ena-STUDY-CNAG-03-12-2019-16:42:47:312-997
Alteration in the Culex pipiens transcriptome reveals the implication of the mosquito immune system during Rift Valley fever phlebovirus infection
Introduction. Rift Valley fever phlebovirus (RVFV) causes an emerging zoonotic disease and is commonly transmitted in endemic areas between wild ruminants and mosquitoes, mainly by mosquitoes of the Culex and Aedes genus. Aedes aegypti-dengue virus (DENV) is the most studied model in terms of gene expression but there is a lack of knowledge about genes involved in vector competence and immune infection-responses in other mosquito-arboviruses pairing, such as RVFV and Culex pipiens mosquitoes. The Cx. pipiens species is the widely distributed mosquito in western Palaearctic region. This specie has been demonstrated to be a competent vector for RVFV. The main objective in the present study was to investigate the molecular responses of Cx. pipiens to RVFV infection focusing mainly on genes implicated in the classical innate immune pathways (Toll, IMD and JAK/STAT), RNAi mechanism, ubiquitination pathway and apoptosis process. Material & Methods. Mosquitoes were artificially fed with blood spiked with a virulent RVFV strain (RVF 56/74). The full-engorged females were sacrificed and pooled in groups of 4 at 3 different time points: 2 hours post-exposure (hpe), 3- and 14-days post-exposure (dpe). The total RNA from each mosquito pool was submitted to RNA-seq analyses. The ImmunoDB and Gene Ontology databases were used to identify differentially expressed genes (hereafter DEG) related to immune mechanisms.Results. A total of 451 DEG were identified from a de novo transcriptome. Most of the transcriptomic alterations were found at an early infection stage after RVFV exposure. Forty-eight DEG related to immune infection-response were identified. The majority of them were related with the Toll and IMD pathways, the RNAi system and apoptosis. Discussion & Conclusion. Our findings provide for the first time a better understanding of the Cx. pipiens-RVFV interaction, which plays a key role for the control of RVFV spread. While genes from the classical Toll and Imd immune pathways were altered in response to RVFV none of the DEG were related to the JAK/STAT pathway. The early depletion of RNAi pathway by RVFV infection suggests a severe alteration of this pathway at the onset of the RVFV infection to allow viral replication and further virus dissemination in mosquitoes. The fact that most of the DEG involved in Ubiquitin Proteasome Pathway (UPP) or apoptosis were found at an early stage of infection would suggest that apoptosis takes place in Cx. pipiens midgut. These present study elucidate RVFV- Cx. pipiens interaction identifying new molecular targets to further develop potential strategies for vector control.
Introduction. Rift Valley fever phlebovirus (RVFV) causes an emerging zoonotic disease and is commonly transmitted in endemic areas between wild ruminants and mosquitoes, mainly by mosquitoes of the Culex and Aedes genus. Aedes aegypti-dengue virus (DENV) is the most studied model in terms of gene expression but there is a lack of knowledge about genes involved in vector competence and immune infection-responses in other mosquito-arboviruses pairing, such as RVFV and Culex pipiens mosquitoes. The Cx. pipiens species is the widely distributed mosquito in western Palaearctic region. This specie has been demonstrated to be a competent vector for RVFV. The main objective in the present study was to investigate the molecular responses of Cx. pipiens to RVFV infection focusing mainly on genes implicated in the classical innate immune pathways (Toll, IMD and JAK/STAT), RNAi mechanism, ubiquitination pathway and apoptosis process. Material & Methods. Mosquitoes were artificially fed with blood spiked with a virulent RVFV strain (RVF 56/74). The full-engorged females were sacrificed and pooled in groups of 4 at 3 different time points: 2 hours post-exposure (hpe), 3- and 14-days post-exposure (dpe). The total RNA from each mosquito pool was submitted to RNA-seq analyses. The ImmunoDB and Gene Ontology databases were used to identify differentially expressed genes (hereafter DEG) related to immune mechanisms.Results. A total of 451 DEG were identified from a de novo transcriptome. Most of the transcriptomic alterations were found at an early infection stage after RVFV exposure. Forty-eight DEG related to immune infection-response were identified. The majority of them were related with the Toll and IMD pathways, the RNAi system and apoptosis. Discussion & Conclusion. Our findings provide for the first time a better understanding of the Cx. pipiens-RVFV interaction, which plays a key role for the control of RVFV spread. While genes from the classical Toll and Imd immune pathways were altered in response to RVFV none of the DEG were related to the JAK/STAT pathway. The early depletion of RNAi pathway by RVFV infection suggests a severe alteration of this pathway at the onset of the RVFV infection to allow viral replication and further virus dissemination in mosquitoes. The fact that most of the DEG involved in Ubiquitin Proteasome Pathway (UPP) or apoptosis were found at an early stage of infection would suggest that apoptosis takes place in Cx. pipiens midgut. These present study elucidate RVFV- Cx. pipiens interaction identifying new molecular targets to further develop potential strategies for vector control.