Influenza virus shows high rates of mutation and recombination that soon renders immunization ineffective and requires yearly production of vaccines. In addition, up to 85% of isolates are resistant to available antiviral molecules targeted against the virus itself. These factors demonstrate an unmet medical need for drugs that target host-encoded functions and that are therefore not subject to viral selection. Furthermore, highly lethal strains of influenza (e.g., 1918 flu, bird flu) occasionally arise, causing morbidity/mortality through the propensity of these viruses to induce a "cytokine storm" that mediates lung cell dysfunction and damage (acute respiratory distress syndrome or ARDS). Such pathogenic changes include disruptions in alveolar fluid transport, apoptosis of alveolar epithelial cells, and infiltration/destruction of lung tissue by neutrophils and monocytes. Currently, effective treatments to prevent lung damage do not exist. Similar changes occur with other pathogens including SARS-Coronovirus and anthrax, where host-directed therapies developed for influenza are also expected to be effective. Nox enzymes are NADPH-oxidases that generate superoxide and secondary reactive oxygen species (ROS) that act as signaling molecules, and in high concentrations directly damage biomolecules. We propose a signaling cascade involving both epithelial Nox1- and monocyte/PMN Nox2-generated ROS as key steps that: a) facilitate viral replication and/or spread and b) mediate lung damage. The generation of epithelial ROS by Nox1 is among the earliest events that trigger the cytokine storm and cellular functional changes. Using Nox knockout mice and inhibitors, preliminary evidence suggests that inhibition of Nox1 and Nox2 will be therapeutically beneficial in influenza infection. This application represents a collaborative effort between Emory and the Centers for Disease Control (CDC), where studies using highly virulent strains of influenza (PR8, H5N1 bird flu) can be carried out. The Lambeth Laboratory, known for its expertise in Nox discovery, enzymology and cell biology, has discovered (using high- and low-throughput screens) four chemical series of small molecule Nox inhibitors. In collaboration with the Emory Institute for Drug Discovery, our group will further develop these inhibitors, improving their potency, isoform selectivity, metabolic stability, and pharmacological properties and will coordinate preclinical development as candidate drugs. The Gangappa Laboratory, part of the Influenza group at the CDC will: 1) infect live virus into genetically deleted mice to demonstrate proof-of-concept for Nox1 and/or Nox2 as therapeutic targets, and 2) test drug candidates in infected and non-infected WT mice. The overall goal is to develop novel pre-clinical drug candidates that target Nox-generated ROS, thereby blocking host signaling pathways that lead to lung tissue damage and viral replication/spread. Such compounds will be generally useful in the treatment of all strains of influenza and likely other pathogens (SARS-CoV, anthrax) that result in severe lung dysfunction/pathology.
Highly lethal types of flu and other viruses (e.g., SARS-coronavirus) arise occasionally (bird flu, 1918 flu), and the lack of effective vaccines can result in pandemics that cause large numbers of fatalities. These viruses are lethal because of their tendency to cause a cytokine storm resulting in damage to the lung as well as changes in the way the lungs keep fluids from accumulating. The goal of this grant application is to develop and test in animal models compounds that target enzymes in lung cells called NADPH-oxidases (Nox enzymes) and that can be further developed into drugs that inhibit viral replication and treat or prevent the lung damage that occurs in pandemic influenza.
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