The RNA chaperone Hfq is required for virulence of Bordetella pertussis

Area of Science:

• Bacteriology
• Molecular Biology
• Pathogenesis

Background:

• Bordetella pertussis causes whooping cough, a significant human respiratory illness.
• The RNA chaperone Hfq regulates gene expression post-transcriptionally in bacteria.
• Hfq's role in B. pertussis virulence, particularly its impact on virulence factor production, remains incompletely understood.

Purpose of the Study:

• To investigate the function of the RNA chaperone Hfq in Bordetella pertussis virulence.
• To characterize an hfq deletion mutant (Δhfq) and assess its impact on virulence factor production and bacterial fitness.

Main Methods:

• Construction and characterization of an hfq deletion mutant (Δhfq) in B. pertussis 18323.
• Quantification of virulence factors (adenylate cyclase toxin, pertussis toxin, filamentous hemagglutinin) in wild-type and Δhfq strains.
• In vitro assessment of macrophage survival and in vivo evaluation of virulence in a mouse respiratory infection model.

Main Results:

• The Δhfq strain exhibited significantly reduced production of adenylate cyclase toxin, a key virulence factor.
• Pertussis toxin and filamentous hemagglutinin production were less affected in the Δhfq strain.
• In vitro, the Δhfq strain showed impaired survival within macrophages compared to the wild-type strain.
• In vivo, the Δhfq strain demonstrated attenuated virulence in mice, with reduced lung colonization and an increased 50% lethal dose.
• Mixed-infection experiments revealed the Δhfq strain was outcompeted by the wild-type strain.

Conclusions:

• Hfq plays a critical role in Bordetella pertussis virulence, primarily through regulating adenylate cyclase toxin.
• The reduced virulence of the Δhfq mutant suggests a broader role for Hfq in bacterial fitness and host-pathogen interactions.
• These findings underscore the importance of small noncoding RNA regulation mediated by Hfq in B. pertussis pathogenesis.