The ability of passive antibody to protect against EBOV has been investigated in a number of animal models. The guinea pig and mouse models use EBOVs that have been serially passaged to adapt to replication in the respective animals and are highly lethal. Protection has been demonstrated in the guinea pig model using neutralizing horse, sheep, and goat immunoglobulin G (IgG) against EBOV [12, 13] and the human anti-EBOV GP mAb, IgG KZ52. This antibody neutralizes ZEBOV (1995, Kikwit) with a 50% inhibitory concentration (IC 50 ) of 0.05-0.3 lg/ml and an IC 90 of 0.5-2.6 lg/ml in Vero cells [11, 14] and an IC 50 of approximately 0.05-1 lg/ml and a IC 90 of 0.5-2 lg/ml in primary human monocytes/macrophages [14] . We showed that when administered subcutaneously at a dosage of 25 mg/kg up to 1 h after challenge, the antibody protects against robust ZEBOV challenge (10,000 plaque-forming units [pfu] ) in the guinea pig model [6] .