Biotechnologie et biomatériaux

Abstrait

Activation of Neutrophils by the Extracellular Polymeric Substance of S.Epidermidis Biofilms is Mediated by The Bacterial Heat Shock Protein Groel

Susanne Maurer, Philippe Fouchard, Eva Meyle, Birgit Prior, Gertrud M Hänsch and Ulrike Dapunt

In patients with implant-associated osteomyelitis, formation of bacterial biofilms on osteosynthesis materials or endoprosthetic devices is considered the “common cause of persistent infection”. As we showed previously for Staphylococcus aureus or S. epidermidis implant infection, activation of the local host response with infiltration of phagocytic cells and release of bactericidal and potentially cytotoxic entities, as well as production of proinflammatory and osteolysis-inducing cytokines contributes greatly to the persistence of the infection and the ensuing tissue damage with bone degradation. In this study we addressed the question, how phagocytic cells, particularly neutrophils, recognise bacterial biofilms. We found that the protein fraction of the biofilm extracellular substance (EPS) activated neutrophils: up-regulation of defence-relevant functions, among others increased surface expression of the adhesion proteins CD11b and CD66b was seen, as was production of oxygen-radicals. Subsequently, we identified the bacterial heat-shock protein GroEL as a likely candidate: GroEL is present in the EPS; depletion of GroEL from the EPS reduced neutrophil activation, culture of neutrophils with recombinant GroEL up-regulated CD11b and CD66b surface expression, and induced oxygen radical production. According to the literature GroEL and its human homologue heat shock protein (HSP)60 may bind to different surface receptors, including toll-like receptor (TLR)4 and scavenger receptors. Under our experimental conditions, the TLR4 pathway appeared to be crucial for the EPS-induced up-regulation of CD11b and CD66b, but not for induction of oxygen-radical production; suggesting involvement of additional receptors. In conclusion, we identified within the bacterial biofilm the bacterial heat-shock protein GroEL as an activator of the local innate immune response.