Phagocytosis is a process by which invading organisms are taken up by macrophages and targeted to the lysosomes, where they are degraded. However, many pathogens modulate this central process of macrophage-mediated killing by inhibiting their transport to the lysosomes through a variety of pathogen-derived mechanisms. Given the importance of Rab proteins in the regulation of intracellular transport pathways, we investigated the role of different host endocytic Rabs on the maturation ofSalmonella-containing phagosomes in macrophages. Initially, we have developed a ligand mixing assay to measure the transport of theSalmonella-containing phagosomes to lysosomes. Using this assay we have shown thatSalmonelladecline their transport to the lysosomes. In order to determine whether inhibition ofSalmonellatransport to lysosomes is due to their sustained fusion with early endosomes, we have developed an in vitro fusion assay betweenSalmonella-containing phagosomes and early endosomes. Here, we have discussed how these methodologies are helpful to determine the mechanism of evasion ofSalmonellatransport to the lysosomes.
