Multiple LDLR family members act as entry receptors for yellow fever virus.

Infection by yellow fever virus (YFV), the prototype Orthoflavivirus, induces a febrile syndrome in humans that can progress to liver failure, haemorrhage and death1. Despite decades of study, the entry receptors for YFV remain unclear. Here, using a surface protein-targeted CRISPR-Cas9 screen, we identified LRP4, a low-density lipoprotein receptor (LDLR) family member, as a candidate entry receptor for YFV. Genetic ablation of LRP4 impaired YFV infection of cells and, reciprocally, complementation or ectopic expression of LRP4 increased infection. Related viruses in the YFV antigenic complex also showed LRP4-dependent infection. LRP4 promoted YFV entry into cells through LDLR type A (LA) domain binding to domain III of the YFV envelope protein. Soluble LRP4-Fc decoy receptors neutralized YFV infection in cell culture and reduced viral burden in vivo. As we observed residual YFV infection in LRP4-deficient cells, we evaluated whether other LDLR family members promote YFV entry. This approach identified LRP1 and VLDLR as additional receptors for YFV infection in cell culture. LRP1-Fc, LRP4-Fc and VLDLR-Fc decoys protected mice from YFV challenge, and LRP1-Fc decoys inhibited YFV infection and liver pathogenesis in mice engrafted with human hepatocytes. A genetic deficiency of LRP1 in primary human hepatocyte cultures also resulted in reduced YFV infection. Our findings establish a role for multiple LDLR family members in YFV entry, infection and pathogenesis, which has implications for receptor use and countermeasure development for multiple emerging orthoflaviviruses.