Macrophage infectivity potentiator protein, a peptidyl prolyl cis-trans isomerase, essential for Coxiella burnetii growth and pathogenesis

PLoS Pathog. 2023 Jul 3;19(7):e1011491. doi: 10.1371/journal.ppat.1011491. eCollection 2023 Jul.

Abstract

Coxiella burnetii is a Gram-negative intracellular pathogen that causes the debilitating disease Q fever, which affects both animals and humans. The only available human vaccine, Q-Vax, is effective but has a high risk of severe adverse reactions, limiting its use as a countermeasure to contain outbreaks. Therefore, it is essential to identify new drug targets to treat this infection. Macrophage infectivity potentiator (Mip) proteins catalyse the folding of proline-containing proteins through their peptidyl prolyl cis-trans isomerase (PPIase) activity and have been shown to play an important role in the virulence of several pathogenic bacteria. To date the role of the Mip protein in C. burnetii pathogenesis has not been investigated. This study demonstrates that CbMip is likely to be an essential protein in C. burnetii. The pipecolic acid derived compounds, SF235 and AN296, which have shown utility in targeting other Mip proteins from pathogenic bacteria, demonstrate inhibitory activities against CbMip. These compounds were found to significantly inhibit intracellular replication of C. burnetii in both HeLa and THP-1 cells. Furthermore, SF235 and AN296 were also found to exhibit antibiotic properties against both the virulent (Phase I) and avirulent (Phase II) forms of C. burnetii Nine Mile Strain in axenic culture. Comparative proteomics, in the presence of AN296, revealed alterations in stress responses with H2O2 sensitivity assays validating that Mip inhibition increases the sensitivity of C. burnetii to oxidative stress. In addition, SF235 and AN296 were effective in vivo and significantly improved the survival of Galleria mellonella infected with C. burnetii. These results suggest that unlike in other bacteria, Mip in C. burnetii is required for replication and that the development of more potent inhibitors against CbMip is warranted and offer potential as novel therapeutics against this pathogen.

MeSH terms

  • Animals
  • Bacteria / metabolism
  • Bacterial Proteins / metabolism
  • Coxiella burnetii*
  • Humans
  • Hydrogen Peroxide / metabolism
  • Macrophages / metabolism
  • Peptidylprolyl Isomerase / metabolism
  • Q Fever*

Substances

  • Peptidylprolyl Isomerase
  • Bacterial Proteins
  • Hydrogen Peroxide

Grants and funding

Funding for HJN’s research team is supported by NHMRC Idea’s grant 2010841. This work was supported by Dstl contract DSTLX-1000051512 to NJH. IHN, CHJ and GM were funded by the UK Ministry of Defence. This work was supported by the North Atlantic Treaty Organization (NATO), Brussels, Belgium grant SPS 984835, and the German Research Foundation (DFG, Bonn, Germany; grant SFB 630) for the development of Mip inhibitors against L. pneumophila and B. pseudomallei, respectively, and The Federal Ministry of Education and Research for the development of Mip inhibitors against T. cruzi and B. pseudomallei, given to UH. This paper includes research that was supported by DMTC Limited (Australia) to MST, AWD, NMB, JI and EAK. The authors have prepared this paper in accordance with the intellectual property rights granted to partners from the original DMTC project. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.