The rapid spread of Zika virus (ZIKV) and its association with abnormal brain development constitute a global health emergency. Congenital ZIKV infection produces a range of mild to severe pathologies, including microcephaly. To understand the pathophysiology of ZIKV infection, we used models of the developing brain that faithfully recapitulate the tissue architecture in early to midgestation. We identify the brain cell populations that are most susceptible to ZIKV infection in primary human tissue, provide evidence for a mechanism of viral entry, and show that a commonly used antibiotic protects cultured brain cells by reducing viral proliferation. In the brain, ZIKV preferentially infected neural stem cells, astrocytes, oligodendrocyte precursor cells, and microglia, whereas neurons were less susceptible to infection. These findings suggest mechanisms for microcephaly and other pathologic features of infants with congenital ZIKV infection that are not explained by neural stem cell infection alone, such as calcifications in the cortical plate. Furthermore, we find that blocking the glia-enriched putative viral entry receptor AXL reduced ZIKV infection of astrocytes in vitro, and genetic knockdown of AXL in a glial cell line nearly abolished infection. Finally, we evaluate 2,177 compounds, focusing on drugs safe in pregnancy. We show that the macrolide antibiotic azithromycin reduced viral proliferation and virusinduced cytopathic effects in glial cell lines and human astrocytes. Our characterization of infection in the developing human brain clarifies the pathogenesis of congenital ZIKV infection and provides the basis for investigating possible therapeutic strategies to safely alleviate or prevent the most severe consequences of the epidemic.A correlation between congenital exposure to the mosquitoborne and sexually transmitted Zika flavivirus (ZIKV) and the increased incidence of severe microcephaly suggests a causal relationship between ZIKV infection and neurodevelopmental abnormalities (1, 2). However, the mechanisms of infection and specifically which cell populations are vulnerable to ZIKV during the course of human brain development remain unclear. Major insights have been drawn from in vitro models of human brain development and primary mouse tissues. In the developing mouse brain, ZIKV has been shown to infect radial glia and neurons (3), whereas studies in human pluripotent stem cell (hPSC)-derived neural cells have highlighted widespread infection and apoptosis of neural progenitor cells (4,5). Because these models do not fully recapitulate the developmental events and cell types present during human brain development, these results may not faithfully represent ZIKV-induced pathology in vivo.During human brain development, radial glial cells, the neural stem cells, give rise to diverse types of neuronal and glial cells, including neurons, oligodendrocytes, and astrocytes, in a temporally controlled pattern. We reasoned that identifying cell types that are especially vulnerable to viral infection wou...
