Vitamin D regulation of the immune system and its implications for COVID-19: A mini review

Abstract

The novel coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is at the origin of the current pandemic, predominantly manifests with severe respiratory symptoms and a heightened immune response. One characteristic of SARS-CoV-2 is its capacity to induce cytokine storm leading to acute respiratory distress syndrome. Consequently, agents with the ability to regulate the immune response, such as vitamin D, could become tools either for the prevention or the attenuation of the most severe consequences of the coronavirus disease 2019 (COVID-19). Vitamin D has shown antimicrobial as well as anti-inflammatory properties. While SARS-CoV-2 promotes the release of proinflammatory cytokines, vitamin D attenuates the release of at least some of these same molecules. Inflammatory cytokines have been associated with the clinical phenomena of COVID-19 and in particular with its most dangerous complications. Therefore, the goals of this article are as follows: first, present the numerous roles vitamin D plays in modulating the immune response; second, gather data currently available on COVID-19 clinical presentation and its relation to cytokines and similar molecules; third, expose what it is known about how coronaviruses elicit an inflammatory reaction; and fourth, discuss the potential contribution of vitamin D in reducing the risk and severity of COVID-19.

Vitamin D Status in Relation to the Clinical Outcome of Hospitalized COVID-19 Patients

“…While SARS-CoV-2 stimulates the release of proinflammatory cytokines, vitamin D inhibits the release of some of these molecules ( 31 ). Furthermore, vitamin D is known to regulate different thrombotic pathways, either directly or indirectly.…”

Efficacy of COVID-19 vaccine in elderly Indian population with Vitamin D and Iron deficiency

“…11 There is substantial variation between individuals in the immune response to vaccination. Vitamin D enhances epithelial integrity and induces antimicrobial peptide (eg, cathelicidin) synthesis in epithelial cells and macrophages 12,13 directly enhancing host defence., The effect of vitamin D on immune system has been recognized, 14 at a cellular and molecular level, They mainly targets helper T cell activity (Th1) by inhibiting the secretion of both IL-2 and IFN-gamma and by suppressing the secretion pro-Th1 cytokine IL-12 by antigen-presenting cells. 15 With the emergence of relatively vaccine-resistant SARS-CoV-2 variants, characterising the speed and duration of response to COVID-19 vaccines in iron deficiency, hypovitaminosis D is necessary to measure the expected benefits of the vaccination.…”

Vitamin D Serum Levels in Subjects Tested for SARS-CoV-2: What Are the Differences among Acute, Healed, and Negative COVID-19 Patients? A Multicenter Real-Practice Study

“…Data from the UK-Biobank showed that although circulating vitamin D levels did not affect the risk of COVID-19 infection, the habitual use of vitamin D supplements was significantly associated with a 34% lower risk of COVID-19 infection (p = 0.034) [12]. Notably, vitamin D plays a physiologic role in regulating normal innate and adaptive immunity [13], and it has been reportedly shown to be able to suppress pro-inflammatory and stimulate anti-inflammatory cytokine formation, which might have a positive impact on COVID-19 patients [13,14]. In this scenario, COVID-19 pandemic has placed under the spotlight the correlation among IL-6, cytokine release syndrome, hyperinflammation state and COVID-19 fatality rate [15,16].…”

“…Our hypothesis is that there might be a strict correlation between vitamin D status and IL-6 serum levels. Nonetheless, albeit a role of vitamin D has been proposed in counteracting COVID-19 [3,4,13,14] through the potential modulation of the immune dysfunction and cytokine storm, to date, there is still a lack of evidence in the literature in terms of differences in serum levels across large cohorts, according to disease status.…”