Deletion ofwboAEnhances Activation of the Lectin Pathway of Complement inBrucella abortusandBrucella melitensis

Fernandez-Prada, Carmen M.; Nikolich, Mikeljon P.; Vemulapalli, Ramesh; Sriranganathan, Nammalwar; Boyle, Stephen M.; Schurig, Gerhardt G.; Hadfield, Ted L.; Hoover, David L.

doi:10.1128/iai.69.7.4407-4416.2001

Cited by 57 publications

(52 citation statements)

References 62 publications

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“…Regarding the interaction of Brucella with human complement, it has been demonstrated that the bacteria are considerably more resistant to the killing action of human serum than other Gram-negative bacteria (5,39). In spite of this, the binding of human complement components to the surface of B. abortus was conspicuous and commensurate with the opsonization of this bacterium by normal serum.…”

Section: Discussionmentioning

confidence: 99%

N -Formyl-Perosamine Surface Homopolysaccharides Hinder the Recognition of Brucella abortus by Mouse Neutrophils

et al. 2016

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c Brucella abortus is an intracellular pathogen of monocytes, macrophages, dendritic cells, and placental trophoblasts. This bacterium causes a chronic disease in bovines and in humans. In these hosts, the bacterium also invades neutrophils; however, it fails to replicate and just resists the killing action of these leukocytes without inducing significant activation or neutrophilia. Moreover, B. abortus causes the premature cell death of human neutrophils. In the murine model, the bacterium is found within macrophages and dendritic cells at early times of infection but seldom in neutrophils. Based on this observation, we explored the interaction of mouse neutrophils with B. abortus. In contrast to human, dog, and bovine neutrophils, naive mouse neutrophils fail to recognize smooth B. abortus bacteria at early stages of infection. Murine normal serum components do not opsonize smooth Brucella strains, and neutrophil phagocytosis is achieved only after the appearance of antibodies. Alternatively, mouse normal serum is capable of opsonizing rough Brucella mutants. Despite this, neutrophils still fail to kill Brucella, and the bacterium induces cell death of murine leukocytes. In addition, mouse serum does not opsonize Yersinia enterocolitica O:9, a bacterium displaying the same surface polysaccharide antigen as smooth B. abortus. Therefore, the lack of murine serum opsonization and absence of murine neutrophil recognition are specific, and the molecules responsible for the Brucella camouflage are N-formyl-perosamine surface homopolysaccharides. Although the mouse is a valuable model for understanding the immunobiology of brucellosis, direct extrapolation from one animal system to another has to be undertaken with caution.

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Section: Discussionmentioning

confidence: 99%

N -Formyl-Perosamine Surface Homopolysaccharides Hinder the Recognition of Brucella abortus by Mouse Neutrophils

et al. 2016

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“…Because CA180 killed macrophages rapidly, we have also postulated that the rough mutants are killed when exposed to complement and other bactericidal factors after the infected macrophages lyse. However, reports of resistance of B. melitensis rough mutants to complement-mediated lysis (16) suggests a different possible fate for such organisms. The fact that rough organisms are rarely identified in clinical specimens suggests that spontaneously occurring rough derivatives may be similar to B. abortus RB51 or B. canis, but characterization of such mutants does not support this contention.…”

Section: Discussionmentioning

confidence: 99%

Brucella abortusRough Mutants Are Cytopathic for Macrophages in Culture

Pei¹,

Ficht²

2004

Infect Immun

148

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Rough mutants of Brucella spp. are attenuated for survival in animal models. However, conflicting in vitro evidence has been obtained concerning the intracellular survival of rough mutants. Transposon-derived rough mutants isolated in our laboratory were previously shown to exhibit small but significant reductions in intracellular survival in a 12-h in vitro assay. Several recent publications report that rough mutants exhibited increased macrophage uptake relative to their smooth parental strains, and a reduction in numbers at the end of the assay has been interpreted as intracellular killing. In an effort to explore the role of O antigen in the interaction between Brucella abortus and macrophages, we have monitored the uptake of rough mutants and survival in vitro by using the murine macrophage cell line J774.A1. The results confirm a 10-to 20-foldincreased uptake of rough mutants over that of smooth organisms under standard conditions. Recovery of the rough mutants persisted up to 8 h postinfection, but at the point when intracellular replication of the smooth organisms was observed, the number of rough organisms recovered declined. Fluorescence microscopy revealed the intracellular multiplication of both smooth and rough organisms, and assays performed in the absence of antibiotic confirmed the replication of the rough organisms. Examination by phase-contrast microscopy revealed the lytic death of macrophages infected with the rough mutants, which was confirmed by the release of lactate dehydrogenase (LDH) from the cell cytoplasm. Thus, the decline in the number of rough organisms was the result of the lysis of macrophages and not from intracellular killing. The cytopathic effect is characterized as necrotic rather than apoptotic cell death based on early LDH release, annexin V and propidium iodide staining, morphological changes of infected cells and nuclei, and glycine protection. The cytopathic effect was observed with macrophages at multiplicities of infection (MOIs) of as low as 20 and was not observed with epithelial cells at MOIs of as high as 2000. These findings suggest a role for O antigen during the early stages of host-agent interaction that is essential in establishing an intracellular niche that maintains and supports persistent intracellular infection resulting in disease.Brucella spp. are facultative intracellular bacteria that cause brucellosis in a variety of animals and undulant fever in humans (3). Brucellosis is a worldwide zoonosis characterized by persistence of the organism in the reticuloendothelial system in secondary hosts and in the reproductive system in primary hosts. The ability of these organisms to survive in professional and nonprofessional phagocytic cells is the basis for disease (18). The gene products and mechanisms that are essential for the intracellular lifestyle are currently under investigation. Among these, the O antigen has been classified as a major virulence determinant of Brucella and is essential for survival of the classical species in the host. Although it is...

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“…This attenuation has been ascribed to the increase in both the antibodyindependent complement activation [3,27,44] and the sensitivity to polycationic bactericidal peptides [3,47,74,105]. In addition, R mutants display altered attachment to cells [32,48,115].…”

Section: Brucella Rough (R) Mutantsmentioning

confidence: 99%

Rough vaccines in animal brucellosis: Structural and genetic basis and present status

Grilló²,

et al. 2004

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-Brucellosis control and eradication requires serological tests and vaccines. Effective classical vaccines (S19 in cattle and Rev 1 in small ruminants), however, induce antibodies to the O-polysaccharide of the lipopolysaccharide which may be difficult to distinguish from those resulting from infection and may thus complicate diagnosis. Rough attenuated mutants lack the O-polysaccharide and would solve this problem if eliciting protective immunity; the empirically obtained rough mutants 45/20 and RB51 have been used as vaccines. Strain 45/20 is reportedly unstable and it is not presently used. RB51 is increasingly used instead of S19 in some countries but it is rifampicin resistant and its effectiveness is controversial. Some controlled experiments have found good or absolute protection in adult cattle vaccinated orally (full dose) or subcutaneously (reduced dose) and in one field experiment, RB51 was reported to afford absolute protection to calves and to perform better than S19. Controlled experiments in calves, however, have shown reduced doses of RB51 to be ineffective, full doses only partially effective, and RB51 less effective than S19 against severe challenges. Moreover, other observations suggest that RB51 is ineffective when prevalence is high. RB51 is not useful in sheep and evidence in goats is preliminary and contradictory. Rough mutants obtained by molecular biology methods on the knowledge of the genetics and structure of Brucella lipopolysaccharide may offer alternatives. The B. abortus manB core (rfbK) mutant seems promising in cattle, and analyses in mice suggest that mutations affecting only the O-polysaccharide result in better vaccines than those affecting both core and O-polysaccharide. Possible uses of rough vaccines also include boosting immunity by revaccination but solid evidence on its effectiveness, safety and practicality is not available.

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Deletion ofwboAEnhances Activation of the Lectin Pathway of Complement inBrucella abortusandBrucella melitensis

Cited by 57 publications

References 62 publications

N -Formyl-Perosamine Surface Homopolysaccharides Hinder the Recognition of Brucella abortus by Mouse Neutrophils

N -Formyl-Perosamine Surface Homopolysaccharides Hinder the Recognition of Brucella abortus by Mouse Neutrophils

Brucella abortusRough Mutants Are Cytopathic for Macrophages in Culture

Rough vaccines in animal brucellosis: Structural and genetic basis and present status

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