Interaction of fibronectin and fibronectin binding protein (FnBP) of Staphylococcus aureus with murine phagocytes and lymphocytes

Abstract

In the present study we examined the in vitro and in vivo interactions of a cloned staphylococcal fibronectin binding protein (FnBP) and plasma fibronectin (Fn) with polymorphonuclear cells (PMNs) and macrophages, and how antibodies against FnBP affect the phagocytosis process in vitro. Moreover, the interaction of FnBP and Fn coupled on latex beads as ‘artificial bacteria’ and ‘artificially opsonized bacteria’ with murine spleen cells and peritoneal macrophages was tested. The major finding of the present study is that antibodies against the FnBP of Staphylococcus aureus (S. aureus) and low concentration of antibodies recognized two IgG‐binding domains of protein A (SpA) are effective in the promotion of phagocytosis in vitro. It was also observed that FnBP has a chemoattractant activity and causes accumulation of PMNs and macrophages in the mouse peritoneal cavity when injected 24 h before irritation of peritoneal exudate. It seems likely that this activity is connected with binding to Fn molecules since formalin inactivation of FnBP (60%) abolished it. In the in vitro phagocytosis assay in the presence of FnBP (in a medium supplemented with serum depleted of Fn), ingestion of bacteria by phagocytes was identical to assay carried out in the presence of BSA. However, addition of plasma fibronectin caused an increased uptake of bacteria by macrophages and to a lesser degree by PMNs. We observed that in a population of normal splenocytes, those cells that effectively bound FnBP‐ and Fn‐coated latex beads were mostly those cells exbiting macrophage and dendritic morphology. In populations of spleen cells of animals infected with S. aureus, T lymphocytes were also found to bind FnBP‐ and Fn‐coated latex beads. These data suggest that FnBP may have the ability to promote aggregation of immune cells, either directly or by interaction with plasma Fn, which can be helpful in certain cell‐cell interactions taking place at the initial stages of specific immune response.

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

“…It has been reported that serum fibronectin (FN) induces the aggregation of S. aureus, and also affects the interaction between bacteria and polymorphonuclear leukocytes (5,24). Macrophages are important phagocytes that produce various kinds of chemical mediators such as superoxide anion, hydrogen peroxide and nitric oxide, and synthesize heat-shock proteins after the ingestion of S. aureus (4,(14)(15)(16)(17)(18).…”

Cellular signaling during the macrophage invasion by Trypanosoma cruzi

“…In mononuclear phagocytes the main receptor for fibronectin is an α5β1 integrin, also named VLA-5 (Ruoslahti 1991). The uptake of Staphylococcus aureus by murine peritoneal macrophages is mediated by a fibronectin-binding protein expressed in the bacteria surface and can be increased by addition of exogenous plasma fibronectin (Rozalska and Wadstrom 1992). The uptake of Staphylococcus aureus by murine peritoneal macrophages is mediated by a fibronectin-binding protein expressed in the bacteria surface and can be increased by addition of exogenous plasma fibronectin (Rozalska and Wadstrom 1992).…”

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

“…We have previously shown that rabbit polyclonal antibodies raised againsl two fibroncctin-binding proteins (gene fusion preparations i.e. gal-FnBP A and ZZ-FnBP A) of Staphylococcus aureus act as specific opsonins in vitro [11]. Bacteria preincubated wiih immune sera were ingested by mouse peritoneal macrophages more effectively than bacteria treated with preimmune serum.…”

“…Mice were infected iniraperiloneally with i", aureu.i Cowan I (2 x 10'). Six and 24 h post infection, the number ofCFU in homogcnales of spleen and liver, and in Ihe peritoneal fluid was determined on blood agar as described previously [ 11 ], The results are expressed as mean ± SD for groups of six animals.…”