TABLE 2.

EBO7 protects cynomolgus macaques against aerosolized EBOV challenge

StudyGroupaVaccineNo. of dosesELISA titerbAerosol challengecClinical findingsdOutcome
VirusS/T (%)
1Group 1EBO71Z, 3.2; S, 3.7ZEBOV3/3 (100%)No clinical signsAll survived
Control AMock1ZEBOV0/1 (0)F, D, A, moderate P, V (d5, 5.6), T, LE↑↑↑Succumbed on day 6
Group A historical controlsSEBOV0/3 (0)D, A, no P, T, dyspnea, no blood workSuccumbed on day 9, 9, or 12
2Group 2EBO71Z, 3.5; S, 3.5*SEBOV2/3 (67)One with clinical signs: D, A, no viremia detectedOne succumbed on day 9
Control BMock1SEBOV0/1 (0)D, A, widespread P, V, LE↑↑Succumbed on day 8
Group B historical controlsSEBOV0/3 (0)D, A, widespread P, V, LE↑↑-↑↑↑Succumbed on day 7, 8, or 9
3Group 3EBO72Z, 3.8; S, 4.7*SEBOV3/3 (100)One with clinical signs: D, A, no viremia detectedAll survived
Control CMock2SEBOV0/1 (0)D, A, widespread P, V (d3, 2.6; d5, 6.1; d7, 7.3), T, LE↑↑↑Succumbed on day 7
  • a Group 1 and 2 macaques were vaccinated with 1 × 1010 PFU of EBO7 28 days before aerosol challenge. Group 3 macaques were vaccinated on days 0 and 71 with 1 × 1010 PFU of EBO7 and then challenged 28 days after the boosting vaccination. Control animals were vaccinated with 1 × 1010 PFU of HC4. In addition to these controls, historical control macaques (n = 7 for ZEBOV, and n = 6 for SEBOV) were used to limit the number of controls.

  • b Geometric mean titers (log10) of total serum immunoglobulin as measured by ELISA using inactivated ZEBOV (Z) or SEBOV (S) preparations as targets. *, SEBOV-specific titers were significantly higher in macaques receiving two doses of EBO7 (group 3) than in macaques receiving a single dose (group 2) (P < 0.02).

  • c Based on back-titration, group 1 and control A were aerosol challenged with 900 to 1,000 PFU of ZEBOV; group A historical controls were aerosol challenged with approximately 20 PFU of SEBOV. Group B historical controls, groups 2 and 3, and controls B and C were aerosol challenged with 100 to 500 PFU of SEBOV. S/T, number of survivors/total number challenged.

  • d Fever (F) was defined as a rectal temperature increase of more than 2°C over baseline; depression (D) and anorexia (A) were assessed subjectively; petechia (P) was defined as mild (barely visible), moderate (visible over focal areas), or widespread; viremia (V) was defined as detectable virus in the serum, with the day (d) of detection and log10 value in PFU/ml shown in parentheses; thrombocytopenia (T) was defined as a ≥35% decrease in platelets; and elevated levels of liver-associated enzymes (LE) were defined as a 2- to 3-fold increase (↑), a 4- to 5-fold increase (↑↑), or a more-than-5-fold increase (↑↑↑) in serum aspartate aminotransferase and alanine aminotransferase over baseline.