Evidence against Ebola virus sGP binding to human neutrophils by a specific receptor.

The issue of whether Ebola secretory glycoprotein (sGP) binds to human neutrophils via the IgG Fc receptor IIIb (FcgammaRIIIb, CD16b) or other receptors has been controversial. To clarify this, FACS analysis, an sGP absorption assay, and direct binding of (125)I-sGP to neutrophils were performed. Results from FACS analysis demonstrated that limited washing conditions leads to the nonspecific formation of immune complexes on the neutrophil surface and this, but not a specific interaction between sGP and CD16b, is responsible for the previous observations. An sGP absorption assay also demonstrated that sGP is not specifically bound but is nonspecifically proteolysed by proteases released from neutrophils. Finally, there was no difference in (125)I-sGP binding to neutrophils compared to other control cell types. Taken together, these results demonstrate that neutrophils do not express a specific receptor for Ebola virus sGP. It is unlikely that sGP plays a role in the Ebola virus pathogenesis through interfering with the innate immunity by targeting neutrophils.