The recently discovered coronavirus now referred to as MERS (for Middle East Respiratory Syndrome) causes an infectious respiratory disease in humans which can be fatal. The virus is thought to be transmitted to humans primarily via contact with dromedary camels. Now researchers led by the German virologist Gerd Sutter at Ludwig-Max University Munich/Germany, in collaboration with teams led by Professor Bart L. Haagmans of the Erasmus Medical Center (MC) in Rotterdam/Netherlands and Professor Albert Osterhaus of the University of Veterinary Medicine Hannover/Germany, Foundation (TiHo), have successfully tested a candidate vaccine against MERS, in camels. The results of the trial appeared in the journal “Science” in January 2016.
Gerd Sutter, who holds the Chair of Virology in the Faculty of Veterinary Medicine at LMU, is currently engaged in a project designed to qualify the candidate vaccine MVA-MERS-S developed in his laboratory for use in clinical trials in humans. As yet, there is no vaccine available that can protect humans from infection by the MERS virus.
The new vaccine, MVA-MERS-S, was developed by Sutter and his team two years ago. In co-operation with researchers based at Philipps University in Marburg/Germany and the team in Rotterdam, he introduced a gene for the so-called spike protein of MERS into the genome of a weakened strain of poxvirus (MVA). The resulting modified poxvirus particles expressed the MERS protein on the surface of infected cells, and these engineered viruses form the basis of the new vaccine. Several preliminary data over the past two years have confirmed the immunogenicity and efficacy of MVA-MERS-S in mice. The scientists now describe the outcome of the first direct test of the vaccine in camels.
The MERS virus was first identified in Saudi Arabia in 2012. To date, some 1,400 cases of MERS have been reported, of which one-third proved fatal. Its primary hosts, however, are dromedary camels, as revealed by the detection of antiviral antibodies and the presence of MERS particles in the nasal cavity in infected animals. Although camels infected with the virus show relatively mild symptoms, all the evidence suggests that they can transmit the pathogen to humans, who can subsequently pass it on to others. Hence, vaccination of camels against MERS virus is an obvious method of choice for the prevention of human infections, the scientists note. Successful immunisation would deprive the virus of its primary host and break the chain of transmission, effectively minimising the risk of future MERS epidemics in human populations.
Clinical trials in humans now planned
MVA-MERS-S can also be used to immunise humans. Thanks to the tests carried out so far, the vaccine already meets many of the most important preconditions that must be fulfilled prior to its use in clinical trials in humans. Gerd Sutter is currently leading a project entitled “GMP manufacture and Phase I clinical investigation of MVA-MERS-S, an experimental prophylactic vaccine against the Middle East Respiratory Virus Syndrome” at the German Center for Infection Research, which is designed to set the scene for the first such tests of the vaccine in humans.
According to the researchers, so far, no candidate vaccines are available that could be used in the event of a large-scale epidemic. Only a few months ago, in the early summer of 2015, more than 180 people were infected with MERS in South Korea. The origin of the outbreak was traced to a single carrier, who had recently returned from the Middle East. All confirmed infections in humans have so far been linked, directly or indirectly, to that part of the world, hence the name Middle East Respiratory Syndrome Coronavirus (MERS-CoV) for the pathogen responsible.
Bart L. Haagmans and others An orthopoxvirus-based vaccine reduces virus excretion after MERS-CoV infection in dromedary camels (Science, 1 January 2016)
Jamal S. M. Sabir and others Co-circulation of three camel coronavirus species and recombination of MERS-CoVs in Saudi Arabia
Candidate vaccine gears up for clinical trials (06.22.2015)
Candidate vaccine passes first test (09.06.2013)