The Antiviral RNA Interference Response Provides Resistance to Lethal Arbovirus Infection and Vertical Transmission in Caenorhabditis elegans

Abstract

SUMMARY The recent discovery of the positive-sense ssRNA Orsay virus (OV) as a natural pathogen of the nematode, Caenorhabditis elegans, has stimulated interest in exploring virus-nematode interactions. However, OV infection is restricted to a small number of intestinal cells, even in nematodes defective in their antiviral RNA interference (RNAi) response, and is neither lethal nor vertically transmitted. Using a fluorescent reporter strain of the negative-sense ssRNA vesicular stomatitis virus (VSV), we show that microinjection of VSV particles leads to a dose-dependent, muscle tissue-tropic, lethal infection in C. elegans. Furthermore, we find nematodes deficient for components of the antiviral RNAi pathway, such as Dicer-related helicase 1 (DRH-1), to display hypersusceptibility to VSV infection as evidenced by elevated infection rates, virus replication in multiple tissue types, and earlier mortality. Strikingly, infection of oocytes and embryos could also be observed in drh-1 mutants. Our results suggest that the antiviral RNAi response not only inhibits vertical VSV transmission but also promotes transgenerational inheritance of antiviral immunity. Our study introduces a new, in vivo virus-host model system for exploring arbovirus pathogenesis and provides the first evidence for vertical pathogen transmission in C. elegans.

Caenorhabditis elegans as an Emerging Model for Virus-Host Interactions

“…These observations suggest that DRH-1 might function as a sensor of viral RNA, analogous to RIG-I, but instead trigger an RNAi response (26). Others have argued that [17,28,43]). Virus infection and replication leads to the production of viral dsRNA that triggers the antiviral RNAi pathway.…”

“…To overcome these limitations and create an in vivo model, we developed techniques to microinject VSV into nematodes (17). Microinjection of VSV particles leads to a dose-dependent, lethal infection that can be scored and tracked in real time using recombinant VSV strains expressing fluorescent proteins.…”

“…Studies of these predominantly extracellular pathogens have largely shaped our understanding of C. elegans immunity. However, with the recent discovery of natural intracellular pathogens of C. elegans (12,13) and the development of nonnatural virus infection models (14)(15)(16)(17)(18), this is beginning to change.…”

Infection of Caenorhabditis elegans with Vesicular Stomatitis Virus via Microinjection

“…To complement the OV model system, we recently reported the generation of a new virus- C. elegans model that uses the negative-sense, ssRNA vesicular stomatitis virus (VSV) (Gammon et al , 2017). Infection of wild-type (N2) worms with VSV is lethal although mutants defective in antiviral responses ( e.g ., drh-1 mutants) succumb to infection more rapidly (Gammon et al , 2017).…”

“…Infection of wild-type (N2) worms with VSV is lethal although mutants defective in antiviral responses ( e.g ., drh-1 mutants) succumb to infection more rapidly (Gammon et al , 2017). Therefore, one can use lifespan assays as a convenient phenotypic readout when comparing different worm backgrounds for virus susceptibilities.…”