Staphylococcus Research Today is a free monthly online journal that collates and summarizes the latest research about Staphylococcus, including details on mrsa, hospitals, infection, antibiotic resistance, superbugs.

Anti-opsonic properties of staphylokinase.

Rooijakkers SH, van Wamel WJ, Ruyken M, van Kessel KP, van Strijp JA

Eijkman Winkler Institute, University Medical Center (UMCU) G04-614, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands. S.H.M.Rooijakkers@lab.azu.nl

Recently we described a novel bacteriophage-encoded pathogenicity island in Staphylococcus aureus that harbors a number of virulence factors that are all involved in the evasion of innate immunity. Here we describe a mechanism by which staphylokinase (SAK), frequently present on this pathogenicity island, interferes with innate immune defenses: SAK is anti-opsonic. By activating human plasminogen (PLG) into plasmin (PL) at the bacterial surface, it creates bacterium-bound serine protease activity that leads to degradation of two major opsonins: human immunoglobulin G (IgG) and human C3b. Incubation of opsonized bacteria with PLG and SAK resulted in removal of anti-staphylococcal IgGs and C3b from the bacterial surface. In phagocytosis assays this proved to be a very efficient mechanism to reduce the opsonic activity of human IgG and serum. The fact that SAK activates human PLG at the bacterial surface and removes IgG as well as C3b makes this protein a unique anti-opsonic molecule.

Published 2 May 2005 in Microbes Infect, 7(3): 476-84.
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