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Middle ear mucin glycoprotein: purification and interaction with nontypable Haemophilus influenzae and Moraxella
M S Reddy1, T F Murphy, H S Faden
1Department of Oral Biology, School of Dental Medicine, State University of New York at Buffalo, USA.
Abstract:
Nontypable Haemophilus influenzae and Moraxella catarrhalis are important pathogens in children and adults. The mechanisms of their adherence to the epithelial cell surface and colonization are not clear. For the pathogen to adhere to the epithelial cell, it must first attach to and penetrate the mucus barrier. Mucin glycoproteins of the mucus layer generally are thought to be involved in bacterial attachment. To understand the precise mechanisms of middle ear mucin-bacterial interactions, we used an overlay binding assay with a highly purified middle ear mucin and outer membrane proteins of both nontypable H. influenzae and M. catarrhalis. Outer membrane proteins P2 and P5 were identified as the major components that medicate the binding between nontypable H. influenzae and human middle ear mucin. Moreover, the 57 kDa protein, CD, of the outer membrane protein of M. catarrhalis was found to be the only protein binding human middle ear mucin. Finally, it appears that a protein-oligosaccharide interaction is responsible for binding because asialo-mucin does not bind to either of the bacteria. Knowledge of the specific bacterial-mucin interaction may provide an understanding of the bacterial-epithelial cell colonization. Conversely, comprehension of this interaction between bacteria and purified mucin may be a strategy to prevent colonization of potential pathogens that cause otitis media and sinusitis in children.
Insights
Nontypable Haemophilus influenzae and Moraxella catarrhalis use outer membrane proteins to bind to middle ear mucins. This protein-oligosaccharide interaction is key to pathogen colonization and may offer strategies to prevent otitis media and sinusitis.
Area of Science:
- Microbiology
- Immunology
- Otorhinolaryngology
Background:
- Nontypable Haemophilus influenzae and Moraxella catarrhalis are significant pathogens causing respiratory infections in all age groups.
- The precise mechanisms by which these bacteria adhere to and colonize epithelial cells, particularly the initial interaction with the mucus barrier, remain unclear.
Purpose of the Study:
- To elucidate the specific molecular interactions between middle ear mucins and outer membrane proteins of nontypable H. influenzae and M. catarrhalis.
- To identify the bacterial components responsible for mucin binding and understand the nature of this interaction.
Main Methods:
- Overlay binding assays were performed using purified human middle ear mucin and outer membrane proteins from nontypable H. influenzae and M. catarrhalis.
- Specific proteins mediating bacterial attachment to mucin were identified.
- The role of oligosaccharide structures in the binding interaction was investigated using asialo-mucin.
Main Results:
- Outer membrane proteins P2 and P5 of nontypable H. influenzae were identified as major mediators of binding to human middle ear mucin.
- The 57 kDa outer membrane protein, CD, of M. catarrhalis was the sole protein found to bind human middle ear mucin.
- Binding was dependent on protein-oligosaccharide interactions, as evidenced by the lack of binding to asialo-mucin.
Conclusions:
- Specific outer membrane proteins of nontypable H. influenzae and M. catarrhalis mediate adherence to middle ear mucins via protein-oligosaccharide interactions.
- Understanding these bacterial-mucin interactions is crucial for comprehending pathogen colonization of epithelial cells.
- This knowledge may inform strategies to prevent infections like otitis media and sinusitis.