With more widespread deployment of the Ebola vaccine to people living and working within hot zones, recently vaccinated people may encounter high-risk exposures to the virus before their body can develop the immunity needed to protect against infection. When a non-vaccinated person is exposed to Ebola virus, the most effective intervention currently available is an antibody treatment. But in someone who was recently vaccinated, experts have been concerned about the possibility of a harmful interaction between the vaccine and the antibody treatment.
According to the latest findings of a collaborative team from The University of Texas Medical Branch at Galveston, Mapp Biopharmaceutical Inc., The National Institute of Allergy and Infectious Diseases and Médecins Sans Frontières, when nonhuman primates were vaccinated and then exposed to a lethal amount of Ebola virus 24 hours later, an antibody treatment successfully protected them against clinical illness and death, even when the antibody treatment was given three days after viral exposure.
“We demonstrated that in nonhuman primates challenged with a uniformly lethal dose of Ebola one day after vaccination, those receiving a monoclonal antibody treatment three days after the viral exposure showed no evidence of clinical illness and survived the challenge,” said UTMB’s Thomas Geisbert, professor in the department of microbiology and immunology. “In contrast, animals receiving only the vaccination or only the postexposure antibody therapy became ill and had decreased chances of survival compared with animals that were vaccinated, exposed to the virus and then treated with the antibody.”
The vaccine used in this study successfully protected more than 200,000 people in the Democratic Republic of Congo during the current Ebola outbreak and has been approved for human use by both the US Food and Drug Administration and the European Union. Study authors Thomas Geisbert and Heinz Feldmann were both were involved in the development of the vaccine.
“We designed our study to model a scenario likely occurring in the current Ebola outbreak in the Democratic Republic of the Congo; namely, high-risk exposure to the Ebola virus shortly after vaccination,” said Geisbert. “When people are exposed to the rabies virus, the standard protocol includes both vaccination and treatment with human rabies antibodies. Our study suggests that a similar approach to treatment may be appropriate for high-risk Ebola exposure and that monoclonal antibody therapy after vaccination may improve outcomes in recently vaccinated people.”