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

摘要

Prolonged residence in the phagosomal compartment of host macrophages is essential for the establishment and maintenance of chronic infection by the brucellae in mammalian hosts. The intracellular brucellae are exposed to a variety of environmental stresses in this compartment, including nutrient deprivation and exposure to low PH and reactive oxygen intermediates. Corresondingly, a significant degree of physiologic adaptation is required in order for these bacteria to survive for prolonged periods within this niche. Studies described in this report indicate that the Erucelia genes that contribute to this physiologic adaptation represent good targets for use in the construction of vaccine candidates. Specifically, these studies have further verified the importance of de nova purine biosynthesis for intracellular survival and replication in host macrophages. Studies described in this report have also determined that the Brucella BacA is required for proper acylation of the libid A component of the LPS. Finally, studies employing the human monocyte- like cell line indicate that a) virulent B. abort us 2308 inhabits two different types of replicative vacuoles in these phagocytes) b) the isogenic hfq mutant Hfq3 is trafficked like 2308 to these vacuoles but cannot replicate therein, and c) the isogenic bacA mutant KL7 displays internalization and trafficking patterns in THP-1 cells that are different form those displayed by B. abortus 2308 or Hfq3.