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Clinical and Vaccine Immunology, July 2007, p. 869-874, Vol. 14, No. 7
1071-412X/07/$08.00+0     doi:10.1128/CVI.00472-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Improved Immunogenicity of a Vaccination Regimen Combining a DNA Vaccine Encoding Brucella melitensis Outer Membrane Protein 31 (Omp31) and Recombinant Omp31 Boosting

Juliana Cassataro,^1,2* Carlos A. Velikovsky,^2, Laura Bruno,² Silvia M. Estein,³ Silvia de la Barrera,⁴ Raúl Bowden,^3, Carlos A. Fossati,² and Guillermo H. Giambartolomei^1,2

Laboratorio de Inmunogenética, Hospital de Clínicas José de San Martín, Facultad de Medicina, Universidad de Buenos Aires (UBA), Buenos Aires, Argentina,¹ Instituto de Estudios de la Inmunidad Humoral (IDEHU-CONICET), Facultad de Farmacia y Bioquímica, UBA, Buenos Aires, Argentina,² Laboratorio de Inmunología, Departamento de Sanidad Animal y Medicina Preventiva, Facultad de Ciencias Veterinarias, Universidad Nacional del Centro de la Provincia de Buenos Aires, Tandil, Argentina,³ Departamento de Inmunologia, Instituto de Investigaciones Hematológicas, Academia Nacional de Medicina, Buenos Aires, Argentina⁴

Received 18 December 2006/ Accepted 21 March 2007

In the present study, we report an attempt to improve the immunogenicity of the Omp31 antigen by a DNA prime-protein boost immunization regimen. We immunized BALB/c mice with an Omp31 DNA vaccine (pCIOmp31) followed by boosting with recombinant Omp31 (rOmp31) in incomplete Freund's adjuvant and characterized the resulting immune responses and the protective efficacy against Brucella ovis and B. melitensis infection. 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. In conclusion, pCIOmp31 priming followed by rOmp31 boosting led to moderately improved protection against a challenge with B. ovis or B. melitensis.

Published ahead of print on 11 April 2007.

Present address: Center for Advanced Research in Biotechnology, Rockville, MD.

Deceased.