Figure 4

Graphic model of glycoprotein display and sGP1 shedding, relevant protein components in LASV virions, and release of viral components from dead cells. (1) LASV glycoprotein mediates virion binding to alpha dystroglycan (αDG) on permissive cells (1a). Following receptor binding the virion fuses with the host cell membrane, resulting in viral entry. Viral replication takes place in the cytoplasm of the infected cell. (2) During replication and before mature virions are assembled GPC is proteolytically processed and a portion of the resulting GP1 is transported to the cell surface and shed as sGP1 (2a). Concurrently, GPC is expressed on the cell surface, mediated by GP2 anchoring in the bilipid membrane, non-covalently associated GP1, and the hydrophobic signal peptide (2b). (3) Budding virions emerge from the cell surface mediated by Z matrix protein as enveloped particles containing membrane lipid and proteins, viral GPC and nucleoprotein. (4) Virions are released from infected cells containing nucleoprotein and associated viral RNA segments, along with non-displayed polymerase and cellular ribosomes. Budded virions will enter the circulation and can be detected in whole antigen capture assays or by western blot identification of individual proteins, as performed in these studies. Presence of intact virions should permit the identification of GP1, GP2, and nucleoprotein. (5) Nucleoprotein and glycoproteins can shed from dead or dying cells, with compromised cell membrane integrity. This phenomenon is observed in vitro, and may occur in vivo, hence the detection of only NP in some serum samples. A graphic representation of each relevant component in the outlined pathway is shown in the legend box. EC: extracellular; IC: intracellular; CM: cell membrane.