The effects of vitamin D on immune responses relevent to acute respiratory infections in chidren

Background:
Nationally, mortality due to acute respiratory infection (ARI) is more than nine times higher among First Nations infants compared to non-First Nations infants. Acute respiratory infections are the most common cause of hospitalisation and preventable death among First Nations infants in the Northern Territory (NT). Vitamin D deficiency is common among First Nations mothers during late pregnancy, and infants at birth and in early infancy and is associated with an increased risk of infant ARI in the first year of life. Vitamin D is an important micronutrient with broad regulatory effects on the immune response to ARI. Vitamin D exerts its protective effect against ARI via simultaneous promotion of antimicrobial activity and control of inflammatory processes. However, the relationship between vitamin D and immune responses specific to ARI pathogens (Respiratory syncytial virus; RSV and Streptococcus pneumoniae) is complex and remains poorly understood.
Methods:
In the first chapter of my PhD project, I will use an in vitro respiratory cell-culture model to investigate the immunological actions of vitamin D at the respiratory surface in response to RSV and S. pneumoniae. The second and third chapter of my PhD will address the immunological outcomes of a current randomised control trial (D-Kids) that aims to determine whether perinatal vitamin D supplementation (versus placebo) can reduce the incidence of ARIs among NT First Nations infants during their first 12 months of life. The influence of vitamin D supplementation on neonatal immune function will be determined using cord blood collected from D-Kids participants. Multiparameter immunological techniques will be used to characterise cord blood immune cell profiles and the functional immune capacity at birth.
Significance:
My PhD research will enhance our understanding of the mechanistic immunomodulatory role of vitamin D in response to ARI pathogens, potentially providing valuable insight into the early immunity in infants at risk of ARIs. This is essential to extend the global knowledge surrounding the immunomodulatory properties of vitamin D and will guide the utility of vitamin D supplementation strategies. This may have profound implications in reducing ARIs and achieving sustainable improvements in the respiratory health of First Nations children in the NT and other high ARI-risk infants globally.