A single dose of the vaccine – which uses Profectus’s VesiculoVax vector platform – protected the monkeys against the Makona strain of Ebola (previously known as the Ebola Guinea strain), according to a study published this week in Nature.
The trial tested two VesiculoVax-vectored Ebola vaccines, with different levels of attenuation.
All eight vaccinated macaques remained disease-free 28 days after exposure to lethal levels of the Makona Ebola virus. Two unvaccinated control macaques showed infection after seven and eight days.
Viral vector
VesiculoVax (rVSVN4CT1) is an attenuated delivery method, using replication-competent recombinant vesiculoviruses that have been genetically attenuated to avoid causing illness.
Profectus’s Ebola vaccine is based on a strain of vesicular stomatitis virus (rVSV) engineered to express the surface protein from the disease’s Zaire and Sudan forms.
The vector has already been trialled in humans in an HIV vaccine which passed safety and immunogenicity studies.
The Nature study showed a large reduction in vaccine-associated viraemia (when viruses enter the bloodstream), the authors said, indicating “a significant increase of in vivo attenuation for these next-generation rVSV/ZEBOV vaccine vectors, which should translate into greater safety and reduced adverse events in humans.
They added that “ZEBOV genome sequencing from cases later during the West Africa outbreak has revealed little drift in the [glycoprotein] gene, suggesting that this vaccine platform could also be efficacious against currently circulating ZEBOV.
“These findings pave the way for the identification and manufacture of safer, single-dose, high efficacy vaccine(s) to combat current and future filovirus outbreaks in Africa and their potential use as biological weapons,” the paper concluded.
Other vaccines
Profectus’s Chief Scientific Officer stressed the importance of a vaccine that can act quickly in a single dose.
"This is the first demonstration of a vaccine that is able to rapidly confer single-dose protection against the current Makona strain of Zaire Ebola virus that is responsible for more than 10,000 deaths in the ongoing epidemic in West Africa,” said John Eldridge.
The vaccine is designed for pre- and post-exposure Ebola protection.
Profectus is also working on a trivalent vaccine for protection against all Ebola and Marburg viruses, which uses the same highly attenuated rVSVN4CT1 VesiculoVax vector. It has begun non-human primate testing, funded by the National Institute of Allergy and Infectious Diseases and the Department of Defense.
The Makona study was authored by scientists from Profectus and the University of Texas Medical Branch (UTMB) at Galveston. UTMB’s Geisbert laboratory helped the pharma company develop the vaccine, as well as the National Institutes of Health, the US Department of Health and Human Services, Biomedical Advanced Research and Development Authority (BARDA), and the Department of Defense Joint Vaccine Acquisition Program (JVAP).
Source: ‘Single-Dose Attenuated VesiculoVax Vaccines Protect Primates Against Ebola Makona Virus,’ Nature, April 9, 2015
DOI: http://www.nature.com/nature/journal/vnfv/ncurrent/full/nature14428.html