• Vaccine Ontology ID: VO_0000436
• Type: DNA vaccine with recombinant protein
• Status: Research
• Antigen: Omp31 protein
• Adjuvant: Incomplete Freund's Adjuvant
• Preparation: For the propagation of plasmids, Escherichia coli strain JM109 was used. For the expression of the recombinant protein, strain BL21(DE3) was employed. Bacterial strains were routinely grown, and rOmp31 was obtained and treated as described by (Estein et al., 2003). Purity was determined by Coomassie blue staining as described by (Cassataro et al., 2005). The plasmid pCIOmp31 was obtained as described in (Cassataro et al., 2005).
• Immunization Route: Intramuscular injection (i.m.)
• Description: A regimen of DNA prime and protein boost is followed, increasing the efficacy of the vaccine compared to DNA or protein alone (Cassataro et al., 2007).

Mouse Response

• Vaccination Protocol: BALB/c mice was immunized with an Omp31 DNA vaccine (pCIOmp31) followed by boosting with recombinant Omp31 (rOmp31) in incomplete Freund's adjuvant (Cassataro et al., 2007).
• Immune Response: Immunoglobulin G1 (IgG1) and IgG2a titers were higher in sera from pCIOmp31/rOmp31-immunized mice than in sera from mice immunized with pCIOmp31 or rOmp31 alone. Splenocytes from pCIOmp31/rOmp31-immunized mice produced significantly higher levels of gamma interferon than did those from mice given rOmp31 alone. In contrast, interleukin 2 (IL-2) production levels were comparable between the two groups of immunized mice. Cells from all immunized mice produced undetectable levels of IL-4. Notably, rOmp31 stimulated IL-10 production in the pCIOmp31/rOmp31-immunized group but not in the pCIOmp31- or rOmp31-immunized group. Although the prime-boost regimen induced specific cytotoxic responses, these responses could not reach the levels achieved by the pCIOmp31 immunization (Cassataro et al., 2007).
• Challenge Protocol: Immunized mice were challenged, by intravenous inoculation, with 1x10⁵ B. melitensis H38S organisms or 1x10⁵ B. ovis organisms. Mice were sacrificed 30 days after the bacterial challenge, and their spleens were removed, homogenized, plated, and incubated. The number of CFU per spleen or liver was counted, and the results were given as the mean log number of CFU (Cassataro et al., 2007).
• Efficacy: pCIOmp31 priming followed by rOmp31 boosting led to moderately improved protection against a challenge with B. ovis or B. melitensis (Cassataro et al., 2007).