# Dysregulation of microRNAs in the Brains of Mice Infected with Powassan Virus

## TL;DR

This study explores how microRNAs in the brains of mice change during Powassan virus infection, revealing insights into viral effects and host responses.

## Contribution

This is the first study to evaluate miRNA modulation in the brain following Powassan virus infection.

## Key findings

- POWV infection caused progressive dysregulation of miRNAs in the mouse brain over time.
- Early upregulation of miR-1983, miR-19a, and miR-216b and downregulation of miR-500 were observed.
- miRNA changes correlated with viral spread and activation of pathways like TR/RXR, PTEN, and cell death.

## Abstract

microRNAs (miRNAs) are known to play critical roles in the regulation of gene expression during neurodegenerative diseases and neurotropic viral infections. However, their specific contribution to the pathogenesis of Powassan virus (POWV) infection in the brain remains poorly understood. Understanding miRNA dynamics in the brain during POWV infection may reveal novel insights into viral neuropathogenesis and host antiviral responses. Therefore, in the present study, we analyzed miRNA expression profiles in the mouse brain at different time points following a peripheral POWV infection. A total of 599 miRNAs were examined at day 3, 6, and 9 post-infection. Infection with POWV resulted in the modulation of several miRNAs in the brain at all time points. There was a progressive increase in the number of dysregulated miRNAs over the course of infection. This correlated with POWV dissemination into the brain with a progressive increase in viral RNA levels that peaked at day 9 post-infection. There was an early upregulation of miR-1983, miR-19a, and miR-216b that persisted until day 9 post-infection. POWV infection also resulted in the downregulation of miR-500 at all examined time points. Using IPA, we determined the significant canonical pathways affected by miRNA dysregulation. POWV infection modulated the activation of the thyroid hormone receptor and retinoid X receptor (TR/RXR) and the regulation of the phosphatase and tensin homolog (PTEN). Additionally, macrophage classical activation and growth arrest and DNA damage-inducible 45 (GADD45) signaling were activated as early as day 3 post-infection and persisted until day 9 post-infection. Furthermore, our analysis revealed the activation of cell death pathways such as necrosis and apoptosis and the inhibition of cell cycle progression, as well as leukopoiesis. To our knowledge, this is the first study to evaluate the modulation of miRNAs in the brain following POWV infection.