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Pilus-mediated adherence of Haemophilus influenzae to human respiratory mucins
1Department of Medicine, University of Florida, Gainesville, Florida 32611, USA.
Abstract:
Haemophilus influenzae, especially the nontypeable strains, are among the most common pathogens encountered in patients with chronic lung disease and otitis media. We and others have demonstrated that respiratory isolates of nontypeable H. influenzae bind to human mucins, but the mechanism of binding is not entirely clear. We have therefore examined the role of pili in the adherence of both type b and nontypeable H. influenzae to human respiratory mucins. We used isogenic H. influenzae strains with a mutation in the structural gene for pilin (hifA), a laboratory H. influenzae strain transformed with a type b pilus gene cluster (from strain C54), antibodies raised against H. influenzae HifA, and Escherichia coli strains carrying a cloned type b pilus gene cluster (from strain AM30) in these studies. All bacteria lacking HifA or the pilus gene cluster had decreased adherence of piliated H. influenzae to mucins, and Fab fragments of anti-HifA antibodies inhibited the adherence. E. coli strains carrying the cloned type b pilus gene cluster were six to seven times more adhesive than strains carrying the vector. The role of other putative adhesins was not examined and thus cannot be excluded, but these studies support a role for pili in the binding of H. influenzae to human respiratory mucins.
Insights
Pili play a key role in how nontypeable Haemophilus influenzae (H. influenzae) bacteria attach to respiratory mucins. This finding is crucial for understanding infections like chronic lung disease and otitis media.
Area of Science:
- Microbiology
- Infectious Diseases
- Respiratory Health
Background:
- Nontypeable Haemophilus influenzae (H. influenzae) are common causes of chronic lung disease and otitis media.
- H. influenzae adherence to human respiratory mucins is known but not fully understood.
- The specific bacterial mechanisms facilitating this binding require further investigation.
Purpose of the Study:
- To investigate the role of pili in the adherence of H. influenzae to human respiratory mucins.
- To elucidate the mechanism by which H. influenzae binds to mucins, focusing on pilus involvement.
- To compare the adhesive properties of different H. influenzae strains and their pilus expression.
Main Methods:
- Utilized isogenic H. influenzae strains with mutations in the pilin structural gene (hifA).
- Employed a laboratory H. influenzae strain engineered with a type b pilus gene cluster.
- Tested antibodies against H. influenzae HifA and Escherichia coli strains harboring cloned type b pilus gene clusters.
Main Results:
- Bacteria lacking HifA or the pilus gene cluster exhibited reduced adherence to mucins.
- Fab fragments of anti-HifA antibodies significantly inhibited bacterial adherence.
- E. coli strains expressing the type b pilus gene cluster showed a six- to sevenfold increase in adherence compared to vector controls.
Conclusions:
- Pili are essential for the binding of H. influenzae to human respiratory mucins.
- The findings support a significant role for pili in H. influenzae-mucin interactions.
- Further research may explore other potential adhesins, but pili are confirmed key players.