Fat-soluble vitamin A, D and E in HBV and SARS-CoV-2 infections: a narrative review

Vitamins are micronutrients essential for many biological functions in animals and humans. Fat-soluble vitamins A, D and E, influencing chemical-physical properties of cell plasmatic membranes, modify their rigidity and fluidity. These compounds modulate the ability of viruses to bind to specific cell surface receptors and enter cells and they influence the transcriptional processes of a wide range of genes, interacting with their promoter regions. Some of these genes regulate the function of the immune system in both its innate and adaptive arms and determine immunomodulatory effects with beneficial and protective roles in infectious diseases. Hepatitis B Virus (HBV) and Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) represent serious public health problems. About 250 million individuals worldwide are chronically infected by HBV and are at increased risk of developing severe liver- and extra-hepatic diseases. SARS-CoV-2 emerged in China in 2019, causing a well-characterized disease known as Coronavirus Disease-19 (COVID-19). This pathogen caused approximately 757.2 million of infection and 7 million deaths worldwide. This review describes the viral, host, and environmental characteristics, the ability of these pathogens to infect cells and to induce systemic diseases, and the mechanisms by which vitamins A, D, and E exert their activity against these two pathogens.