The extracellular matrix (ECM) provides physical scaffolding for cellular constituents and initiates biochemical and biomechanical cues that are required for physiological activity of living tissues. influenza virus infection and highlights the potential for development of ADAMTS5-based therapeutic strategies to reduce morbidity and mortality. Author Summary Movement of immune cells is critical for effective clearance of pathogens. The response to influenza virus infection requires immune cell trafficking between the lung mediastinal lymph node and other peripheral lymphoid organs such as the spleen. We set out to assess the contribution of a specific extracellular matrix enzyme ADAMTS5 to migration of lymphocytes and overall pathogenesis following infection. In our studies we demonstrate that mice lacking have fewer influenza-specific lymphocytes in the lung and spleen following infection. These observations correlated with an accumulation of influenza-specific lymphocytes in the mediastinal lymph node and increased virus titres. This work suggests that ADAMTS5 is necessary for immune cell migration to the periphery where lymphocyte function is required to fight infection. Introduction Influenza A virus infection is responsible for substantial global morbidity and mortality (>500 0 deaths each year ) and largely afflicts high-risk groups Tuberstemonine including the very young and elderly. There are currently two countermeasures employed to control influenza virus infection: vaccines and antivirals. Although generally effective the imperfect proofreading capacity of the RNA-dependent RNA polymerase drives constant genetic drift. Moreover a segmented genome facilitates rapid genetic shift resulting in the need for reformulation of seasonal MUC12 vaccines or the emergence of resistance following administration of antivirals leading to suboptimal prophylactic or therapeutic intervention . T cells are a vital component of the adaptive immune response following influenza virus infection. Critically trafficking of activated influenza-specific T cells from draining lymph nodes (including the mediastinal lymph node [MLN]) to Tuberstemonine the site of primary infection in the lung requires direct contact and interaction with the extracellular matrix (ECM) . The ECM provides adhesive Tuberstemonine substrates such as proteoglycans and collagen to encourage and facilitate lymphocyte trafficking . Expression and remodelling of ECM components is strictly regulated to control movement of immune cells. Therefore Tuberstemonine it is not surprising that perturbations in substrate availability and ECM remodelling significantly impact granulocyte and lymphocyte migration in a number of model systems [5-7]. The A Disintegrin-like and Metalloproteinase with Thrombospondin-1 motifs (ADAMTS) family are a group of secreted metalloproteinases found within the zinc-dependent metzincin super-family that also consists of matrix metalloproteinases (MMPs) and ADAMs . The ADAMTS family comprises 19 mammalian ADAMTs enzymes . ADAMTS5 is one of the most highly characterised and well-known proteinases in this family and has been shown to cleave the hyalectan class of chondroitin sulphate proteoglycans (CSPGs) including aggrecan brevican neurocan and versican [10-13]. Hyalectans/CSPGs are large aggregating macromolecules that hydrate tissue and confer rigidity to the extracellular space. ADAMTS5 has become a major drug target for arthritis therapy as ADAMTS5 knockout mice (mice) are resistant to aggrecan cleavage in articular cartilage and are thus protected from experimentally induced arthritis [14 15 Aside from the documented role in arthritis ADAMTS5 has been shown to play a role in embryonic development including limb and cardiac morphogenesis and skeletal muscle development through its versican remodelling properties [11 16 17 Importantly its role in viral immunity is currently undefined. Versican a substrate of ADAMTS5 is a widely expressed tissue proteoglycan involved in cell adhesion proliferation and migration . The two predominant splice-variants of versican that harbour ADAMTS cleavage sites in their shared glycosaminoglycan (GAG)-β domain are V0 and V1 . GAG chains provide interactive points for antigen recognition receptors (Toll-like receptor 2 and 4) chemokines (MCP-1 MCP-2 CCL5) and cell surface markers (CD62L CD44) some of.