Influenza virus infects the epithelial cells that line the respiratory tract. Productive replication of the virus is restricted to this site because of the requirement for a locally expressed trypsin-like enzyme to cleave nascent viral hemagglutinin (HA) surface protein into its active conformation. Cytotoxic CD8+ T cells (CTL) must traffic to the mucosal epithelium to mediate elimination of infected cells. The CTL directly engage infected epithelial cells, yet the mechanisms that allow them to enter the tissue, migrate and locate infected cells remain poorly defined. The respiratory epithelium is comprised of a thick basement membrane (BM) made of extracellular matrix (ECM) proteins, and an epithelial cell layer (the targets of the virus) firmly attached to the BM. The antiviral T cells physically interact with the ECM components of the BM, and react to changes in that environment as the infection and immune response progresses. Ultimately, after the virus is cleared, a population of sentinel resident memory T cells is established to provide protection from future encounters with the virus. Receptors specific for ECM components, expressed by the T cells, have been shown to be critical to the establishment of these tissue memory T cells, though its function appears to shift as the infection progresses from acute to recovery phases. Our overall hypothesis is that active remodeling of the basement membrane occurs during influenza infection and after recovery that regulate the migration of T cells in the tissue and the formation of tissue memory.
Our aims are to: 1) Define the relationship between remodeling of extracellular matrix proteins (ECM) in the trachea during influenza infection and dynamics of T cell migration. 2) Test the hypothesis that integrin dependent and independent T cell migration in the influenza-infected trachea depends on tissue architecture and composition. 3) Test the prediction that al integrin regulates CD8 T cell accumulation in the epithelium during resolution and formation of resident memory T cells after influenza infection. Until now, the methods used to assess T cell localization and memory in the tissues have not revealed dynamic functions. Innovative technology has been developed to image influenza-specific T cells by combining dynamic and static imaging techniques with the ability to quantitate changes to the tissue architecture and composition that together reveal critical molecular interactions of T cells with their environment in the tissue.
The proposed studies are significant because they focus on the key immune cell responsible for controlling influenza infection, a disease that kills hundreds of thousands of people each year. Understanding the molecular basis of cell migration in airways and formation of resident tissue immunity has the potential to lead to new ways to improve control of influenza infection and pathogenesis, and will translate into infectious, allergic, autoimmune, and neoplastic diseases that occur in mucosal and epithelial tissues.