First identified in 2012, Middle East respiratory syndrome (MERS) is caused by 
an emerging human coronavirus, which is distinct from the severe acute 
respiratory syndrome coronavirus (SARS-CoV), and represents a novel member of 
the lineage C betacoronoviruses. Since its identification, MERS coronavirus 
(MERS-CoV) has been linked to more than 1372 infections manifesting with severe 
morbidity and, often, mortality (about 495 deaths) in the Arabian Peninsula, 
Europe, and, most recently, the United States. Human-to-human transmission has 
been documented, with nosocomial transmission appearing to be an important route 
of infection. The recent increase in cases of MERS in the Middle East coupled 
with the lack of approved antiviral therapies or vaccines to treat or prevent 
this infection are causes for concern. We report on the development of a 
synthetic DNA vaccine against MERS-CoV. An optimized DNA vaccine encoding the 
MERS spike protein induced potent cellular immunity and antigen-specific 
neutralizing antibodies in mice, macaques, and camels. Vaccinated rhesus 
macaques seroconverted rapidly and exhibited high levels of virus-neutralizing 
activity. Upon MERS viral challenge, all of the monkeys in the 
control-vaccinated group developed characteristic disease, including pneumonia. 
Vaccinated macaques were protected and failed to demonstrate any clinical or 
radiographic signs of pneumonia. These studies demonstrate that a consensus MERS 
spike protein synthetic DNA vaccine can induce protective responses against 
viral challenge, indicating that this strategy may have value as a possible 
vaccine modality against this emerging pathogen.