Zika virus cell tropism in the developing human brain and inhibition by azithromycin

Significance

Zika virus (ZIKV) is a mosquito-borne flavivirus that has rapidly spread through the Americas and has been associated with fetal abnormalities, including microcephaly. To understand how microcephaly develops, it is important to identify which cell types of the developing brain are susceptible to infection. We use primary human tissue to show that radial glia and astrocytes are more susceptible to infection than neurons, a pattern that correlates with expression of a putative viral entry receptor, AXL. We also perform a screen of Food and Drug Administration-approved compounds, with an emphasis on drugs known to be safe in pregnancy. We identify an antibiotic, azithromycin, that reduces viral proliferation in glial cells, and compare its activity with daptomycin and sofosbuvir, two additional drugs with anti-ZIKV activity.

Abstract

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 virus-induced 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.