Molecular Genetics of Bunyaviruses  


  HEADBOULOY Michèle / mbouloy@pasteur.fr
  MEMBERSALEXANDRE Jocelyne/ ARIAS-GOETA Camilo/ BABIN Divya /BENFERHAT Rima Dr/ BILLECOCQ Agnès Dr/ CARMI-LEROY Annick / CARNEC Xavier Dr/ CHOUMET Valérie Dr / CORNET Muriel Dr/ COTTE Violaine Dr/COUEILLE Solange/ ERMONVAL Myriam Dr/ FAILLOUX-MANUELLAN Anna-Bella Dr/ FERNANDEZ José/ FERQUEL Elisabeth/FLAMAND Marie Dr/ GARNIER Martine/ KREHER Felix/LARA Estelle/ LEGER Psylvia Dr/ MARTIN Estelle/ MEIGNAN Marie-Laurence/ MOUSSON Laurence/ SERTOUR Natacha/ TAMIETTI Carole/ VAZEILLE Marie Dr.


  Annual Report

Arthropod-borne viruses (arboviruses) are the causative agents of some of the most important emerging infectious diseases, circulating mostly in tropical and subtropical areas and raising threat for developed countries. Among them, some Flaviviruses, Alphaviruses and Bunyaviruses like dengue (DENV), chikungunya (CHIKV) and Rift Valley fever (RVFV) viruses have a large public health impact. Vaccines and antiviral drugs are so far dramatically lacking.

Our efforts focus on the pathogenesis of hemorrhagic fevers associated to RVFV and DENV in mammals and on the molecular basis underlying the lack of pathogenicity in the mosquito vector using RVFV or CHIKV as models. With the aim to extend such studies to another vector borne disease, Lyme disease, our Research unit hosts also the National Reference Center for Borrelia.

Role of nonstructural proteins in pathogenesis

The RVFV nonstructural protein NSs is a factor of virulence antagonizing interferon-ß (IFN-ß) gene transcription. We identified two cellular partners interacting with this protein, p44 of the general transcription factor TFIIH and SAP30 of Sin3A repression complex. Our data show that NSs protein inhibits cellular transcription by two different mechanisms: it prevents assembly of TFIIH through the sequestration of p44 and it maintains the IFN-ß promoter in a repressed state through the formation of repression complexes. To ascertain the role of the interaction of NSs with the cellular partners, RVFV mutants disrupting NSs interaction were produced by reverse genetics and found to be avirulent.

Dengue nonstructural protein NS1 participates to the intracellular stages of viral replication and is associated to the plasma membrane where it modulates the complement system. In addition, it is secreted by infected cells and circulates in the plasma of dengue virus (DENV)-infected patients. We have shown that the NS1 protein represents a hallmark of acute DENV infections and established a diagnostic assay based on NS1 antigen capture in plasma. The kit is commercialized worldwide by Bio-Rad since 2006. Efforts are currently being made to characterize the biological activities of DENV NS1 and define its contribution to viral pathogenesis and the occurrence of hemorrhagic fevers.

Arthropod vector competence

Ae. Albopictus was the vector of CHIKV during the CHIKV outbreak in the Indian Ocean in 2005-2006. This contrasts with RVFV which can be transmitted by more than 30 mosquito species, including Aedes and Culex mosquitoes. Using an artificial feeding system, we investigated the impact of CHIKV and RVFV infection on the life history traits and the reproductive success of these mosquitoes. Moreover, ongoing studies are focused on the vertical transmission of mosquitoes, the influence of the endosymbiotic bacterium Wolbachia in virus transmission, the role of RNA interference as a mosquito antiviral defence, and genetic and fitness changes of an arbovirus related to the alternating host replication.

To better characterize the mechanisms implicated in viral transmission, we have developed a differential proteomics-based approach of Aedes aegypti salivary glands and midguts non-infected and infected with CHIKV and DENV-2 using two-dimensional electrophoresis. Proteins modified in their level of expression or post-translational modifications were identified by MALDI-TOF-MS/MS. These observations will serve as a basis for future work concerning the possible role of these proteins in the interaction between Aedes aegypti, arboviruses and the mammalian host.

Borreliosis, another vector borne disease

In 2009, the National Reference Centre for Borrelia had an active surveillance of Lyme Borreliosis and Ixodes ricinus populations in France (Ile de France), Multilocus sequence analysis (MLST) has been used successfully to delineate a new pathogenic species B. bavariensis sp. nov. B. hispanica and B. crocidurae relapsing fever species were detected in humans and Ornithodoros in Morocco and Tunisia, respectively.

Keywords: arbovirus, pathogenesis, virus-host interactions, mosquito, vectorial competence

bouloy.jpg

Fig 1. The NSs protein forms a nuclear filament where NSs colocalizes with subunits p44 and XPB of TFIIH as shown by immunofluorescence. (HM:high magnification). Le May et al 2004.



  Publications

Bouloy M. and Flick R. 2009. Reverse genetics technology for Rift Valley fever virus: Current and future applications for the development of therapeutics and vaccines. Antiviral Res. 2009 Nov;84(2):101-18. Epub 2009 Aug 12. Review.

M. SARIH, M. GARNIER, N. BOUDEBOUCH, A. BOUATTOUR, A. RIHANI, M. HASSAR, L. GERN, D. POSTIC, M. CORNET. Borrelia hispanica Relapsing Fever, Morocco. Emerg Infect Dis. 2009: 15; 1626-8.

DUBRULLE M., MOUSSON L., MOUTAILLER S., VAZEILLE M. AND A.-B. FAILLOUX. 2009. Chikungunya virus and Aedes mosquitoes: saliva is infectious as soon as two days after oral infection. PLoS ONE 4(6): e5895.

Le May N, Z Mansuroglu, P Léger, T Josse, G Blot, A Billecocq, R Flick, Y Jacob, E Bonnefoy and M. Bouloy. 2008 A SAP30 Complex inhibits IFN-b Expression in Rift Valley Fever virus infected cells. Plos Path 4(1) e13 doc101371/journal ppat 0040013

Schul W, Liu W, Xu HY, Flamand M, Vasudevan SG. 2007. A Dengue fever viremia model in mice shows reduction in viral replication and suppression of the inflammatory response after treatment with antiviral drugs. J Infect Dis. 195(5) : 665-74



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Activity Reports 2009 - Institut Pasteur
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