Aedes aegypti uses RNA interference in defense against Sindbis virus infection.
BACKGROUND
RNA interference (RNAi) is an important anti-viral defense mechanism. The Aedes aegypti genome encodes RNAi component orthologs, however, most populations of this mosquito are readily infected by, and subsequently transmit flaviviruses and alphaviruses. The goal of this study was to use Ae. aegypti as a model system to determine how the mosquito's anti-viral RNAi pathway interacts with recombinant Sindbis virus (SINV; family Togaviridae, genus Alphavirus).


RESULTS
SINV (TR339-eGFP) (+) strand RNA, infectious virus titers and infection rates transiently increased in mosquitoes following dsRNA injection to cognate Ago2, Dcr2, or TSN mRNAs. Detection of SINV RNA-derived small RNAs at 2 and 7 days post-infection in non-silenced mosquitoes provided important confirmation of RNAi pathway activity. Two different recombinant SINV viruses (MRE16-eGFP and TR339-eGFP) with significant differences in infection kinetics were used to delineate vector/virus interactions in the midgut. We show virus-dependent effects on RNAi component transcript and protein levels during infection. Monitoring midgut Ago2, Dcr2, and TSN transcript levels during infection revealed that only TSN transcripts were significantly increased in midguts over blood-fed controls. Ago2 protein levels were depleted immediately following a non-infectious bloodmeal and varied during SINV infection in a virus-dependent manner.


CONCLUSIONS
We show that silencing RNAi components in Ae. aegypti results in transient increases in SINV replication. Furthermore, Ae. aegypti RNAi is active during SINV infection as indicated by production of virus-specific siRNAs. Lastly, the RNAi response varies in a virus-dependent manner. These data define important features of RNAi anti-viral defense in Ae. aegypti.
Campbell
Corey L
CL
Arthropod-borne Infectious Diseases Laboratory; Microbiology, Immunology, and Pathology Department, Colorado State University, Fort Collins, USA. corey.campbell@colostate.edu
Keene
Kimberly M
KM
Brackney
Douglas E
DE
Olson
Ken E
KE
Blair
Carol D
CD
Wilusz
Jeffrey
J
Foy
Brian D
BD
D000330:Aedes / Q000276:immunology* / Q000821:virology*; D018354:Alphavirus Infections / Q000276:immunology* / Q000517:prevention & control*; D000818:Animals; D060565:Argonaute Proteins; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D029721:Drosophila Proteins / Q000096:biosynthesis / Q000235:genetics; D041981:Gastrointestinal Tract / Q000276:immunology / Q000821:virology; D020869:Gene Expression Profiling; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000096:biosynthesis; D034743:RNA-Induced Silencing Complex / Q000096:biosynthesis / Q000235:genetics; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000096:biosynthesis / Q000235:genetics; D012845:Sindbis Virus / Q000276:immunology*; D016019:Survival Analysis
C433807:AGO2 protein, Drosophila; D060565:Argonaute Proteins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D034741:RNA, Small Interfering; D034743:RNA-Induced Silencing Complex; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand