Immunogenicity of recombinant Omp31 from Brucella melitensis in rams and serum bactericidal activity against B. ovis

ESTEIN S.M., CHEVES P.C., FIORENTINO M. A., CASSATARO J., PAOLICCHI F.A., BOWDEN R.A.

VETERINARY MICROBIOLOGY

Elsevier

Año: 2004 vol. 102 p. 203 - 213

0378-1135

Detergent-extracted recombinant Omp31 (rOmp31 extract) from Brucella melitensis produced in Escherichia coli was previouslyidentified as a protective immunogen against B. ovis in mice. In this study, we evaluated the immunogenicity ofrOmp31extract in rams. This immunogen was emulsified in an oil adjuvant and administered three times with 4 and 8 weeks intervals.Antibody response was measured in serum by whole B. ovis ELISA. Specific antibodies to purified rOmp31 (pET-Omp31)were detected by Western blotting and indirect ELISA. In addition, isotype specific antibodies were measured in tears. Serumbactericidal activity against B. ovisin the presence of complement was measured in vitro. Cellular immune response was exploredby intradermal testing with purified rOmp31. Immunization with rOmp31 extract induced IgG specific antibodies in serum able tobind to whole B. ovis cells. Furthermore, strong inhibition in a competitive ELISA (with an Omp31-specific monoclonal antibody)suggested that a proportion of Omp31-specific antibodies were directed against a loop containing a protective epitope. Serumantibodies killed efficiently B. ovis in vitro in the presence of either guinea pig or ovine serum. Tears had both IgG and IgA antibodiesto equivalent titers. Finally, immunized rams showed skin reactivity to Omp31. These data demonstrate that B. melitensisOmp31, a protective antigen identified in the mouse model, induces antibody and cellular immune mechanisms in sheep.© 2004 Elsevier B.V. All rights reserved.