A study from Washington University School of Medicine in St. Louis has found in mice that a drug, an inhalable form of a normal immune protein called GM-CSF, could reduce the risk of life-threatening lung infections common among premature infants.
The researchers used mice with a genetic defect that prevents their lung macrophages from maturing normally, gave these newborn mice GM-CSF intra-nasally for the first 24 hours after birth. The number of lung macrophages increased immediately, and since they are very long-lived cells, the mice were protected from pneumonia even into adulthood.
The researchers have tried giving premature infants GM-CSF intravenously or subcutaneously. "When you give GM-CSF this way, it mobilizes neutrophils, a different immune cell that is also very important for fighting off infections in general, but is not the crucial immune cell type in the lungs," said senior author Celeste Morley, an associate professor of pediatrics and of pathology and immunology.
"GM-CSF injections did not lower the risk of pneumonia. What we did differently is we administered the drug to the lungs directly, by inhalation, which triggered the development of lung macrophages instead of neutrophils. And then we saw long-lasting protection against pneumonia," Morley added.
Morley stressed that the key point in the treatment is that the drug has to be given within the first day after birth. "These specialized macrophages are only made in the first couple of days after birth. After that, the maturation window is over and you've missed your chance to intervene."
GM-CSF is an FDA-approved drug, and has been used safely in previous clinical trials in premature infants.
The findings have been published in Science Advances.