Seasonal influenza causes 0.25-0.5 million deaths/year world-wide and mortality increases substantially in pandemic years. Although influenza vaccines are developed annually, only 49% of the US population was vaccinated in 2010-2011, and not all subjects develop robust protective immune responses to these vaccines. Current anti-viral drugs (e.g. oseltamivir) target only the virus and do not prevent influenza-associated mortality in all individuals. Thus, there is an urgent need to develop more effective therapies that limit the mortality and high health care burden that are associated with influenza A viral (IAV) infections. MMP-8 cleaves pro- inflammatory mediators to regulate inflammatory responses to various stimuli, but its contributions to the pathogenesis of IAV disease have not been evaluated. My novel preliminary data strongly link Matrix metalloproteinase-8 (Mmp-8) to adverse outcomes in animals infected with IAV. Plasma MMP-8 levels are significantly upregulated in patients diagnosed with pandemic H1N1 and seasonal IAV infections, and levels correlate inversely with the PaO2/FiO2 ratio. Mmp-8 lung levels are also increased in the lungs of H1N1- infected WT mice and localized to airway epithelial cells and airway macrophages. Compared with WT mice, Mmp-8-/- mice have reduced H1N1 IAV-induced mortality; lower lung viral burdens; increased lung levels of type I interferons (IFNs) and products of activated M1 macrophages, and increased necroptosis of virally- infected epithelial cells. Thus, our data identifying MMP-8 for the first time as a novel therapeutic target during serious IAV infections. The goal of this postdoctoral fellowship is to test the central hypotheses: Mmp-8 deficiency in leukocytes (macrophages) reduces lung viral burdens and improves outcomes in IAV-infected mice by increasing: 1) M1 macrophage polarization to induce a more effective (Th1) adaptive immune response to IAV; 2) the lung macrophage type I IFN response; and 3) type I IFN induced-necroptosis of IAV- infected epithelial cells to limit IAV viral replication and spreading. Small molecule MMP-8 inhibitors are not selective and have off-target toxic effects. Our studies will also determine the extent to which a novel nanobody inhibitor (Nb14_NbAlb) that selectively inhibits this host protein has therapeutic efficacy in a pre-clinical model of IAV infection. Successful completion of these studies will pave the way for future IND-enabling studies to test the safety and efficacy of a ?first in class? therapeutic targeting the host response to reduce the morbidity and mortality associated with serious IAV infections.
Current therapies for serious influenza viral infections that target viral proteins and are not fully effective in preventing influenza-associated deaths. Our studies will provide novel insights into the mechanisms by which a host protein (Mmp-8) increases the severity of IAV infections in mice. In addition, we will test the therapeutic efficacy of a nanobody that selectively inhibits Mmp-8 in reducing IAV-induced mortality and lung disease in mice.
