Discoveries in Childhood Asthma

KELLY PRICE

New Vanderbilt Research Shows Old Culprit

If you heard that Real-Time Reverse Transcription-Polymerase Chain Reaction (RT-PCR) saved the day, you might think it was the latest superhero sci-fi gear. In a way, it is.

RT-PCR, a form of DNA testing, helped researchers at Monroe Carell Jr. Children's Hospital at Vanderbilt implicate a new virus in a well-known childhood illness.

Using the RT-PCR technology, lead author Kathryn Miller, MD, and colleagues were able to advance their study of a newly-described group of rhinoviruses called HRV-C to connect them to the old, but growing, problem of childhood asthma.

HRV-C has been difficult to find in the past because no one had been able to culture the virus that Vanderbilt investigators were able to find by using the RT-PCR testing.

Between 2001 and 2003, Miller and her fellow researchers surveyed children age five and younger who were hospitalized for respiratory illness and fever in Nashville and Monroe County, NY.

The study, which was published online by the Journal of Allergy and Clinical Immunology at the end of 2008, found HRV-C accounted for almost half of rhinovirus-related asthma.

"HRV-C was associated with wheezing, and we saw it distinctly in the fall. That held true in both years. This study begs the question of whether HRV-C explains the fall spike in asthma," Miller said.

The children were swabbed, and the viruses in the samples were DNA-tested to determine the presence of rhinoviruses. About a quarter of the children had rhinoviruses, but two types, HRV-A and the previously undescribed HRV-C were the most common.

"While this virus has not been described in years past, we believe it has been around for a long time because of its prevalence in this study and other studies in Jordan, Hong Kong and Australia," said Miller.

Using the RT-PCR technology, Miller was not only able to show rhinovirus is associated with about a quarter of pediatric asthma hospitalizations, but also that HRV-C specifically shows up in the fall and tends to affect children who are a little older (a median age of 15 months vs. 7 months.)

"With this study, and some that are still under way, we are finding that HRV-C may be the more dangerous of the two prominent groups (HRV-A and C) but more study is needed," she said.

It isn't known whether HRV-C or other rhinoviruses cause asthma or are simply triggers for the disease in children who are already susceptible.

Miller said that while it has become clear that rhinovirus plays a major role in asthma exacerbations, more research will be required to understand the mechanisms and ultimately to take steps to prevent such attacks.