Orthoflaviviruses use diverse binding modes to engage LDLR family receptors

Orthoflaviviruses are major human pathogens that cause substantial morbidity and mortality worldwide. The viral envelope (E) mediates entry of orthoflaviviruses into host cells by interacting with cellular receptors, including members of the low-density lipoprotein receptor (LDLR) family. Here, we determined cryo-electron microscopy (cryo-EM) structures of yellow fever virus (YFV) E bound to low-density lipoprotein receptor-related protein 4 (LRP4) and LRP8, and of tick-borne encephalitis virus (TBEV) E bound to LRP8. Structural and functional studies reveal that YFV engages two low-density lipoprotein receptor class A (LA) repeats of LRP4 and LRP8 primarily through domain III (DIII) and the DI-DIII linker of its E protein, with each LA repeat making distinct contacts. In contrast, TBEV relies on a distinct surface on domain II (DII) of its E protein to interact with LRP8. Despite these differences, both viruses require engagement of two sequential receptor LA repeats for binding. Our findings identify key determinants of receptor specificity for these two orthoflaviviruses, with implications for vaccine development and therapeutic antibody targeting.