Characterization of a Protective Monoclonal AntibodyRecognizing Staphylococcus aureus MSCRAMM ProteinClumping FactorA

Abstract

The Staphylococcus aureus MSCRAMM (microbial surface components recognizing adhesive matrix molecules) protein clumping factor A (ClfA) has been shown to be a critical virulence factor in several experimental models of infection. This report describes the generation, characterization, and in vivo evaluation of a murine monoclonal antibody (MAb) against ClfA. Flow cytometric analysis revealed that MAb 12-9 recognized ClfA protein expressed by all of the clinical S. aureus strains obtained from a variety of sources. In assays measuring whole-cell S. aureus binding to human fibrinogen, MAb 12-9 inhibited S. aureus binding by over 90% and displaced up to 35% of the previously adherent S. aureus bacteria. Furthermore, a single infusion of MAb 12-9 was protective against an intravenous challenge with a methicillin-resistant strain of S. aureus in a murine sepsis model (P < 0.0001). These data suggest that anti-ClfA MAb 12-9 should be further investigated as a novel immunotherapy for the treatment and prevention of life-threatening S. aureus infections.

A Recombinant Clumping Factor A-Containing Vaccine Induces Functional Antibodies to Staphylococcus aureus That Are Not Observed after Natural Exposure

“…Recombinant polypeptides representing various segments of the A domain of ClfA from S. aureus strain PFESA0237 were expressed and purified as previously described (7,14). The N1-N2-N3 fragment corresponds to amino acids 40 to 559, the N2-N3 fragment corresponds to amino acids 221 to 559, the N2 fragment corresponds to amino acids 221 to 369, and the N3 fragment corresponds to amino acids 370 to 559 (7).…”

“…For a ClfA-containing vaccine, elicitation of functional antibodies that prevent the binding of S. aureus cells to immobilized Fg constitutes a critical measure of the neutralization of this virulence factor. Enzyme-linked immunosorbent assay (ELISA)-based whole-cell S. aureus ClfA-Fg binding assays have previously been used to define Fg ␥-chain peptide and ClfA sequences responsible for S. aureus Fg binding and to identify a monoclonal antibody (MAb) that can interfere with this interaction (14,15,27). A radiometric assay to measure ClfA immune serum titers in response to a DNA vaccine has also been described (4).…”

The Staphylococcus aureus “superbug”

“…A number of companies are developing products intended for active or passive immunization against S. aureus infections, including a capsular polysaccharide vaccine that has been subjected to a clinical trial with hemodialysis patients (24), a monoclonal antibody (25), and human immunoglobulin that is enriched for antibodies that recognize clumping factor A (26).…”

Antibodies toStaphylococcus aureuscapsular polysaccharides 5 and 8 perform similarlyin vitrobut are functionally distinctin vivo

“…23,49,50 Considering the complexity of the S. aureus disease spectrum, it is likely that a cocktail of mAbs targeting distinct staphylococcal virulence factors may serve to protect against diverse Figure 7. Quantitation of cell-associated and soluble CP5 or CP8 produced by clinical isolates of S. aureus cultivated in RMPI C 1% casamino acids.…”