Bacillus anthracis Spore Surface Protein BclA Mediates Complement Factor H Binding to Spores and Promotes Spore...

Area of Science:

• Immunology
• Microbiology
• Infectious Diseases

Background:

• Bacillus anthracis spores persist in host lungs, but the mechanism is unclear.
• Understanding spore persistence is crucial for treating anthrax.

Purpose of the Study:

• To elucidate the mechanism of Bacillus anthracis spore persistence in host lungs.
• To investigate the role of BclA in immune evasion and spore persistence.

Main Methods:

• Investigated the interaction between B. anthracis spores and complement factor H (CFH).
• Utilized wild type and complement-deficient mice (C57BL/6) to assess spore persistence and immune responses.
• Compared immune responses to wild-type and BclA-deletion (ΔbclA) spores.

Main Results:

• BclA mediates direct binding of CFH to B. anthracis spores.
• Bound CFH retains cofactor activity, degrading C3 and inhibiting complement activation.
• BclA promotes spore persistence in mouse lungs and dampens antibody responses in a C3-dependent manner.
• Exposure to ΔbclA spores conferred protection against lethal B. anthracis challenge, unlike parent spores.

Conclusions:

• BclA and CFH interaction is a novel immune evasion mechanism for B. anthracis spores.
• This mechanism promotes in vivo spore persistence and impairs protective immunity.
• Complement plays a significant role in persistent infections, with broad implications for anthrax and other diseases.