FRIDAY, SEPTEMBER 30, 2016

Scientists develop MERS-CoV strain to use in vaccine

Scientists developed a strain of the Middle East respiratory syndrome coronavirus that could be used as a vaccine against the deadly disease, according to a study to be published in mBio.

The mutated virus, known as rMERS-CoV-ΔE, was genetically engineered to make it capable of infecting a cell and replicating its genetic material while rendering it incapable of spreading and causing disease. The researchers said that by adding additional safeguards into the virus, it could be used as a safe and effective live-attenuated MERS-CoV vaccine.

"Our achievement was a combination of synthetic biology and genetic engineering," Luis Enjuanes, a co-author of the study, said. "The injected vaccine will only replicate in a reduced number of cells and produce enough antigen to immunize the host."

Enjuanes and his colleagues used research on the molecular biology of coronavirus to synthesize an infectious complementary DNA clone of the MERS-CoV genome. After inserting the viral chromosome into a bacterial artificial chromosome, the researchers mutated genes one-by-one to study the effects on viral infection, replication and reinfection. By mutating the envelope protein, the researchers were able to prevent the virus from propagating.

"To grow the virus, we create what are called 'packaging cells' that express the E protein missing in the virus," Enjuanes said. "The gene to encode this protein is integrated in the cell chromosomes and will not mix with the viral genes. Therefore, in these cells, and only within them, the virus will grow by borrowing the E protein produced by the cell. When the virus in administered to a person for vaccination, this person will not be able to provide the E protein to the defective virus."

Enjuanes said that after producing antigens to train the human immune system to fight MERS-CoV, the virus will die off.

Enjuanes said that further work was required before beginning clinical trials. The U.S. Food and Drug Administration requires that recombinant live attenuated vaccine strains include at least three safeguards to make sure viruses don't revert back to their virulent form.

Since its identification in June 2012, the World Health Organization was notified of 108 cases of MERS-CoV infection, including 50 deaths. There is not yet a reliable vaccine against the disease.