Immunogenicity of recombinant Escherichia coli expressing the omp31 gene of Brucella melitensis in BALB/c mice

BALB/c mice were immunized with recombinant Escherichia coli expressing the omp31 gene of Brucella melitensis, a gene coding for a major outer membran e protein. Immunization resulted in the production of specific antibodies t o B. melitensis in the serum, the production of which was considerably incr eased after boosting with a dose ten times lower than the first. A signific ant specific proliferative response of immune spleen cells to B, melitensis was observed 5 weeks after the first immunization but this response did no t persist. Despite the induction of systemic humoral and cellular immune re sponses by recombinant E. coli expressing the B. melitensis omp31 gene, no significant protection against a challenge with smooth B. melitensis H38S w as observed in immunized mice. These results demonstrate that despite the s trong antibody response induced in mice, immunization with the recombinant Omp31 of B. melitensis does not confer any protective effect against a viru lent smooth B. melitensis. However, its potential protective effect for pro tection against rough Brucella would be worth testing. (C) 1998 Elsevier Sc ience Ltd. All rights reserved.