Serological characterization of the enterobacterial common antigen substitution of the lipopolysaccharide of "Yersinia enterocolitica" O:3

Enterobacterial common antigen (ECA) is a polysaccharide present in all members of Enterobacteriaceae anchored either via phosphatidylglycerol (PG) or LPS to the outer leaflet of the outer membrane (ECAPG and ECALPS, respectively). Only the latter form is ECAimmunogenic. We previously demonstrated that Yersinia enterocolitica O: 3 and its rough (Ospecific polysaccharide-negative) mutants were ECA-immunogenic, suggesting that they contained ECALPS; however, it was not known which part of the LPS core region was involved in ECA binding. To address this, we used a set of three deep-rough LPS mutants for rabbit immunization. The polyvalent antisera obtained were: (i) analysed for the presence of anti-LPS and anti-ECA antibodies; (ii) treated with caprylic acid (CA) to precipitate IgM antibodies and protein aggregates; and (iii) adsorbed with live ECA-negative bacteria to obtain specific anti-ECA antisera. We demonstrated the presence of antibodies specific for both ECAPG and ECALPS in all antisera obtained. Both CA treatment and adsorption with ECA-negative bacteria efficiently removed anti-LPS antibodies, resulting in specific anti-ECA sera. The LPS of the ECALPS-positive deepest-rough mutant contained only lipid A and 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo) residues of the inner core, suggesting that ECALPS was linked to the Kdo region of LPS in Y. enterocolitica O:3

Gd III and Ga III complexes with a new tris-3,4-HOPO ligand as new imaging probes: complex stability, magnetic properties and biodistribution

International audienceThe development of metal-based multimodal imaging probes is a highly challenging field in coordination chemistry. In this context, we have developed a bifunctional hexadentate tripodal ligand (H3L2) with three 3,4-HOPO moieties attached to a flexible tetrahedral carbon bearing a functionalizable nitro group. Complexes formed with different metal ions have potential interest for diagnostic applications, namely magnetic resonance imaging (MRI) and positron emission tomography (PET). The capacity of the ligand to coordinate GdIII and GaIII was studied and the thermodynamic stability constants of the respective complexes were determined by potentiometry and spectrophotometry. The ligand forms stable 1 : 1 ML complexes though with considerably higher affinity for GaIII than for GdIII (pGa = 26.2 and pGd = 14.3 at pH 7). The molecular dynamics simulations of the GdIII complex indicate that two water molecules can coordinate the metal ion, thus providing efficient paramagnetic enhancement of water proton relaxation. The relaxation and the water exchange properties of the GdIII chelate, assessed by a combined 17O NMR and 1H NMRD study, showed associative activated water exchange with a relatively low rate constant, k298ex = (0.82 ± 0.11) × 107 s−1, and some aggregation tendency. Biodistribution studies of the 67Ga-L2 complex suggested good in vivo stability and quick renal clearance. Further anchoring of this ligand with specific biotargeting moieties might open future prospectives for applications of labelled conjugates in both MRI and 68Ga-PET diagnostic imaging

Serological characterization of the enterobacterial common antigen substitution of the lipopolysaccharide of Yersinia enterocolitica O : 3

Enterobacterial common antigen (ECA) is a polysaccharide present in all members of Enterobacteriaceae anchored either via phosphatidylglycerol (PG) or LPS to the outer leaflet of the outer membrane (ECAPG and ECALPS, respectively). Only the latter form is ECAimmunogenic. We previously demonstrated that Yersinia enterocolitica O: 3 and its rough (Ospecific polysaccharide-negative) mutants were ECA-immunogenic, suggesting that they contained ECALPS; however, it was not known which part of the LPS core region was involved in ECA binding. To address this, we used a set of three deep-rough LPS mutants for rabbit immunization. The polyvalent antisera obtained were: (i) analysed for the presence of anti-LPS and anti-ECA antibodies; (ii) treated with caprylic acid (CA) to precipitate IgM antibodies and protein aggregates; and (iii) adsorbed with live ECA-negative bacteria to obtain specific anti-ECA antisera. We demonstrated the presence of antibodies specific for both ECAPG and ECALPS in all antisera obtained. Both CA treatment and adsorption with ECA-negative bacteria efficiently removed anti-LPS antibodies, resulting in specific anti-ECA sera. The LPS of the ECALPS-positive deepest-rough mutant contained only lipid A and 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo) residues of the inner core, suggesting that ECALPS was linked to the Kdo region of LPS in Y. enterocolitica O:3