Pathogens residing within similar intracellular vacuoles elicit discordant host responses

Coxiella burnetii (bacterium) and Leishmania mexicana (eukaryote) are the only organisms that thrive within lysosome-derived vacuoles in human macrophages. We hypothesized that as highly divergent organisms that cause different disease, they will elicit distinct host responses. We studied this parallel evolution of host cell regulation by comparing gene expression in macrophages infected with Coxiella or Leishmania. At 5 d post-infection, Coxiella and Leishmania induced robust, non-overlapping host responses at gene and isoform level and altered expression of apoptosis-related microRNAs. By comparing host responses, we can elucidate evolutionary processes enabling a bacterium and a eukaryote to occupy the same extreme environment.