title: Bacterial evasion of the antibody response: human IgG antibodies neutralize soluble but not bacteria-associated group B streptococcal C5a-ase.
abstract: Most strains of group B streptococci (GBS) possess an enzyme that inactivates the human anaphylatoxin C5a by cleaving a heptapeptide from the carboxyl terminus of C5a. This enzyme, called GBS C5a-ase, has been purified to homogeneity and cleaves and inactivates C5a in physiologic buffer. The enzymatic activity of soluble C5a-ase is completely inhibited, however, in the presence of plasma or serum from normal human adults. The neutralization of soluble C5a-ase by plasma and serum results largely from naturally occurring IgG antibodies directed against C5a-ase. IgG does not neutralize C5a-ase present on intact encapsulated type III GBS but does neutralize the C5a-ase activity associated with a transposon-induced mutant strain of type III GBS that lacks capsule. The location of GBS C5a-ase on the surface of encapsulated type III GBS permits the C5a-ase to inactivate C5a while evading neutralization by IgG antibodies.
authors.affiliation: Department of Pediatrics, University of Utah, School of Medicine, Salt Lake City 84132.
authors.forename: J F
authors.initials: JF
authors.lastname: Bohnsack
authors.forename: X N
authors.initials: XN
authors.lastname: Zhou
authors.forename: J N
authors.initials: JN
authors.lastname: Gustin
authors.forename: C E
authors.initials: CE
authors.lastname: Rubens
authors.forename: C J
authors.initials: CJ
authors.lastname: Parker
authors.forename: H R
authors.initials: HR
authors.lastname: Hill
mesh_terms: D018829:Adhesins, Bacterial; D015936:Complement C5a / Q000378:metabolism*; D003169:Complement Inactivator Proteins / Q000276:immunology* / Q000378:metabolism; D010450:Endopeptidases / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology*; D016756:Immunoglobulins, Intravenous / Q000276:immunology; D013292:Streptococcus agalactiae / Q000201:enzymology / Q000276:immunology*
chemical_list: D018829:Adhesins, Bacterial; D003169:Complement Inactivator Proteins; D007074:Immunoglobulin G; D016756:Immunoglobulins, Intravenous; D015936:Complement C5a; D010450:Endopeptidases; C053088:C5a peptidase