September 7, 2014

expert reaction to Ebola immunity generated in nonhuman primates

A study published in Nature Medicine reported the use of two vaccines to protect against Ebolavirus in macaques, with protection seen up to ten months after vaccination.

Prof Martin Hibberd, Professor of Emerging Infectious Disease, London School of Hygiene & Tropical Medicine, said:

“The paper by Sullivan and colleagues describes a novel vaccine approach to Ebola that gives hope for a successful trial in humans, with the innovative prime-boost method overcoming a known limitation of this method. However, this chimpanzee adenovirus vaccine may still have an unusually large barrier to overcome when transferring to humans, so I hope these trials can begin as soon as possible. A long lasting protective immunisation process is just what is needed.”

Prof Jonathan Ball, Professor of Molecular Virology, University of Nottingham, said:

“This is really encouraging data. The authors have tried two different vaccines on nonhuman primates – one based on an adenovirus isolated from chimpanzees that has been rendered non-infectious, and the other a modified cowpox virus.  Both vaccines have been engineered to deliver the surface protein of Ebolavirus Zaire or Sudan strains in attempt to bring about protection against both strains of Ebola.

“By combining the two different Ebolavirus protein delivery systems, the authors were able to protect the animals from lethal Ebolavirus infection, even when challenged 10 months after vaccination.

“The degree of protection seen with the chimpanzee adenovirus alone – which will be used in one of the human clinical trials planned for the UK, Mali and the Gambia – was still pretty impressive, especially when the animals received Ebolavirus within a few weeks of vaccination.  This is important as it would keep the dosing regimen simple and could still provide good protection in the sort of outbreak that we are seeing in Western Africa at the moment.

“For longer term protection to prevent future outbreaks one could envisage using the combination – the so-called prime / boost – approach.

“Crucially, similar approaches to protect against hepatitis C and malaria have shown promising results in early clinical trial. But a key question will be how well the chimpanzee vaccines perform in regions where we know humans are exposed to chimpanzee adenovirus (which could mean people in these regions have antibodies to chimp adenovirus, which could be a hurdle), as these are exactly the areas where ebolavirus is most likely to break out.  Research so far has suggested that this may not be a significant problem and the planned trials in Mali and Gambia will no doubt go some way to answering this.”

‘Chimpanzee adenovirus vaccine generates acute and durable protective immunity against ebolavirus challenge’ by Daphne Stanley et al. published in Nature Medicine on Sunday 7 September 2014.

All our previous output on this subject can be seen at this weblink:

http://www.sciencemediacentre.org/ebola-outbreak/

Declared interests

None declared