TABLE 2.

Expression and function information for various virulence determinants for B. pertussis and B. bronchiseptica

Virulence determinantDescriptionGene expressionProtein expressiona
B. pertussisB. bronchisepticaB. pertussisB. 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++++
    Vag895-kDa outer membrane protein++++
    BrkA73-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++++
    SphB1Subtilisin-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 secretionAllows 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 NO˙ production++++
LPS
    wlb locusConsists of 12 genes required for LPS (band A) biosynthesis++++
    wbm locusEncodes O antigen; may be important for confering serum resistance++
    PagPMediates palmitoylation modification of lipid A; may be important for persistence and resistance to serum killing++
Additional loci
    FlagellaPeritrichous cell surface appendages required for motility; highly antigenic; ectopic expression of flagella in the Bvg+ phase is detrimental to the infection cycle++
    Type IV piliPolar pili usually with an N-methylated phenylalanine as the N-terminal residue; possible functions include adherence, twitching motility, and DNA uptakeΔNDNAND
    CapsuleA 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 environmentΔNDNDND
    AlcaliginA 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 lociSeveral loci of uncharacterized function++
  • a +, positive for expression; −, no expression; Δ, genome contains deletion mutations in these genes; ND, not determined; NA, not applicable.