MERS virus weakened by mutations, researchers found

Scientists have identified antibodies which neutralize the MERS-Coronavirus, a breakthrough that could lead to a treatment.

MERS, which emerged in Saudi Arabia two years ago, appears to have become more virulent in recent weeks: the kingdom has confirmed a spike of 143 more cases in April alone, raising its total number of infections to 339.

Wayne Marasco and colleagues at the Dana-Farber Cancer Institute, in Boston, collaborating with a research team from the University of North Carolina in Chapel Hill, screened a vast selection of human antibodies and identified seven that bind to the MERS-CoV spike protein¹.

The spike protein normally interacts with receptors on the surface of the host cell, allowing the virus to enter so it can replicate. The researchers showed that the seven antibodies they identified prevent this interaction by attaching to one of three different sites within the spike protein receptor-binding region.

They also examined how the virus changes upon exposure to the antibodies, revealing that the same mutations that allow it to evade being detected by them also weakened its ability to replicate.

Another research team, led by Liwei Jiang of Tsinghua University in Beijing, used a different approach. They screened a library of antibody fragments displayed on the surface of yeast cells. They then used a purified version of the MERS-CoV spike protein to identify two monoclonal antibodies that interact with it, and isolated them with magnetic beads².

Last month, the Saudi Arabian Ministry of Health announced it was discussing the development of a MERS-CoV vaccine with drug companies. These new studies are a step towards developing an effective prophylactic treatment.

Many of the new confirmed MERS cases were among staff at hospitals in the Saudi capital, Riyadh. The United States confirmed its first case last week; the patient, a Saudi Arabian who worked in one of the Riyadh hospitals housing MERS patients, was visiting relatives in Indiana, was hospitalized there and is now said to be recovering well. Marasco and his colleagues note that their study "offers the possibility of developing human monoclonal antibody-based immunotherapy, especially for healthcare workers."

"The findings are promising, but it's highly unlikely that these antibodies will make their way to the market soon," says Islam Hussein, a virologist at the Massachusetts Institute of Technology. Most likely a cocktail of antibodies will be needed to overcome the emergence of mutants [that] escape from neutralization."

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