54G10 (Vanderbilt University)

Respiratory syncytial virus and human metapneumovirus are leading causes of respiratory illness worldwide, but limited treatment options are available. To better target these viruses, we examined key aspects of the viral life cycle in three-dimensional (3-D) human airway tissues. Both viruses establish efficient infection through the apical surface, but efficient spread and apical release were seen for respiratory syncytial virus (RSV) but not human metapneumovirus (HMPV). Both viruses form inclusion bodies, minimally composed of nucleoprotein (N), phosphoprotein (P), and viral RNA (vRNA), indicating that these structures are critical for replication in this more physiological model. HMPV formed significantly more long, filamentous actin-based extensions in human airway epithelial (HAE) tissues than RSV, suggesting HMPV may promote cell-to-cell spread via these extensions. Lastly, RSV entry and spread were fully inhibited by neutralizing antibodies palivizumab and the novel nirsevimab. In contrast, while HMPV entry was fully inhibited by 54G10, a neutralizing antibody, spread was only modestly reduced, further supporting a cell-to-cell spread mechanism.