Monkeys Protected from MERS Infection by Synthetic DNA Vaccine

A synthetic DNA vaccine directed against the Middle East Respiratory Syndrome's (MERS) spike protein was found to completely protect rhesus macaques from developing pneumonia after having been exposed to the live virus.

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 in 2012, 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. During a recent outbreak in South Korea that infected more than 181 people and caused more than 30 deaths, rapid human-to-human transmission was documented with in-hospital transmission the most common route of infection.

Investigators at the University of Pennsylvania (Philadelphia, USA) and colleagues from several other research institutions reported in the August 19, 2015, online edition of the journal Science Translational Medicine that they had developed 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.

Results presented in this paper 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.

"The significant recent increase in MERS cases, coupled with the lack of effective antiviral therapies or vaccines to treat or prevent this infection, have raised significant concern," said senior author Dr. David B. Weiner, professor of pathology and laboratory medicine at the University of Pennsylvania. "Accordingly the development of a vaccine for MERS remains a high priority."

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