Scientists decode genomes of all known rhinoviruses, first step towards cure
|Feb. 12, 2009|
Provided by: The Canadian Press
Written by: Helen Branswell, Medical Reporter, THE CANADIAN PRESS
TORONTO - Scientists have decoded the genetic blueprints of all known strains of rhinoviruses - a.k.a. the common cold.
The ambitious project, the results of which were published Thursday, should fast-forward efforts to combat these viral nuisances. But the vast genetic variation seen across the various strains suggests it is unlikely pharmaceutical scientists could concoct one single drug to treat all versions, the senior author of the study admitted.
"These things really are different. And they're different enough that we need to come up with a more sophisticated way of attacking them for treatment," said Dr. Stephen Liggett, of the University of Maryland.
Liggett, who did the work with colleagues from his university, the University of Wisconsin and the J. Craig Venter Institute in Rockville, Md., said he believes the variation explains the failure of previous attempts to find cures for the common cold.
"Because we have sub-families or subgroups of rhinoviruses that have different genetic makeups - that probably is going to mean that we may need three or four drugs," he said, though he insisted the variation was not so broad as to put effective treatments for human rhinoviruses or HRVs out of reach.
The work was done without external funding. The findings were reported Thursday in the journal Science.
The team performed full genome sequencing on the 99 known types of rhinoviruses stored in the official repository, the American Type Culture Collection in Rockville, Md. But it's clear there are more strains being discovered and the total now tops 100.
The viruses break down into three confirmed species or groupings. Liggett said it's likely a fourth will soon be added to that list.
One scientist who wasn't involved in the work said it should open up study into a virus that's been called "a poor orphan" of medical research.
"It is like the impact of the completion of human genome sequences on the study of human biology and diseases," said Wai-Ming Lee, from the department of pediatrics at the University of Wisconsin at Madison.
Colds can be caused by a number of different viruses. But highly infectious rhinoviruses are far and away the most common agent to trigger colds, hence the virus family's nickname as the cause of the common cold.
It's impossible to put a dollar figure on the economic toll these viruses inflict.
But a study done in 2003 provides some insight. It suggested colds cost the U.S. economy US$40 billion a year in lost wages, health-care costs and spending on over-the-counter cough and cold products.
Dr. Mark Fendrick, a researcher at the University of Michigan and lead author of that paper, said Thursday he hasn't updated the work, largely because there is no funding for cold research.
"We are hopeful that these scientific advances ... regarding the genetics of the common cold will lead to more funding and research to ultimately produce an agent or a set of agents that will safely and cost-effectively treat this public health menace," he said.
While Liggett is hopeful the work will ignite renewed interest in rhinoviruses research, others are skeptical that the logistics of dispensing a cold cure will make this work attractive to drug makers or the health-care system.
"It's not a killer for most people. It's a nuisance. It's not something that people are going to want to invest a tremendous amount of new additional costs in to get minimal gain," said Dr. Aaron Glatt, a spokesperson for the Infectious Diseases Society of America.
Glatt said the multiple drug scenario Liggett predicts would require people with colds to seek a doctor's care, get tested to see whether a rhinovirus is responsible and if it is, from which family the virus hails.
That's a lot of work - and additional cost to the medical system - for an illness that people generally start to recover from on their own within a few days, he said.
"It doesn't make sense," said Glatt, who is an infectious diseases physician and CEO and president of New Island Hospital in Long Island, N.Y. "To add hundreds of dollars to the medical budget for really no benefit is a tough sell, even if we had such a perfect drug available."
"Until you come up with a very, very simple treatment, you're not going to go anywhere with it.... It's going to always be the poor orphan in terms of research. It's going to be the poor orphan in terms of public health support for it."
But Liggett said medical science shouldn't give up on the possibility of effectively treating colds.
An asthmatic himself, he noted rhinovirus infections exacerbate asthma and chronic obstructive pulmonary disorder (COPD). And a bad rhinovirus infection in a child under age two can essentially program the child's immune system to develop asthma, he said.
"Though it may be disheartening to think that we may have to use multiple drugs, I still think it's better than not treating, because it is a major medical burden," Liggett said.
The group now plans to sequence contemporary rhinoviruses taken from 1,000 people across the United States and compare them to those in the repository, which were mainly collected in the 1970s. That comparison should provide clues as to how fast rhinoviruses mutate.
And Liggett said the team also wants to try to match viruses to the illness they cause, effectively trying to find out whether some rhinoviruses are nastier than others.