The Role of Interleukin-22 during Systemic and Mucosal Infection with Listeria Monocytogenes

Listeria monocytogenes (LM) is a gram-positive bacterium and is a common contaminant in processed meats and dairy products. In humans, ingestion of LM can result in intracellular infection in the spleen and liver, which ultimately leads to septicemia, meningitis, and spontaneous abortion. Interleukin (IL)-23 is a cytokine that regulates immune responses by inducing the production of IL-17A, IL-17F, and IL-22, and is required for clearance of LM. IL-17A and IL-17F have been shown to recruit neutrophils to sites of infection, while IL-22 has been shown to induce secretion of anti-microbial peptides and has the ability to protect tissues from damage by preventing apoptosis. The role that IL-22 might play in LM bacterial clearance and resistance during an innate or adaptive immune response has not been thoroughly investigated. During infection, we have found that LM induced the production of IL-22, and during primary infection, IL-23 is required for IL-22 production. However, our findings suggest that IL-22 is not required for clearance of LM and does not seem to be required for the protection of the spleen and liver during a LM infection during a primary or secondary systemic or mucosal infection. Understanding the role of IL-22 will enable us to better understand the immune response against LM as well as similar pathogens. This knowledge will aid in the generation of effective vaccines against intracellular pathogens.