CTSD and infection: Whereas infection of a single cell by multiple C. burnetii usually leads to formation of a single vacuole due to homotypic fusion of the individual CCVs, the vacuoles containing cig2 mutants do not display the same propensity to fuse with each other inside the host cell, which results in a single host cell having multiple CCVs that each display LAMP1 and cathepsin D localization at the limiting membrane of the proteolytic lysosome-derived organelle.