Showing papers by "Edgardo Moreno published in 2005"
TL;DR: It is shown that the cyclic β-1,2-glucans synthesized by brucella is important for circumventing host cell defenses and is a virulence factor that interacts with lipid rafts and contributes to pathogen survival.
Abstract: Pathogenic brucella bacteria have developed strategies to persist for prolonged periods of time in host cells, avoiding innate immune responses Here we show that the cyclic beta-1,2-glucans (CbetaG) synthesized by brucella is important for circumventing host cell defenses CbetaG acted in lipid rafts found on host cell membranes CbetaG-deficient mutants failed to prevent phagosome-lysosome fusion and could not replicate However, when treated with purified CbetaG or synthetic methyl-beta-cyclodextrin, the mutants were able to control vacuole maturation by avoiding lysosome fusion, and this allowed intracellular brucella to survive and reach the endoplasmic reticulum Fusion between the endoplasmic reticulum and the brucella-containing vacuole depended on the brucella virulence type IV secretion system but not on CbetaG Brucella CbetaG is thus a virulence factor that interacts with lipid rafts and contributes to pathogen survival
274 citations
TL;DR: Brucella is a facultative intracellular bacterium responsible for brucellosis that possesses an unconventional non-endotoxic lipopolysaccharide that confers resistance to anti-microbial attacks and modulates the host immune response, which makes lipopoly Saccharide an important virulence factor for Brucella survival and replication in the host.
253 citations
TL;DR: It is found that during infection of macrophages, Brucella avoids activation of Toll-like receptor 4 at 6 h but activates TLR4, TLR2, and myeloid differentiation factor 88 (MyD88) at 24 h postinfection, and even though its activation is delayed, MyD88 is important for host defense against BrucellA infection in vivo.
Abstract: It is not clear how the host initially recognizes and responds to infection by gram-negative pathogenic Brucella spp. It was previously shown (D. S. Weiss, B. Raupach, K. Takeda, S. Akira, and A. Zychlinsky, J. Immunol. 172:4463-4469, 2004) that the early macrophage response against gram-negative bacteria is mediated by Toll-like receptor 4 (TLR4), which signals in response to lipopolysaccharide (LPS). Brucella, however, has a noncanonical LPS which does not have potent immunostimulatory activity. We evaluated the kinetics of TLR4 activation and the cytokine response in murine macrophages after Brucella infection. We found that during infection of macrophages, Brucella avoids activation of TLR4 at 6 h but activates TLR4, TLR2, and myeloid differentiation factor 88 (MyD88) at 24 h postinfection. Interestingly, even though its activation is delayed, MyD88 is important for host defense against Brucella infection in vivo, since MyD88(-/-) mice do not clear the bacteria as efficiently as wild-type, TLR4(-/-), TLR2(-/-), or TLR4/TLR2(-/-) mice.
96 citations
TL;DR: It is proposed that in Brucella the outer membrane homeostasis depends on the functioning of BvrS/BvrR, thus contributing to the severe attenuation manifested by bvrS and bvrR mutants.
Abstract: The two-component BvrS/BvrR system is essential for Brucella abortus virulence It was shown previously that its dysfunction abrogates expression of some major outer membrane proteins and increases bactericidal peptide sensitivity Here, we report that BvrS/BvrR mutants have increased surface hydrophobicity and susceptibility to killing by nonimmune serum The bvrS and bvrR mutant lipopolysaccharides (LPSs) bound more polymyxin B, chimeras constructed with bvrS mutant cells and parental LPS showed augmented polymyxin B resistance, and, conversely, parental cells and bvrS mutant LPS chimeras were more sensitive and displayed polymyxin B-characteristic outer membrane lesions, implicating LPS as being responsible for the phenotype of the BvrS/BvrR mutants No qualitative or quantitative changes were detected in other envelope and outer membrane components examined: periplasmic β(1-2) glucans, native hapten polysaccharide, and phospholipids The LPS of the mutants was similar to parental LPS in O-polysaccharide polymerization and fine structure but showed both increased underacylated lipid A species and higher acyl-chain fluidity that correlated with polymyxin B binding These lipid A changes did not alter LPS cytokine induction, showing that in contrast to other gram-negative pathogens, recognition by innate immune receptors is not decreased by these changes in LPS structure Transcription of Brucella genes required for incorporating long acyl chains into lipid A (acpXL and lpxXL) or implicated in lipid A acylation control (bacA) was not affected We propose that in Brucella the outer membrane homeostasis depends on the functioning of BvrS/BvrR Accordingly, disruption of BvrS/BvrR damages the outer membrane, thus contributing to the severe attenuation manifested by bvrS and bvrR mutants
79 citations
TL;DR: The bactericidal and anti-endotoxic properties of pEM-2, combined with its relatively low toxicity towards eukaryotic cells, highlight it as a promising candidate for further evaluation of its antimicrobial potential in vivo.
76 citations
TL;DR: It is demonstrated that phospholipase A2-derived peptides may have the potential to counteract microbial infections and encourage further evaluations of their actions in vivo.
Abstract: The activities of short synthetic, nonhemolytic peptides derived from the C-terminal region of myotoxin II, a catalytically inactive phospholipase A 2 homologue present in the venom of the snake Bothrops asper , have been shown to reproduce the bactericidal activity of the parent protein. They combine cationic and hydrophobic-aromatic amino acids, thus functionally resembling the antimicrobial peptides of innate defenses. This study evaluated the antimicrobial and antiendotoxic properties of a 13-mer derivative peptide of the C-terminal sequence from positions 115 to 129 of myotoxin II, named pEM-2. This peptide (KKWRWWLKALAKK) showed bactericidal activity against both gram-positive and gram-negative bacteria. In comparison to previously described peptide variants derived from myotoxin II, the toxicity of pEM-2 toward eukaryotic cells in culture was significantly reduced, being similar to that of lactoferricin B but lower than that of polymyxin B. The all-d enantiomer of pEM-2 [pEM-2 (d)] retained the same bactericidal potency of its l-enantiomeric counterpart, but it showed an enhanced ability to counteract the lethal activity of an intraperitoneal lipopolysaccharide challenge in mice, which correlated with a significant reduction of the serum tumor necrosis factor alpha levels triggered by this endotoxin. Lethality induced by intraperitoneal infection of mice with Escherichia coli or Salmonella enterica serovar Typhimurium was reduced by the administration of pEM-2 (d). These results demonstrate that phospholipase A 2 -derived peptides may have the potential to counteract microbial infections and encourage further evaluations of their actions in vivo.
55 citations