Dissecting host-virus interactions in epithelial cells

ABSTRACT
Epithelial cells are exposed to a wide range of environmental pathogens due to their location at body
surfaces. Aside from functioning as a physical barrier, epithelial cells also coordinate immune defenses through
receptor-mediated signaling. However, we do not fully understand the mechanisms that shape pathogen
recognition and immune signaling in epithelial cells. The overall goal of this proposal is to elucidate the molecular
mechanisms that regulate the outcome of viral infection in epithelial cells. There is a critical need for an in vivo
animal model that facilitates mechanistic studies of epithelial immunity. Infection with Orsay virus–a naturally
occurring intestinal pathogen of the nematode Caenorhabditis elegans–provides an innovative approach to study
cellular interactions between a virus and its natural host in the context of a whole-animal model. An obligate,
intracellular pathogen, Orsay virus invades C. elegans intestinal cells and induces the activation of the
Intracellular Pathogen Response (IPR), a transcriptional defense program that confers pathogen resistance
(Sowa et al. 2020). This antiviral transcriptional response requires DRH-1, a homolog of mammalian RIG-I-like
receptors (RLRs). RLRs are intracellular pattern-recognition receptors (PRRs) that detect viral RNA to initiate an
antiviral immune response. Notably, DRH-1/RLR is one of the few PRRs conserved between C. elegans and
humans. Despite the similarity between RLRs and DRH-1, C. elegans lacks sequence-based homologs to the
downstream signaling components of the RLR pathway–including MAVS, IRF3, NF-κB and interferon. It is
unclear which host determinants are involved in DRH-1-mediated activation of the IPR and where DRH-1 is
required to induce the IPR. The proposed studies integrate molecular tools and a natural infection model to
address the central hypothesis that DRH-1 signals through a non-canonical RLR signaling pathway and functions
in intestinal cells to induce the IPR. The central hypothesis will be tested through two specific aims. Aim 1.
Determine how DRH-1 signals to activate the Intracellular Pathogen Response. Aim 2. Define the tissue
specificity and subcellular localization of DRH-1 during Orsay virus infection. The expected outcome of this
project is a mechanistic understanding of how C. elegans DRH-1 coordinates host-virus interactions at the
epithelial barrier. This work will highlight either the evolutionary conservation or rewiring of RLR signaling in
epithelial cells. Collectively, the proposed studies will reveal a novel form of antiviral immunity in C. elegans.
More broadly, the proposed studies will have positive translational impact by elucidating a novel antiviral pathway
that may provide insight into the regulation of innate immune responses during viral infection in humans.

Grant Number: 5F31AI176729-02
NIH Institute/Center: NIH
Principal Investigator: Lakshmi Batachari