A promising therapy, EBOTAb, which is a pool of intact ovine immunoglobulin G, protected guinea pigs against Ebola virus-induced disease as much as 72 hours after exposure to the deadly virus, according to a recently-published study in the Journal of Infectious Diseases.
Stuart David Dowall, of Public Health England, and colleagues wrote, “EBOTAb is cost-effective, thus reducing the economic burden that results from the emergence of highly pathogenic viruses, especially in developing regions.”
Female adult Dunkin-Hartley guinea pigs, weighing 250 g to 350 g, were exposed to Ebola virus-induced disease in two experiments.
Test animals received intravenous EBOTAb starting at either 6, 48, or 72 hours following EBOV challenge, according to the researchers. Repeat administrations were delivered, equating to 10 doses for the 6-hour group, 8 doses for the 47-hour group, and 7 doses for the 72-hour groups. A volume of 0.5 mL containing 25 mg of ovine immunoglobulin was administered at each treatment.
EBOTAb was assessed for neutralization activity, with results showing a geometric mean titer of 11,585 against the Mayinga Ebola virus strain and 9,743 against Makona Ebola virus strain. For both strains, the geometric mean titer for the control ovine immunoglobulin G was <4.
Guinea pigs were challenged with Ebola virus and researchers administered 25 mg IV EBOTAb in a volume of 0.5 mL 6 hours after challenge, followed by daily dosing until day 6 and dosing every 2 days until day 12.
Six hours after challenge, 6 test animals had 100% survival compared with 17% of the untreated animals. Animals treated with EBOTAb showed no evidence of weight loss after challenge and did not exhibit fever or clinical symptoms.
In a second experiment that looked at extending the treatment window, test animals were challenged with Ebola virus and 25 mg IV EBOTAb in a volume of 0.5 mL either 48 hours or 72 hours after challenge. EBOTAb was administered daily until day 7, followed by treatment every 2 days until day 11.
Survival was 100% (6 of 6 animals) in the 48-hour group and 75% (3 of 4 animals) in the 72-hour group, a result that was statistically significant (untreated vs 48 hours, P<.001; untreated vs 72 hours, P=.002).
The researchers added that clinical parameters, including weight, temperature, and clinical signs, were reduced in EBOTAb-treated animals as compared with controls.
1. Dowall SD, Callan J, Zeltina A, Al-Abdullah I, et al. Development of a Cost-effective Ovine Polyclonal Antibody-Based Product, EBOTAb, to Treat Ebola Virus Infection J Infect Dis. 2016, doi:10.1093/infdis/jiv565