Influenza-Induced Lung-Cell Senescence as a determinant of lung damage severity and post-viral lung disease – INFLUENZAGING

Influenza A virus (IAV) infection causes substantial morbidity and mortality worldwide despite vaccination and antiviral treatment. We found that sublethal IAV infection in mice induced severe lung damage and massive accumulation of senescent cells that persisted after complete clearance of the virus. We postulate that lung-cell senescence, resulting from IAV infection and the previous history of the host, directly increases IAV infection severity, amplifies viral replication, delays airway epithelium recovery and, subsequently, leads to post-viral lung pathology. Counteracting the cell-senescence process or eliminating senescent lung cells might limit infection duration and lung damage severity, expedite epithelial repair, hasten viral clearance, and protect against secondary infections and post-viral lung sequelae.
Our goal is to evaluate whether IAV-induced lung-cell senescence is a major mechanism involved in the severity and duration of IAV lung infection and whether senescent lung-cell persistence after IAV infection governs the recovery time and underlies the development of post-viral lung disease.
Aim 1: To evaluate and characterise lung-cell senescence induced by IAV infection in mouse models and human lung cells and to explore the underlying mechanisms. We will determine which lung or immune cells are infected by the virus and/or are senescent, whether senescence occurs only in infected cells or also in uninfected cells, and whether senescence is due to a DNA damage response (DDR) to the virus and/or to ROS production or inflammation.
Aim2: To assess the impact of cell senescence on the extent of lung viral infection and clearance, with emphasis on airway epithelium repair. We will test whether activating the DDR pathway in lung cells rendered senescent promotes IAV replication and whether eliminating senescent cells (genetically or pharmacologically, as in Aim 3) at the early phase of H1N1 infection impacts IAV replication, modifies lung IAV propagation, and/or modifies infection duration, using young mice compared to mice exhibiting lung senescent-cell accumulation, i.e., aged mice, cigarette smoke-exposed mice, and elastase-treated mice.
Aim 3. To explore the impact of IAV-induced lung-cell senescence on the development of lung pathology. We will determine whether eliminating senescent cells genetically (by ATTAC transgene activation in p16 ATTAC mice), or pharmacologically (using the senolytic drug Navitoclax) or inactivating p16 (homozygous luciferase knock-in mice, p16luc/luc mice) protects against the extensive lung damage induced by IAV infection (within the first month) and post-viral chronic lung disease (at 3 months) and affects the increased vulnerability of aged, cigarette smoke-exposed, and elastase-treated mice. Using p16-ATTAC mice with a floxed stop codon, we will evaluate the specific roles of senescent lung epithelial cells and inflammatory cells.
Aim 4. To test whether senolytic drugs given via inhalation to specifically target the lung can be used therapeutically. To mimic the clinical setting, when the disease is already declared, administration of senolytics (the FOXO4-p53 interfering peptide or Navitoclax) will be started on day 5 after IAV infection, at the viral-load peak and occurrence of respiratory distress.
Aim 5. To validate the concept of IAV-induced lung-cell senescence in human pathology, we will investigate biological samples (airway brush samples and bronchoalveolar lavage) from patients with acute respiratory distress due to IAV infection whose lung function will be assessed after hospital discharge.
Impact
We expect to demonstrate a prominent role for lung-cell senescence in the short- and long-term pathogenesis of influenza (and potentially other respiratory viruses), to describe the role for host factors predisposing to senescence, and to propose inhaled senolytics as novel treatments for severe IAV infection.