Viral infections in infants can contribute towards asthma development
11th September 2012
A team of researchers at the University of Pittsburgh School of Medicine, have found that viral infections in newborns cripple part of the immune system and increase the risk of asthma later in life. They showed infections by the respiratory syncytial virus (RSV), stripped immune cells of their ability to calm down inflammation in the lung's airways. The idea that asthma is linked to viral infection is not new. Numerous epidemiological studies have linked the two in humans. But it has not been clear whether the virus itself causes asthma, or whether children who are more susceptible to viruses and subsequently develop wheezing coughs, are also more susceptible to asthma. The researchers also go on to say that their findings, published in the Journal Nature Medicine, will help develop ways of preventing asthma. The charity Asthma UK said the study had really exciting potential. One Swedish study showed showed 39% of infants taken to hospital with RSV, had asthma when they were 18. However only 9% of infants who were not ill developed asthma. How the virus might be able to do this was unknown. However now the team of researchers at the University of Pittsburgh School of Medicine, believe they have an explanation. Their experiments on mice showed the virus impaired the ability of a specific part of the immune system, called regulatory T cells, to calm inflammation. Tina Hartert of Vanderbilt University in Nashville, Tennessee, says, “The paper is an important step towards identifying a biological mechanism and determining a stage during development, that doctors could focus on to prevent asthma. There are already drugs that can target T regulatory cells and block the allergic response. The researchers hope to test what effect these drugs have in primates that have been infected with RSV.” “But it remains to be seen whether the results in mice will translate to humans. For instance, mice are not normally susceptible to RSV, so they had to be exposed multiple times to develop an infection. By contrast, a human infant who wheezes after a single infection with RSV is more likely to develop asthma.” “Additionally, lab mice are genetically identical, whereas humans have a great deal of genetic variation that plays a major role in determining who develops asthma. Pollution, environmental factors and insufficient exposure to bacteria also contribute to the disease.” The researchers said, “There might be a window in early life when the cells are vulnerable to being crippled.” They think the finding could help scientists devise treatments which prevent some people developing asthma. They go on to say, “We feel that both prophylactic and therapeutic approaches can be developed. This is especially desirable in infants who have a strong family history of asthma.” In conclusion Malayka Rahman, from Asthma UK said, “This research provides vital information on how viruses interact with our immune cells and why this might lead to an increased risk of asthma. What's really exciting is the potential of these findings to translate into new treatments for asthma in the future.”