Scientists find key mechanism of childhood respiratory disease

March 7, 2011, University of Texas Medical Branch at Galveston

Researchers have identified a critical part of the process by which one of the world's most common and dangerous early childhood infections, respiratory syncytial virus, causes disease.

The discovery could lead to badly needed new therapies for RSV, which in 2005 was estimated to have caused at least 3.4 million hospitalizations and 199,000 deaths among children under five worldwide.

By analyzing samples taken from infected infants and data from laboratory-mouse experiments, University of Texas Medical Branch at Galveston scientists determined that RSV interferes with airway cells' ability to produce enzymes that keep highly damaging molecules known as under control. The virus does this by preventing the activation of a single protein needed for the expression of a variety of detoxifying enzymes. Reactive oxygen species then accumulate, causing cell-killing oxidative stress and inflammation in both infected and uninfected airway cells — a major factor in the damage done by RSV infection.

"The role of oxidative stress has been studied in everything from aging to asthma, but this is really the first study to implicate it in lung inflammation associated with viral infections," said Dr. Antonella Casola, an associate professor at UTMB Health and lead author of a paper on the research, published online March 4 in the "Articles in Press" section of the American Journal of Respiratory and Critical Care Medicine. "We've been working on this project for a while — starting in cells, then moving to animal models and finally getting results in patients — so we're very excited about this paper."

The UTMB Health researchers followed up earlier studies in human cell cultures with experiments that showed a substantial reduction in the expression and activation of antioxidant enzymes in the lungs of RSV-infected mice. Further investigations revealed that mice infected by RSV had much lower levels of a called Nrf2 — a "transcription factor" needed to prompt the production of enzymes that clean up reactive oxygen species.

"What was really striking is that Nrf2 is a kind of master switch controlling the machinery of these antioxidant enzymes, and it appears the virus blocks its activity," said UTMB Health professor Dr. Roberto Garofalo, also a lead author on the study. "This is interesting because genetic factors have been shown to be associated with other airway diseases, and the obvious question now is do the children who develop the most severe disease in response to RSV also have an Nrf2 gene that favors a low level of expression of these antioxidant enzymes? Are we seeing a combination of two hits, one from the virus and one from genetics?"

The apparent involvement of Nrf2 also opens an intriguing therapeutic possibility, Garofalo said, because compounds that induce to make more of the transcription factor are already in clinical trials as potential cancer therapies. Another possibility is the delivery of short-term genetic therapy via a genetically engineered virus licensed by the National Heart, Lung and Blood Institute.

Any such intervention will have to await further human studies like the one described in the AJRCCM paper. In that part of the investigation, the researchers measured biochemical markers of reactive oxygen species and levels of antioxidant enzymes in nasal samples from 30 infants with RSV infections. The severity of the babies' disease ranged from relatively minor upper respiratory tract infections to full-blown lung disease requiring respiratory support from a ventilator.

"Our findings in patients were very consistent with what we saw in mice, " Garofalo said. "We found a significant increase in markers of oxidative injury and a significant decrease in antioxidant expression corresponding to the severity of the disease."

Because the study was conducted in a relatively small number of human subjects, Garofalo and Casola plan to conduct larger human investigations under the auspices of UTMB Health's Institute for Translational Research. In future research, they also hope to examine the possible role of other viruses in inhibiting antioxidant enzymes, produce a more detailed profile of virus-induced changes in antioxidant levels and detail the magnitude and type of oxidative damage done to airways by RSV infection.

More information: http://ajrccm.atsjournals.org/articlesinpress.dtl

Related Stories

Recommended for you

Fabric imbued with optical fibers helps fight skin diseases

February 23, 2018
A team of researchers with Texinov Medical Textiles in France has announced that their PHOS-ISTOS system, called the Fluxmedicare, is on track to be made commercially available later this year. The system consists of a piece ...

DNA gets away: Scientists catch the rogue molecule that can trigger autoimmunity

February 22, 2018
A research team has discovered the process - and filmed the actual moment - that can change the body's response to a dying cell. Importantly, what they call the 'Great Escape' moment may one day prove to be the crucial trigger ...

Low-calorie diet enhances intestinal regeneration after injury

February 22, 2018
Dramatic calorie restriction, diets reduced by 40 percent of a normal calorie total, have long been known to extend health span, the duration of disease-free aging, in animal studies, and even to extend life span in most ...

Gut microbes protect against sepsis—mouse study

February 22, 2018
Sepsis occurs when the body's response to the spread of bacteria or toxins to the bloodstream damages tissues and organs. The fight against sepsis could get a helping hand from a surprising source: gut bacteria. Researchers ...

Artificial intelligence quickly and accurately diagnoses eye diseases and pneumonia

February 22, 2018
Using artificial intelligence and machine learning techniques, researchers at Shiley Eye Institute at UC San Diego Health and University of California San Diego School of Medicine, with colleagues in China, Germany and Texas, ...

Fertility breakthrough: New research could extend egg health with age

February 22, 2018
Women have been told for years that if they don't have children before their mid-30s, they may not be able to. But a new study from Princeton University's Coleen Murphy has identified a drug that extends egg viability in ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.