A new article entitled “The lytic polysaccharide monooxygenase CbpD promotes Pseudomonas aeruginosa virulence in systemic infection” has just been published in Nature Communications by an interdisciplinary team of researchers with affiliations to universities and research institutes in Norway, The Netherlands and the USA.
Since the discovery that the opportunistic pathogen Pseudomonas aeruginosa secretes an enzyme named chitin-binding protein D (CbpD) belonging to the group of lytic polysaccharide monooxygenases (LPMO) in 2000 (Jindra Folders et al., J. Bacteriol., 182, 1257-1263 (2000)), little data has been established regarding the impact of CbpD on the pathogenicity of Pseudomonas aeruginosa. Therefore, in the new study, extensive and complex data were elaborated to investigate a potential association of CbpD and the virulence of Pseudomonas aeruginosa. The experiments conducted in the study aimed at the (i) elucidation of structural features of the protein as well as of (ii) the physiological role of CbpD and its pathophysiological impact. The latter was approached by numerous analyses which were mostly based on a comparison of the effects of a wildtype (WT) Pseudomonas aeruginosa strain vs. a mutant lacking CbpD (ΔCbpD) on various parameters ex vivo and in vivo.
In one experiment focusing on the effect of an infection with the WT vs. the ΔCbpD mutant on host immune system, a histopathological evaluation of splenic tissue samples of infected mice was conducted. The H&E-stained spleen sections were scanned with the Microvisioneer manualWSI software to subsequently determine the extent of infiltration of neutrophils.
Overall, the authors could show that CbpD is required for Pseudomonas aeruginosa to establish a lethal systemic infection, and to evade bacterial clearance by the host. To maintain the virulence function, CbpD needs to be secreted, and to be catalytically active.
Further, it was observed that a loss of CbpD lead to significant bacterial proteome changes in the ΔCbpD mutant compared to the WT. The loss of CbpD was also reflected by pronounced changes in the host splenic proteome upon infection when compared to the effects of an infection with the WT.
With regards to a potential mechanism of action, an attenuation of the terminal complement cascade during innate immune response was observed for the WT but not for the ΔCbpD mutant, which could thus be considered as one interaction underlying a CbpD-mediated virulence of Pseudomonas aeruginosa.
Taken together, this comprehensive new study substantiates previous hypotheses on a role of the LPMO CbpD in the virulence of the important pathogen Pseudomonas aeruginosa and adds to a more complete picture of the complex implications and interactions to be associated with CbpD.
Fatemeh Askarian, Satoshi Uchiyama, Helen Masson, Henrik Vinther Sørensen, Ole Golten, Anne Cathrine Bunæs, Sophanit Mekasha, Åsmund Kjendseth Røhr, Eirik Kommedal, Judith Anita Ludviksen, Magnus Ø. Arntzen, Benjamin Schmidt, Raymond H. Zurich, Nina M. van Sorge, Vincent G. H. Eijsink, Ute Krengel, Tom Eirik Mollnes, Nathan E. Lewis, Victor Nizet, Gustav Vaaje-Kolstad: The lytic polysaccharide monooxygenase CbpD promotes Pseudomonas aeruginosa virulence in systemic infection, Nature Communications, 2021