A human cerebral organoid model of West Nile virus encephalitis shows innate immunocompetency

Abstract West Nile virus (WNV), an arbovirus of emerging global interest, can cause neuroinvasive disease in humans. Currently, no protective vaccine or specific treatment is available for human WNV encephalitis. The virus induces neuronal cell death, while astrocytes and microglia, cells important in the antiviral defense of the central nervous system, are suspected to contribute to WNV pathology. Hence, understanding their role is crucial for future treatment approaches. However, human data is limited, and animal models as well as in vitro monocultures have inherent limitations. In this study, human cerebral organoids forming complex 3D in vitro structures including neurons, astrocytes and microglia were used as a novel WNV encephalitis model. Exposure of 100-day-old cerebral organoids to WNV resulted in robust infection leading to heterogenous courses. An early strong viral replication was shown to potentially result in viral clearance, while a late peak resulted in more long-term infection. Viral foci were seen in cortical-like areas, rich in neurons and astrocytes, however void of microglia. Pro-inflammatory cytokines (IL-6, TNF-α, IL-18), chemokines (CXCL10, CCL17, CX3CL1, CCL2) and biomarkers (IL-1RA, sTREM-1, sRAGE, BDNF) were increasingly released. Conclusively, human cerebral organoids make suitable novel WNV encephalitis models with outstanding properties to study acute and long-term infection.