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Structural and functional properties of a 69-kilodalton outer membrane protein of Bordetella pertussis
M J Brennan1, Z M Li, R D Shahin
1Division of Bacterial Products, Food and Drug Administration, Bethesda, MD 20892.
Abstract:
A-69-kDa outer membrane protein present on virulent Bordetella pertussis cells is recognized by the agglutinating monoclonal antibodies BPE3, BPD8, and BPE8. The amino acid composition of this protein, purified from heat extracts of B. pertussis BP353 cells, is different from that of the two major fimbrial antigens of B. pertussis, which is consistent with its being a nonfimbrial protein based on other criteria. Western blot analysis using the monoclonal antibody BPE3 demonstrated that a slightly larger but antigenically cross-reactive protein is also expressed by Bordetella bronchiseptica and Bordetella parapertussis. In addition, a large molecular weight species of about 180-kDa is found in outer membrane extracts of B. bronchiseptica which may represent a precursor form of the protein or indicate that the protein can exist as an oligomer. The monoclonal antibody BPD8 directed against the 69-kDa protein almost completely inhibited the enzymatic activity of adenylate cyclase purified from B. pertussis and also inhibited the intoxication of mammalian cells by this enzyme. Since little enzymatic activity was found associated with the purified 69-kDa protein, these data suggest a role for the 69-kDa protein in regulating the adenylate cyclase toxin of B. pertussis. An additional monoclonal antibody directed against the 69-kDa protein, BPE8, decreases lymphocytosis and delays death in mice receiving a respiratory challenge of virulent B. pertussis cells. These studies suggest that further investigation into the role of this protein as a protective antigen and vaccine candidate is warranted.
Insights
A novel 69-kDa outer membrane protein from Bordetella pertussis shows potential as a vaccine candidate. This protein regulates adenylate cyclase toxin and offers protection against pertussis infection in mice.
Area of Science:
- Microbiology
- Immunology
- Bacteriology
Background:
- Virulent Bordetella pertussis possesses a 69-kDa outer membrane protein.
- This protein is recognized by specific monoclonal antibodies (BPE3, BPD8, BPE8).
- Its amino acid composition differs from major fimbrial antigens, indicating a nonfimbrial nature.
Purpose of the Study:
- To characterize the 69-kDa outer membrane protein of Bordetella pertussis.
- To investigate its role in regulating adenylate cyclase toxin.
- To evaluate its potential as a protective antigen and vaccine candidate.
Main Methods:
- Purification of the 69-kDa protein from B. pertussis heat extracts.
- Western blot analysis using monoclonal antibodies.
- Enzymatic activity assays of purified adenylate cyclase.
- Inhibition assays of mammalian cell intoxication.
- Mouse models for respiratory challenge with B. pertussis.
Main Results:
- The 69-kDa protein is nonfimbrial and antigenically related proteins are found in B. bronchiseptica and B. parapertussis.
- A 180-kDa species in B. bronchiseptica may be a precursor or oligomer.
- Monoclonal antibody BPD8 inhibited adenylate cyclase activity and cell intoxication.
- Monoclonal antibody BPE8 reduced lymphocytosis and delayed mortality in mice.
- Little enzymatic activity was associated with the purified 69-kDa protein itself.
Conclusions:
- The 69-kDa protein likely regulates Bordetella pertussis adenylate cyclase toxin.
- It demonstrates protective effects in a mouse model, suggesting its potential as a vaccine candidate.
- Further research is warranted to explore its role as a protective antigen.