A recent Seoul National University College of Medicine study shows that the current strategy for developing a vaccine for the Middle East Respiratory Syndrome coronavirus (MERS-CoV) needs to be improved, as the virus mutates during an outbreak so that it becomes less virulent.
MERS-CoV results in serious respiratory infections, with a global mortality rate of approximately 35 percent. Like other coronaviruses, it uses a glycoprotein with a large surface spike to invade CD26 cells in humans. This results in an infection.
Most recently, there was a large MERS outbreak in May through July last year. A traveler from the Arabian Peninsula had MERS, and the disease spread through South Korea where 186 people contracted the disease, and 38 people died.
"The unexpected outbreak raised strong concerns about the possible generation of mutant viruses and prompted us to investigate the MERS viruses infecting Korean patients," Dr. Nam Hyuk Cho, principal investigator of the study, said.
This research, available in the online open-access journal from the American Society for Microbiology called mBio, used 13 new viral genomes taken from 14 patients infected with MERS. Twelve of these genomes had mutation points within the viral spike protein. The mutations demonstrate that the virus grows less virulent, not more virulent, over time.
“Strikingly, both mutations resulted in reduced affinity of RBD to human CD26 compared to wild-type RBD," Cho said. "This is an interesting strategy of coronavirus evolution to survive in nature and live together with the new host. The virus may tune down its power to attack for the sake of longer survival in the new host. The unexpected findings suggest that MERS-CoV adaptation during human-to-human spread may be driven by host immunological pressure such as neutralizing antibodies, resulting in reduced affinity to the host receptor."