A chronic strain of the cystic fibrosis pathogen Pandoraeapulmonicola expresses a heterogenous hypo-acylated lipid A

Pandoraeasp. is an emerging Gram-negative pathogen in cystic fibrosis causing severe and persistent inflammation and damageof the lungs. The molecular mechanisms underlying the high pathogenicity ofPandoraeaspecies are still largely unknown. AsGram-negatives,Pandoraeasp. express lipopolysaccharides (LPS) whose recognition by the host immune system triggers aninflammatory response aimed at the bacterial eradication from the infected tissues. The degree of the inflammatory responsestrongly relies on the fine structure of the LPS and, in particular, of its glycolipid moiety, i.e. the lipid A. Here we report thestructure of the lipid A isolated from the LPS of a chronic strain ofP. pulmonicola(RL 8228), one of the most virulent identifiedso far among thePandoraeaspecies. Our data demonstrated that the examined chronic strain produces a smooth-type LPS with acomplex mixture of hypoacylated lipid A species displaying, among other uncommon characteristics, the 2-hydroxylation ofsome of the acyl chains and the substitution by an additional glucosamine on one or both the phosphate groups

Pairing Bacteroides vulgatus LPS structure with its immunomodulatory effects on human cellular models

15 p.-5 fig.-1 tab.-1 graph abst. This paper is dedicated to Prof. Jesús Jiménez-Barbero for his 60th birthday.The gut microbiota guide the development of the host immune system by setting a systemic threshold for immune activation. Lipopolysaccharides (LPSs) from gut bacteria are able to trigger systemic and local proinflammatory and immunomodulatory responses, and this capability strongly relies on their fine structures. Up to now, only a few LPS structures from gut commensals have been elucidated; therefore, the molecular motifs that may be important for LPS–mammalian cell interactions at the gut level are still obscure. Here, we report on the full structure of the LPS isolated from one of the prominent species of the genus Bacteroides, Bacteroides vulgatus. The LPS turned out to consist of a particular chemical structure based on hypoacylated and mono-phosphorylated lipid A and with a galactofuranose-containing core oligosaccharide and an O-antigen built up of mannose and rhamnose. The evaluation of the immunological properties of this LPS on human in vitro models revealed a very interesting capability to produce anti-inflammatory cytokines and to induce a synergistic action of MD-2/TLR4- and TLR2-mediated signaling pathways.F.D.L. acknowledges Progetto STAR 2018 Linea 1 grant E66C18001330003. S.M.S. acknowledges Spanish Ministry of Science (ref. CTQ2017-88353-R). A.M., F.D.L., and A.S.acknowledge H2020 Marie Skłodowska-Curie ITN 2018 “SweetCrossTalk” grant 814102. A.M. acknowledges progetto POR SATIN POR-FESR 2014−2 0 2 0 g r a n t B61C17000070007 (OR3) and Progetto POR Campania Oncoterapia 2014−2020 grant B61G18000470007. A.S. acknowledges PRIN-MIUR 2017 Glytunes project. A.S. and F.C. acknowledge COST (European Cooperation in Science and Technology) Action CA18103 (INNOGLY). F.C. was financially supported by the NWO Spinoza award of Y.K.Peer reviewe

Lipopolysaccharide from Gut‐Associated Lymphoid‐Tissue‐Resident Alcaligenes faecalis

AbstractAlcaligenes faecalis is the predominant Gram‐negative bacterium inhabiting gut‐associated lymphoid tissues, Peyer's patches. We previously reported that an A. faecalis lipopolysaccharide (LPS) acted as a weak agonist for Toll‐like receptor 4 (TLR4)/myeloid differentiation factor‐2 (MD‐2) receptor as well as a potent inducer of IgA without excessive inflammation, thus suggesting that A. faecalis LPS might be used as a safe adjuvant. In this study, we characterized the structure of both the lipooligosaccharide (LOS) and LPS from A. faecalis. We synthesized three lipid A molecules with different degrees of acylation by an efficient route involving the simultaneous introduction of 1‐ and 4′‐phosphates. Hexaacylated A. faecalis lipid A showed moderate agonistic activity towards TLR4‐mediated signaling and the ability to elicit a discrete interleukin‐6 release in human cell lines and mice. It was thus found to be the active principle of the LOS/LPS and a promising vaccine adjuvant candidate