RT Journal Article SR Electronic(1) A1 Kuipers, Annemarie A1 Stapels, Daphne A. C. A1 Weerwind, Lleroy T. A1 Ko, Ya-Ping A1 Ruyken, Maartje A1 Lee, Jean C. A1 van Kessel, Kok P. M. A1 Rooijakkers, Suzan H. M.YR 2016 T1 The Staphylococcus aureus polysaccharide capsule and Efb-dependent fibrinogen shield act in concert to protect against phagocytosis JF Microbiology, VO 162 IS 7 SP 1185 OP 1194 DO https://doi.org/10.1099/mic.0.000293 PB Microbiology Society, SN 1465-2080, AB Staphylococcus aureus has developed many mechanisms to escape from human immune responses. To resist phagocytic clearance, S. aureus expresses a polysaccharide capsule, which effectively masks the bacterial surface and surface-associated proteins, such as opsonins, from recognition by phagocytic cells. Additionally, secretion of the extracellular fibrinogen binding protein (Efb) potently blocks phagocytic uptake of the pathogen. Efb creates a fibrinogen shield surrounding the bacteria by simultaneously binding complement C3b and fibrinogen at the bacterial surface. By means of neutrophil phagocytosis assays with fluorescently labelled encapsulated serotype 5 (CP5) and serotype 8 (CP8) strains we compare the immune-modulating function of these shielding mechanisms. The data indicate that, in highly encapsulated S. aureus strains, the polysaccharide capsule is able to prevent phagocytic uptake at plasma concentrations <10 %, but loses its protective ability at higher concentrations of plasma. Interestingly, Efb shows a strong inhibitory effect on both capsule-negative and encapsulated strains at all tested plasma concentrations. Furthermore, the results suggest that both shielding mechanisms can exist simultaneously and collaborate to provide optimal protection against phagocytosis at a broad range of plasma concentrations. As opsonizing antibodies will be shielded from recognition by either mechanism, incorporating both capsular polysaccharides and Efb in future vaccines could be of great importance., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.000293