Vitamin D: A Potential Mitigation Tool for the Endemic Stage of the COVID-19 Pandemic?

The impact of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic and associated development of clinical symptoms of COVID-19 have presented an enormous global impact on our health care systems, public health and economy. To date several observational epidemiological studies consistently found that vitamin D deficiency, measured as low levels of circulating 25-hydroxyvitamin D, is associated with cardiovascular diseases, diabetes, certain cancers, autoimmune diseases and many infectious diseases, including acute respiratory infections. Since vitamin D is not merely immunosuppressive but also acts as an immunomodulator in tolerance and homeostasis, many experts have considered a role of vitamin D in the prevalence and severity of immune mediated inflammatory diseases, such as SARS-CoV-2, adding to the evidence of the importance of vitamin D in the immune response against viral respiratory infections and reinforcing the need for targeted vitamin D supplementation, with a focus on high-risk populations and a high-dose supplementation treatment for COVID-19 hospitalized patients. The expected transition to endemicity of SARS-CoV-2 even further corroborates as a potential of vitamin D as an potential mitigation tool for the prevention of COVID-19. The aim of this paper is to analyse the current evidence regarding vitamin D and present a hypothesis of its potential role in the current COVID-19 pandemic and in the future as a potential preventive measurement in public health

Vitamin D and allergy susceptibility during gestation and early life

Worldwide, the prevalence of allergies in young children, but also vitamin D deficiency during pregnancy and in newborns is rising. Vitamin D modulates the development and activity of the immune system and a low vitamin D status during pregnancy and in early life might be associated with an increased risk to develop an allergy during early childhood. This review studies the effects of vitamin D during gestation and early life, on allergy susceptibility in infants. The bioactive form of vitamin D, 1,25(OH)2D, inhibits maturation and results in immature dendritic cells that cause a decreased differentiation of naive T cells into effector T cells. Nevertheless, the development of regulatory T cells and the production of interleukin-10 was increased. Consequently, a more tolerogenic immune response developed against antigens. Secondly, binding of 1,25(OH)2D to epithelial cells induces the expression of tight junction proteins resulting in enhanced epithelial barrier function. Thirdly, 1,25(OH)2D increased the expression of anti-microbial peptides by epithelial cells that also promoted the defense mechanism against pathogens, by preventing an invasive penetration of pathogens. Immune intervention by vitamin D supplementation can mitigate the disease burden from asthma and allergy. In conclusion, our review indicates that a sufficient vitamin D status during gestation and early life can lower the susceptibility to develop an allergy in infants although there remains a need for more causal evidence.</p

Receptor Mediated Effects of Advanced Glycation End Products (AGEs) on Innate and Adaptative Immunity : Relevance for Food Allergy

As of late, evidence has been emerging that the Maillard reaction (MR, also referred to as glycation) affects the structure and function of food proteins. MR induces the conformational and chemical modification of food proteins, not only on the level of IgG/IgE recognition, but also by increasing the interaction and recognition of these modified proteins by antigen-presenting cells (APCs). This affects their biological properties, including digestibility, bioavailability, immunogenicity, and ultimately their allergenicity. APCs possess various receptors that recognize glycation structures, which include receptor for advanced glycation end products (RAGE), scavenger receptors (SRs), galectin-3 and CD36. Through these receptors, glycation structures may influence the recognition, uptake and antigen-processing of food allergens by dendritic cells (DCs) and monocytes. This may lead to enhanced cytokine production and maturation of DCs, and may also induce adaptive immune responses to the antigens/allergens as a result of antigen uptake, processing and presentation to T cells. Here, we aim to review the current literature on the immunogenicity of AGEs originating from food (exogenous or dietary AGEs) in relation to AGEs that are formed within the body (endogenous AGEs), their interactions with receptors present on immune cells, and their effects on the activation of the innate as well as the adaptive immune system. Finally, we review the clinical relevance of AGEs in food allergies