Common denominator for common cold.

Common denominator for common cold

The rhinovirus, responsible for up to half of all common colds, is such a quick-change artist that no vaccine is likely to be able to prime the body against all the variants of the virus. So scientists at Merck Sharp & Dohme Research Laboratories in West Point, Pa., have taken a different tack: They have developed a monoclonal antibody that, like a fat person stuck in the doorway, denies the virus access to cells.

There are at least 115 variants, or serotypes, of the virus. "What we set out to do was to find a common denominator to these serotypes," says research head Richard J. Colonno. "And what we found was that 90 percent of the serotypes would attack the cell through a single cellular receptor."

The researchers treated a culture of human nasal cells with a monoclonal antibody specific to that receptor protein. Of 88 serotypes tested, 78 were unable to bind with the treated cells. (The remaining serotypes competed for a second receptor.) When the researchers allowed the virus to bind to cells before adding antibody to the culture, they found that "the antibody will literally knock the virus off the cells and replace it," Colonno says.

In the first clinical trial of the receptor blockade, conducted by Frederick G. Hayden and Jack Gwaltney at the University of Virginia in Charlottesville, 26 volunteers used noese drops containing either antibody or placebo; three hours later, all sprayed a specific rhinovirus serotype into their noses. They continued periodic treatment with antibody or placebo for 39 hours. Though nearly identical numbers in each group developed colds (11 of the antibody group, 12 of the placebo group), cold symptoms were delayed by up to two days in the antibody group, and were only about 60 percent as severe. The researchers observed no side effects from the antibody.

The fact that the antibody had any effect at all shows the promise of the approach, says Colonno, since "we know virtually nothing about the number of receptors that need to be blocked by the antibody, or their turnover rate."

The work changes the odds for rhinovirus researchers: There may be 115 serotypes, but their common receptors mean researchers can now deal with just a few receptor types. The researchers hope the work will lead to a nasal spray with prophylactic and therapeutic effects against colds.