Scientists stalking the more than 115 viruses that cause most common colds reported a different type of progress yesterday, not in destroying the organisms, but in blocking their entry to the nasal passages.
The work of Dr. Richard Colonno and his team at Merck Sharp & Dohme Research Laboratories was presented here yesterday at the annual meeting of the American Society for Microbiology and was praised by his colleagues as a novel approach to an old problem.
Scientists have been stumped in attempts to develop drugs that combat the cold or develop a vaccine to prevent it because of the extraordinary number of viruses that can cause colds, including at least 115 rhinoviruses.
Colonno, whose team works at commercial laboratories in West Point, Pa., reported yesterday preliminary but "very encouraging" results in outsmarting the rhinoviruses.
The group discovered that 90 percent of such viruses appear to gain entry to the body's nasal cells only by attaching themselves to a specific receptor on the cells' outer surfaces. The rest, it said, apparently gain entry through a second nasal receptor.
"That simplified the problem dramatically," Colonno said.
Using a versatile new molecular technology, the group designed a very specific agent, called a "monoclonal antibody," that could be targeted to block the cold viruses' main receptor site.
In laboratory tests, the agent was successful not only in blocking the site before cold viruses could attach but also in "literally" knocking "viruses out of the way" once infection had begun, he said.
"This is a very, very potent blocking agent," he said.
Colonno said a "pilot study" involving 26 human volunteers showed recently that the antibody, administered in nose drops during a 39-hour period, delayed the onset of colds by as much as two days and reduced severity of cold symptoms by about 40 percent.
He said the human study, conducted for Merck by researchers at the University of Virginia School of Medicine, demonstrated that the concept was a "feasible approach." But more studies are needed to understand how many receptors are in the nose and what dose might be needed to block them, he said.
Colonno cautioned that several years may be needed to develop a product for widespread use. His three years of experiments have indicated no toxic side effects, he said.
His goal, he said, is developing an agent that can prevent colds and stop one in progress, but he conceded that it is "doubtful" that the common cold will be completely cured.
While rhinoviruses are thought to be responsible for as many as half of colds, various other types of viruses can cause nagging upper-respiratory symptoms that become colds.
Another unusual study reported at the meeting used poker-playing students and challenged conventional scientific wisdom that colds are most often transmitted by hand contamination.
Dr. Elliot Dick of the University of Wisconsin presented studies that he said showed that transmission of colds through the air -- by sneezing, coughing and nose-blowing -- may be more significant than recent studies have indicated.
He said use of a virus-killing tissue that he helped develop, and improved indoor air-circulation units, might reduce such air transmission.