Reversion of advanced Ebola virus disease in nonhuman primates with ZMapp

Abstract

Without an approved vaccine or treatments, Ebola outbreak management has been limited to palliative care and barrier methods to prevent transmission. These approaches, however, have yet to end the 2014 outbreak of Ebola after its prolonged presence in West Africa. Here we show that a combination of monoclonal antibodies (ZMapp), optimized from two previous antibody cocktails, is able to rescue 100% of rhesus macaques when treatment is initiated up to 5 days post-challenge. High fever, viraemia and abnormalities in blood count and blood chemistry were evident in many animals before ZMapp intervention. Advanced disease, as indicated by elevated liver enzymes, mucosal haemorrhages and generalized petechia could be reversed, leading to full recovery. ELISA and neutralizing antibody assays indicate that ZMapp is cross-reactive with the Guinean variant of Ebola. ZMapp exceeds the efficacy of any other therapeutics described so far, and results warrant further development of this cocktail for clinical use.

Extended Data Figure 1. Clinical scores for each ZMapp^™-treated group

Arrows indicate treatment days. Dashed line represents humane endpoint threshold. Faded symbols/lines are the other two treatment groups, for comparison. Control group (Group G) is shown in black on all three panels. (a) Clinical score of Group D (blue); (b) Clinical score of Group E (orange); (c) Clinical score of Group F (green).

Extended Data Figure 2. Viremia for each ZMapp^™-treated group

Arrows indicate treatment days. Faded symbols/lines are the other two treatment groups, for comparison. Control group (Group G) is shown in black on all three panels. (a) TCID₅₀ of Group D (blue); (b) TCID₅₀ of Group E (orange); (c) TCID₅₀ of Group F (green). (d) Viremia by RT-qPCR of Group D (blue); (e) Viremia by RT-qPCR of Group E (orange); (f) Viremia by RT-qPCR of Group F (green).

Figure 1. Post-exposure protection of EBOV-infected nonhuman primates with ZMapp1 and ZMapp2

Rhesus macaques were challenged with EBOV-K, and 50 mg/kg of ZMapp1 (Group A) or ZMapp2 (Group B) were administered on days 3, 6, and 9 (n=6 per treatment group, n=2 for controls). Non-specific IgG mAb or PBS was administered as a control (Group C). (a) Kaplan-Meier survival curves. (b) Clinical score. (c) Rectal temperature. (d) EBOV viremia by TCID₅₀. Blood parameters: (e) white blood cell count; (f) lymphocyte count; (g) lymphocyte percentage; (h) platelet count; (i) neutrophil count; (j) neutrophil percentage; (k) ALT; (l) ALP; (m) BUN; (n) CRE; (o) GLU.

Figure 2. Post-exposure protection of EBOV-infected nonhuman primates with ZMapp

^™. (a to f) Rhesus macaques (n=6 per ZMapp^™ treatment group, n=3 for controls) were challenged with EBOV-K, and 50 mg/kg of ZMapp^™ were administered beginning at 3 (Group A), 4 (Group B) or 5 (Group C) days after challenge. Non-specific IgG mAb or PBS was administered as a control (Group D). (a) Timeline of infection, treatment and sample days. (b) Kaplan-Meier survival curves. (c) Clinical scores; the dashed line indicates the minimum score requiring mandatory euthanasia. (d) Rectal temperature. (e) Percentage body weight change. (f) EBOV viremia by TCID₅₀. (g to l) Selected clinical parameters of Group A to D animals. (g) ALT. (h) ALP. (i) TBIL. Counts for (j) Lymphocytes, (k) Neutrophils and (l) Platelets over the course of the experiment.

Figure 3. Amino acid alignment of the Kikwit and Guinea variants of EBOV, and in vitro antibody assays of mAbs c13C6, c2G4 and c4G7 with EBOV-G or EBOV-K virions

(a) Sequence alignment of the EBOV glycoprotein from the Kikwit (EBOV-K) and Guinea (EBOV-G) variants, with the binding epitopes of ZMapp^™ pointed with an arrow, and (b) an ELISA (for each antibody, the EC₅₀ are different (p < 0.05, regression analysis) between the two antigens) as well as (c) a neutralizing antibody assay showing the activity of the individual mAbs composing ZMapp^™ against EBOV-K (black) and EBOV-G (purple), and the samples were run in triplicate.