Scientists have identified natural human antibodies against the virus that causes Middle East Respiratory Syndrome (MERS), a step toward developing treatments for the newly emerging and often-fatal disease.

The researchers found that these "neutralizing" antibodies prevented a key part of the virus, known as MERS CoV, from attaching to protein receptors that allow the virus to infect human cells. The research was led by Wayne Marasco , MD, an infectious disease expert at Dana-Farber.

Marasco and colleagues found the MERS antibodies using a "library" of some 27 billion human antibodies they have created and maintain in a freezer at Dana-Farber; it is one of the largest such libraries in the world.

Antibodies are proteins made by the immune system that recognize foreign viruses and bacteria. A neutralizing antibody is one that not only recognizes a specific virus but also prevents it from infecting host cells, so eventually the infection is "cleared" from the individual.

The research team plucked seven MERS-specific neutralizing antibodies from the library after using samples of the virus to screen for them.

MERS CoV (CoV stands for coronavirus) has on its surface an array of spike-shaped proteins that bind to host cells - specifically to receptor proteins called DPP4 on the surface of cells that line human airways. The neutralizing antibodies identified in the study prevented the virus' spikes from binding to the DPP4 receptors.

The researchers selected one of the antibodies, labeled 3B11, as a "lead" candidate for further research. Marasco said the antibody has been produced in sufficient quantities to begin testing in non-human primates and mice to determine if they protect against the virus. However these studies have been delayed because no good animal model for MERS has been developed, added Marasco.

The lab studies have been reported in the Proceedings of the National Academy of Sciences (PNAS).