Cathelicidin administration protects mice from Bacillus anthracis spore challenge

Area of Science:

• Immunology
• Microbiology
• Biochemistry

Background:

• Cathelicidins are mammalian cationic peptides with known antimicrobial and immunomodulatory functions.
• Bacillus anthracis poses a significant biothreat, necessitating novel therapeutic strategies.

Purpose of the Study:

• To investigate the efficacy of human, mouse, and pig cathelicidins against Bacillus anthracis.
• To elucidate the mechanisms by which cathelicidins confer protection against anthrax.

Main Methods:

• In vitro assays assessing bacterial growth inhibition, spore germination, and vegetative outgrowth.
• Time lapse phase contrast microscopy, transmission electron microscopy, and flow cytometry were employed.
• In vivo studies using C57BL/6 mice to evaluate protection against B. anthracis spore-induced death.

Main Results:

• All tested cathelicidins inhibited B. anthracis growth in vitro.
• Pig cathelicidin uniquely arrested vegetative outgrowth and killed bacilli within the exosporium.
• In vivo, all cathelicidins provided dose- and time-dependent protection against anthrax.
• Porcine cathelicidin acted bactericidally, while human and mouse variants promoted neutrophil recruitment.

Conclusions:

• Cathelicidins demonstrate therapeutic potential for anthrax treatment.
• Different cathelicidins employ distinct mechanisms, including direct bactericidal activity and immune modulation.
• These findings support the use of cathelicidins to enhance innate immunity against B. anthracis.