part of virion attachment to host cell virion attachment to host cell pilus The process by which a virion attaches to a host cell by binding to a pilus on the host cell surface. Pili are retractile filaments that protrude from gram-negative bacteria. Filamentous viruses can attach to the pilus tip, whereas icosahedral viruses can attach to the pilus side. viral attachment to host cell pilus 2013-08-29T13:31:10Z pilus-mediated viral attachment to host cell pilus-adsorption protein GO:0039666 bf pilus-mediated viral adsorption onto host cell biological_process VZ:981 symbiont entry into host cell