Human fibronectin binding to staphylococcal surface protein and its relative inefficiency in promoting phagocytosis by human polymorphonuclear leukocytes, monocytes, and alveolar macrophages

Abstract

The interaction between human fibronectin and 17 strains of staphylococci was studied in an attempt to elucidate the staphylococcal cell wall component(s) involved in fibronectin binding and to determine the influence of fibronectin upon phagocytosis by three types of phagocytic cells. Purified, radiolabeled fibronectin bound to a similar degree to six laboratory strains and three fresh clinical isolates of Staphylococcus aureus; similar binding of fibronectin was found with S. aureus strains deficient in cell wall teichoic acid or clumping factor and coagulase, as well as with three strains of S. epidermidis. There was minimal binding of fibronectin to encapsulated S. aureus and to Escherichia coli. Fibronectin bound to intact cells and to a crude cell wall preparation of S. aureus H, but not to purified cell walls or peptidoglycan. Trypsinization of staphylococci prevented subsequent fibronectin binding, but binding did not correlate well with the protein A content in S. aureus cell walls. At physiological concentrations, fibronectin binding to staphylococci did not promote phagocytosis of bacteria by human polymorphonuclear leukocytes, monocytes, or alveolar macrophages. Also, depletion of fibronectin from normal human serum did not result in a measurable loss of opsonic activity for staphylococci. It is concluded that fibronectin binding to staphylococci involves a surface protein shared among strains of S. aureus and S. epidermidis, and that in comparison to C3b and IgG, fibronectin plays a relatively minor role as an opsonin for staphylococci.

Different Effects of Fibronectin on the Phagocytosis of Staphylococcus aureus and Coagulase‐Negative Staphylococci by Murine Peritoneal Macrophages

“…It has been reported that FN associates with CNS as well as to S. aureus (31). In the present study as well, the binding of FN to all three strains was detected, and the content of bound FN did not seem to differ.…”

“…In our preliminary study, a remarkable difference in the affinity to FN and the maximum number binding to FN was not found among these cocci. A previous report also demonstrated that CNS binds FN as well as the Cowan I strain (31). In addition, the binding of FN to the heat-inactivated bacteria of these three strains was also observed.…”

“…This difference between the two CNS strains may have resulted from another type of phagocytosis in which macrophages recognize other bacterial surface components such as teichoic acids and lipoteichoic acids (19). Some reports have presented the effect of FN treatment of S. aureus on phagocytosis by different types of phagocytes, alveolar macrophages (31,34), PMN (20,21,31,34), monocytes (31,34) and macrophage cell lines (34). These reports have not necessarily shown identical results on whether or not FN shows an opsonic effect.…”

HUMAN SERUM AND PLASMA INCREASE MOUSE MORTALITY IN STAPHYLOCOCCUS AUREUS INTRAPERITONEAL INFECTION

“…The binding of human fibronectin to S.aureus also mediates clumping of the bacteria (9), and it has been proposed that fibronectin opsonizes S.aureus for phagocytosis by polymorphonuclear leukocytes (2 1). However, these results are not conclusive (2 1, 25,28). Fibronectin binds to a receptor mechanism on S.aureus, which is different from the binding sites for IgG and fibrinogen (9,18,25).…”

“…However, these results are not conclusive (2 1, 25,28). Fibronectin binds to a receptor mechanism on S.aureus, which is different from the binding sites for IgG and fibrinogen (9,18,25).…”