SLC11A2 affects nutritional immunity in the gut epithelium

There is a constant tug-of-war for transition metals at the pathogen-host interface. A goal of the vertebrate host is to modulate the availability of metals to pathogens, in a process known as nutritional immunity, but pathogens have evolved numerous countermeasures to regulate intracellular trace metal levels. The bioavailability of trace metals therefore shapes the outcome of disease. In the human body, epithelial cells lining the intestine are a major site of metal absorption. Intestinal epithelial cells (IECs) are also a target for invading enteric pathogens but the contribution of epithelium-intrinsic factors towards nutritional immunity has been understudied. Using Salmonella enterica serovar Typhimurium (STm) harboring metal-responsive fluorescent reporters in a bovine ligated intestinal loop infection model, we mapped the spatiotemporal nature of metal competition during enteric salmonellosis. We show that STm experiences a temporal, cell-specific restriction of iron, manganese, and zinc in the intestinal mucosa during the early stages of infection. We have further studied the contribution of the broad specificity metal cation transporter, SLC11A2, in IECs to nutritional immunity against STm. Knockout of SLC11A2 in IECs leads to enhanced replication of STm, indicating a protective role for this transporter. Using fluorescence-based biosensors and bacterial gene deletion mutants, we pinpoint manganese and iron restriction as the mechanism by which SLC11A2 limits bacterial proliferation. We conclude that SLC11A2-mediated sequestration of metals is an intrinsic defense mechanism of the intestinal epithelium against enteric bacteria.