Immunoglobulin A1 protease production by Haemophilus influenzae and Streptococcus pneumoniae

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Abstract
Bacterial strains of Haemophilus species and S. pneumoniae were examined for synthesis of the enzyme immunoglobulin (Ig) A1 protease. Of 36 H. influenzae strains examined, 35 produced IgA1 protease; strains included all 6 capsular types, unencapsulated variants of types b and d and untypable H. influenzae. Eight Haemophilus strains (non-H. influenzae) were studied and 2 produced IgA1 protease. All 10 strains of S. pneumoniae produced IgA1 protease; these strains included 9 different capsular polysaccharide types and 1 untypable strain. Both IgA1 proteases cleaved [human] myeloma IgA1 and secretory IgA but not myeloma IgA2, IgM or IgG as determined by immunoelectrophoresis. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that both enzymes cleaved IgA1 myeloma sera, but not IgA2, into 2 fragments. The apparent MW of the cleaved fragments were dependent on the specific IgA1 protease assayed and the specific IgA1 substrate utilized. Carbohydrate variation between the IgA1 substrates studied and the ability of S. pneumoniae glycosidases to cleave carbohydrates from glycoprotein may explain the different fragment sizes observed.