sGP Serves as a Structural Protein in Ebola Virus Infection

Methods. We expressed ZEBOV GP(1,2), VP40, and NP proteins, together with sGP protein, from expression plasmids and examined the resultant virus-like particles by using Western blot. Cells expressing GP(2) in combination with either GP(1) or sGP were analyzed by using flow cytometry with the KZ52 antibody, which recognizes a GP(1,2) conformational epitope. A VSV pseudotype, VSV delta G*, which expresses a GFP reporter gene instead of the G protein, was used to produce pseudotyped viruses encoding sGP and variants of GP to test the contribution of sGP to infectivity. Results. Western blot and flow cytometric analyses suggested the existence of a covalently linked sGP-GP(2) molecule. VSV delta G*(sGP + GP(2)) and VSV delta G*(GP(1,2)) infected Vero E6 cells and were neutralized by the KZ52 antibody. Overexpression of sGP reduced the titer of VSV delta G*(GP(1,2)). Conclusions. ZEBOV sGP can substitute for GP(1), forming a sGP-GP(2) complex and conferring infectivity. Our studies suggest a novel role for sGP as a structural protein.