Human Lung Responses to Respiratory Pathogens

Study Summary

For most individuals, the lung has a remarkable ability to deal with exposure to a variety of inhaled bacteria. Some individuals, however, do have recurrent bacterial infections, usually in the form of acute or chronic bronchitis and, in some instances, pneumonia. The reasons for this variability in bacterial infections between otherwise healthy subjects, between types of lung disease, and within the same type of lung disease are poorly understood. Variability in susceptibility to bacterial infections is partially explained by differences in exposure to infectious agents, genetic susceptibility and innate (or early) immune responses. It is of interest that the incidence and severity of bacterial infections is greatest during the winter months. Other than viral infections, there are few variables that change with season. Vitamin D is one known immune modulator with a seasonal periodicity. The hypothesis of this study is that levels of vitamin D are an important determinant of the innate defense of the lung against inhaled bacteria. The investigators further postulate that vitamin D has effects on the innate immune function of both alveolar macrophages and lung epithelial cells.

Primary Outcome

We investigated the effect of vitamin D3 supplementation on airway surface liquid antimicrobial activity using a bioluminescent bacterial challenge. We challenged airway surface liquid samples with bioluminescent bacteria and measured live bacteria by relative light units (RLU) after 2 minutes as a surrogate of antimicrobial activity. We interpreted a reduction in live bacteria after challenge in relative light units as increased antimicrobial activity

Interventions

• DIETARY_SUPPLEMENT Vitamin D3 (cholecalciferol)
• DIETARY_SUPPLEMENT Placebo Sugar Pill