Table 1.
The main known CWA proteins of S. agalactiae.
| Protein | Ligand and binding mechanism | Function | Reference |
|---|---|---|---|
| CWA as adhesins/invasins and immunity regulators | |||
| Alpha C protein (ACP) | Heparin and glycosaminoglycans | Invasion of non-phagocytic cells | (36–38) |
| α1β1 integrin | Internalization of non-phagocytic cells | (39) | |
| β protein, Bac | Cα2/Cα3 interdomain in human IgA-Fc | Interference with IgA effector function | (40–44) |
| Consensus repeats 8–11 and 12–14 of human Factor H | Regulation of complement activation | (45, 46) | |
| Human lectins Siglec-5 and Siglec-14 | Modulation of innate immunity | (47, 48) | |
| GBS immunogenic bacterial adhesion protein (BibA) | Human C4-binding protein | Regulation of complement activation | (21) |
| Unknown ligand | Attachment to epithelial cells | (21) | |
| Serine rich repeat protein 1 and 2 (Srr1 and Srr2) | Tandem repeats 6–8 of fibrinogen Aα chain; (dock, lock, and latch mechanism) | Adhesion to immobilized fibrinogen; attachment to endothelial cells | (49–51) |
| C-terminal region of cytokeratin 4 | Attachment to epithelial cells | (52, 53) | |
| Leucine-rich repeat protein of GBS (LrrG) | Unknown Ligand | Attachment to epithelial cells | (54) |
| Group B Streptococcus surface protein A (BspA) | Gp340 | Attachment to epithelial cells | (55) |
| Fibrinogen-binding surface protein A (FbsA) | Fibrinogen | Adhesion to immobilized fibrinogen; anti-phagocytic activity; aggregation of platelets | (10, 56) |
| Unknown ligand | Adhesion to endothelial and epithelial cells | (57, 58) | |
| Plasminogen-binding surface protein (PbsP) | Plasminogen | Extracellular proteolytic activity | (20) |
| Unknown ligand | Transmigration across brain endothelial cells | (20) | |
| Hypervirulent GBS adhesion (HvgA) | Unknown ligand | Attachment to endothelial and epithelial cells | (59) |
| Fibrinogen-binding surface protein C (FbsC) | Fibrinogen | Attachment to and invasion of epithelial cells | (60, 61) |
| Unknown ligand | Biofilm formation | (60) | |
| Bacterial surface adhesin of GBS (BsaB) | Fibronectin, laminin | Attachment to epithelial cells | (62) |
| Unknown ligand | Biofilm formation | (62) | |
| CWA proteins with enzymatic activities | |||
| Streptococcus agalactiae pullulanase (SAP) | Pullulan, glycogen and starch | Attachment to epithelial and glycogen-rich alveolar cells | (63, 64) |
| C5a peptidase (ScpB) | C5a | Cleavage of C5a and inhibition of neutrophil recruitment to the infection site | (65, 66) |
| Integrins | Adherence/invasion to epithelial cells? | (67) | |
| Fibronectin | Adherence to extracellular matrix | (68, 69) | |
| Cell-surface-associated protein (CspA) | Aα subunit of fibrinogen | Cleavage of fibrinogen and increased lethality of GBS strains | (70) |
| Chemokines | Inhibition of recruitment of activated neutrophils to sites of infection | (71) | |