Vaccine comprising Brucella abortus which has O polysaccharide antigen absent

Abstract

The present invention is an improved vaccine against Brucella abortus which permits differentiation between vaccinated and field strain infected cattle. The vaccine can be administered in two different forms: (1) cell envelopes isolated from an O polysaccharide antigen deficient, stable transposon mutant of B. abortus or (2) an O polysaccharide antigen deficient, stable transposon mutant of B. abortus.