With all of the medical advances in recent history, it is sometimes surprising that we have not yet found a cure for the common cold. But a new model for rhinovirus C shows unexpected structural differences, creating potential for the development of new cold drugs.

Researchers from the University of Wisconson-Madison, led by Prof. Ann Palmenberg, successfully constructed a 3D model of the cold virus, rhinovirus C, which has been called the “missing link” cold.

Results of their findings, which employ the genetic sequencing of this particular cold virus to make a topographical model of the capsid – protein shell – were published recently in the journal Virology.

Though 3D structures of the A and B families of cold virus have long been known, rhinovirus C was only first discovered in 2006, when researchers discovered it had been “lurking” in human cells along with the A and B strains.

The researchers explain that antiviral drugs operate by attaching themselves to the surfaces of a virus, modifying them along the way. They describe this process as finding the right piece of a jigsaw puzzle, which must properly “fit and lock into the virus.”

Because the scientific community has not been able to accurately describe the surface of rhinovirus C, that meant pharmaceutical companies that were designing cold drugs were essentially “flying blind.”

rhinovirus C and rhinovirus A species modelsShare on Pinterest
The shell of the rhinovirus C virus (right) has structural differences from rhinovirus A (left), which explains why current drugs have not been able to stop the common cold.
Credit: Palmenberg/University of Wisconsin-Madison

To build a model of the cold virus, Prof. Palmenberg and her team used advanced bioinformatics and the genetic sequences of 500 rhinovirus C genomes. They say these supplied the 3D “coordinates” of the viral protein shell.

“The question we sought to answer was how is it different and what can we do about it? We found it is indeed quite different,” says Prof. Palmenberg.

She notes that the new structure, which is significantly different from other strains of cold viruses, shows why previous drugs have failed in trials against rhinovirus.

The team says the drugs that work well against the A and B strains were designed specifically to take advantage of their surface features. These structures were determined years ago using a technique called X-ray crystallography, but it could not identify the rhinovirus C structure.

Holly A. Basta, lead author and a graduate student working with Prof. Palmenberg, says that based on the new structure, “we predict you’ll have to make a C-specific drug. All the [existing] drugs we tested did not work.”

The researchers say that it is widely believed rhinovirus C is responsible for up to half of all childhood colds, and it can be a serious complication for those who suffer from respiratory conditions, such as asthma.

Along with the A and B strains, the C virus is responsible for millions of illnesses each year, costing the US more than $40 billion annually.

When thinking of developing new drugs, Prof. Palmenberg says this new C structure will cause drug developers to re-think the design:

It has a different receptor and a different receptor-binding platform. Because it’s different, we have to go after it in a different way.”

In 2012, Medical News Today reported on a study suggesting that cold virus proteins give new clues for cancer therapy by showing how small proteins in a cold virus hijack molecular mechanisms inside healthy cells.