# Sensing of Ebinur Lake virus by distinct pattern recognition receptors dictates cell-type specific innate immunity and pathogenesis

## TL;DR

This study explores how different immune receptors detect Ebinur Lake virus in various cell types, influencing immune responses and disease progression.

## Contribution

The study reveals cell-specific roles of RIG-I, MDA5, and TLR7 in sensing Ebinur Lake virus and triggering distinct immune responses.

## Key findings

- RIG-I is essential for interferon and inflammatory responses in HEK293 and A549 cells.
- TLR7 mediates systemic cytokine production in dendritic cells without affecting interferon responses.
- RIG-I and MDA5 differentially sense viral RNA segments and replication intermediates.

## Abstract

Ebinur Lake virus (EBIV) is a recently identified orthobunyavirus with broad host range and zoonotic potential, posing a public health risk. However, the mechanisms underlying EBIV pathogenesis and host innate immune responses remain unclear. Here, we investigated the pattern recognition receptors (PRRs) responsible for sensing EBIV infection and subsequent pathogenesis. EBIV infects diverse cell types and exhibits broad tissue tropism in vivo. In vitro, RIG-I was essential for type I interferon (IFN-I) and inflammatory responses in HEK293 and A549 cells. In contrast, both RIG-I and MDA5 contributed to IFN-I induction in Huh-7 and HCT116 cells, correlating with the specific accumulation of viral dsRNA intermediates in these cell types. Both RIG-I and MDA5 preferentially recognize RNA derived from the viral S segment; however, they have different abilities in sensing incoming viral genomic RNA bearing a 5'-phosphate motif and the replication intermediates. In vivo, RIG-I deficiency severely impairs host defense, while MDA5 deficiency has a more restricted effect in the spleen and liver. In addition to RIG-I and MDA5, TLR7, which is predominantly expressed in dendritic cells, also plays a crucial role for host defense by mediating systemic inflammatory cytokine production without significantly impacting IFN-I response. Our findings suggest that multiple innate sensing receptors, including RIG-I, MDA5, and TLR7, are differentially involved in host defense against EBIV by mediating IFN-I and inflammatory responses, respectively, in a cell-specific manner.

This study elucidates the complex mechanisms by which host RIG-I, MDA5, and TLR7 sense the emerging EBIV and trigger cell-specific immune responses. These findings not only clarify crucial aspects of EBIV-host interactions, particularly the differential sensing of viral RNA by distinct PRRs, but also underscore how this differential sensing dictates cell-specific innate immune activation (IFN-I vs. inflammatory responses) and viral pathogenesis, providing critical insights for understanding and combating EBIV and related emerging bunyaviruses.