Brucella abortus Strain RB51 Leucine Auxotroph as an Environmentally Safe Vaccine for Plasmid Maintenance and Antigen Overexpression

To avoid potentiating the spread of an antibiotic resistance marker, a plasmid expressing a leuB gene and a heterologous antigen, green fluorescent protein (GFP), was shown to complement a leucine auxotroph of cattle vaccine strain Brucella abortus RB51, which protected CD1 mice from virulent B. abortus 2308 and elicited GFP antibodies.