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Shigella spp. are pathogenic bacteria that cause bacillary dysentery in humans by invading the colonic and rectal mucosa where they induce dramatic inflammation. Here, we have analyzed the role of the soluble PRR Pentraxin 3 (PTX3), a key component of the humoral arm of innate immunity. Mice that had been intranasally infected with S. flexneri were rescued from death by treatment with recombinant PTX3. In vitro PTX3 exerts the antibacterial activity against Shigella, impairing epithelial cell invasion and contributing to the bactericidal activity of serum. PTX3 is produced upon LPS-TLR4 stimulation in accordance with the lipid A structure of Shigella. In the plasma of infected patients, the level of PTX3 amount only correlates strongly with symptom severity. These results signal PTX3 as a novel player in Shigella pathogenesis and its potential role in fighting shigellosis. Finally, we suggest that the plasma level of PTX3 in shigellosis patients could act as a biomarker for infection severity. [ABSTRACT FROM AUTHOR]

The structural elucidation of lipopolysaccharides (LPSs) from Gram‐negative marine bacteria, along with the assessment of their immunological properties, is a fascinating and active research field. Such studies can aid understanding of adaptation phenomena that occur in the marine environment, but they can also open up new perspectives on the design and development of new immunoregulatory drugs. In this paper, we report the structural characterization of the lipid A component of the LPS isolated from the marine bacterium Cobetia pacifica KMM 3879T, which is characterized by a family of structures differing in their acylation patterns. The structural assignment was achieved through extensive chemical analysis and matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry. Moreover, cellular immunology studies on the LPS highlighted its low immunostimulatory impact, as well as a very interesting and promising inhibitory activity of the toxic effects of Escherichia coli LPS. [ABSTRACT FROM AUTHOR]

Pseudomonas aeruginosa can establish life-long airways chronic infection in patients with cystic fibrosis (CF) with pathogenic variants distinguished from initially acquired strain. Here, we analysed chemical and biological activity of P. aeruginosa Pathogen-Associated Molecular Patterns (PAMPs) in clonal strains, including mucoid and non-mucoid phenotypes, isolated during a period of up to 7.5 years from a CF patient. Chemical structure by MS spectrometry defined lipopolysaccharide (LPS) lipid A and peptidoglycan (PGN) muropeptides with specific structural modifications temporally associated with CF lung infection. Gene sequence analysis revealed novel mutation in pagL, which supported lipid A changes. Both LPS and PGN had different potencies when activating host innate immunity via binding TLR4 and Nod1. Significantly higher NF-κB activation, IL-8 expression and production were detected in HEK293hTLR4/MD2-CD14 and HEK293hNod1 after stimulation with LPS and PGN respectively, purified from early P. aeruginosa strain as compared to late strains. Similar results were obtained in macrophages-like cells THP-1, epithelial cells of CF origin IB3-1 and their isogenic cells C38, corrected by insertion of cystic fibrosis transmembrane conductance regulator (CFTR). In murine model, altered LPS structure of P. aeruginosa late strains induces lower leukocyte recruitment in bronchoalveolar lavage and MIP-2, KC and IL-1b cytokine levels in lung homogenates when compared with early strain. Histopathological analysis of lung tissue sections confirmed differences between LPS from early and late P. aeruginosa. Finally, in this study for the first time we unveil how P. aeruginosa has evolved the capacity to evade immune system detection, thus promoting survival and establishing favourable conditions for chronic persistence. Our findings provide relevant information with respect to chronic infections in CF. [ABSTRACT FROM AUTHOR]

The structural elucidation of lipopolysaccharides (LPSs) from Gram‐negative marine bacteria, along with the assessment of their immunological properties, is a fascinating and active research field. Such studies can aid understanding of adaptation phenomena that occur in the marine environment, but they can also open up new perspectives on the design and development of new immunoregulatory drugs. In this paper, we report the structural characterization of the lipid A component of the LPS isolated from the marine bacterium Cobetia pacifica KMM 3879T, which is characterized by a family of structures differing in their acylation patterns. The structural assignment was achieved through extensive chemical analysis and matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry. Moreover, cellular immunology studies on the LPS highlighted its low immunostimulatory impact, as well as a very interesting and promising inhibitory activity of the toxic effects of Escherichia coli LPS. [ABSTRACT FROM AUTHOR]

The structure and the immunology of the lipopolysaccharide (LPS) of Pseudomonas entomophila , an entomopathogenic bacterium isolated from the fruit fly Drosophila melanogaster , was characterized. The O-antigen portion was established and resulted to be built up of a repetitive unit constituted by four monosaccharide residues, all L configured, all deoxy at C-6 and with an acetamido function at C-2: →3)-α- l -FucNAc-(1→4)-α- l -FucNAc-(1→3)-α- l -FucNAc-(1→3)-β- l -QuiNAc-(1→ The structural analysis of lipid A, showed a mixture of different species. The diphosphorylated glucosamine backbone carries six fatty acids consistent with the composition C10:0 3(OH), C12:0 2(OH) and C12:0 3(OH), whereas other species differs by the number of phosphates and/or of fatty acids. The immunology experiments demonstrated that the LPS structure of P. entomophila displayed a low ability to engage the TLR4-mediated signaling correlated to a significant antagonistic activity toward hexa-acylated LPS structures. [ABSTRACT FROM AUTHOR]