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© Christine Schmitt, Meriem El Ghachi, Jean-Marc Panaud
Bactérie Helicobacter pylori en microscopie électronique à balayage. Agent causal de pathologies de l'estomac : elle est responsable des gastrites chroniques, d'ulcères gastriques et duodénaux et elle joue un rôle important dans la genèse des cancers gastriques (adénocarcinomes et lymphomes).
Publication : PLoS pathogens

Leptospiral LPS escapes mouse TLR4 internalization and TRIF‑associated antimicrobial responses through O antigen and associated lipoproteins.

Scientific Fields
Diseases
Organisms
Applications
Technique

Published in PLoS pathogens - 13 Aug 2020

Bonhomme D, Santecchia I, Vernel-Pauillac F, Caroff M, Germon P, Murray G, Adler B, Boneca IG, Werts C,

Link to Pubmed [PMID] – 32790743

Link to DOI [DOI] – 10.1371/journal.ppat.1008639

PLoS Pathog. 2020 08; 16(8): e1008639

Leptospirosis is a worldwide re-emerging zoonosis caused by pathogenic Leptospira spp. All vertebrate species can be infected; humans are sensitive hosts whereas other species, such as rodents, may become long-term renal carrier reservoirs. Upon infection, innate immune responses are initiated by recognition of Microbial Associated Molecular Patterns (MAMPs) by Pattern Recognition Receptors (PRRs). Among MAMPs, the lipopolysaccharide (LPS) is recognized by the Toll-Like-Receptor 4 (TLR4) and activates both the MyD88-dependent pathway at the plasma membrane and the TRIF-dependent pathway after TLR4 internalization. We previously showed that leptospiral LPS is not recognized by the human-TLR4, whereas it signals through mouse-TLR4 (mTLR4), which mediates mouse resistance to acute leptospirosis. However, although resistant, mice are known to be chronically infected by leptospires. Interestingly, the leptospiral LPS has low endotoxicity in mouse cells and is an agonist of TLR2, the sensor for bacterial lipoproteins. Here, we investigated the signaling properties of the leptospiral LPS in mouse macrophages. Using confocal microscopy and flow cytometry, we showed that the LPS of L. interrogans did not induce internalization of mTLR4, unlike the LPS of Escherichia coli. Consequently, the LPS failed to induce the production of the TRIF-dependent nitric oxide and RANTES, both important antimicrobial responses. Using shorter LPS and LPS devoid of TLR2 activity, we further found this mTLR4-TRIF escape to be dependent on both the co-purifying lipoproteins and the full-length O antigen. Furthermore, our data suggest that the O antigen could alter the binding of the leptospiral LPS to the co-receptor CD14 that is essential for TLR4-TRIF activation. Overall, we describe here a novel leptospiral immune escape mechanism from mouse macrophages and hypothesize that the LPS altered signaling could contribute to the stealthiness and chronicity of the leptospires in mice.

https://pubmed.ncbi.nlm.nih.gov/32790743