Characterization of Junin arenavirus cell entry

Junin virus (JUNV) entry is conducted by receptor-mediated endocytosis. To explore the cellular entry mechanism of JUNV, inhibitory effects of drugs affecting the main endocytic pathways on JUNV entry into Vero cells were analysed. Compounds that impair clathrin-mediated endocytosis were shown to reduce virus internalization without affecting virion binding. In contrast, drugs that alter lipid-raft microdomains, impairing caveola-mediated endocytosis, were not able to block virus entry. To show direct evidence of JUNV entry, transmission electron microscopy was performed; it showed JUNV particles of about 60-100 nm in membrane depressions that had an electron-dense coating. In addition, JUNV particles were found within invaginations of the plasma membrane and vesicles that resembled those of pits and clathrin-coated vesicles. Taken together, these results demonstrate that clathrin-mediated endocytosis is the main JUNV entry pathway into Vero cells and represent an important contribution to the characterization of the arenavirus multiplication cycle.