Tuesday, December 12, 2006

RNA interference in mosquitoes is an important innate immune defense against arbovirus infection

Brian D. Foy, brian.foy@colostate.edu, Rodman Tompkins, Kimberly Keene, Carol D. Blair, Kenneth E. Olson, and Corey L. Campbell. Colorado State University, Arthropod Borne Infectious Diseases Lab, Department of Microbiology Immunology & Pathology, 1682 Campus Delivery, Fort Collins, CO

Vector innate immunity is an important component of determining vector competence for arboviruses. We are defining molecular pathways that mosquitoes use to limit arboviral dissemination and characterizing real-time alphavirus/mosquito interactions by employing recombinant fluorescent protein-producing alphaviruses. We have shown that the RNAi pathway proteins Dicer-2 and Argonaute-2 are key in limiting the spread of O’nyong-nyong virus throughout Anopheles gambiae mosquitoes and of Sindbis virus throughout Aedes aegypti and Culex spp. mosquitoes. Artificial silencing of these proteins through the administration of exogenous double-stranded RNAs causes significant increases in viral replication and dissemination in these mosquitoes. Furthermore, silencing of the RNA interference pathway also causes significantly higher mortality in virus-fed adults presumably because virus spreads unchecked through these mosquitoes as compared with controls. Natural fluctuations in Dicer-2, Argonaute-2, and Tudor SN transcipts were also assessed by quantitative PCR after oral infection with one of four viruses representing three arbovirus families. Most transcripts exhibited variable fluctuations; however, Dengue-2 virus significantly induced Dicer-2 and Argonaute-2 transcription in Aedes aegypti midguts 1 day post-infection. Our data demonstrates that RNA interference is a primary innate immune defense employed by many mosquitoes against alphaviruses.

Species 1: Diptera Culicidae Aedes aegypti
Species 2: Diptera Culicidae Anopheles gambiae
Species 3: Diptera Culicidae Culex pipiens

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