Joan Mecsas

A major focus of the laboratory is to understand the interactions between bacterial pathogens, host mucosal surfaces, and the innate immune system. To this end, we are building 3-D tissue model systems of the GI tract with primary cells derived from human enteroids to study interactions between enteric pathogens and mucosal surfaces. We are enhancing the complexity of systems by inducing development of additional intestinal cell types, adding critical innate immune cells and introducing flow and 3D topology.
A second major focus is investigating how gram-negative bacterial pathogens, Yersinia pseudotuberculosis and Klebsiella pneumoniae interact with neutrophils and inflammatory monocytes in lungs and other tissues. Y. pseudotuberculosis uses a type 3 secretion system (T3SS) to inject "effector" proteins, called Yops, from the bacterial cytoplasm into neutrophils and inflammatory monocytes. We discovered that YopH targets and inactivates Slp-76/SKAP-2/PRAM and Plc.2 in neutrophils in infected tissues and are dissecting the role of this signaling axis during infection and how it contributes to the bactericidal activities of neutrophils. Using next generation sequencing and large transposon libraries of Y. pseudotuberculosis and K. pneumoniae, we have identified genes that are critical for survival in wildtype and/or immunocompromised mice. We are unraveling how these factors promote bacterial growth in different host states and tissues, how these genes function to help the pathogen escape bactericidal effects of neutrophils and inflammatory monocytes.
A third focus of the laboratory to identify and study factors that interfere with critical functions in infected tissues. we have shown that amino acid biosynthetic pathways are druggable targets for multi-drug resistant Klebsiella and in lungs of immunocompetent and immunocompromised lungs. In addition, we carried out a high-throughput screen to identify small molecules which inhibit effector protein delivery into host cells. These findings have led to a productive collaboration with Microbiotix and Dr. Hauser in which we are investigating the protein target of several small molecule inhibitors with a particular focus on small molecules that target the needle protein of the T3SS, YscF and PscF.