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INRA
24, chemin de Borde Rouge –Auzeville – CS52627
31326 Castanet Tolosan CEDEX - France

Dernière mise à jour : Mai 2018

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Dynamics of Interactions between Densoviruses and Insects (DIDI)

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The overall goal of our research is to address the fundamental questions raised by the use of viruses to control insect pests and vectors:
i) what are the mechanisms involved in virus-host interaction,
ii) what determines virus specificity and how viruses adapt to new hosts
iii) what are the prevalence and the diversity of viruses associated with insects and how viruses circulate in natural and “anthropized” ecosystems. 

We are virologists, particularly interested in the potential of insect parvoviruses (densoviruses) for insect biocontrol. To address the basic questions underlying the use of these viruses, we develop an integrated framework to study virus-host interactions at different scales, from molecules to populations of insects and viruses.  

Our host-virus interaction model is the highly phytophagous caterpillars belonging to the Spodoptera genus (S. frugiperda and S. littoralis) and the Junonia coenia densovirus (JcDV), the type species of the Ambidensovirus genus. 

Spodoptera sp. is a complex gathering  30 species causing major threats to crops worldwide. S. frugiperda was until recently limited to the Americas. This polyphagous species has been introduced in Africa in 2016, and now spreading in numerous countries and various cropping systems. 

JcDV has been discovered in 1972 causing epizootics in the caterpillar of Junonia coenia in the US (Berkeley area; Long and Rivers, 1972). It is also pathogenic for S. frugiperda and we have numerous tools to dissect its functioning making this virus a great model to address fundamental virology issues. 

1- Mechanism of virus-gut interaction

JcDV is an orally transmitted virus and we are interested in the early step of its pathogenesis, which is the interaction with the gut barrier of the caterpillar.

Overcoming the gut barrier is a major issue for orally transmitted viruses. Our research focus on the molecular mechanisms involved in gut recognition of the viral particles. The gut of insects is covered by an impermeable cuticle in its anterior and posterior parts (foregut and hindgut respectively) while the middle part (midgut) is covered by a semi-permeable acellular matrix made of chitin and proteins, the peritrophic matrix. The midgut is the portal of entry for most pathogens.

JcDV crosses the gut of the caterpillar by transcytosis, which consequently affects the gut permeability. Our research decipher the molecular and cellular mechanisms involved in these complex interactions that determine virus invasion. 

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2- Mechanism of virus specificity and host range

Like most pathogens, densoviruses can be specialists (one virus infects one host species) or generalists (one virus can infect several species) and is a correlation between the host range and the host phylogeny. Our research focuses on i) the virus determinants of specificity (capsid and genome) using an “a priori” approach based on motif-candidate on the capsid and we are developing a high throughput approach to decipher the virus determinants.  ii) the mechanim of virus adaptation to new hosts using experimental evolution in different host species. 

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3- Virus hunting and Viral Ecology 

Densoviruses have been mostly discovered in arthropods but recently, Hewson’s lab (@Cornell University) discovered that densoviruses were associated with a lethal disease causing massive mortality in sea star populations extending densovirus host range to echninoderms. The diversity of densovirus host range, sequence and genomic organization contrast with the relative low number of genomes sequenced so far, which strongly suggests that we know very little about densovirus diversity and prevalence in the ecosystems.

We develop a viral metagenomic approach to investigate virus associated with insects, particularly focusing on the densovirus prevalence and diversity in natural and agro- ecosystems.

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Our understanding of the pathoglogy has moved from the Koch concept of “one pathogen-one disease” to the “Pathobiome”  concept, which integrates the pathogen in a complex environment where the host (being an animal or a plant) becomes an ecosystem and must be studied with meta-omic tools. Virology is jumping in this new area and we are now in a community of “Pathobiomers” including pathologists (bacteria, virus, fungi), ecologists, mathematicians. For details http://www.mem.inra.fr/    

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4- Teaching and scientific dissemination

We are highly involved in teaching ( L to M) in different universities and at Ecole Pratique des Hautes Etudes (EPHE) in Virology, Molecular and Cellular Biology, System Biology; see also the “Teaching” of the DGIMI lab for more details. We are also involved in the organisation of the next IGEM contest (2018). 

We are always happy to participate to any events promoting Science (Fête de la Science, mediation to scholars, “Bar des Sciences”, “Pint of Science”, etc). 

 

5- Applied virology: Biocontrol with viruses and Insect viral pathologies

We do collaborate with companies or association interested in biocontrol with viruses or those concerned by viral pathologies in rearing facilities.

Don’t hesitate to contact us !

 

Our collaborators

  • Insect gut physiology : Morena Casartelli, Universitat degli Studii, Milano – Italy
  • Insect viruses : Salvatore Herrero, Universitat de Valencia, Valencia – Spain
  • Insect evolution and virus evolution : Matthieu Sicart. ISEM, University of Montpellier – France. Rémy Froissart, MIVEGEC, Montpellier – France.
  • Viral ecology : Philippe Roumagnac, BGPI, Montpellier – France
  • Applied Virology : Biotop Company.

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