Insect response to Alphavirus infection

Abstract

Invertebrate cells survive Alphavirus infections to establish viral persistence, in contrast to cell death seen soon after infection in mammalian cells. Invertebrate response to prototype alphavirus, Sindbis, has been studied to a certain extent, using mosquitoes and cell lines derived from mosquitoes. Some of the observations made in studies using mosquito systems include formation of intracellular vesicles soon after infection with Sindbis, identification of antiviral activity in the media used to grow the mosquito cell lines and in Sindbis-infected mosquito cell lysates, controlled levels of virus production as persistence is established and superinfection exclusion by Sindbis-infected cells.

The study presented here is designed to utilize array of genomic and genetic information available in Drosophila model to identify the candidate genes ⁄ gene products playing a role in establishment of alphavirus persistence. Observations described in Chapter I establish Drosophila S2 cells as a suitable invertebrate system to study alphavirus-insect interactions. Gene expression analysis identified increased expression of 18 transcripts coding for membrane trafficking and cytoskeletal components and 10 transcripts coding for Notch pathway components, at 5 days post-infection. Identification of upregulation of Notch pathway suggests similarities between mechanism of establishment of persistence of Alphaviruses and Herpesviruses. Transcript coding for TEP II, a wide-spectrum protease inhibitor is increased in expression at 5 days post-infection and upon superinfection at 5 days post-infection. We probed for inhibition of viral protease activity during early persistence and upon superinfection of Sindbis-infected cells with Sindbis. Inhibition of Sindbis viral protease nsP2 is identified to be involved in establishment of viral persistence and superinfection exclusion in cells derived from Mosquito and Drosophila