Identification of Secondary Mutations Which Enhance and Stabilize the Attenuation of Brucella HTRA Mutants: Improving Brucella HTRA-Based Strains as Vaccine Candidates

摘要

Results to date from the studies funded under this contract suggest that Brucella genes involved in maintaining efficient stationary phase physiology and allowing the brucellae to make effective use of the nutrients available in the phagosomal compartment make good targets for the construction of mutants with defined levels of attenuation which may prove useful as vaccine candidates. For example, the well characterized antioxidants KatE and SodC protect B. abortus from reactive oxygen intermediate (ROI)-mediated killing in in vitro assays, but experiments employing katE and sodC mutants indicate that these antioxidants are probably more important for protecting the intracellular brucellae from the endogenous ROIs generated by stationary phase metabolism than they are for detoxifying the products of the oxidative burst of host macrophages. The brucellae also experience significant nutrient deprivation in the phagosomal compartment, and preliminary results suggest that the bacA gene product functions in iron acquisition in this environment. Tn5 mutants of B. abortus which display nutritional defects in vitro and are unable to survive and replicate in cultured murine macrophages have also been identified and are presently being characterized.