Avirulent phenotype promotes Bordetella pertussis adaptation to the intramacrophage environment

ABSTRACT

Bordetella pertussis, the causative agent of whooping cough, is an extracellular, strictly human pathogen. However, it has been shown that B. pertussis cells can escape phagocytic killing and survive in macrophages upon internalization. Our time-resolved RNA-seq data suggest that B. pertussis efficiently adapts to the intramacrophage environment and responds to host bactericidal activities. We show that this adaptive response is multifaceted and, surprisingly, related to the BvgAS two-component system, a master regulator of virulence. Our results show that the expression of this regulatory circuit is downregulated upon internalization. Moreover, we demonstrate that the switch to the avirulent Bvg⁻ phase augments a very complex process based on the adjustment of central and energy metabolism, cell wall reinforcement, maintenance of appropriate redox and metal homeostasis, and repair of damaged macromolecules. Nevertheless, not all observed effects could be simply attributed to the transition to Bvg⁻ phase, suggesting that additional regulators are involved in the adaptation to the intramacrophage environment. Interestingly, a large number of genes required for the metabolism of sulphur were strongly modulated within macrophages. In particular, the mutant lacking two genes encoding cysteine dioxygenases displayed strongly attenuated cytotoxicity toward THP-1 cells. Collectively, our results suggest that intracellular B. pertussis cells have adopted the Bvg⁻ mode to acclimate to the intramacrophage environment and respond to antimicrobial activities elicited by THP-1 cells. Therefore, we hypothesize that the avirulent phase represents an authentic phenotype of internalized B. pertussis cells.

KEYWORDS:

• Bordetella pertussis
• BvgAS
• intramacrophage environment
• adaptation to stress
• cysteine toxicity
• avirulent phase

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

RNA-seq data from the sequencing runs were deposited in the European Nucleotide Archive under project accession number PRJEB33395 and will be available immediately from the date of publication.

Additional information

Funding

This work was supported by grant 23-05634S (to B.V.) from the Czech Science Foundation (www.gacr.cz), GAUK grant 301221 from the Grant Agency of Charles University in Prague (to A.S.), by funding from RVO61388971 and from the project National Institute of Virology and Bacteriology (Programme EXCELES, ID Project No. LX22NPO5103) funded by the European Union – Next Generation EU.