Structural basis of anthrax edema factor neutralization by a neutralizing antibody

Area of Science:

• Immunology
• Molecular Biology
• Biochemistry

Background:

• Anthrax edema factor (EF) is a key virulence factor.
• Neutralizing monoclonal antibodies are crucial for combating anthrax.
• Understanding antibody-epitope interactions is vital for therapeutic development.

Purpose of the Study:

• To perform fine epitope mapping of the neutralizing monoclonal antibody EF13D against anthrax edema factor (EF).
• To identify specific residues on EF domain III (DIII) critical for EF13D binding.
• To elucidate the molecular mechanism of EF neutralization by EF13D.

Main Methods:

• Construction and screening of a random mutagenesis yeast surface display library of EF DIII.
• Identification of key residues through binding assays.
• Computational protein-protein docking to model antibody-epitope interactions.

Main Results:

• Identified Leu 667, Ser 668, Arg 671, and Arg 672 on EF DIII as critical for EF13D binding.
• These residues form a contiguous surface patch on the DIII four-helix bundle.
• EF13D's heavy chain complementarity-determining region 3 (HCDR3) binds within a hydrophobic cleft, explaining high affinity and CaM competition.

Conclusions:

• The identified epitope provides a molecular basis for EF13D's potent neutralization of EF.
• This epitope mapping has significant implications for designing novel anthrax vaccines and therapeutics.
• Understanding the interaction site aids in developing strategies to block EF activity.