title: Protease inhibitors decrease IgG shedding from Staphylococcus aureus, increasing complement activation and phagocytosis efficiency.
abstract: Staphylococcus aureus is a major pathogen for immunologically intact humans and its pathogenesis is a model system for evasion of host defences. Antibodies and complement are essential elements of the humoral immune system for prevention and control of S. aureus infections. The specific hypothesis for the proposed research is that S. aureus modifies humoral host defences by cleaving IgG that has bound to the bacterial surface, thereby inhibiting opsonophagocytosis. S. aureus was coated with pooled, purified human IgG and assayed for the shedding of cleaved IgG fragments using ELISA and Western blot analysis. Surface-bound IgG was shed efficiently from S. aureus in the absence of host blood proteins. Broad-spectrum protease inhibitors prevented cleavage of IgG from the S. aureus surface, suggesting that staphylococcal proteases are responsible for IgG cleavage. Serine protease inhibitors and cysteine protease inhibitors decreased the cleavage of surface-bound IgG; however, a metalloprotease inhibitor had no effect. Using protease inhibitors to prevent the cleavage of surface-bound IgG increased the binding of complement C3 fragments on the surface of S. aureus, increased the association with human neutrophils and increased phagocytosis by human neutrophils.
authors.affiliation: Department of Pediatrics, Eastern Virginia Medical School, Norfolk, VA, USA.
authors.forename: Maria F
authors.initials: MF
authors.lastname: Fernandez Falcon
authors.affiliation: Department of Pediatrics, Eastern Virginia Medical School, Norfolk, VA, USA.
authors.forename: Charlene G
authors.initials: CG
authors.lastname: Echague
authors.affiliation: Department of Pediatrics, Eastern Virginia Medical School, Norfolk, VA, USA.
authors.forename: Pamela S
authors.initials: PS
authors.lastname: Hair
authors.affiliation: Department of Microbiology and Molecular Cell Biology, Eastern Virginia Medical School, Norfolk, VA, USA.
authors.forename: Julius O
authors.initials: JO
authors.lastname: Nyalwidhe
authors.affiliation: The Children's Hospital of The King's Daughters, Norfolk, VA, USA.|Children's Specialty Group, Norfolk, VA, USA.|Department of Pediatrics, Eastern Virginia Medical School, Norfolk, VA, USA.
authors.forename: Kenji M
authors.initials: KM
authors.lastname: Cunnion
mesh_terms: D015153:Blotting, Western; D002478:Cells, Cultured; D003167:Complement Activation; D004797:Enzyme-Linked Immunosorbent Assay; D006805:Human Experimentation; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology* / Q000378:metabolism*; D009504:Neutrophils / Q000276:immunology / Q000382:microbiology; D010587:Phagocytosis; D011480:Protease Inhibitors / Q000378:metabolism*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism
chemical_list: D007074:Immunoglobulin G; D011480:Protease Inhibitors