Japanese encephalitis virus (JEV) is a neurotropic mosquito-borne flavivirus capable of causing severe encephalitis leading to death of the infected individuals. Despite the substantial burden of the infection, the mechanisms of JEV neurovirulence are poorly understood. To date, JEV neural infection is primarily studied in mouse model despite the potential species-specific differences in virus-host interactions, while the biologically relevant human infection model is lacking.
Herein, we have established a human brain organoid (hBO) model for JEV infection and compared it to the mouse model using scRNA-Seq. 60-days old hBOs were infected with 10^5 FFU of JEV and dissociated by papain treatment at 2dpi. 6-8-weeks-old C57BL/6J mice were inoculated with 3.5x10^3 FFU of JEV, brain tissue was collected from the animals that developed encephalitis and dissociated using Miltenyibiotec Adult Brain Dissociation kit. The scRNA-Seq was performed using 10xGenomics Chromium Fixed RNA Profiling platform and sequenced on Illumina NextSeq2000. The scRNA-Seq data was analysed using Seurat R package.
We found that in hBOs JEV predominantly targeted neural progenitor cells (NPCs) and immature neurons with only a small number of astrocytes being infected. In contrast, in mouse brain we observed infection and elimination of mature neurons. In addition, in hBOs neurons did not express interferons (IFNs) and only a small number of glial cells infected with virus produced antiviral cytokines. Furthermore, infected and uninfected neurons developed little to no response to IFN as indicated by expression of interferon-stimulated genes (ISGs). However, we observed profound antiviral response in astrocytes and immature neural cells. This differs from the responses in mouse brain. We link these differences to species-specific expression profiles of pattern-recognition receptors and the components of IFN-signalling in human and murine neural tissues