-infected female and male adults containing Wolbachia compared to flies lacking the endosymbionts. Our results reveal that Wolbachia endosymbionts in D. melanogaster affect innate immune signaling activity in a sex-specific manner, which in turn influences host resistance to Zika virus infection. This information contributes to a better understanding of the complex interrelationship between insects, their endosymbiotic bacteria, and viral infection. Interpreting these processes will help us design more effective approaches for controlling insect vectors of infectious disease

Twenty-five new viruses associated with the drosophilidae (Diptera)

Drosophila melanogaster is an important laboratory model for studies of antiviral immunity in invertebrates, and Drosophila species provide a valuable system to study virus host range and host switching. Here, we use metagenomic RNA sequencing of about 1600 adult flies to discover 25 new RNA viruses associated with six different drosophilid hosts in the wild. We also provide a comprehensive listing of viruses previously reported from the Drosophilidae. The new viruses include Iflaviruses, Rhabdoviruses, Nodaviruses, and Reoviruses, and members of unclassified lineages distantly related to Negeviruses, Sobemoviruses, Poleroviruses, Flaviviridae, and Tombusviridae. Among these are close relatives of Drosophila X virus and Flock House virus, which we find in association with wild Drosophila immigrans. These two viruses are widely used in experimental studies but have not been previously reported to naturally infect Drosophila. Although we detect no new DNA viruses, in D. immigrans and Drosophila obscura, we identify sequences very closely related to Armadillidium vulgare iridescent virus (Invertebrate iridescent virus 31), bringing the total number of DNA viruses found in the Drosophilidae to three.This work was funded by a Wellcome Trust Research Career Development Fellowship (WT085064) to DJO. BL was supported by grants from the UK Natural Environment Research Council (NE/L004232/1) and the European Research Council (281668, Drosophila Infection). SHL was supported by a Natural Environment Research Council Doctoral Training Grant (NERC DG NE/J500021/1). Work in DJO’s laboratory is partly supported by a Wellcome Trust strategic award to the Centre for Immunity, Infection and Evolution (WT095831). The authors confirm that the funder had no influence over the study design, content of the article, or selection of this journal

Costs and benefits of sub-lethal Drosophila C Virus infection

Viruses are major evolutionary drivers of insect immune systems. Much of our knowledge of insect immune responses derives from experimental infections using the fruit fly Drosophila melanogaster. Most experiments, however, employ lethal pathogen doses through septic injury, frequently overwhelming host physiology. While this approach has revealed several immune mechanisms, it is less informative about the fitness costs hosts may experience during infection in the wild. Using both systemic and oral infection routes we find that even apparently benign, sub-lethal infections with the horizontally transmitted Drosophila C Virus (DCV) can cause significant physiological and behavioral morbidity that is relevant for host fitness. We describe DCV-induced effects on fly reproductive output, digestive health, and locomotor activity, and we find that viral morbidity varies according to the concentration of pathogen inoculum, host genetic background and sex. Notably, sub-lethal DCV infection resulted in a significant increase in fly reproduction, but this effect depended on host genotype. We discuss the relevance of sub-lethal morbidity for Drosophila ecology and evolution, and more broadly, we remark on the implications of deleterious and beneficial infections for the evolution of insect immunity

Navigating infection risk during oviposition and cannibalistic foraging in a holometabolous insect

Deciding where to eat and raise offspring carries important fitness consequences for all animals, especially if foraging, feeding and reproduction increase pathogen exposure. In insects with complete metamorphosis, foraging mainly occurs during the larval stage, while oviposition decisions are made by adult females. Selection for infection avoidance behaviours may therefore be developmentally uncoupled. Using a combination of experimental infections and behavioral choice assays, we tested if Drosophila melanogaster fruit flies avoid infectious environments at distinct developmental stages. When given conspecific fly carcasses as a food source, larvae did not discriminate between carcasses that were clean or infected with the pathogenic Drosophila C Virus (DCV), even though cannibalism was a viable route of DCV transmission. When laying eggs, DCV-infected females did not discriminate between infectious and non-infectious carcasses. Healthy mothers however, laid more eggs near a clean rather than an infectious carcass. Avoidance during oviposition changed over time: after an initial oviposition period, healthy mothers stopped avoiding infectious carcasses. We attribute this to a trade-off between infection risk and reproduction. Laying eggs near potentially infectious carcasses was always preferred to sites containing only fly food. Our findings suggest infection avoidance contributes to how mothers provision their offspring and underline the need to consider infection avoidance behaviors at multiple life-stages

Sex-specific behavioural symptoms of viral gut infection and Wolbachia in Drosophila melanogaster

AbstractAll organisms are infected with a range of symbionts spanning the spectrum of beneficial mutualists to detrimental parasites. The fruit fly Drosophila melanogaster is a good example, as both endosymbiotic Wolbachia, and pathogenic Drosophila C Virus (DCV) commonly infect it. While the pathophysiology and immune responses against both symbionts are the focus of intense study, the behavioural effects of these infections have received less attention. Here we report sex-specific behavioural responses to these infections in D. melanogaster. DCV infection caused increased sleep in female flies, but had no detectable effect in male flies. The presence of Wolbachia did not reduce this behavioural response to viral infection. We also found evidence for a sex-specific cost of Wolbachia, as male flies infected with the endosymbiont became more lethargic when awake. We discuss these behavioural symptoms as potentially adaptive sickness behaviours

Pathologies tissu spécifiques induites par deux virus à ARN chez la Drosophile

Les insectes sont exposés dans leur environnement à de nombreux virus, et ces infections peuvent avoir un impact économique ou médical. Peu de choses sont connues sur les mécanismes physiopathologiques impliqués dans la susceptibilité aux infections virales. Nous avons utilisé l'organisme modèle drosophile pour étudier la pathologie induite par deux virus à ARN: le virus C de la drosophile (DCV) et le Flock House virus (FHV). La comparaison du transcriptome de mouches infectées par ces deux virus montre que l'infection par le DCV conduit à la forte répression de plusieurs centaines de gènes, principalement exprimés dans l'intestin moyen des mouches. Parmi eux, plusieurs sont également réprimés dans des conditions jeûne, ce qui suggère que les mouches infectées cessent de se nourrir. Cependant, les mouches infectées par les DCV continuent à se nourrir et leur poids augmente. Cela est dû à une excrétion diminuée, associée à une obstruction dans l'intestin moyen de la mouche. La pathologie induite par le DCV est due à la présence du virus dans un tissu particulier, plutôt que de l'effet néfaste de la réponse immunitaire de l'hôte. Nous avons identifié le gène dSUR, codant la sous-unité d'un canal potassium ATP dépendant (KATP). dSUR est exprimé dans le cœur des mouches, et les mutants pour ce gène sont plus sensibles à l'infection par le FHV et contiennent des charges virales plus élevées que les témoins. Nous avons montré que FHV est cardiotropique et que l'activité des KATP cardiaques est liée au mécanisme antiviral de l'interférence ARN. Nous montrons que DCV et FHV, qui semblent très similaires à première vue, induisent des pathologies très différentes chez la drosophile.Insects are exposed in their environement to many viruses, and these infections can have a significant economic or medical impact. At present, little is known about the pathophysiological mechanisms involved in susceptibility to viral infections. We used the model organism Drosophila melanogaster to study the pathology induced by two RNA viruses: the Drosophila C virus (DCV) and the Flock House Virus (FHV).We compared the transcriptome of DCV and FHV-infected flies by using genome-wide microarrays. DCV infection leads to the strong repression of several hundred of genes, mainly expressed in the midgut of the fly. Many genes repressed by the DCV are also repressed under conditions of starvation, suggesting that infected flies stop feeding. However, DCV-infected flies continue to feed and gain weight until their death. This is due to decreased excretion, associated with an intestinal obstruction in the anterior midgut of the fly that probably occurs at the level of the cardia. The pathology induced by DCV results from the presence of the virus in a particular tissue, rather than from the adverse effect of the host s immune response. On the other hand, we identified the gene dSUR, which encode the subunit of an ATP-dependent potassium channel (KATP). dSUR is expressed in the Drosophila heart and mutants for this gene are more sensitive to FHV and contain higher viral loads than controls. We showed that FHV is cardiotropic virus and that the cardiac KATP activity is related to the major antiviral mechanism RNA interference. Our work shows that DCV and FHV, which appear very similar at first sight, induce very different, organ-specific pathologies in Drosophila

Pathologies tissu spécifiques induites par deux virus à ARN chez la Drosophile

Les insectes sont exposés dans leur environnement à de nombreux virus, et ces infections peuvent avoir un impact économique ou médical. Peu de choses sont connues sur les mécanismes physiopathologiques impliqués dans la susceptibilité aux infections viralInsects are exposed in their environement to many viruses, and these infections can have a significant economic or medical impact. At present, little is known about the pathophysiological mechanisms involved in susceptibility to viral infections. We use

Tissue-specific pathologies induced by two RNA viruses in drosophila melanogaster

Les insectes sont exposés dans leur environement à de nombreux virus, et ces infections peuvent avoir un impact économique ou médical. Peu de choses sont connues sur les mécanismes physiopathologiques impliqués dans la susceptibilité aux infections virales. Nous avons utilisé l'organisme modèle drosophile pour étudier la pathologie induite par deux virus à ARN: le virus C de la drosophile (DCV) et le Flock House virus (FHV). La comparaison du transcriptome de mouches infectées par ces deux virus montre que l’infection par le DCV conduit à la forte répression de plusieurs centaines de gènes, principalement exprimés dans l’intestin moyen des mouches. Parmi eux, plusieurs sont également réprimés dans des conditions jeûne, ce qui suggère que les mouches infectées cessent de se nourrir. Cependant, les mouches infectées par les DCV continuent à se nourrir et leur poids augmente. Cela est dû à une excrétion diminuée, associée à une obstruction dans l'intestin moyen de la mouche. La pathologie induite par le DCV est due à la présence du virus dans un tissu particulier, plutôt que de l'effet néfaste de la réponse immunitaire de l'hôte. Nous avons identifié le gène dSUR, codant la sous-unité d'un canal potassium ATP dépendant (KATP). dSUR est exprimé dans le cœur des mouches, et les mutants pour ce gène sont plus sensibles à l’infection par le FHV et contiennent des charges virales plus élevées que les témoins. Nous avons montré que FHV est cardiotropique et que l'activité des KATP cardiaques est liée au mécanisme antiviral de l'interférence ARN. Nous montrons que DCV et FHV, qui semblent très similaires à première vue, induisent des pathologies très différentes chez la drosophile.Insects are exposed in their environement to many viruses, and these infections can have a significant economic or medical impact. At present, little is known about the pathophysiological mechanisms involved in susceptibility to viral infections. We used the model organism Drosophila melanogaster to study the pathology induced by two RNA viruses: the Drosophila C virus (DCV) and the Flock House Virus (FHV). We compared the transcriptome of DCV and FHV-infected flies by using genome-wide microarrays. DCV infection leads to the strong repression of several hundred of genes, mainly expressed in the midgut of the fly. Many genes repressed by the DCV are also repressed under conditions of starvation, suggesting that infected flies stop feeding. However, DCV-infected flies continue to feed and gain weight until their death. This is due to decreased excretion, associated with an intestinal obstruction in the anterior midgut of the fly that probably occurs at the level of the cardia. The pathology induced by DCV results from the presence of the virus in a particular tissue, rather than from the adverse effect of the host’s immune response. On the other hand, we identified the gene dSUR, which encode the subunit of an ATP-dependent potassium channel (KATP). dSUR is expressed in the Drosophila heart and mutants for this gene are more sensitive to FHV and contain higher viral loads than controls. We showed that FHV is cardiotropic virus and that the cardiac KATP activity is related to the major antiviral mechanism RNA interference. Our work shows that DCV and FHV, which appear very similar at first sight, induce very different, organ-specific pathologies in Drosophila