Several players are working on vaccines for Middle East respiratory syndrome (MERS), including the NIH and tandem GeneOne and Inovio ($INO), both of which had successful animal trials for their candidates. Now, a new study out of South Korea--showing that the MERS virus mutated during the outbreak there--could help vaccine developers pinpoint their target on the surface of the MERS virus.
South Korea experienced the largest MERS outbreak outside the Middle East, with 186 confirmed cases and 38 deaths. It was so unexpected that it prompted a team of South Korean researchers to investigate the MERS virus infecting Korean patients.
Using whole-genome sequencing, the team isolated 13 viral genomes from MERS patients and found that 12 of them had two mutations on this spike protein. The mutations were specifically in the receptor-binding domain of the spike, which made the virus less able to bind to human cells and cause infection.
While this seems like good news, it just means the virus is lying dormant in the bloodstream potentially to attack later. "The virus may tune down its power to attack for the sake of longer survival in the new host," said Nam Hyuk Cho, principal investigator of the study and a professor at the Seoul National University College of Medicine, as quoted by an mBio blog post.
Strategies for vaccine development should then take these antibody-escaping mutants into consideration, Cho said. According to the blog, most MERS candidates use the spike as a target against which to produce antibodies. Cho added that the target needs to be more specific: "Vaccines for MERS need to target the more stable and conserved region of the spike."
Inovio and GeneOne's MERS candidate is currently undergoing a Phase I trial at the Walter Reed Army Institute of Research. Meanwhile, the NIH completed animal studies for its candidate in July last year, and a European team's candidate demonstrated protection in camels in December.
- here's the mBio blog post
- and here is the study