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.


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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.

Reference

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