Caspase‐1 dependent macrophage death induced by Burkholderia pseudomallei

Summary Burkholderia pseudomallei is the causative agent for melioidosis, an infectious disease endemic in South- east Asia and northern Australia. Infection can result in a wide spectrum of clinical outcomes, including asymtomatic, acute or chronic conditions. The ability of the bacteria to survive intracellularly within phago- cytes and non-phagocytes is postulated to help this pathogen persist in the body during latent chronic conditions. In some Gram-negative bacteria, such as Shigella and Salmonella , the ability to evade mac- rophage killing involves inducing rapid macrophage cell death. In several of these instances, these bacte- ria activate cellular caspase-1 to induce cell death, which is increasingly described to exhibit features more characteristic of oncosis than classical apopto- sis. We found that B. pseudomallei is also capable of inducing caspase-1 dependent death in macrophages and this process requires a functional bsa Type III Secretion System (TTSS). Bacterial internalization and pore formation in the cell membrane is necessary for death. Furthermore, cell death is accompanied by the release of IL-1 b b b and IL-18. We believe that this novel description of macrophage death induced by B. pseudomallei could shed light on the pathogenesis of the bacteria in disease.