Abstract: Certain attenuated mutants of Brucella, especially B. melitensis, B. abortus, B. suis and B. ovis, when administered to a human or animal trigger a protective immune response such that subsequent challenge with virulent Brucella of the same species does not result in disease or results in much less severe symptoms. Functional inactivation of galE, a virB gene or the operon (ORFs 1087-1090) comprising the gene encoding ?-hexosaminidase (BMEI1087) and a lytic murein transglycosylase gene (BMEI1088). A specific example of the attenuated galE mutant which produces a protective immune response is B. melitensis GR024. The specific example of an inactivated ORF1087-1090 operon is B. melitensis GR026; it has an insertion mutation in the promoter region upstream of ORF 1090. Vaccination with live cells of either or both of these mutants results in a T cell response which protects the human or animal against challenge with virulent B. melitensis.

Abstract: Certain attenuated mutants of Brucella, especially B. melitensis, B. abortus, B. suis and B. ovis, when administered to a human or animal trigger a protective immune response such that subsequent challenge with virulent Brucella of the same species does not result in disease or results in much less severe symptoms. Functional inactivation of galE, a virB gene or the operon (ORFs 1087-1090) comprising the gene encoding ?-hexosaminidase (BMEI1087) and a lytic murein transglycosylase gene (BMEI1088). A specific example of the attenuated galE mutant which produces a protective immune response is B. melitensis GR024. The specific example of an inactivated ORF1087-1090 operon is B. melitensis GR026; it has an insertion mutation in the promoter region upstream of ORF 1090. Vaccination with live cells of either or both of these mutants results in a T cell response which protects the human or animal against challenge with virulent B. melitensis.

Abstract: Certain attenuated mutants of Brucella, especially B. melitensis, B. abortus, B. suis and B. ovis, when administered to a human or animal trigger a protective immune response such that subsequent challenge with virulent Brucella of the same species does not result in disease or results in much less severe symptoms. Functional inactivation of galE, a virB gene or the operon (ORFs 1087-1090) comprising the gene encoding ?-hexosaminidase (BMEI1087) and a lytic murein transglycosylase gene (BMEI1088). A specific example of the attenuated galE mutant which produces a protective immune response is B. melitensis GR024. The specific example of an inactivated ORF1087-1090 operon is B. melitensis GR026; it has an insertion mutation in the promoter region upstream of ORF 1090. Vaccination with live cells of either or both of these mutants results in a T cell response which protects the human or animal against challenge with virulent B. melitensis.

Abstract: Inducible gene expression systems and a method thereof. A first inducible gene expression system includes a first vector comprising at least one retroviral promoter and at least one factor to induce the retroviral promoter. At least one gene product is expressed in proportion to retroviral promoter induction. The method includes providing a first vector comprising at least one retroviral promoter and providing at least one factor corresponding to the retroviral promoter. The retroviral promoter is induced with the at least one factor. At least one protein is expressed based on the induction of the retroviral promoter. A second inducing expression system includes first vector means comprising at least one retroviral promoter, means for inducing the retroviral promoter, and means for expressing at least one protein based on the induction of the retroviral promoter.