Of all the common health problems, perhaps none are as familiar as the cold. Inflammation of the upper airways is viral in origin, but as there are many types of rhinoviruses, it is common that each time a new one causes infection.
There is no vaccine against the cold, and treatment boils down to dealing with symptoms - such as a runny nose and cough, muscle aches, head and throat, and malaise - that are not caused by viruses but by the body's reaction to the invasion. Rhinovirus infection is responsible for half of asthma attacks and is a major factor in cases of bronchitis, sinusitis, ear infections and pneumonia.
A big step towards increasing awareness of the important problem has just been taken by researchers in the United States.
In an article published on the journal Science website, the group describes having completed the genomic sequences of all 99 known strains of viruses that cause the common cold.
The sequences were organized into a kind of family tree that shows how viruses are related to each other, their similarities and differences. The authors point out that the work provides a powerful tool that could lead to the development of the first effective cold treatments.
"To date we have not been successful in developing effective drugs to cure the common cold, which may be due to a lack of information about the genetic makeup of all strains," said Stephen Liggett, School of Medicine professor and program director. of Cardiopulmonary Genomics at the University of Maryland, lead author of the study.
“We usually think of colds as a mere inconvenience, but they can be debilitating in young children or the elderly. They can also lead to asthma attacks at any age. In addition, recent studies indicate that rhinovirus infections in young children can program their immune systems to develop asthma in adolescence, ”said Liggett.
Scientists have found that human rhinoviruses are organized into 15 small groups inherited from distant ancestors. The discovery of these multiple groups explains why the “one cold remedy” approach doesn't work.
They also observed that viruses skip a step in protein production, a shortcut that probably increases the microorganism's speed to make the person feel the symptoms soon after infection.
“This is a new insight that would not have been possible without being revealed through genomic analysis.
Information resulting from this discovery may represent a completely different approach to therapy, ”said Claire Fraser-Liggett, director of the University of Maryland Institute of Genomic Sciences, another author of the study.
The study pointed out that some of the human rhinoviruses result from the exchange of genetic material between two distinct virus strains that infect the same individual. Such recombination was not thought possible in human rhinoviruses. During the colder months, when many virus strains cause infections, recombination can quickly produce new strains.
Multiple mutations (about 800) were evident in virus samples obtained by researchers from patients with a cold compared to older rhinovirus reference strains. Some viruses modify themselves through minor changes in certain proteins to prevent them from being destroyed by antibodies in the human immune system. "Mutations have been found in every area of the genome," said Claire.
“The accumulated data from these complete genomic sequences give us an opportunity to reconsider cold vaccines as a possibility, especially as we gather samples from many patients and sequence entire genomes to see how often they experience mutations during the colder months. ”Said Stephen Liggett. This continuation of the now published study is already underway.
The article Sequencing and analysis of all known human rhinovirus genomes reveals structure and evolution, by Stephen Liggett and others, can be read by Science subscribers at (//www.sciencemag.org)
Adapted from: Agência Fapesp - Scientific Dissemination - 02/13/09