MERS vaccine ‘ready for human trials’

29 Jun

Researchers have started planning for the first clinical trial to test a candidate

vaccine to protect against the coronavirus that causes Middle East respiratory

syndrome.

mers cov
The researchers say the MERS-CoV candidate vaccine has passed all the preclinical tests and is ready to start human trials.

The news follows a study led by Ludwig-Maximilians-Universit√§t M√ľnchen in Germany (LMU)

that demonstrated the vaccine’s protective effect in the lab and in mice.

Writing in the Journal of Virology, the researchers conclude that the vaccine –

called MVA-MERS-S – meets important criteria for use in human trials.

Middle East respiratory syndrome (MERS) is a respiratory illness caused by the MERS

coronavirus (MERS-CoV).

At first, infection causes flu-like symptoms, but they can progress to a severe

respiratory illness that can be fatal.

There is currently no vaccine against MERS-CoV, which kills around 36% of people

it infects.

MERS-CoV was first identified in 2012 when it emerged in Saudi Arabia. It has spread to

other countries in the Arabian Peninsula and beyond, including the US and Germany – where the

vaccine has been developed.

The present MERS outbreak in South Korea – where 166 confirmed cases and 12 deaths have

been reported – is the largest so far recorded outside the Middle East.

There have been suggestions that mammals play a role in spreading MERS. For example, one

study has suggested MERS may have started in bats, and

another, that MERS could be carried by camels.

Vaccine based on a safe virus carrying MERS-CoV antigen

Two years ago, Gerd Sutter, a virology professor and chair of LMU’s Institute for Infectious

Diseases and Zoonoses, and his team reported they had developed a candidate vaccine against

MERS-CoV.

As well as researchers from LMU, the vaccine development team includes members from

Marburg University in Germany, and the Erasmus Medical Center of Rotterdam in the

Netherlands.

In the new study, they describe how subsequent preclinical tests confirm that the

vaccine is effective, paving the way for phase 1 trials in humans.

The idea of a vaccine is to prime the immune system to fight a particular disease without

causing the subject to actually have the full-blown disease.

In this study, the team based the candidate vaccine on a safety-tested vaccine virus

called Modified Vaccinia virus Ankara (MVA).

They used MVA as a vehicle to carry an MERS-CoV antigen called the spike glycoprotein

(protein S). An antigen is a part of a virus, bacteria, or other unwanted material that

causes the immune system to produce antibodies to eliminate it.

Once inside the body, the modified virus gets into cells and makes many copies of the

MERS-CoV protein S, displaying them on the cell surface so they can be readily recognized by

the immune system.

When the immune system recognizes the MERS-CoV protein S, it begins to produce antibodies

and T cells against the pathogen.

Tests in cell cultures and mice showed vaccine is effective

As a first step, the researchers showed the vaccine had the desired immune reaction in

cell cultures – it produced protective levels of MERS-CoV-neutralizing antibodies.

Next, the team used mice genetically modified to be susceptible to MERS-CoV infection and

exposed them to varying doses of the vaccine.

Tests showed the MERS virus could not replicate itself in mice that had received the

highest doses of vaccine. They also showed the vaccinated mice had lower levels of MERS DNA

in their lungs than non-vaccinated mice.

Prof. Sutter says the results show the vaccine candidate is both safe and effective,

and:

“Thus, there is no obvious risk that the resulting immune response might

exacerbate rather than prevent the infection.”

Planning for the next step, a phase 1 clinical trial in humans, is already under way with

the help of a €1.5 million ($1.66 million) grant from the German Center for Infection Research

(DIFZ).

Meanwhile, Medical News Today recently covered a report of Thailand’s first confirmed case of MERS. Public health

minister Rajata Rajatanavin said a man who traveled to Thailand from the Middle East has

tested positive for the virus.

Written by Catharine Paddock PhD