Promotion of opsonization by antibodies and phagocytosis of gram-positive bacteria by a afunctional polyacrylamide

• Published in: Biomaterials 2006-07, Vol.27 (19), p.3663-3674
• Main Authors: Krishnamurthy, Vijay M, Quinton, Lee J, Estroff, Lara A, Metallo, Steven J, Isaacs, Jessica M, Mizgerd, Joseph P, Whitesides, George M
• Format: Article
• Language: English
• ISSN: 0142-9612
• DOI: 10.1016/j.biomaterials.2006.02.006

This paper describes the application of a bifunctional polyacrylamide (pA-V-F) presenting both vancomycin and fluorescein groups, to modify the surfaces of multiple species of Gram-positive bacteria (Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, and Enterococcus faecalis) to control molecular recognition of these surfaces. The vancomycin groups allowed the specific recognition of a structural component of the bacterial cell wall: peptides terminated in D-Ala-D-Ala. The fluorescein groups allowed the imaging of binding of polymer to the surfaces of bacteria by fluorescence, and are representative, low molecular weight haptens; their recognition by anti-fluorescein antibodies provides proof-of-principle that bifunctional polymers can be used to introduce haptens onto the surface of the bacteria. Flow cytometry revealed that polymer-labeled S. aureus and S. pneumoniae were opsonized by anti-fluorescein antibodies ~20-fold more than were untreated bacteria; nearly all (~92%) polymer-labeled S. aureus, and a large (76%) fraction of polymer-labeled S. pneumoniae were opsonized. The bound antibodies then promoted phagocytosis of the bacteria by cultured J774 macrophage-like cells. Flow cytometry revealed that macrophages ingested S. aureus decorated with the polymer-antibody complexes ~2-fold more efficiently than S. aureus in control groups, in spite of the high background (caused by efficient antibody-independent ingestion of S. aureus by macrophages). This paper, thus, demonstrates the ability of a bifunctional polymer to carry out three distinct functions based on polyvalent molecular recognition: (i) recognition of the surface of Gram-positive bacteria, (ii) modification of this surface to generate specific binding sites recognized by an antibody, and (iii) promotion of phagocytosis of the opsonized bacteria.