Risk assessing influenza A virus for tropism and pathogenesis using ex vivo explants and in vitro lung injury model

Abstract

Rapid emergence of avian-origin influenza viruses such as H7N9 and H5N6 has urged for better risk assessment tools to predict the potential zoonotic and pandemic threats in the community. The ability of highly pathogenic avian influenza (HPAI) H5N1 virus to cause acute lung injury (ALI) is critical for the pathogenesis. We have previously shown the use of an in vitro lung injury model to determine the potential of influenza virus to cause ALI by measuring the impairment of alveolar fluid clearance (AFC) and protein permeability (APP) in alveolar epithelial cells. On the other hand, different influenza viruses can replicate and infect different parts of human airway, virus tropism in human bronchus will give a better assessment for transmission potential. Therefore, the impairment of AFC and tissue tropism of influenza virus in human airway are major factors of risk assessing the potential of a virus to cause ALI and to transmit. In this study, we proposed the use of human in vitro lung injury and ex vivo respiratory tract explant model as risk assessment tools to study the pathogenicity and transmissibility of influenza A virus. Primary human alveolar epithelial cells will be infected with influenza A virus for the in vitro lung injury model, and human lung and bronchus explants will be used for tropism study. Our results showed that HPAI H5N1, H7N9 and recent H5N6 virus impaired AFC and increased APP compared to the low pathogenic seasonal influenza H1N1 and the 2009 pandemic H1N1 virus. Also, H7N9 and H5N6 virus infect more efficiently than H5N1 in bronchus. In summary, these physiological relevant risk assessment tools are able to provide an understanding for the pathogenesis of influenza viruses as well as an indication for transmission potential.