Project

Brucella abortus is a zoonotic pathogen that affects cattle by inducing abortion. Humans are accidental hosts that acquire the infection through contact with animal fluids from infected animals. The pathogenesis of brucellosis relies in the ability of B. abortus to survive intracellularly. This bacterium enters host cells, evades the lysosomal route and re directs its traffic to the endoplasmic reticulum. The type IV secretion system VirB has been shown to be crucial for the intracellular fate of B. abortus. It has been postulated that through the secretion of bacterial effectors, this system modifies the compartment used by the bacterium to reach the endoplasmic reticulum. We have undertaken a comprehensive proteomic approach to understand the molecular changes induced by B. abortus in this intracellular compartment. Murine macrophages were infected with wild type B. abortus or an isogenic mutant in the type IV secretion system VirB. At 1 and 6 h post infection the cells were disrupted, the compartments were purified using sucrose gradients and after resuspension in triton-containing buffer the bacteria removed by centrifugation. Thus, we obtained fractions representing the compartments and secreted bacterial proteins. These fractions have been analyzed by comprehensive proteomic methods and preliminar analysis indicate that there are consistent differences between the compartments derived from wild type and VirB mutants to believe that we could understand the modulation exerted by the Type IV secretion system. In this project we intend to apply state of the art bioinformatics methods to analyze the already existing proteomic data. We hope to understand in detail the differences in prokaryotic and eukaryotic proteins between compartments derived from wild type and VirB mutants and how the function of the differential proteins might impact the route of the Brucella-containing compartment. These results will allow us to understand how B. abortus directs its intracellular traffic to the endoplasmic reticulum.