Microcephaly-like phenotype triggered by novel reassortant and prototypic Oropouche virus strains in brain organoids

BACKGROUND: Oropouche virus (OROV) is an emerging arbovirus currently spreading across South America, with increasing reports of neurological manifestations, severe systemic disease, and congenital abnormalities. Although traditionally associated with mild febrile illness, the recent geographic expansion and surge in OROV outbreaks have prompted attention to its neurotropic potential. METHODS: We investigated the effects of Oropouche virus (OROV) infection on neural stem cells (NSCs) and brain organoids derived from human induced pluripotent stem cells, using both an emergent reassortant isolate and a prototypical strain. FINDINGS: OROV infected NSCs, leading to cell death, depletion of proliferative progenitors, and disruption of neuroepithelial organisation. Transcriptomic profiling revealed reduction of antiviral response genes and enrichment of signalling pathways related to viral replication, apoptosis, and inhibition of stem cell maintenance and neuronal differentiation. These molecular signatures aligned with phenotypic collapse of progenitor pools and cortical structure observed in organoids, in which OROV infected progenitors, neurons and astrocytes. Proteomic analysis of brain organoids infected with OROV showed regulation of neurodevelopment pathways, which have been previously associated with ZIKV infection, suggesting convergent pathway disruption associated with reduced growth of organoids infected by ZIKV and OROV and highlighting their potential to impair brain development. INTERPRETATION: These results reveal evidence consistent with a previously unrecognised neurodevelopmental pathogenic potential of OROV strains and provide mechanistic insight into their contribution to microcephaly-like outcomes. FUNDING: D'Or Institute, ITpS, CNPq, FAPEMIG, FAPERJ.