In the case of RSV, ‘children are not little adults’

RSV, for respiratory syncytial virus, is one of the most important pathogens causing pulmonary infections in infants. The virus can cause anything from a mild cold-like infection, to more severe pneumonia, bronchitis and bronchiolitis. It is the most frequent cause of hospitalization of infants in the United States and some two million babies die every year because of severe infections in the lungs caused by RSV, but there is no known effective vaccine or anti-viral therapy specific to this pathogen.

For decades, scientists thought that over-reactive immune system in some infants is associated with severe respiratory infections. That cytotoxic killer T cells and an exaggerated Th2 responses are to blame.

Recent studies show this is not true at all.

On the contrary, severe RSV infections in the lower respiratory tract actually are associated with an inadequate immune reaction, such as naturally found in infants.

A research consortium led by Robert Welliver, Sr. of the State University of New York at Buffalo examined autopsies of infants who suffered fatal RSV infections, and they saw no evidence that T cells had been activated. In fact, the cytokines found in the lungs of infected infants were mostly those made by other types of cells of the lung, such as macrophages or epithelial cells.

What does this finding imply for RSV interventions and treatment?

UTMB professor Roberto Garofalo, a senior author on the paper, states, “we all agree that killing the virus with anti-viral drugs, which we still don’t have, is important. But it looks like we also need to find a way to control unwanted inflammation and boost the disease-fighting T-cell response.”

[source: UTMB Newsroom; The Journal of Infectious Diseases 2007;195:1126-1136; editorial commentary at JID]