Scientists have advanced on the sneeze by cracking the code of the common cold.

Researchers at UW-Madison and other institutions have sequenced and analyzed the genetic instructions for the 99 known strains of rhinovirus, the most frequent cause of the cold.

The result: a textbook of viral vulnerabilities that could become targets for new drugs.

"We now have the whole genetic library and can read it from cover to cover," said Ann Palmenberg, a UW-Madison virologist who helped lead the research. "There may well be better drugs that come out of this."

The findings are published in the new edition of the journal Science.

Colds are notoriously resistant to anti-viral drugs.

Palmenberg, head of the university's Institute for Molecular Virology, looked closely at rhinoviruses, one of several types of viruses that cause colds. She was joined by researchers at the University of Maryland and the J. Craig Venter Institute in Maryland.

Rhinoviruses also can cause ear infections, sinus infections, bronchitis and pneumonia, and they account for about half of all asthma attacks, according to the researchers.

Thirty of the 99 strains of rhinovirus already had been sequenced, Palmenberg said. The scientists in Maryland used powerful computers to piece together the genetic codes of the rest, she said.

Palmenberg analyzed the patterns, finding similarities and differences among the strains. Each strain of rhinovirus has 11 genes.

Drugs designed to attack the similarities could prove effective against many colds, Palmenberg said. But the viral differences, which explain why some colds make people feel worse than others, could make it difficult to find a drug that is effective against all strains.

"Perhaps several anti-viral drugs could be developed, targeted to specific genetic regions of certain groups," said Dr. Stephen Liggett, a University of Maryland researcher who helped lead the study, in a news release.

Liggett said the new work also could reinvigorate efforts to develop a vaccine against the cold.

But Palmenberg said that's unlikely. There are too many kinds of rhinovirus for a vaccine to work, she said. And unlike flu viruses, which circulate once a year and can be deadly, cold viruses are almost always present and rarely kill.

"You're not going to make a vaccine for something that's always there," she said.

The study revealed other scientifically important findings. When two strains of rhinovirus infect the same person, the analysis showed, the viruses can swap genetic material and create new strains. That had been thought impossible.

Figuring out the sequences of all previously known rhinoviruses also could help scientists better understand a newly discovered class of the viruses, Palmenberg said. She and Dr. Jim Gern, a UW-Madison allergist and immunologist, are studying samples of the new viruses, which penetrate deep into the lungs.

It could be years before the research leads to new drug candidates for the cold. But the scientific impact is immediate, Palmenberg said.

"This defines what evolution allows with a common cold virus," she said. "Before we were guessing. Now we know."

\ COLD AND FLU FACTS

* The flu is usually worse than a cold.

* The flu usually includes intense fever, body aches, tiredness and dry cough. A cold is more likely to include a runny or stuffy nose.

* Flu activity is just starting to increase in Wisconsin this season, with the peak likely a month away, said Tom Haupt of the state Department of Health Services. There is still time to get flu shots, he said.

* RSV, one of the six kinds of cold viruses tracked by the state, has just peaked for the season, Haupt said. Rhinoviruses occur throughout the year, he said.

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