Sequential B-cell epitopes of Bacillus anthracis lethal factor bind lethal toxin-neutralizing antibodies.

Area of Science:

• Immunology
• Microbiology
• Vaccinology

Background:

• Anthrax lethal toxin (LeTx), composed of protective antigen (PA) and lethal factor (LF), is a primary cause of death in systemic Bacillus anthracis infections.
• Current anthrax vaccines primarily target PA, but antibodies against LF also neutralize LeTx and offer protection.

Purpose of the Study:

• To identify sequential B-cell epitopes on LF.
• To assess the ability of these epitopes to bind neutralizing antibodies.

Main Methods:

• Immunization of mice with recombinant LF.
• Measurement of anti-LF immunoglobulin G titers and LeTx neutralization capacity.
• Epitope mapping using polyclonal antisera and monoclonal antibodies.

Main Results:

• Sera from LF-immunized mice showed high anti-LF reactivity, neutralized LeTx in vitro, and protected against lethal challenge.
• These sera recognized multiple discontinuous epitopes on LF.
• Neutralizing monoclonal antibodies specifically bound sequential epitopes on LF peptides.

Conclusions:

• LF induces high-titer, protective antibodies in vitro and in vivo.
• The identification of specific LF peptide epitopes suggests the feasibility of peptide vaccination for a more effective anthrax vaccine.