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Assessing Respiratory Immune Responses to Haemophilus Influenzae
Published on: June 29, 2021
Immunoglobulin A1 protease production by Haemophilus influenzae and Streptococcus pneumoniae
Abstract:
Bacterial strains of Haemophilus species and Streptococcus pneumoniae were examined for synthesis of the enzyme immunoglobulin A1 (IgA1) protease. Of 36 H. influenzae strains examined, 35 produced IgA1 protease; strains included all six capsular types, unencapsulated variants of types b and d, and untypable H. influenzae. Eight Haemophilus strains (non-H. influenzae) were studied, and two 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 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 two fragments. The apparent molecular weight of the cleaved fragments was dependent both on the apparent molecular weight of the cleaved fragments was dependent both on the specific IgA1 protease assayed and the specific IgA1 substrate utilized. It is postulated that both carbohydrate variation between the IgA1 substrates studied and the ability of S. pneumoniae glycosidases to cleave carbohydrates from glycoprotein offer an explanation for the different fragment sizes observed.
Insights
Most Haemophilus influenzae and Streptococcus pneumoniae strains produce immunoglobulin A1 (IgA1) protease, an enzyme that cleaves IgA1 but not other immunoglobulins, impacting bacterial pathogenesis.
Area of Science:
- Microbiology
- Immunology
- Enzymology
Background:
- Immunoglobulin A1 (IgA1) protease is an enzyme produced by certain bacteria.
- This enzyme plays a role in bacterial pathogenesis by cleaving IgA1, a key antibody in mucosal immunity.
Purpose of the Study:
- To investigate the prevalence of IgA1 protease synthesis in bacterial strains of Haemophilus species and Streptococcus pneumoniae.
- To characterize the enzymatic activity of IgA1 proteases against different immunoglobulin isotypes.
Main Methods:
- Screening of 36 Haemophilus influenzae strains, 8 other Haemophilus strains, and 10 Streptococcus pneumoniae strains for IgA1 protease production.
- Enzymatic activity was assessed using immunoelectrophoresis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).
Main Results:
- 35 out of 36 H. influenzae strains and all 10 S. pneumoniae strains produced IgA1 protease.
- The enzymes cleaved myeloma IgA1 and secretory IgA but not IgA2, IgM, or IgG.
- SDS-PAGE revealed IgA1 cleavage into two fragments, with sizes varying based on the protease and substrate.
Conclusions:
- Haemophilus species and Streptococcus pneumoniae frequently produce IgA1 protease.
- The enzyme specifically targets IgA1, suggesting a role in evading host immune defenses.
- Variations in fragment sizes may be attributed to substrate carbohydrate content and bacterial glycosidase activity.
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