Ebola virus (EBOV)
glycoprotein (GP), responsible for mediating host-cell attachment and membrane fusion, contains a heavily glycosylated
mucin-like domain hypothesized to shield GP from
neutralizing antibodies. To test whether the
mucin-like domain inhibits the production and function of anti-GP
antibodies, we vaccinated mice with Ebola virus-like particles (VLPs) that express
vesicular stomatitis virus G, wild-type EBOV GP (EBGP), EBOV GP without its
mucin-like domain (ΔMucGP), or EBOV GP with a Crimean-Congo hemorrhagic fever virus
mucin-like domain substituted for the EBOV
mucin-like domain (CMsubGP). EBGP-VLP immunized mice elicited significantly higher serum antibody titers toward EBGP or its mutants, as detected by western blot analysis, than did VLP-ΔMucGP. However, EBGP-, ΔMucGP- and CMsubGP-VLP immunized mouse sera contained
antibodies that bound to cell surface-expressed GP at similar levels. Furthermore, low but similar
neutralizing antibody titers, measured against a
vesicular stomatitis virus (VSV) expressing EBGP or ΔMucGP, were present in EBGP, ΔMucGP, and CMsubGP sera, although a slightly higher neutralizing titer (2- to 2.5-fold) was detected in ΔMucGP sera. We conclude that the EBOV GP
mucin-like domain can increase relative anti-GP titers, however these titers appear to be directed, at least partly, to denatured GP. Furthermore, removing the
mucin-like domain from immunizing VLPs has modest impact on
neutralizing antibody titers in serum.