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Ollivier, E.

Publications and source records attributed to Ollivier, E..

2 recordsLinked to original sources
bioRxiv2025

Complementary killing activities of Pbunavirus LS1 and Bruynoghevirus LUZ24 phages on planktonic and sessile Pseudomonas aeruginosa PAO1 derivatives

Four P. aeruginosa phages active against a representative panel of strains, and with complementary spectra of action were chosen with the goal of using them for phage therapy. Two of them were myoviruses belonging to the Pbunavirus LS1 species, and two were podoviruses belonging to the Bruynoghevirus LUZ24 species. In order to better apprehend the interactions of these phages with their P. aeruginosa host bacteria, we undertook the characterization of their bacterial receptors, using a PAO1 derivative as a recipient strain. Whereas the receptor of the P. LS1 phage Ab27 had already been characterized as the O-antigen chain of the lipopolysaccharides, no information was available at the onset of this work on the receptor used by the phages of the B. LUZ24 species. We show that the surface polysaccharide Psl is this receptor. Psl stands for polysaccharide synthesis locus, and it is an important component of the biofilm matrix in a large panel of P. aeruginosa strains, including PAO1. Remarkably, the B. LUZ24 phages were more active against PAO1 in minimal medium compared to rich medium. Consistently, this was correlated with larger amounts of Psl bound at the bacterial surface during exponential growth in the minimal medium compared to the rich medium. Biofilms formed on a medical intubation device, as well as in in 96-well plates, were degraded to different extent by the two phage species: biofilms grown for 7 hours on tubing device were degraded more efficiently by the B. LUZ24 than the P. LS1 phage, whereas mature biofilms (16 hours) formed in 96-well plates were degraded more rapidly by P. LS1 than by B. LUZ24 phage. The frequency of genetic mutants resisting to each phage were determined in liquid medium by a fluctuation assay and found in the range of 10-5 to 10-6 per generation. Interestingly, most of the P. LS1 resisting mutants were more sensitive to the B. LUZ24 phage. We conclude that the combination of the four selected phages has very promising properties, which should be relevant in the framework of phage therapy.

microbiology↗
bioRxiv2020

SARS-CoV-2 proteases cleave IRF3 and critical modulators of inflammatory pathways (NLRP12 and TAB1): implications for disease presentation across species and the search for reservoir hosts.

The genome of SARS-CoV-2 (SARS2) encodes for two viral proteases (NSP3/ papain-like protease and NSP5/ 3C-like protease or major protease) that are responsible for cleaving viral polyproteins for successful replication. NSP3 and NSP5 of SARS-CoV (SARS1) are known interferon antagonists. Here, we examined whether the protease function of SARS2 NSP3 and NSP5 target proteins involved in the host innate immune response. We designed a fluorescent based cleavage assay to rapidly screen the protease activity of NSP3 and NSP5 on a library of 71 human innate immune proteins (HIIPs), covering most pathways involved in human innate immunity. By expressing each of these HIIPs with a genetically encoded fluorophore in a cell-free system and titrating in the recombinant protease domain of NSP3 or NSP5, we could readily detect cleavage of cognate HIIPs on SDS-page gels. We identified 3 proteins that were specifically and selectively cleaved by NSP3 or NSP5: IRF-3, and NLRP12 and TAB1, respectively. Direct cleavage of IRF3 by NSP3 could explain the blunted Type- I IFN response seen during SARS-CoV-2 infections while NSP5 mediated cleavage of NLRP12 and TAB1 point to a molecular mechanism for enhanced production of IL-6 and inflammatory response observed in COVID-19 patients. Surprisingly, both NLRP12 and TAB1 have each two distinct cleavage sites. We demonstrate that in mice, the second cleavage site of NLRP12 is absent. We pushed this comparative alignment of IRF-3 and NLRP12 homologs and show that the lack or presence of cognate cleavage motifs in IRF-3 and NLRP12 could contribute to the presentation of disease in cats and tigers, for example. Our findings provide an explanatory framework for in-depth studies into the pathophysiology of COVID-19 and should facilitate the search or development of more effective animal models for severe COVID-19. Finally, we discovered that one particular species of bats, Davids Myotis, possesses the five cleavage sites found in humans for NLRP12, TAB1 and IRF3. These bats are endemic from the Hubei province in China and we discuss its potential role as reservoir for the evolution of SARS1 and SASR2.

molecular biology↗