In recent years, new data have been obtained on the significant prevalence of vitamin D (VD) deficiency in the population, and knowledge about the role of vitamin D in the regulation of many physiological processes in the body, including the functioning of the immune system, has increased. The SARS-CoV-2 pandemic has further highlighted the issue of an adequate immune response in vitamin D deficiency.
OBJECTIVE OF THE REVIEW
To present and summarize the evidence on the role of VD in different parts of the immune response in COVID-19, to analyze available studies of the VD status effect on the course and outcome of COVID-19 in patients from different population groups.
MATERIAL AND METHODS
A search of domestic and foreign literature on the role of VD in the immune response in respiratory viral infections and SARS-CoV-2, as well as practical measures of VD-status correction in COVID-19, was performed. We used Scopus, Web of Science, PubMed, Google Scholar, eLibrary, and Cyberleninka databases.
RESULTS
Numerous clinical and observational studies have found an association between 25-hydroxyvitamin D levels, COVID-19 severity, and mortality. This association can be explained by the multifaceted role of vitamin D in the physiology of the human immune and endocrine systems. On the immunological side, the active form of VD promotes the secretion of antimicrobial peptides responsible for inhibiting viral replication and stimulates autophagy by increasing the level of Beclin1 protein and decreasing the level of mTOR protein regulating cellular homeostasis. It leads to the presentation of antigens followed by activation of the antiviral pathway of type I interferons. VD also stabilizes intercellular junctions, including those in the airway epithelium, reducing their permeability to pathogens, stimulates the activity of angiotensin-converting enzyme-2, whose receptors are a conduit for SARS-CoV-2 into cells, and several pathophysiological responses associated with the disease symptoms and acute lung injury. Adequate vitamin D status can provide significant benefits during the pandemic.
CONCLUSION
To date, ideas about the role of vitamin D in regulating the immune response in respiratory infections have significantly expanded. However, its use in the complex preventive measures and adjuvant therapy of viral infections, including COVID-19, should be the subject of further scientific research.
