Structures of phlebovirus glycoprotein Gn and identification of a neutralizing antibody epitope

Abstract

Significance Bunyaviruses are emerging zoonotic pathogens of public-health concern. Lack of structures for proteins on the viral membrane (“envelope”) surface limits understanding of entry. We describe atomic-level structures for the globular “head” of the envelope protein, glycoprotein N (Gn), from two members, severe fever with thrombocytopenia syndrome virus (SFTSV) and Rift Valley fever virus (RVFV), of Phleboviruses genus in the bunyavirus family, and a structure of the SFTSV Gn bound with a neutralizing antibody Fab. The results show the folded Gn structure and define virus-specific neutralizing-antibody binding sites. Biochemical assays suggest that dimerization, mediated by conserved cysteines in the region (“stem”) connecting the Gn head with the transmembrane domain, is a general feature of bunyavirus envelope proteins and that the dimer is probably the olimeric form on the viral surface.