Brucella abortus is the causative agent of bovine brucellosis, a disease that causes spontaneous abortion in cows. The most effective form of protection against this pathogen is immunization; however, Brucella abortus strain 19 (the standard vaccine against Brucella abortus) is not completely protective. The vaccination of laboratory mice with the heat shock protein, hsp60 derived from Brucella abortus, using live attenuated recombinant Salmonella typhimurium expressing this protein (hsp60) as a delivery system, and the characterization of the immune response to Brucella abortus hsp60 over a 12 week time course following vaccination is described;Infection of BALB/c strain of laboratory mice with recombinant Salmonella typhimurium [chi]4064 expressing the hsp60 gene of Brucella abortus (B-hsp60) was found to be an effective antigen delivery system for B-hsp60. Humoral responses were elicited during the course of the recombinant Salmonella infection, directed against both the Salmonella live carrier, as well as B-hsp60. The immune responses directed against B-hsp60 were qualitatively similar to the immune responses directed against Salmonella typhimurium [chi]4064. The cell mediated immune response was characterized by elevated secretion of the cytokines, Interferon-gamma (IFN-[gamma]), and Interleukin-10 (IL-10) by splenocytes of recombinant Salmonella infected mice, in response to in vitro stimulation with purified B-hsp60 protein, as well as Salmonella typhimurium [chi]4064 soluble antigen. An additional cell mediated immune response was demonstrated late in the course of the recombinant Salmonella infection, where splenocytes from recombinant Salmonella infected mice exhibited cytolytic activity against J774 target cells pulsed with B-hsp60 protein, or Salmonella typhimurium [chi]4064 soluble antigen. These data indicate that vaccination of mice with recombinant Salmonella typhimurium [chi]4064 expressing Brucella abortus hsp60 can protect these animals against a subsequent infection with Brucella abortus. This hypothesis is currently being tested.