Severe RSV Infections Can Damage the Lungs

Children who are younger than 2 years of age who get respiratory syncytial virus (RSV) are likely to have long-term changes to their lungs, according to a recent study published in the American Journal of Physiology-Lung Cellular and Molecular Physiology.

RSV is a common virus that can lead to potentially serious respiratory illness. The virus can affect the lungs and breathing passages of an infected person and can potentially cause severe illness in young infants, older adults, and those with certain chronic medical conditions. Among children younger than 5 years of age in the United States, RSV infections account for about 2.1 million outpatient visits and 58,000 hospitalizations each year.

New research from the University of Michigan in Ann Arbor has found that a severe infection with RSV can compromise children’s lung function and could affect respiratory health later in life.

To study severe RSV, the researchers measured lung function and the development of alveoli in infant mice. Alveoli are the sacs in the lungs responsible for exchanging oxygen and carbon dioxide. The development of alveoli continues into adulthood but has maximum production between 2 and 3 years of age. Production of large numbers of immune cells occurs around the same time.

The researchers — led by Carrie-Anne Malinczak, Ph.D., now head of Nutritional Biology & Safety at Helaina — measured these markers in mice at five weeks and three months after the initial RSV infection and again after a reinfection with the virus. They focused on male mice because previous research has found that both male human infants and mice are more susceptible for severe RSV. Previous research has also shown there to be an increase in inflammatory cells after infection with RSV early in life.

Researchers in the current study found defects in the ability of the lungs to stretch and expand during breathing. Structural changes to the mice’s lungs included an increase in alveoli size but fewer individual alveoli after RSV infection.

“These data indicate that the lungs of mice following an early-life RSV infection have a decreased lung function even at [three months] postinfection,” the research team wrote. “Importantly, the structural defects of the early-life infected mice largely mimic the clinical setting where severe exacerbations are observed in children for several years following a severe early-life respiratory infection, especially RSV.”

Researchers said the structural defects of the early-life infected mice mimic infection in human children. They said the mechanisms for these changes are “complex and associated with an inappropriate immune environment, specific cellular responses, and control of lung mesenchymal/epithelial cell maturation.”