ABSTRACT Human parainfluenza virus 3 (HPIV3) infection is driven by the coordinated action of viral surface glycoproteins hemagglutinin-neuraminidase (HN) and fusion protein (F). Receptor-engaged HN activates F to insert into the target cell membrane and drive virion-cell membrane fusion. For F to mediate entry. its precursor (F0) must first be cleaved by host proteases. https://www.roneverhart.com/Katin-Mens-Shirt-Whitney/