Chronic stress-induced activation of the hypothalamus-pituitary-adrenal (HPA) axis can influence the primary immune response to a pathogen, and can have significant impact on the outcome to an infectious disease. Whether chronic stress alters the generation of the memory T cell response, and whether a secondary response to pathogen challenge is affected by priming T cells under a "stressed environment" are not well established. In this proposal, we test the central hypothesis that chronic non-habituating stress induces repeated activation of the HPA axis, hindering the development and/or effector function of Listeria- specific memory CD8+ T cells. This model will yield information that reflects how physical and/or psychological stress in humans may affect immune responses to pathogens, and can impact the effectiveness of profilactic and therapeutic vaccines.