Showing papers by "Jean-Pierre Gorvel published in 2018"

Immunomodulatory properties of Brucella melitensis lipopolysaccharide determinants on mouse dendritic cells in vitro and in vivo.

Abstract: The lipopolysaccharide (LPS) is a major virulence factor of Brucella, a facultative intracellular pathogenic Gram-negative bacterium. Brucella LPS exhibits a low toxicity and its atypical structure was postulated to delay the host immune response, favouring the establishment of chronic disease. Here we carried out an in-depth in vitro and in vivo characterisation of the immunomodulatory effects of Brucella LPS on different dendritic cell (DC) subpopulations. By using LPSs from bacteria that share some of Brucella LPS structural features, we demonstrated that the core component of B. melitensis wild-type (Bm-wt) LPS accounts for the low activation potential of Brucella LPS in mouse GM-CSF-derived (GM-) DCs. Contrary to the accepted dogma considering Brucella LPS a poor TLR4 agonist and DC activator, Bm-wt LPS selectively induced expression of surface activation markers and cytokine secretion from Flt3-Ligand-derived (FL-) DCs in a TLR4-dependent manner. It also primed in vitro T cell proliferation by FL-DCs. In contrast, modified LPS with a defective core purified from Brucella carrying a mutated wadC gene (Bm-wadC), efficiently potentiated mouse and human DC activation and T cell proliferation in vitro. In vivo, Bm-wt LPS promoted scant activation of splenic DC subsets and limited recruitment of monocyte- DC like cells in the spleen, conversely to Bm-wadC LPS. Bm-wadC live bacteria drove high cytokine secretion levels in sera of infected mice. Altogether, these results illustrate the immunomodulatory properties of Brucella LPS and the enhanced DC activation ability of the wadC mutation with potential for vaccine development targeting Brucella core LPS structure.

Persistence of Brucella abortus in the Bone Marrow of Infected Mice

Abstract: Brucellosis is a zoonotic bacterial infection that may persist for long periods causing relapses in antibiotic-treated patients. The ability of Brucella to develop chronic infections is linked to their capacity to invade and replicate within the mononuclear phagocyte system, including the bone marrow (BM). Persistence of Brucella in the BM has been associated with hematological complications such as neutropenia, thrombocytopenia, anemia, and pancytopenia in human patients. In the mouse model, we observed that the number of Brucella abortus in the BM remained constant for up to 168 days of postinfection. This persistence was associated with histopathological changes, accompanied by augmented numbers of BM myeloid GMP progenitors, PMNs, and CD4+ lymphocytes during the acute phase (eight days) of the infection in the BM. Monocytes, PMNs, and GMP cells were identified as the cells harboring Brucella in the BM. We propose that the BM is an essential niche for the bacterium to establish long-lasting infections and that infected PMNs may serve as vehicles for dispersion of Brucella organisms, following the Trojan horse hypothesis. Monocytes are solid candidates for Brucella reservoirs in the BM.

Cyclic β-glucans at the bacteria-host cells interphase: One sugar ring to rule them all.

Abstract: Cyclic β-1,2-D-glucans (CβG) are natural bionanopolymers present in the periplasmic space of many Proteobacteria. These molecules are sugar rings made of 17 to 25 D-glucose units linked exclusively by β-1,2-glycosidic bonds. CβG are important for environmental sensing and osmoadaptation in bacteria, but most importantly, they play key roles in complex host-cell interactions such as symbiosis, pathogenesis, and immunomodulation. In the last years, the identification and characterisation of the enzymes involved in the synthesis of CβG allowed to know in detail the steps necessary for the formation of these sugar rings. Due to its peculiar structure, CβG can complex large hydrophobic molecules, a feature possibly related to its function in the interaction with the host. The capabilities of the CβG to function as molecular boxes and to solubilise hydrophobic compounds are attractive for application in the development of drugs, in food industry, nanotechnology, and chemistry. More importantly, its excellent immunomodulatory properties led to the proposal of CβG as a new class of adjuvants for vaccine development.

Identification of lptA, lpxE, and lpxO, Three Genes Involved in the Remodeling of Brucella Cell Envelope

Abstract: This research was supported by the Institute for Tropical Health funders (Obra Social la CAIXA, Fundaciones Caja Navarra and Roviralta, PROFAND, Ubesol, ACUNSA, and Artai) and grants MINECO (AGL2014-58795-C4-1-R, Bru-Epidia 291815-FP7/ERANET/ANIHWA), Aragon Government (Consolidated Group A14), and Marie Curie Career Integration Grant U-KARE (PCIG13-GA-2013-618162). TLB is the recipient of a Ph.D. Fellowship funded by the Department for Employment and Learning (Northern Ireland, United Kingdom).

Contribution of bacterial effectors and host proteins to the composition and function of Salmonella‐induced tubules

Abstract: Cells infected with Salmonella are characterised by the appearance of membrane tubular structures that stretch from the bacterial vacuole The formation of these tubules requires the translocation of Salmonella effector proteins within the infected cell Different types of Salmonella-induced tubules with varying host protein compositions have been identified This variability probably reflects the ability of these tubules to interact with different host compartments Membrane tubules decorated with effector proteins but essentially devoid of host proteins and named LAMP1-negative (LNT) were observed LNTs wrap around LAMP1-positive vesicles and may promote recruitment of lysosomal glycoproteins to bacterial vacuole and the formation of a replication niche We conducted a biochemical and functional characterisation of LNTs We show that the effector proteins SseF and SseG are necessary for their formation The absence of these tubules is associated with decreased recruitment of LAMP1 to SCVs, decreased intracellular replication of Salmonella, and decreased virulence in mice We found that the process leading to the recruitment of lysosomal glycoproteins to tubules involves the C-terminal domain of the effector protein SifA and the GTPase Arl8b Overall, these data suggest that Salmonella-induced tubules promote the establishment of the replication niche by promoting recruitment of host proteins to the bacterial vacuole

Aminopeptidases Of Intestinal Brush Border Membrane

Abstract: Intestinal aminopeptidase A and aminopeptidase N are respectively responsible for the hydrolysis of acidic and neutral N-terminal residues of synthetic substrates such as p-nitroanilides and of the peptides resulting from protein degradation by pancreatic enzymes. They are among the more abundant hydrolases of the brush border membrane. In the absence of EDTA in an isotonic medium the brush border membrane spontaneously forms vesicles. An improved technique has been devised for the purification of large amounts of these vesicles. Electron micrographs of negative staining and thin sections of this material showed that vesicles are very homogeneous in size. The first type of vesicle preparation has been used for the topological studies of the external components of the membrane. The second type of vesicle preparation is performed; it is easy to trap into vesicles a high molecular weight reagent present in the medium as their formation proceeds.