Differentiated human airway organoids to assess the infectivity of emerging influenza virus Jie Zhou, Cun LI, Man Chun Chiu, Bosco Wong, Hin Chu, Honglin Chen, Hans Clevers, Kwok Yung Yuen 1Department of Microbiology, The University of Hong Kong; 2Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences
Novel reassortant avian influenza H7N9 virus and 2009 pandemic H1N1 (H1N1pdm) virus cause human infections, while avian H7N2 and swine H1N1 virus mainly infect birds and pigs, respectively. There is no robust in vitro model for assessing the infectivity of emerging viruses in humans. Based on a recently established method, we generated long-term expanding 3D human airway organoids which accommodate four types of airway epithelial cells: ciliated, goblet, club, and basal cells. We report differentiation conditions which increase ciliated cell numbers to a nearly physiological level with synchronously beating cilia readily discernible in every organoid. In addition, the differentiation conditions induce elevated levels of serine proteases, which are essential for productive infection of human influenza viruses, low-pathogenic avian influenza viruses and other respiratory viruses. We also established improved 2D monolayer culture conditions for the differentiated airway organoids. To evaluate the ability of differentiated airway organoids to identify human-infective virus, 3D and 2D differentiated airway organoids are applied to assess two pairs of viruses with known infectivity in humans, H7N9/Ah versus H7N2 and H1N1pdm versus an H1N1 strain isolated from swine (H1N1sw). The human infective H7N9/Ah virus replicated more robustly than the poorly human-infective H7N2 virus; the highly human-infective H1N1pdm virus replicated to a higher titer than the counterpart H1N1sw. Collectively, we developed differentiated human airway organoids which can morphologically and functionally simulate human airway epithelium. These differentiated airway organoids can be applied for rapid assessment of the infectivity of emerging respiratory viruses in humans.