Another important process in MARV entry is believed to occur while virions are being trafficked within endocytic vesicles; the proteolytic cleavage of GP 1 . Endosomal cleavage of GP has been shown to be critical for the efficient entry of MARV [179, 180] . The current model for MARV entry involves the cleavage of GP 1 by host endosomal cysteine proteases. This removal of a large portion of GP 1 (including the mucin-like domain) is believed to expose the putative receptor-binding domain based on studies conducted with EBOV GP [181, 182] .