Brucellosis vaccines: assessment of Brucella melitensis lipopolysaccharide rough mutants defective in core and O-polysaccharide synthesis and export

The brucellae are facultative intracellular bacteria that cause brucellosis, one of the major neglected zoonoses. In endemic areas, vaccination is the only effective way to control this disease. Brucella melitensis Rev 1 is a vaccine effective against the brucellosis of sheep and goat caused by B. melitensis, the commonest source of human infection. However, Rev 1 carries a smooth lipopolysaccharide with an O-polysaccharide that elicits antibodies interfering in serodiagnosis, a major problem in eradication campaigns. Because of this, rough Brucella mutants lacking the O-polysaccharide have been proposed as vaccines. METHODOLOGY/PRINCIPAL FINDINGS: To examine the possibilities of rough vaccines, we screened B. melitensis for lipopolysaccharide genes and obtained mutants representing all main rough phenotypes with regard to core oligosaccharide and O-polysaccharide synthesis and export. Using the mouse model, mutants were classified into four attenuation patterns according to their multiplication and persistence in spleens at different doses. In macrophages, mutants belonging to three of these attenuation patterns reached the Brucella characteristic intracellular niche and multiplied intracellularly, suggesting that they could be suitable vaccine candidates. Virulence patterns, intracellular behavior and lipopolysaccharide defects roughly correlated with the degree of protection afforded by the mutants upon intraperitoneal vaccination of mice. However, when vaccination was applied by the subcutaneous route, only two mutants matched the protection obtained with Rev 1 albeit at doses one thousand fold higher than this reference vaccine. These mutants, which were blocked in O-polysaccharide export and accumulated internal O-polysaccharides, stimulated weak anti-smooth lipopolysaccharide antibodies. CONCLUSIONS/SIGNIFICANCE: The results demonstrate that no rough mutant is equal to Rev 1 in laboratory models and question the notion that rough vaccines are suitable for the control of brucellosis in endemic areas

Conception d'un référentiel comme colonne vertébrale d'un Master en alternance en génie analytique

peer reviewedConfrontée au défi d’adapter sa formation, un master en alternance en génie analytique, à la réalité et aux besoins émergents des industries, l’équipe de coordination a entrepris de définir un référentiel de compétences. Cette communication présente la méthodologie utilisée pour élaborer ce référentiel et décrit le dispositif de formation ainsi que les nécessaires ajustements à réaliser pour veiller à sa cohérence. Elle met en évidence les implications d’une telle réflexion aussi bien au niveau institutionnel que pédagogique

Effect of omp10 or omp19 Deletion on Brucella abortus Outer Membrane Properties and Virulence in Mice

The distinctive properties of Brucella outer membrane have been considered to be critical for Brucella sp. virulence. Among the outer membrane molecules possibly related to these properties, Omp10 and Omp19 are immunoreactive outer membrane lipoproteins. Moreover, these proteins of Brucella could constitute a new family of outer membrane proteins specifically encountered in the family Rhizobiaceae. We evaluated the impact of omp10 or omp19 deletion on Brucella abortus outer membrane properties and virulence in mice. The omp10 mutant was dramatically attenuated for survival in mice and was defective for growth in minimal medium but was not impaired in intracellular growth in vitro, nor does it display clear modification of the outer membrane properties. Significantly fewer brucellae were recovered from the spleens of mice infected with the omp19 mutant than from those of mice infected with the parent strain at 4 and 8 weeks postinfection. The omp19 mutant exhibited an increase in sensitivity to the polycation polymyxin B and to sodium deoxycholate. These results indicate that inactivation of the omp19 gene alters the outer membrane properties of B. abortus

The two-component system PrlS/PrlR of <em>Brucella melitensis</em> is required for persistence in mice and appears to respond to ionic strength

International audienceBacterial adaptation to environmental conditions is essential to ensure a maximal fitness in front of several stresses. In this context, two-component systems (TCS) represent a predominant signal transduction mechanism allowing stimuli sensing to mount an appropriate response. As facultative intracellular pathogens, Brucella spp. are facing various environmental conditions and an adequate response will warrant a successful infection process. Recently, bioinformatics analysis of Brucella genomes predicted a set of 15 bona fide TCS pairs among which some were previously investigated. In this report, we characterized a new TCS locus called prlS/R for probable proline sensor/regulator. It encodes a hybrid histidine kinase (PlrS) with a peculiar Na+/solute symporter N-terminal domain and a transcriptional regulator (belonging to the luxR family) (PrlR). In vitro, Brucella spp. with a functional PrlR/S system trigger the formation of bacterial aggregates that seems to be an adaptive response to a hypersaline environment while a prlS/R mutant does not. We identified the ionic strength as a possible signal sensed by this TCS. Finally, this work correlates the absence of functional PrlR/S system with the lack of hypersaline-induced aggregation in peculiar marine Brucella spp