title: Specific proteolysis of human IgA by Streptococcus pneumoniae and Haemophilus influenzae.
abstract: Streptococcus pneumoniae and Haemophilus influenzae are among the most common bacterial pathogens responsible for respiratory tract infections in otherwise healthy humans. Thirty-six strains of S. pneumoniae, 62 strains of H. influenzae, six hospital-acquired respiratory pathogens, and a strain of Streptococcus pyogenes were examined for production of IgA protease, a bacterial enzyme whose only known substrate is human IgA1. IgA protease was produced by 100% of the isolates of S. pneumoniae and 98% of the isolates of H. influenzae. The enzyme from both species cleaved human serum and secretory IgA1 proteins, but not human IgA2, IgG, or human serum albumin. None of the hospital-acquired pathogens had detectable IgA protease activity, a finding indicating that the production of this enzyme distinguishes S. pneumoniae and H. influenzae from the opporunistic respiratory pathogens.
mesh_terms: D000907:Antibodies, Bacterial / Q000145:classification / Q000276:immunology / Q000378:metabolism; D005088:Exocrine Glands / Q000276:immunology; D006193:Haemophilus influenzae / Q000201:enzymology*; D006801:Humans; D007070:Immunoglobulin A / Q000378:metabolism; D009093:Mucus / Q000276:immunology; D010447:Peptide Hydrolases / Q000378:metabolism*; D012697:Serine Endopeptidases; D013296:Streptococcus pneumoniae / Q000201:enzymology*
chemical_list: D000907:Antibodies, Bacterial; D007070:Immunoglobulin A; D010447:Peptide Hydrolases; D012697:Serine Endopeptidases; C021433:IgA-specific serine endopeptidase