A pair of landmark studies resulted in a 3-D model of the cold virus and, as a result, a clear reason as to why no cure exists for the common cold.
The A and B families of cold virus, as well as their structures, have been known for years. However, because rhinovirus C was only discovered in 2006 and resists culturing, its true form eluded scientists.
The new research built the cold virus model "in silico," employing advanced bioinformatics and the genetic sequences of 500 rhinovirus C genomes. This resulted in the 3-D coordinates of the virus's shell, which, the researchers subsequently discovered, is distinct from those belonging to the strains of cold viruses. This is the reason drug candidates failed, since the surface features that allow rhinovirus C to dock with host cells and circumvent the immune system differed from those of rhinovirus A and B, the researchers explain.
"It's a very high-resolution model," said University of Washington biochemist Ann Palmenberg. Palmenberg's group, along with a team from the University of Maryland, was the first to map the genomes for all known common cold virus strains in 2009. "We can see that it fits the data."
Given the findings, lead author of the study and University of Washington graduate student Holly Basta said they "predict you'll have to make a C-specific drug," adding that "All the [existing] drugs we tested did not work."
Experts estimate that rhinovirus C is responsible for up to half of all childhood colds, in addition to representing a complicating factor for respiratory conditions such as asthma. All three viruses combined sicken millions of Americans every year and carry with them a combined price tag of more than $40 billion in annual costs.
The study was published in the journal Virology.