The Marburgvirus-Neutralizing Human Monoclonal Antibody MR191 Targets a Conserved Site to Block Virus Receptor Binding.

Since their first identification 50 years ago， marburgviruses have emerged several times， with 83%-90% lethality in the largest outbreaks. Although no vaccines or therapeutics are available for human use， the human antibody MR191 provides complete protection in non-human primates when delivered several days after inoculation of a lethal marburgvirus dose. The detailed neutralization mechanism of MR191 remains outstanding. Here we present a 3.2 Å crystal structure of MR191 complexed with a trimeric marburgvirus surface glycoprotein (GP). MR191 neutralizes by occupying the conserved receptor-binding site and competing with the host receptor Niemann-Pick C1. The structure illuminates previously disordered regions of GP including the stalk， fusion loop， CXCC switch， and an N-terminal region of GP2 that wraps about the outside of GP1 to anchor a marburgvirus-specific "wing" antibody epitope. Virus escape mutations mapped far outside the MR191 receptor-binding site footprint suggest a role for these other regions in the GP quaternary structure.