Pathogenic Species of the Genus Haemophilus and Streptococcus pneumoniae Produce Immunoglobulin A1 Protease

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Abstract
Strains (37) of the genus Haemophilus and 5 strains of S. pneumoniae were examined for their ability to produce extracellular enzyme that cleaves immunoglobulin (Ig) molecules. All H. influenzae, H. aegyptius and S. pneumoniae strains elaborated enzyme that selectively cleaved human IgA1 myeloma proteins but was inactive against a variety of other proteins including human IgA2, IgG and IgM, porcine and bovine secretory IgA, human and bovine serum albumins and ovalbumin. Although susceptible, human secretory IgA remained largely undigested. Two H. pleuropneumoniae [H. parahaemolyticus] strains isolated from fatally infected pigs cleaved porcine secretory IgA but had no effect on human IgA proteins. None of 16 strains that belonged to non-pathogenic Haemophilus species produced IgA protease. Analyses of the cleavage products of human IgA1 and secretory IgA proteins by immunochemical methods, sodium dodecyl sulfate-polyacrylamide gel electrophoresis and analytical ultracentrifugation revealed that Fab and Fc fragments were produced. Production of IgA1 protease by Neisseria meningitidis, H. influenzae and S. pneumoniae may be a property of all 3 major etiological agents of bacterial meningitis. IgA1 protease production may be an important factor in pathogenesis of this disease.