Scientists have managed to grow a recently discovered species of human rhinovirus (HRV), the most frequent cause of the common cold, in culture, on sinus tissue removed during surgery.
Researchers at the University of Wisconsin-Madison found that the virus, which is associated with up to half of all HRV infections in children, has reproductive properties that differ from those of other members of the HRV family.
The report sheds light on HRV-C, a new member of the HRV family that also includes the well known HRV-A and HRV-B.
Discovered five years ago, HRV-C has been notoriously difficult to grow in standard cell cultures and, therefore, impossible to study.
"We now have evidence that there may be new approaches to treating or preventing HRV-C infections," senior author James Gern, professor of medicine at the UW-Madison School of Medicine and Public Health and an asthma expert at American Family Children's Hospital, said.
Gern said future drugs could be especially useful for children and adults who have asthma and other lung problems.
Like other scientists, Yury Bochkov, a virologist in Gern's lab, was unable to grow HRV-C in standard cell lines. So he turned to nasal tissue he collected following sinus surgery-and was surprised to find success.
He grew significant amounts of two forms of HRV-C, then sequenced the complete virus genome and engineered an identical copy of it in a plasmid vector.
Studying the reproduction of the living, growing virus, he found that HRV-C replication appeared to occur in specific kinds of cells localized in nasal epithelium tissue.
"We also found that HRV-C does not attach to the two receptors that HRV-A and HRV-B use," Bochkov said.
"HRV-C uses a distinct, yet unknown, receptor that is absent or under-expressed in many cell lines," he stated.
HRV-C also responded differently to antibodies that block receptor binding.
"Antibodies that normally keep HRV-A and HRV-B from binding to their receptors did not prevent HRV-C from binding to them," Bochkov revealed.
Gern said the findings suggest that new approaches are needed to treat HRV-C.
"Previous drug candidates for the common cold were tested only against HRV-A and HRV-B. For more effective medications, we need to also target HRV-C," he stated.
Bochkov will continue to use the organ culture system to study details of HRV-C biology.
"It's now clear that these viruses have unique growth requirements," he added.
The findings have been reported in Nature Medicine on April 11.