| Virulence factor | Molecular weight | Function / mechanism | Role in pathogenesis | Vaccine relevance |
|---|---:|---|---|---|
| Pertussis toxin (PT) | ~117 kDa | AB-type exotoxin with S1 enzymatic subunit and S2-S5 binding subunits; ADP-ribosylates inhibitory Gα proteins, disrupting GPCR signaling and downstream cAMP regulation (pqac-00000007, pqac-00000012) | Major B. pertussis-specific toxin; promotes respiratory colonization, suppresses chemokine release and neutrophil recruitment, delays antibody-mediated clearance, and is associated with leukocytosis, hyperinsulinemia, histamine sensitization, and severe disease/poor outcomes (pqac-00000010, pqac-00000011, pqac-00000012, pqac-00000013) | Core antigen in acellular pertussis vaccines; major correlate/target of vaccine-induced antibodies; also a target for next-generation therapeutics and live-attenuated vaccine detoxification strategies such as BPZE1 (pqac-00000018, pqac-00000023, pqac-00000052, pqac-00000057) |
| Adenylate cyclase toxin (ACT/CyaA, AC-Hly) | Not specified in retrieved evidence | Toxin that enters/acts on phagocytes and elevates intracellular cAMP; inhibits phagocytosis and opsonization, induces macrophage apoptosis, has hemolytic/cytotoxic activity, and can disrupt epithelial tight junctions (pqac-00000007, pqac-00000010, pqac-00000012) | Protects bacteria from innate immune killing, impairs neutrophil, dendritic-cell, and macrophage function, and contributes to invasion/persistence in the respiratory tract (pqac-00000007, pqac-00000010, pqac-00000012) | Not a standard component of current acellular vaccines, but an important candidate antigen/target for next-generation vaccines and antibody-based protection strategies (pqac-00000017, pqac-00000023) |
| Filamentous hemagglutinin (FHA) | ~220 kDa | Filamentous surface adhesin mediating attachment to ciliated respiratory epithelium; also modulates host responses by inhibiting NF-κB signaling in macrophages and epithelial cells (pqac-00000006, pqac-00000007, pqac-00000011) | Critical for initiation of colonization and tight adhesion in the upper airway; suppresses early inflammation and cell recruitment, aiding persistence (pqac-00000006, pqac-00000011) | Common antigen in acellular vaccines and serologic assays; antigen loss/variation has been implicated in pathogen adaptation and vaccine-pressure discussions (pqac-00000018, pqac-00000038) |
| Pertactin (PRN) | ~69 kDa | Outer-membrane autotransporter adhesin enabling attachment to host cells; contributes to membrane interactions and resistance to host clearance (pqac-00000007, pqac-00000008, pqac-00000011) | Supports adherence, inflammation, cell recruitment, shedding/transmission, and resistance to neutrophil-mediated clearance (pqac-00000008, pqac-00000011) | Major antigen in many acellular vaccines; pertactin-deficient strains are a key example of vaccine-driven evolution and resurgence-associated adaptation (pqac-00000018, pqac-00000037, pqac-00000039, pqac-00000044) |
| Fimbriae (FIM2/FIM3) | Not specified in retrieved evidence | Surface appendages mediating initial interactions with respiratory epithelial cells and contributing to tight adhesion with FHA (pqac-00000006, pqac-00000011) | Help establish colonization of ciliated airway surfaces and support persistence in the respiratory tract (pqac-00000006, pqac-00000011) | Included in some multicomponent acellular vaccines; fimbrial variation/negative strains have been described among circulating isolates (pqac-00000018, pqac-00000041) |
| Tracheal cytotoxin (TCT) | Not specified in retrieved evidence | Peptidoglycan-derived cytotoxin that damages ciliated respiratory cells and disrupts epithelial/tight-junction integrity (pqac-00000006, pqac-00000012) | Causes ciliary injury and epithelial damage, promoting local tissue dysfunction and aiding colonization/pathology in the airway (pqac-00000006, pqac-00000012) | Not part of licensed acellular vaccines; detoxification/inactivation of TCT is part of the attenuation strategy for BPZE1 live vaccine development (pqac-00000057) |
| Dermonecrotic toxin (DNT) | Not specified in retrieved evidence | Toxin associated with tissue injury; interacts functionally with TCT and LOS and contributes to virulence programs regulated by BvgAS (pqac-00000007) | Contributes to respiratory tract tissue damage and overall virulence (pqac-00000007) | Not a standard antigen in current acellular vaccines; inactivated in BPZE1 as part of live-attenuated vaccine design (pqac-00000057) |
| Lipooligosaccharide (LOS) | Not specified in retrieved evidence | Endotoxin-like outer-membrane glycolipid; activates TLR4 and cytokine release (including IL-8 and TNF-α), though with weaker stimulation than B. bronchiseptica LPS; terminal trisaccharide contributes to defense evasion (pqac-00000009, pqac-00000010) | Required for efficient nasal colonization in mice; shapes inflammatory tone and neutrophil recruitment, contributing to colonization and persistence while limiting clearance (pqac-00000009, pqac-00000010) | Not used as a purified routine vaccine antigen, but naturally present in OMV-based vaccine platforms where it contributes adjuvanticity/immunogenicity (pqac-00000019, pqac-00000020) |
| Type III secretion system (T3SS) | Multi-protein apparatus; no single MW | Secretion apparatus that injects effectors such as BteA and modulates host signaling, including VIP/VPAC2 pathways; suppresses IFN-γ responses and promotes persistence (pqac-00000006, pqac-00000009, pqac-00000055) | Supports immune evasion, lower-respiratory colonization, persistence, and lung pathology modulation (pqac-00000006, pqac-00000009, pqac-00000055) | Not a component of current vaccines but a potential therapeutic and next-generation vaccine target because of its role in immune manipulation and persistence (pqac-00000017, pqac-00000055) |


*Table: This table summarizes the major Bordetella pertussis virulence determinants, their known mechanisms, roles in disease, and relevance to current or emerging vaccine strategies. It is useful for linking pathogenesis to diagnostics, therapeutic targeting, and vaccine design.*