Table 1.

Key Components of the Bordetella pertussis Organism

Component	Biological Activity
Pertussis toxin (PT)	A secreted exotoxin that induces lymphocytosis, sensitivity to histamine, and pancreatic islet cell activation. Antibodies to PT are associated with clinical immunity to pertussis.
Filamentous hemagglutinin (FHA)	Involved in attachment to ciliated respiratory epithelium. Mice immunized with FHA are protected against lethal respiratory challenge, and serum antibodies to FHA are found after natural infection and after immunization.
Pertactin (PRN)	An outer-membrane protein that promotes adhesion to ciliated respiratory epithelium. PRN is highly immunogenic. Antibodies to it are found after natural disease and immunization. Mice with antibodies to PRN are highly resistant to an otherwise fatal aerosol challenge with virulent B pertussis.
Fimbriae (FIM)	Involved in attachment to ciliated respiratory epithelium. Antibodies to FIM agglutinate B pertussis and are found almost universally after natural disease or immunization.
Tracheal cytotoxin (TCT)	Induces paralysis and destruction of respiratory ciliated epithelium.
Adenylate cyclase toxin (ACT)	Inhibits phagocytic function. ACT-deficient mutants have reduced ability to cause lethal infection. ACT is not included in any current acellular pertussis vaccines due to protein stability issues.
Heat-labile (dermonecrotic) toxin (HLT)	Causes dermal necrosis and vasoconstriction in animals. It is a weak immunogen and antibodies to it are nonprotective in animal challenge tests.
BrkA	An outer-membrane protein involved in adherence and complement resistance. Similar in structure to PRN. Antibodies to BrkA augment killing of B pertussis.
Endotoxin	Similar to endotoxin in other Gram-negative organisms. Contributes to fever and local reactions.