Stanislaus County Health Services Agency
Childhood respiratory virus fools immune system
July 30, 2001

NEW YORK (Reuters Health) - Scientists have uncovered a trick that a potentially serious respiratory virus uses to elude attacks by the immune system.

They have found that a protein on the surface of a virus called respiratory syncytial virus (RSV), the leading cause of lower respiratory infections in children, mimics a chemical that signals the immune system.

The discovery may boost the drive to develop a vaccine against RSV, which has proven difficult, researchers report in the August issue of the journal Nature Immunology.

Infection with RSV is common, and most people are infected by age 2 and experience cold-like symptoms that eventually improve without treatment. But in some infants and in adults with weakened immune systems or lung disease, the virus can cause pneumonia and other potentially life-threatening complications. RSV infection is the leading cause of hospital admissions in young children.

Attempts to develop a vaccine that protects against RSV without causing harm have not been successful, in part because scientists have not understood how the virus is able to overcome the immune system.

Now researchers led by Dr. Ralph A. Tripp of the Centers for Disease Control and Prevention in Atlanta, Georgia, have found that the G glycoprotein, a molecule found on the surface of RSV, tricks the immune system into believing that it is a chemical called fractalkine. Disguised as fractalkine, G glycoprotein links with a receptor called CX3CR1, altering the movement of infection-fighting white blood cells.

There is still a lot of uncertainty about the action of G glycoprotein, but Tripp's team speculates that the disguise may slow down the clearance of the virus from the body, change the body's inflammatory response to the virus, or make it easier for RSV to infect cells.

The unmasking of G glycoprotein may make it easier to develop ways to prevent or treat RSV infection, Tripp told Reuters Health in an interview.

The research "now allows us possibly to address better approaches for vaccine development," he said. By looking at ways to block G glycoprotein from binding with the receptor, scientists may be able to develop an effective vaccine, he explained.

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