A novel Ebola virus antibody-dependent cell-mediated cytotoxicity (Ebola ADCC) assay

Ebolaviruses are highly virulent pathogens that cause Ebola viral disease (EVD). Data from non-human primate (NHP) models and from human survivors of EVD suggest that anti-Ebola antibodies play an integral role in protection. Antibody-dependent cell-mediated cytotoxicity (ADCC) is a potential mechanism through which anti-Ebola antibodies may mediate protection. We developed a robust Ebola-specific ADCC assay for use in ongoing trials of Ebola vaccines. Stable cell lines for inducible Zaire ebolavirus glycoprotein (EBOV GP) expression were developed to provide a uniform source of target cells in the assay, and were combined with an existing human natural killer (NK) cell line as the effector cell. When applied to commercially available anti-EBOV GP monoclonal antibodies, the assay clearly differentiated antibody with high ADCC activity from those with low or no ADCC activity. Anti-EBOV ADCC activity was also detected in plasma samples from rhesus macaques immunized with a candidate Ebola vaccine. The Ebola ADCC assay reported here will be a useful tool in studying the functionality of anti-EBOV GP antibodies elicited by Ebola vaccines in ongoing and future clinical trials.