Discovery of the unique way certain viruses invade healthy cells opens the door to new therapies that could block those viruses. 
 N. Rama Krishn

Viruses typically bind to an antigen on the cell surface to gain access to the cell.

UAB researchers on an international team reported they have used a special nuclear magnetic resonance (NMR) technique to precisely identify the point of entry of rabbit hemorrhagic disease virus (RHDV) into a healthy cell. The findings were reported in the March issue of the Journal of the American Chemical Society .

The NMR studies definitively identified the main target of the RHDV virus as L-fucose, a sugar found on antigens on the surface of the target cell.

“We now know the chemical signature of the sugar that RHDV zeroes-in on as it invades a cell,” said N. Rama Krishna, Ph.D., professor of biochemistry and molecular genetics and study co-author. “We can counterattack by designing a drug with the same signature but made even more attractive to the virus, so that the virus binds to the drug instead of the target cell.”

Can be used for similar viruses
Krishna says the real significance is that this NMR technique can be used to design anti-viral drugs for similar viruses including other caliciviruses like RHDV, a family that includes Norwalk and Hepatitis E viruses that cause disease in humans. An editorial on the study appearing in the April 17 issue of the journal Nature highlighted this work for its impact on the potential development of novel anti-viral drugs.

“This application can be widely used to search for and identify the likely contact points on cell-surface antigens that different viruses use as their point of entry to the cell,” Krishna said. “By inducing the virus to preferentially bind with a drug that mimics the contact point, we think we can prevent it from infecting a cell.”

Krishna’s laboratory at UAB, one of the most sophisticated in the world in the quantitative use of the special technique called saturation-transfer difference NMR (STD-NMR), collaborated with Thomas Peters and Christoph Rademacher of the University of Luebeck, Monica Palcic of the Carlsberg Laboratory, and Francisco Parra of Instituto Universitario de Biotecnologia de Asturias in identifying the sugar recognized by the RHDV virus.

They placed antigens from the cell bodies in a solution with virus-like particles (VLPs), essentially an inactive virus. The hydrogen signals from the virus were irradiated with radiofrequency pulses. The energy received by the VLPs, called saturation, is passed on to the cell antigens at the binding site.  The amount of saturation in those antigens can be measured, thus identifying which particular sugar on the antigens gets “hot.” Those sugars on the antigens, in this case the L-fucose, are the virus target.

 “This is a compelling argument for the routine use of the STD-NMR technique in drug design and development in general – it is not limited to antivirals. The method originally was developed in Germany for screening compound libraries and now is a popular technique in the pharmaceutical industry for identifying lead compounds,” Krishna said.