Structural insight into rabies virus neutralization revealed by an engineered antibody scaffold

Area of Science:

• Virology
• Structural Biology
• Immunology

Background:

• Rabies virus (RABV) enters host cells via its glycoprotein (G) spikes.
• These spikes are the main target for neutralizing antibodies.
• Several antigenic sites on RABV glycoprotein are targeted by neutralizing monoclonal antibodies (mAbs).

Purpose of the Study:

• To determine the epitope of the potent neutralizing human mAb, CR57.
• To understand the structural basis of CR57's neutralization of RABV.
• To provide a structural perspective on RABV inhibition by a human antibody.

Main Methods:

• Engineered the CR57 mAb into a diabody format for crystallization.
• Determined crystal structures of the CR57 diabody alone and in complex with RABV-G domain III.
• Utilized cell-cell fusion assays to assess CR57's inhibitory function.

Main Results:

• Reported the crystal structure of CR57 diabody alone (2.38 Å) and complexed with RABV-G domain III (2.70 Å).
• The CR57-RABV-G structure identified critical interactions targeting the conserved "KLCGVL" peptide and proximal residues.
• CR57 effectively inhibited RABV-G-mediated fusion by obstructing spike protein transitions.

Conclusions:

• The CR57 antibody targets a conserved epitope on RABV glycoprotein.
• Structural insights reveal CR57 neutralizes RABV by blocking viral fusion.
• This study provides a structural mechanism for potent antibody-mediated inhibition of rabies virus.