A human/murine chimeric fab antibody neutralizes anthrax lethal toxin in vitro

Area of Science:

• Immunology
• Microbiology
• Biotechnology

Background:

• Antibiotic treatment for human anthrax is limited by residual anthrax toxin.
• Lethal toxin (LeTx) from Bacillus anthracis, containing lethal factor (LF), is a major virulence factor.
• Murine monoclonal antibodies (mAbs) against LF exist but may cause human incompatibility.

Purpose of the Study:

• To develop a human/murine chimeric Fab mAb (LF8-Fab) from a murine anti-LF mAb (LF8).
• To engineer LF8-Fab to reduce potential human incompatibility for clinical applications.
• To evaluate the efficacy of LF8-Fab in neutralizing LeTx and protecting cells.

Main Methods:

• Antibody engineering to create a human/murine chimeric Fab fragment (LF8-Fab).
• Expression of LF8-Fab in Escherichia coli.
• Affinity measurement using LF.
• LeTx neutralization assay and in vitro cell protection assay using J774A.1 cells.

Main Results:

• LF8-Fab specifically identified LF with high affinity (3.46 × 10^7 L/mol).
• LF8-Fab neutralized LeTx with an EC50 of 85 μg/mL.
• LF8-Fab demonstrated protection of J774A.1 cells against LeTx challenge in vitro.

Conclusions:

• The developed LF8-Fab antibody is effective in neutralizing anthrax lethal toxin.
• LF8-Fab shows potential for clinical applications in treating anthrax infections.
• Further characterization of LF8-Fab is warranted for potential therapeutic use.