Influenza continues to be a significant health problem and the virus causes a wide disease span from mild to fatal. The elderly are an at-risk population for developing severe influenza disease, but immunological correlates are not understood. We hypothesize that immune responses at the site of infection are critical to determine disease outcome. To study this, we sample blood and airways of adult patients with symptoms of influenza-like illness or confirmed respiratory virus infection across disease severity and age. Using our unique patient cohort samples, we study innate and adaptive immune responses in blood and the respiratory tract and link experimental data with clinical outcome. We have recently shown that innate and adaptive immune responses early after SARS-CoV-2 infection predicts subsequent development of severe COVID-19. We also have preliminary data that points to interesting age differences in respiratory and systemic immune responses to influenza that we now explore further using state-of-the-art methodology. Influenza is overall well-studied, but we know little about immune responses at the site of infection, particularly in elderly populations. The knowledge we generate on mechanisms of immunopathogenesis can aid treatment of individuals and vulnerable groups as well as guide society in handling influenza.

Anna Smed-Sorensen is invited by Anne Hosmalin.