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Protective antigen (Bacillus anthracis) (PA)

Target: PA
Molecular classification: Other (Bacterial exotoxin component), Antigen (Vaccine immunogen)

Overview

Protective antigen (PA) is a critical 83 kDa protein secreted by *Bacillus anthracis*, which assembles on host cell surfaces and binds to specific cell surface receptors (ANTXR1/TEM8 and ANTXR2/CMG2). After proteolytic activation, PA oligomerizes and serves as a channel for the entry of lethal factor and edema factor, leading to cytotoxicity and the symptoms of anthrax. Because it is the only component of the anthrax toxin that interacts directly with the immune system and host cell surface, PA is a key target for vaccines and antibody therapies. Immunization with PA or its fragments stimulates protective immunity by inducing neutralizing antibodies, making it the principal antigen in anthrax vaccines.

Other names: Bacillus anthracis protective antigenanthrax protective antigenPA83PA63 (forms)anthrax toxin protective antigen

Mechanism of action

Vaccine stimulation of adaptive immune responses (generating neutralizing antibodies). Neutralization of PA by antibodies, preventing toxin entry into host cells and subsequent cytotoxicity.

Biological functions

Immune response (as a vaccine immunogen)Host cell entry for Bacillus anthracis toxin (mediates cell intoxication by binding to ANTXR1/ANTXR2 receptors)

Disease associations

Infection (essential for pathogenesis of anthrax)[Indirect] Immunoprophylaxis (targeted by vaccines against anthrax)

Safety considerations

Vaccine-related: injection site reactions, allergic reactions, rare risk of serious adverse events(For monoclonal antibodies): hypersensitivity reactions

Interacting drugs

Anthrax vaccines (e.g., BioThrax/AVA, AVP)

3 more in the full profile.

Biomarkers

Anti-PA antibody titer (used to assess vaccine response or protection against anthrax)

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