|
| Virulence factor | Function |
|
| Capsule | (i) Prevents entrapment in nasal mucus [70] |
| (ii) Exhibits antiphagocytic activity [71] |
| (iii) Facilitates adherence and colonisation of nasopharyngeal epithelial cells [72] |
| Pili | Enhances bacterial adhesion and ability to cause invasive disease [73, 74] |
| Pilus subunit (RrgA) | (i) Binds fibronectin, collagen I, and laminin [75] |
| (ii) Prevents CR3-mediated phagocytosis [76] |
| (iii) TLR2 agonist [77] |
| Biofilm | (i) Reduces susceptibility to antimicrobial agents [78] |
| (ii) Prevents recognition and phagocytosis by the immune system [78] |
| H2O2 | (i) Causes ciliary slowing and epithelial damage [79] |
| (ii) Facilitates colonisation of nasopharyngeal epithelial cells [80] |
| (iii) Bactericidal action against competing bacteria [81] |
| Pneumolysin | (i) Binds to cytoplasmic membrane cholesterol [82] |
| (ii) Disrupts integrity of epithelial monolayer [83] |
| (iii) Exhibits cytolytic activity [84] |
| (iv) Modulates host inflammatory and immune responses [85] |
| Autolysin (LytA) | (i) Involved in autolysis resulting in the release of pneumolysin [86, 87] |
| (ii) Facilitates colonisation of nasopharyngeal epithelial cells [88] |
| Choline binding protein A (CbpA) | (i) Promotes adhesion to human cell conjugates [83] |
| (ii) Binds laminin [89] |
| Choline binding protein E (CbpE) | Mediates attachment to plasminogen [90] |
| Pneumococcal surface protein A (PspA) | (i) Inhibits complement-dependent phagocytosis [91] |
| (ii) Binds lactoferrin [92] |
| Pneumococcal surface protein C (PspC) | Inhibits deposition of the terminal complement complex [93] |
| Pneumococcal adherence and virulence factor A (PavA) | Mediates attachment to plasminogen [94, 95] |
| Pneumococcal adherence and virulence factor B (PavB) | Mediates attachment to plasminogen and fibronectin [96] |
| Pneumococcal surface adhesin A (PsaA) | (i) Binds E-cadherin [97] |
| (ii) Facilitates invasion of nasopharyngeal epithelial cells [98] |
| Plasmin and fibronectin binding protein A (PfbA) | Mediates attachment to plasminogen and fibronectin [99] |
| Pneumococcal serine-rich repeat protein (PsrP) | (i) Facilitates adherence to nasopharyngeal epithelial cells [100] |
| (ii) Mediates biofilm production [101] |
| Putative histidine triad protein (PhpA) | Degrades C3 [102] |
| Neuraminidase (sialidase) | (i) Facilitates adherence and colonisation of nasopharyngeal epithelial cells [92, 103–105] |
| (ii) Mediates biofilm production [103, 106] |
| Hyaluronidase | (i) Facilitates colonisation of nasopharyngeal epithelial cells [84] |
| (ii) Aids the dissemination of the bacteria [84] |
| Endonuclease A (EndA) | Degrades neutrophil extracellular traps [107, 108] |
| Zinc metalloproteinase (ZmpB) | (i) Induces TNF production in the respiratory tract [109] |
| (ii) Cleaves secretory IgA [110] |
| Streptococcus-specific glycosyl hydrolase (GHIP) | Facilitates invasion of nasopharyngeal epithelial cells [111] |
| ClpP protease | Induces apoptosis [112] |
| Ser/Thr kinase (StkP) | Regulator of cell division [113] |
|
