Protective Opsonic Activity of Antibodies against Fibronectin‐Binding Proteins (FnBPs) of Staphylococcus aureus

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Abstract
In this report, opsonic activity of hyperimmune rabbit IgG against fibronectin‐binding proteins (gal‐FnBP A and ZZ‐FnBP B) ofStaphylococcus aureus is described. Moreover, the action of IgG purified from serum of rabbits immunized with ‘combined vaccine’ (fibronectin‐binding protein A + collagen‐binding protein 4‐α‐toxoid) is shown. The opsonic activity has been studied in an in vitro phagocytosis assay as well as in vivo. Mice which had been infected inlraperitoncally with S. aureus strain Cowan l pretreated (opsonized in vitro) with specific anti‐FnBPs IgG were able to eliminate the staphylococci from the peritoneal cavity and liver more rapidly than controls. Also, clearance from the bloodstream of intravenously injected 5. aureus Cowan l as well as S. aureus U320, opsonized with IgG anti‐FnBPs or anti‐FnBP+CnBP +α‐toxoid. was more effective than observed in control groups. In other in vivo experiments it was shown that mice passively immunized with hyperimmune IgG anti‐FnBP (one or two doses, intravenously) before challenge with S. aureus Cov/an l eliminated the bacteria belter than controls injected only with preimmune IgG.