Immunogenicity of a chimeric subcellular vaccine in ovine brucellosis

SILVIA M. ESTEIN; MARIA A. FIORENTINO; FERNANDO A. PAOLICCHI; JULIANA CASSATARO; GUILLERMO H. GIAMBARTOLOMEI; LORENA CORIA; VANESA ZYLBERMAN; CARLOS A. FOSSATI; FERNANDO A. GOLDBAUM

Ouro Preto, Brazil

Simposio; 8th International Veterinary Immunology Symposium; 2007

Brucella ovis causes an infectious disease in sheep characterized by epididymitis and infertility in rams and abortion in ewes. Vaccination programs are the only viable means for the control of B. ovis in countries with a high incidence. B. melitensis Rev.1 is considered the best vaccine for the prophylaxis of ovine brucellosis but has important disadvantages. Accordingly, research is under way to develop effective subcellular vaccines. Detergent-extracted recombinant Omp31 from B. melitensis was previously identified as a protective immunogen against B. ovis in rams. Moreover, our previous results demonstrate that a chimera of Brucella lumazine synthase (BLS) that contains an immunodominant epitope of Omp31 delivered as a protein (BLS-Omp31) or plasmidic DNA vaccine (pCIbls-Omp31) conferred protection against B. ovis infection in mice. In this work, we evaluated the immunogenicity of these vaccines in rams using different strategies of immunisation. Seventy rams four-five- months-old were randomly distributed in following groups of immunisation: G1) BLS-Omp31 in Freund´s incomplete adjuvant (FIA), G2) BLS-Omp31 in QUIL A adjuvant, G3) pCIbls-omp31 with electroporation (INOVIO, Norway), G4) pCIbls-omp31 without electroporation, G5) Prime-boost, G6) HS (hot saline) extract in FIA, G7) PBS. Animals were vaccinated three times, four weeks apart. G5 received four injections (DNA prime-protein boost). Rams were bled after each immunization. Antibody responses in serum were evaluated in indirect ELISA against BLS-Omp31. Immunisation with the protein chimera formulated with adjuvant induced IgG specific antibodies significantly higher than chimerical DNA vaccine. However, humoral immune response was enhanced in electroporated sheep. Combination of a plasmid DNA priming step followed by a boost with the homologous protein resulted in improved humoral antigen-specific response. These results indicate that the chimerical subunit vaccine was immunogenic in rams and would be considered as potential vaccine in ovine brucellosis.