Cold virus clue found

Scientists have gained a new understanding of how the immune system combats common cold viruses.

Discovery may open new path to antiviral drugs, scientist says

Scientists have gained a new tool for understanding how the immune system fights common cold viruses.

British researchers said Tuesday that they've identified a previously unknown mechanism used by antibodies, the proteins that identify and neutralize disease-causing bacteria and viruses.

Previously, scientists believed antibodies could reduce infection only by attacking viruses outside cells and by blocking their entry into cells. The new research shows antibodies stay attached when viruses enter healthy cells, said Leo James of the Medical Research Council's Laboratory of Molecular Biology in Cambridge.

"Although these are early days, and we don’t yet know whether all viruses are cleared by this mechanism, we are excited that our discoveries may open multiple avenues for developing new antiviral drugs," James said.

James and his colleagues reported the findings in Tuesday's online issue of the journal Proceedings of the National Academy of Sciences.

Improving the 'disposal' process

The researchers said that once a virus enters a cell, a protein called TRIM21 recognizes the antibody and pulls the virus into a disposal system used by the cell to get rid of unwanted material. Normally, the disposal process occurs before a virus has a chance to damage the cell.

Increasing the amount of TRIM21 protein in cells helps the disposal system work better. Protection from the antibodies "continues inside the cell to provide a last line of defence against infection."

Scientists are interested in the findings because of their potential applications for fighting infections as common as the cold.

"This is a natural defence mechanism, but obviously once we've understood this new mechanism, we can add drugs that can enhance or sustain that response and help the body to do this," said Prof. Hugh Pelham of the Medical Research Council.

People fall sick with colds so often because more than 200 viruses can cause the infection, according to the Canadian Centre for Occupational Health & Safety.  

And the body only produces antibodies against a virus if it has already been infected by that same virus. It won't work the first time the body encounters the virus, said David Proud, a cold virus researcher at the University of Calgary.

"I think it actually is a new concept, and that's always very important," said Proud. "But it's a long way from a cure for the common cold."

The researchers hope the findings may also apply to norovirus, which causes vomiting, and rotavirus, which the Canadian Pediatric Society calls the most common cause of serious diarrhea in babies and young children.