• Vaccine Name: B. melitensis lipopolysaccharide (LPS) vaccine
• Target Pathogen: Brucella spp.
• Target Disease: Brucellosis
• Vaccine Ontology ID: VO_0000311
• Type: subunit vaccine
• Antigen: B. melitensis strain 16M lipopolysaccharide (LPS)
• Preparation: The LPS was extracted from killed cells and purified by a modification of the method of Bundle et al (Bhattacharjee et al., 2006).
• Virulence: None.
• Description: LPS, an outer membrane endotoxin common to gram negative bacteria, consists of three parts: Lipid A, a core oligosaccharide, and an O-antigen. The O-antigen is found in smooth strains only.

Mouse Response

• Vaccination Protocol: Groups of female BALB/c mice (Harlan Sprague-Dawley) were immunized by either i.n. or s.c. with purified B. melitensis LPS or LPS-GBOMP noncovalent complex vaccine. Control mice were immunized subcutaneously with sterile saline. Briefly, 25 µl of vaccine containing either 10 µg LPS or 10 µg LPS and 7.5 µg GBOMP contained in sterile saline was administered dropwise into the nostrils of anesthetized mice. Two doses of vaccine were given four weeks apart. For subcutaneous immunization, mice were given 10 µg vaccine in 200 µl sterile saline under the right hind thigh. A second dose of vaccine was given four weeks after the first dose. Blood was collected from five euthanized mice from each group four weeks after the first dose and four weeks after the second dose of vaccine. Sera were collected and stored at –20°C until analyzed for antibody. An enzyme-linked immunosorbent assay (ELISA) was used (Bhattacharjee et al., 2006).
• Challenge Protocol: Groups of immunized mice (15 to 20 mice in each group) were challenged intranasally 4 weeks after the second dose of vaccine with 1x10^4 CFU of B. melitensis 16M suspended in 30 µl phosphate-buffered saline (PBS) (0.01 M sodium phosphate, 0.14 M sodium chloride; pH 7.5) as described previously (21). Blood, spleens, lungs, and livers were aseptically collected from anesthetized mice 8 weeks postchallenge. The numbers of Brucella CFU in organs were determined by dilution and culture on brucella agar as described previously (17). Serum was separated and stored at –20°C until it was used (Bhattacharjee et al., 2006).
• Efficacy: Mice immunized subcutaneously with LPS vaccine showed significant protection against infection of the spleen (P < 0.001), liver (P < 0.001), and lungs (P < 0.05).