Experimental vaccine triggers the production of Ebola virus neutralizing antibodies

Early tests of experimental vaccine triggers the production of Ebola virus neutralizing antibodies, researchers say.

GENEVA, SWITZERLAND (April 1, 2015) (REUTERS) – The first results of the phase 1 clinical trial at the University Hospitals of Geneva (HUG) show that the VSV-ZEBOV vaccine candidate triggers the production of antibodies capable of neutralizing the Ebola virus, said HUG researcher and WHO representative on Tuesday (April 1).

The phase 3 clinical trials recently launched in West Africa will determine whether the immune response triggered by this vaccine is able to protect the population against the Ebola virus, and if large-scale vaccination campaigns are feasible.

“I want to emphasize, because the first question is: ‘does this vaccine protect?’. We don’t know. Why we don’t know? Because we do not know the level of antibodies needed to protect against Ebola when confronted with an infectious patient,” Prof. Claire-Anne Siegrist, Principal Investigator and Head of the Vaccinology Centre at HUG, told a news conference.

Most of the observed side effects were mild to moderate (fever and muscle pain for one or two days), but around 20% of the volunteers reported mild to moderate joint pain for a couple of weeks. The VSV-ZEBOV experimental vaccine has potential, but researchers continue to develop other vaccines in parallel.

“We hope that if these first vaccines are not perfects, because they don’t protect for example, the entire population, once again, which we don’t know at all for now, or if the side effects are maybe too important for vaccinating an entire population, we have, here, other candidates who could be used in Africa if they are effective,” said Dr Marie-Paule Kieny, Assistant Director-General of WHO Health Systems and Innovation.

At the HUG, all the volunteers who received 10 or 50 million vaccine particles of VSV-ZEBOV produced antibodies able to bind to the envelope of Ebola virus. According to HUG, levels of neutralizing antibodies increase with dose and are at their optimal level with a dose of 20 million vaccine particles. These results are based on a total of 158 volunteers in Europe and Africa.

“We don’t think for now, that Ebola control will be fast enough to keep us from recruiting the volunteers that we will need. Because, of course, I didn’t mention it, but all these contact are obviously volunteers. They are adults, because right now we don’t have security data for children, pregnant women are not part of it and everybody is volunteers. We had no problem for recruiting volunteers, but we think that we will be able to recruit all the “belts” before mid-June,” said Dr Marie-Paule Kieny.

The so-called vaccination “belt” is to identify recently infected patients and vaccinate their relatives to create an “immunity belt” around them and thus stop the spread of the virus.

“For the current epidemic we have the chance, and that’s probably a chance seen from a certain angle, the future will tell, that the virus is almost unchanged, that is, we did not feel that the virus has already accumulated a lot of mutation or has the ability to accumulate mutations. So if that was the case, the virus will be potentially able to escape from vaccines or antivirals. So currently we are in a rather favourable situation relative to the biology of the virus, I mean the virus that affects the West Africa at this time, the variant called the Makona,” concluded Prof. Laurent Kaiser, Head of the Infectious Diseases Department at HUG.

Over 10,000 people have died in Liberia, Guinea and Sierra Leone after contracting Ebola.