Table 1.
Listeria monocytogenes virulence factors and their function.
| Virulence Factors | Protein/Gene | Function | |
|---|---|---|---|
| Protein Regulatory Factor | PrfA | Regulator of expression of many virulence proteins | |
| Sigma B | σB | Regulation of stress and virulence genes | |
| Adhesion Proteins | Listeria adhesion protein | LAP | Adhesion to intestinal epithelial cells; disruption of intestinal epithelial barrier |
| Listeria adhesion protein B | LapB | Adhesion and invasion into host cells | |
| Autolysin amidase | Ami | Adhesion to hepatocytes | |
| Fibronectin binding protein | FbpA | Adhesion to cells and serves as a chaperone to stabilise and secrete LLO, InlB | |
| Internalin J | InlJ | Adhesion to epithelial cells and binds to human intestinal mucin-2 (MUC2) | |
| Internalin F | InlF | The crossing of blood–brain barrier | |
| Autolysin IspC | - | Adhesion to non-phagocytic cells | |
| Lmo1656 | - | Transcytosis in goblet cells | |
| Invasion | Internalin | InlA | Promotes bacterial internalisation into enterocytes and bacterial transcytosis across the intestinal barrier |
| Internalin B | InlB | Acts in the invasion of enterocytes and passage through M-cells of Peyer’s patches | |
| Virulence invasion protein | Vip | Invasion of epithelial cells | |
| LAP | - | Induces junctional protein dysregulation and increases epithelial permeability (translocation) | |
| Lysis of vacuole | Listeriolysin (LLO) | hlyA | A haemolysin helps bacteria escape from the phagosome inside the cell by disrupting the vacuolar membrane |
| Phospholipase | (plcA–PI-PLC; plcB–PC-PLC) | Lyses of vacuole membrane | |
| Cell-to-cell spread | Actin polymerisation protein | ActA | Nucleation of actin tail for bacterial movement inside the cytoplasm |
| PC-PLC | - | Lyses of vacuole membrane | |
| Metalloprotease | Mpl | Helps synthesis of PLC | |
| Miscellaneous | P60 (cell wall hydrolase) | - | Adhesion/invasion |
| Bile salt hydrolase | BSH | Survival in gut | |
| Fructose-1,6- bisphosphate aldolase | FAB | Moonlighting protein: (i) adhesion to the host’s cells and (ii) role in the pathogenesis | |
| Internalin C | InlC | Perturbs apical cell junctions | |
| Internalin H (InlH) | InlH | Contributes to systemic listeriosis | |
| Autolysin amidase | Ami | Bacteriolysin: enhances the host immune response | |
| LAP | - | Upregulates TNF-a and IL-6 expression in intestinal cells | |
| Listeriolysin (LLO) | hlyA | Induces lymphocyte apoptosis and suppresses proinflammatory cytokines | |
| Listeria nuclear-targeted protein A | IntA | Decreases the host’s immune response | |
| Listeriolysin S | - | Haemolytic and cytotoxic; bacteriocin (bactericidal) | |