TABLE 2.
Expression and function information for various virulence determinants for B. pertussis and B. bronchiseptica
| Virulence determinant | Description | Gene expression
|
Protein expressiona
|
||
|---|---|---|---|---|---|
| B. pertussis | B. bronchiseptica | B. pertussis | B. bronchiseptica | ||
| Adhesins | |||||
| Filamentous hemagglutinin (FHA) | 220-kDa surface-associated and secreted protein; dominant adhesin; required for tracheal colonization; highly immunogenic; primary component of acellular pertussis vaccines | + | + | + | + |
| Fimbriae (FIM) | Filamentous cell surface structures; required for persistent tracheal colonization; component of some acellular pertussis vaccines: required for protective immunity to infection | + | + | + | + |
| Autotransporters | |||||
| Pertactin (PRN) | 68-70-kDa surface protein; mediates eukaryotic cell binding in vitro; enhances protective immunity | + | + | + | + |
| Vag8 | 95-kDa outer membrane protein | + | + | + | + |
| BrkA | 73-kDa surface-associated N-terminal passenger domain with 30-kDa outer membrane C-terminal protein; putative adhesin; confers serum resistance and protection against antimicrobial peptides in B. pertussis | + | + | + | + |
| SphB1 | Subtilisin-like Ser protease/lipoprotein required for FHA maturation in B. pertussis | + | + | + | + |
| Tracheal colonization factor (TcfA) | 60-kDa secreted protein; role in tracheal colonization in murine model | + | − | + | − |
| Toxins | |||||
| Pertussis toxin (PT) | A-B-toxin; ADP-ribosylates G proteins; responsible for pertussis-associated lymphocytosis; strong adjuvant and primary component of pertussis vaccines | + | − | + | − |
| Adenylate cyclase (CyaA) | Calmodulin-activated RTX family toxin with dual adenylate cyclase/hemolysin activity; acts as anti-inflammatory and antiphagocytic factor during infection | + | + | + | + |
| Type III secretion | Allows Bordetella to translocate effector proteins directly into host cells; required for persistent tracheal colonization; inhibits host immune response; activates ERK1/2; mislocalizes NF-κB; causes caspase-independent cell death | + | + | − | + |
| Dermonectrotic toxin (DNT) | 160-kDa heat-labile secreted toxin; activates Rho; induces necrosis in vitro | + | + | + | + |
| Tracheal cytotoxin (TCT) | Disaccharide-tetrapeptide monomeric by-product of peptidoglycan synthesis; causes mitochondrial bloating, disruption of tight junctions, damage to cilia, IL-1α and NȮ production | + | + | + | + |
| LPS | |||||
| wlb locus | Consists of 12 genes required for LPS (band A) biosynthesis | + | + | + | + |
| wbm locus | Encodes O antigen; may be important for confering serum resistance | − | + | − | + |
| PagP | Mediates palmitoylation modification of lipid A; may be important for persistence and resistance to serum killing | − | + | − | + |
| Additional loci | |||||
| Flagella | Peritrichous cell surface appendages required for motility; highly antigenic; ectopic expression of flagella in the Bvg+ phase is detrimental to the infection cycle | − | + | − | + |
| Type IV pili | Polar pili usually with an N-methylated phenylalanine as the N-terminal residue; possible functions include adherence, twitching motility, and DNA uptake | Δ | ND | NA | ND |
| Capsule | A type II polysaccharide coat predicted to be comprised of an N-acetylgalactosaminuronic acid Vi antigen-like polymer; possible role in protection against host defense mechanisms or survival in the environment | Δ | ND | ND | ND |
| Alcaligin | A siderophore for complexing iron, which is internalized through outer membrane receptors (B. bronchiseptica encodes 16 such receptors while B. pertussis encodes 12); iron uptake may be important for survival within mammalian hosts | + | + | + | + |
| Vrg loci | Several loci of uncharacterized function | + | − | + | − |
a
+, positive for expression; −, no expression; Δ, genome contains deletion mutations in these genes; ND, not determined; NA, not applicable.