Breast milk protein osteopontin may shield infants from respiratory infections

QIMR Berghofer researchers have discovered how breast milk supports infant immunity through a protein called osteopontin. Their study, published in the journal Cell, reveals that osteopontin triggers a series of biological signals that boost immune cell development in a baby's liver and lungs, protecting against potentially deadly respiratory infections.

While high levels of osteopontin are present in breast milk during the first weeks postpartum, the specific mechanisms of its influence on infant health were previously unknown. Professor Simon Phipps from QIMR Berghofer's Respiratory Immunology Lab expressed amazement at the impact of osteopontin on lung cell health in preclinical models.

When osteopontin was absent, lung cells lining the airways showed stark differences. The researchers found that osteopontin altered the infant's microbiota composition, leading to an increase in bacterial metabolites that act as hormones. These metabolites activate growth factors in both liver and lung cells, enhancing the infant's immune system.

In a significant finding, the team discovered that the diabetes drug rosiglitazone could mimic osteopontin's effects by activating the same immune-supporting pathway. The metabolite responsible for this action is already present in approved drugs like rosiglitazone, demonstrating a similar protective effect against respiratory infections in preclinical models.

The discovery suggests the potential for developing new approaches to support immune development in infants and improving infant formula products. Osteopontin may also help prevent allergic diseases like eczema and asthma by boosting immune regulatory pathways, although this requires further formal testing. The study enhances understanding of the complex bioactive components in human milk and their influence on infant development during critical early life windows.