Mutants in the lipopolysaccharide of Brucella ovis are attenuated and protect against B. ovis infection in mice

• DOI: 10.1186/s13567-014-0072-0
• Publication Date: 2014-07-16T21:24:52Z
• Authors: Pedro Soler-Lloréns; Yolanda Gil-Ramírez; Ana Zabalza-Baranguá; Maite Iriarte; Raquel Conde-Álvarez; Amaia Zúñiga-Ripa; Beatriz San Román; Michel S Zygmunt; Nieves Vizcaíno; Axel Cloeckaert; María-Jesús Grilló; Ignacio Moriyón; Ignacio López-Goñi
• Keywords: Lipopolysaccharides; vaccin; brucella ovis; Rough lipopolysaccharide; mouton; chèvre; [SDV]Life Sciences [q-bio]; Brucella ovis; Host-range; Molecular Sequence Data; Monoclonal-antibodies; Brucella Vaccine; Oligosaccharides; Sheep Diseases; Polymerase Chain Reaction; Brucellosis; Linked immunosorbent assay; Mice; 03 medical and health sciences; Bacterial Proteins; Animals; brucellose; Vaccines; Mice, Inbred BALB C; 0303 health sciences; Sheep; Virulence; Research; Microbiology and Parasitology; parasite intracellulaire; Glycosyltransferases; O-polysaccharide; lipopolisaccharide; Melitensis; Sequence Analysis, DNA; veterinary(all); Antibodies, Bacterial; Microbiologie et Parasitologie; 3. Good health; [SDV] Life Sciences [q-bio]; DNA polymorphism; Outer membrane protein; Female; OMP25/OMP31 family; Autre (Sciences du Vivant)

Brucella spp. are Gram-negative bacteria that behave as facultative intracellular parasites of a variety of mammals. This genus includes smooth (S) and rough (R) species that carry S and R lipopolysaccharides (LPS), respectively. S-LPS is a virulence factor, and mutants affected in the S-LPS O-polysaccharide (R mutants), core oligosaccharide or both show attenuation. However, B. ovis is naturally R and is virulent in sheep. We studied the role of B. ovis LPS in virulence by mutating the orthologues of wadA, wadB and wadC, three genes known to encode LPS core glycosyltransferases in S brucellae. When mapped with antibodies to outer membrane proteins (Omps) and R-LPS, wadB and wadC mutants displayed defects in LPS structure and outer membrane topology but inactivation of wadA had little or no effect. Consistent with these observations, the wadB and wadC but not the wadA mutants were attenuated in mice. When tested as vaccines, the wadB and wadC mutants protected mice against B. ovis challenge. The results demonstrate that the LPS core is a structure essential for survival in vivo not only of S brucellae but also of a naturally R Brucella pathogenic species, and they confirm our previous hypothesis that the Brucella LPS core is a target for vaccine development. Since vaccine B. melitensis Rev 1 is S and thus interferes in serological testing for S brucellae, wadB mutant represents a candidate vaccine to be evaluated against B. ovis infection of sheep suitable for areas free of B. melitensis.