Limits...
The differential interaction of Brucella and ochrobactrum with innate immunity reveals traits related to the evolution of stealthy pathogens.

Barquero-Calvo E, Conde-Alvarez R, Chacón-Díaz C, Quesada-Lobo L, Martirosyan A, Guzmán-Verri C, Iriarte M, Mancek-Keber M, Jerala R, Gorvel JP, Moriyón I, Moreno E, Chaves-Olarte E - PLoS ONE (2009)

Bottom Line: During evolution, innate immunity has been tuned to recognize pathogen-associated molecular patterns.The results suggest that Brucellaceae ancestors carried molecules not readily recognized by innate immunity, so that non-drastic variations led to the emergence of stealthy intracellular parasites.They also suggest that some critical envelope properties, like selective permeability, are profoundly altered upon modification of pathogen-associated molecular patterns, and that this represents a further adaptation to the host.

View Article: PubMed Central - PubMed

Affiliation: Programa de Investigación en Enfermedades Tropicales, Escuela de Medicina Veterinaria, Universidad Nacional, Heredia, Costa Rica.

ABSTRACT

Background: During evolution, innate immunity has been tuned to recognize pathogen-associated molecular patterns. However, some alpha-Proteobacteria are stealthy intracellular pathogens not readily detected by this system. Brucella members follow this strategy and are highly virulent, but other Brucellaceae like Ochrobactrum are rhizosphere inhabitants and only opportunistic pathogens. To gain insight into the emergence of the stealthy strategy, we compared these two phylogenetically close but biologically divergent bacteria.

Methodology/principal findings: In contrast to Brucella abortus, Ochrobactrum anthropi did not replicate within professional and non-professional phagocytes and, whereas neutrophils had a limited action on B. abortus, they were essential to control O. anthropi infections. O. anthropi triggered proinflammatory responses markedly lower than Salmonella enterica but higher than B. abortus. In macrophages and dendritic cells, the corresponding lipopolysaccharides reproduced these grades of activation, and binding of O. anthropi lipopolysaccharide to the TLR4 co-receptor MD-2 and NF-kappaB induction laid between those of B. abortus and enteric bacteria lipopolysaccharides. These differences correlate with reported variations in lipopolysaccharide core sugars, sensitivity to bactericidal peptides and outer membrane permeability.

Conclusions/significance: The results suggest that Brucellaceae ancestors carried molecules not readily recognized by innate immunity, so that non-drastic variations led to the emergence of stealthy intracellular parasites. They also suggest that some critical envelope properties, like selective permeability, are profoundly altered upon modification of pathogen-associated molecular patterns, and that this represents a further adaptation to the host. It is proposed that this adaptive trend is relevant in other intracellular alpha-Proteobacteria like Bartonella, Rickettsia, Anaplasma, Ehrlichia and Wolbachia.

Show MeSH

Related in: MedlinePlus

O. anthropi cells but not its LPS fix complement.(A) Rabbit serum was incubated with the indicated amounts of O. anthropi or B. abortus cells. After incubation, the ability of the serum to lyze pre-sensitized erythrocytes was determined and expressed as percentage of hemolysis. (B) The indicated bacteria were incubated in the presence of bovine serum for 90 min and their relative resistance was calculated.(C) Rabbit serum was incubated with the indicated concentrations of OaLPS, BaLPS or SeLPS. After incubation the ability of the serum to lyse pre sensitized erythrocytes was determined. Values of O. anthropi in were significant different at p<0.001 (**) with respect to B. abortus.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2691993&req=5

pone-0005893-g005: O. anthropi cells but not its LPS fix complement.(A) Rabbit serum was incubated with the indicated amounts of O. anthropi or B. abortus cells. After incubation, the ability of the serum to lyze pre-sensitized erythrocytes was determined and expressed as percentage of hemolysis. (B) The indicated bacteria were incubated in the presence of bovine serum for 90 min and their relative resistance was calculated.(C) Rabbit serum was incubated with the indicated concentrations of OaLPS, BaLPS or SeLPS. After incubation the ability of the serum to lyse pre sensitized erythrocytes was determined. Values of O. anthropi in were significant different at p<0.001 (**) with respect to B. abortus.

Mentions: Both Brucella cells and LPS are very poor complement activators [3]. To assess whether O. anthropi shares this property, we incubated rabbit serum with B. abortus and O. anthropi and then measured the lytic activity remaining in the supernatants using antibody-sensitized erythrocytes. Whereas B. abortus practically did not consume complement, O. anthropi completely abrogated the lytic activity, demonstrating an effective surface binding and the subsequent activation (Fig. 5A). Next, we tested the bactericidal activity of bovine serum against these bacteria. In agreement with the high avidity of the complement for the O. anthropi surface, this bacterium was considerable more susceptible to the bactericidal action of serum than B. abortus (Fig. 5B). Since LPS is one of the main molecules responsible for complement activation by Gram negative cell surfaces, we tested whether the O. anthropi LPS (OaLPS) consumed complement. Surprisingly, OaLPS was less effective than BaLPS in depleting complement activity, even both were less effective than the LPS from S. enterica (SeLPS) (Fig. 5C). Therefore, other O. anthropi surface molecules, such as capsule polysaccharides, may be responsible for binding complement.


The differential interaction of Brucella and ochrobactrum with innate immunity reveals traits related to the evolution of stealthy pathogens.

Barquero-Calvo E, Conde-Alvarez R, Chacón-Díaz C, Quesada-Lobo L, Martirosyan A, Guzmán-Verri C, Iriarte M, Mancek-Keber M, Jerala R, Gorvel JP, Moriyón I, Moreno E, Chaves-Olarte E - PLoS ONE (2009)

O. anthropi cells but not its LPS fix complement.(A) Rabbit serum was incubated with the indicated amounts of O. anthropi or B. abortus cells. After incubation, the ability of the serum to lyze pre-sensitized erythrocytes was determined and expressed as percentage of hemolysis. (B) The indicated bacteria were incubated in the presence of bovine serum for 90 min and their relative resistance was calculated.(C) Rabbit serum was incubated with the indicated concentrations of OaLPS, BaLPS or SeLPS. After incubation the ability of the serum to lyse pre sensitized erythrocytes was determined. Values of O. anthropi in were significant different at p<0.001 (**) with respect to B. abortus.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2691993&req=5

pone-0005893-g005: O. anthropi cells but not its LPS fix complement.(A) Rabbit serum was incubated with the indicated amounts of O. anthropi or B. abortus cells. After incubation, the ability of the serum to lyze pre-sensitized erythrocytes was determined and expressed as percentage of hemolysis. (B) The indicated bacteria were incubated in the presence of bovine serum for 90 min and their relative resistance was calculated.(C) Rabbit serum was incubated with the indicated concentrations of OaLPS, BaLPS or SeLPS. After incubation the ability of the serum to lyse pre sensitized erythrocytes was determined. Values of O. anthropi in were significant different at p<0.001 (**) with respect to B. abortus.
Mentions: Both Brucella cells and LPS are very poor complement activators [3]. To assess whether O. anthropi shares this property, we incubated rabbit serum with B. abortus and O. anthropi and then measured the lytic activity remaining in the supernatants using antibody-sensitized erythrocytes. Whereas B. abortus practically did not consume complement, O. anthropi completely abrogated the lytic activity, demonstrating an effective surface binding and the subsequent activation (Fig. 5A). Next, we tested the bactericidal activity of bovine serum against these bacteria. In agreement with the high avidity of the complement for the O. anthropi surface, this bacterium was considerable more susceptible to the bactericidal action of serum than B. abortus (Fig. 5B). Since LPS is one of the main molecules responsible for complement activation by Gram negative cell surfaces, we tested whether the O. anthropi LPS (OaLPS) consumed complement. Surprisingly, OaLPS was less effective than BaLPS in depleting complement activity, even both were less effective than the LPS from S. enterica (SeLPS) (Fig. 5C). Therefore, other O. anthropi surface molecules, such as capsule polysaccharides, may be responsible for binding complement.

Bottom Line: During evolution, innate immunity has been tuned to recognize pathogen-associated molecular patterns.The results suggest that Brucellaceae ancestors carried molecules not readily recognized by innate immunity, so that non-drastic variations led to the emergence of stealthy intracellular parasites.They also suggest that some critical envelope properties, like selective permeability, are profoundly altered upon modification of pathogen-associated molecular patterns, and that this represents a further adaptation to the host.

View Article: PubMed Central - PubMed

Affiliation: Programa de Investigación en Enfermedades Tropicales, Escuela de Medicina Veterinaria, Universidad Nacional, Heredia, Costa Rica.

ABSTRACT

Background: During evolution, innate immunity has been tuned to recognize pathogen-associated molecular patterns. However, some alpha-Proteobacteria are stealthy intracellular pathogens not readily detected by this system. Brucella members follow this strategy and are highly virulent, but other Brucellaceae like Ochrobactrum are rhizosphere inhabitants and only opportunistic pathogens. To gain insight into the emergence of the stealthy strategy, we compared these two phylogenetically close but biologically divergent bacteria.

Methodology/principal findings: In contrast to Brucella abortus, Ochrobactrum anthropi did not replicate within professional and non-professional phagocytes and, whereas neutrophils had a limited action on B. abortus, they were essential to control O. anthropi infections. O. anthropi triggered proinflammatory responses markedly lower than Salmonella enterica but higher than B. abortus. In macrophages and dendritic cells, the corresponding lipopolysaccharides reproduced these grades of activation, and binding of O. anthropi lipopolysaccharide to the TLR4 co-receptor MD-2 and NF-kappaB induction laid between those of B. abortus and enteric bacteria lipopolysaccharides. These differences correlate with reported variations in lipopolysaccharide core sugars, sensitivity to bactericidal peptides and outer membrane permeability.

Conclusions/significance: The results suggest that Brucellaceae ancestors carried molecules not readily recognized by innate immunity, so that non-drastic variations led to the emergence of stealthy intracellular parasites. They also suggest that some critical envelope properties, like selective permeability, are profoundly altered upon modification of pathogen-associated molecular patterns, and that this represents a further adaptation to the host. It is proposed that this adaptive trend is relevant in other intracellular alpha-Proteobacteria like Bartonella, Rickettsia, Anaplasma, Ehrlichia and Wolbachia.

Show MeSH
Related in: MedlinePlus