Vitamin D represses rhinovirus replication in cystic fibrosis cells by inducing LL-37

Fish oil and vitamin D in pregnancy for the prevention of early childhood asthma: study protocol for two double-blinded, randomised controlled trials

INTRODUCTION

Previous randomised controlled trials (RCTs) have indicated a protective role of pregnancy supplementation with fish oil and high-dose vitamin D, respectively, on offspring asthma, infections and several other disorders in early childhood. However, current evidence is not considered sufficient for recommending these supplements in pregnancy. In two RCTs, we aim to investigate whether these protective effects can be confirmed in larger trials with the goal of changing clinical practice and improving child health.

METHODS AND ANALYSIS

Randomisation of 4000 pregnant women to either (1) (n=2000) the fish oil trial of 2.4 g/day (55% eicosapentaenoic acid (EPA) and 37% docosahexaenoic acid (DHA)) in triacylglycerol form versus placebo or (2) (n=2000) the vitamin D trial of high-dose (3200 IU/day) vitamin D versus placebo on top of the recommended 400 IU/day. Supplementation begins in gestational week 24 (22-26) until 1 week after delivery. Allocation to the trials will be determined based on the preinterventional maternal blood levels of EPA+DHA with a dried blood screening test. Women with low levels (below 4.7% of total fatty acids) will be assigned to the fish oil RCT, and women with high levels will be assigned to the vitamin D RCT. Maternal blood will be used for genetic, metabolomic and proteomic profiling. A 3-year follow-up of the children with longitudinal registration of parent-reported symptoms, diagnoses, medication use and hospitalisations will be performed. The primary outcome is persistent wheeze or asthma until age 3 years, with predefined analyses of effect modification by maternal genotypes. Secondary outcomes are lower respiratory tract infections, gastrointestinal infections, croup, troublesome lung symptoms, eczema, allergy, bone fractures, developmental milestones, mental health, cognition and growth until age 3 years. A follow-up on both primary and secondary outcomes is planned after unblinding, from age 3-6 years.

ETHICS AND DISSEMINATION

The RCTs are approved by the Danish local ethics committee (H-23055833). The studies are registered at ClinicalTrials.gov (NCT06560255 and NCT06570889). Study results will be communicated to the medical community, including publications in peer-reviewed journals. All results will be published and available on www.copsac.com.

TRIAL REGISTRATION NUMBER

NCT06560255 and NCT06570889.

Assessment of Supplementation with Different Biomolecules in the Prevention and Treatment of COVID-19

Consequences of the disease produced by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have led to an urgent search for preventive and therapeutic strategies. Besides drug treatments, proposals have been made for supplementation with biomolecules possessing immunomodulatory and antioxidant properties. The objective of this study was to review published evidence on the clinical usefulness of supplementation with vitamin D, antioxidant vitamins (vitamin A, vitamin E, and vitamin C), melatonin, lactoferrin and natural products found in food (curcumin, luteolin, ginger, allicin, magnesium and zinc) as supplements in SARS-CoV-2 infection. In general, supplementation of conventional treatments with these biomolecules has been found to improve the clinical symptoms and severity of the coronavirus disease (COVID-19), with some indications of a preventive effect. In conclusion, these compounds may assist in preventing and/or improving the symptoms of COVID-19. Nevertheless, only limited evidence is available, and findings have been inconsistent. Further investigations are needed to verify the therapeutic potential of these supplements.

Vitamin D Primary Prevention of Respiratory Infections and Asthma in Early Childhood: Evidence and Mechanisms

Respiratory infections are a leading cause of child morbidity worldwide, and asthma is the most common chronic disorder in childhood. Both conditions associate with high socioeconomic costs and are major reasons for medication prescriptions and hospitalizations in children. Vitamin D deficiency has concomitantly increased with asthma prevalence and is hypothesized to play a key role in the development. Current evidence suggests that high prenatal and early childhood vitamin D could be protective against respiratory infections and asthma in some studies where several mechanisms are proposed. However, other studies have reported no effects on these outcomes. Therefore, future large intervention studies on this topic are warranted. Mechanistic studies have shown that vitamin D holds antimicrobial properties by inducing production of several peptides through altered gene expression. Others have shown a complex interplay between asthma risk genotypes, the sphingolipid pathway, and prenatal vitamin D in early childhood asthma. Vitamin D has also been suggested to change both airway immune and microbiota profiles, which are directly related to asthma risk. Finally, systemic low-grade inflammation seems to be regulated by vitamin D exposure. This review presents the current literature of the primary preventive effect of vitamin D on early childhood asthma and respiratory infections. Mechanisms of actions are discussed, and gaps in knowledge are highlighted to facilitate planning of future intervention trials.

Vitamin D deficiency in patients with cystic fibrosis: a systematic review and meta-analysis

AIM

Vitamin D is a prominent modulator of immunity and respiratory function. It plays a vital role in respiratory diseases such as cystic fibrosis (CF). S. However, there is a dearth of information on patients with CF. The purpose of the meta-analysis is to highlight the importance of following the existing guidelines regarding maintenance of Vitamin D serum levels in patients with CF.

METHODS

The systematic search was conducted without utilizing any time or language limitations in original database from the beginning until March 2022. The meta-analysis was performed using a random-effects model. Heterogeneity was determined by I2 statistics and Cochrane Q test.

RESULTS

Pooled analysis using the random-effects model of the 8 case-control studies with 13 effect sizes revealed that the serum 25-OH-vitamin D in participants with cystic fibrosis was significantly lower than controls in pediatrics and adolescences (WMD: - 3.41 ng/ml, 95% CI - 5.02, - 1.80, p =  < 0.001) and adults (WMD: - 2.60 ng/ml, 95% CI - 4.32, - 0.89, p = 0.003). Based on data from 12 studies (21 effect sizes) with a total of 1622 participants, the prevalence of vitamin D levels of 20-30 ng/ml in CF patients was 36% among pediatrics/adolescents and 63% among adults. In addition, 27% of pediatric/adolescent CF patients and 35% of adult CF patients had vitamin D levels of below 20 ng/ml.

CONCLUSIONS

As a result, according to the existing guidelines, our results proved the need to pay attention to the level of vitamin D in these patients.

Organic Synthesis of New Secosteroids from Fucosterol, Its Intestinal Absorption by Caco-2 Cells, and Simulation of the Biological Activities of Vitamin D

We previously examined the cellular uptake of six types of vitamin D in human intestinal Caco-2 cells. Since vitamins D5-D7 were commercially unavailable, we synthesized these compounds organically before studying them. This process led us to understand that new secosteroids could be generated as vitamin D candidates, depending on the sterol used as the starting material. We obtained two new secosteroids-compounds 3 and 4-from fucosterol in the current study. We investigated the intestinal absorption of these compounds using Caco-2 cells cultured in Transwells and compared the results with vitamin D3, a representative secosteroid. The intestinal absorption of compound 4 was comparable to that of vitamin D3. Compound 3 showed similar uptake levels but transported about half as much as vitamin D3. These compounds demonstrated intestinal absorption at the cellular level. Vitamin D is known for its diverse biological activities manifest after intestinal absorption. Using PASS online simulation, we estimated the biological activity of compound 3's activated form. In several items indicated by PASS, compound 3 exhibited stronger biological activity than vitamins D2-D7 and was also predicted to have unique biological activities.

Role of vitamin D in pathogenesis and severity of COVID-19 infection

Coronavirus disease (COVID-19) is an infectious disease caused by a new virus that causes respiratory illness. Older adults and individuals who have pre-existing chronic medical conditions are at higher risk for more serious complications from COVID-19. Hypovitaminosis D is attributed to the increased risk of lung injury and acute respiratory distress syndrome (ARDS) as well as diabetes, cardiovascular events and associated comorbidities, which are the main causes of severe clinical complications in COVID-19 patients. Considering the defensive role of vitamin D, mediated through modulation of the innate and adaptive immune system as well as inhibition of the Renin Angiotensin System (RAS), vitamin D supplementation might boost the immune system of COVID-19 patients and reduce severity of the disease in vitamin D deficient individuals.

Fish Oil and Vitamin D Supplementations in Pregnancy Protect Against Childhood Croup

BACKGROUND

Croup is a prevalent respiratory disorder in early childhood most often caused by parainfluenza virus infections. There are no preventive strategies; therefore, we investigated the potential effects of prenatal micronutrient supplementations.

OBJECTIVE

To investigate the supplementation effects of (1) 2.4-g n-3 long-chained polyunsaturated fatty acid (n-3 LCPUFA) (fish oil) versus olive oil and (2) high-dose (2800 IU/d) versus standard-dose (400 IU/d) of vitamin D from pregnancy week 24 until 1 week after birth on the risk for offspring croup during the double-blinded first 3 years of life in a secondary analysis of a 2 × 2 factorial designed randomized controlled trial.

METHODS

The study was completed in the Danish population-based single-center Copenhagen Prospective Studies on Asthma in Childhood 2010 mother-child cohort, which included 736 pregnant women. Croup was diagnosed by physicians' clinical examinations and medical record checks. Potential mediating mechanisms were investigated using blood metabolomics, airway cytokines, and airway microbiome.

RESULTS

Of 695 children, 97 had croup before age 3 years (14%). The risk of croup was reduced in the n-3 LCPUFA (n_cases / n_total = 38/346; 11%) versus olive oil group (59 of 349 children; 17%) (hazard ratio = 0.62; 95% CI, 0.41-0.93; P = .02) and in the high-dose vitamin D group (32 of 295 children; 11%) versus the standard-dose group (51 of 286 children; 18%) (hazard ratio = 0.60; 95% CI, 0.38-0.93; P = .02). There was no evidence of interaction or additive effects between the supplements (P_interaction = .56). Furthermore, the results did not change when they were adjusted for each other, persistent wheeze, and lower respiratory tract infection.

CONCLUSIONS

This analysis of the double-blinded period of the Copenhagen Prospective Studies on Asthma in Childhood 2010 randomized controlled trial of n-3 LCPUFA and high-dose vitamin D supplementation during pregnancy demonstrated a reduced risk of croup in early childhood.

Vitamin D: a potentially important secosteroid for coping with COVID-19

COVID-19 is a disease that has caused a high number of deaths in the world, and despite being controlled, it requires attention and the search for new quick and economical therapeutic strategies. In this sense, vitamin D stands out, an immunomodulator that has shown beneficial effects in decreasing the risk and severity of acute respiratory tract infections, including COVID-19. Therefore, this review presents a number of experimental, observational and clinical studies on the importance of vitamin D against viral infections with an emphasis on COVID-19, highlighting the relationship between vitamin D, Renin-Angiotensin System and cytokine storms with decreased inflammatory lesions in patients with COVID-19. In addition, aspects of pathophysiology, metabolism, risk factors, sources and recommendations of vitamin D are described. We conclude that vitamin D plays a protective role against inflammatory lesions and can decrease the risk of infections and the severity of COVID-19. Therefore, it is essential to maintain adequate levels of vitamin D to avoid complications related to its deficiency.

Role of LL-37 in thrombotic complications in patients with COVID-19

Blood clot formation induced by dysfunctional coagulation is a frequent complication of coronavirus disease 2019 (COVID-19) and a high-risk factor for severe illness and death. Neutrophil extracellular traps (NETs) are implicated in COVID-19-induced immunothrombosis. Furthermore, human cathelicidin, a NET component, can perturb the interaction between the SARS-CoV-2 spike protein and its ACE2 receptor, which mediates viral entry into cells. At present, however, the levels of cathelicidin antimicrobial peptides after SARS-CoV-2 infection and their role in COVID-19 thrombosis formation remain unclear. In the current study, we analyzed coagulation function and found a decrease in thrombin time but an increase in fibrinogen level, prothrombin time, and activated partial thromboplastin time in COVID-19 patients. In addition, the cathelicidin antimicrobial peptide LL-37 was upregulated by the spike protein and significantly elevated in the plasma of patients. Furthermore, LL-37 levels were negatively correlated with thrombin time but positively correlated with fibrinogen level. In addition to platelet activation, cathelicidin peptides enhanced the activity of coagulation factors, such as factor Xa (FXa) and thrombin, which may induce hypercoagulation in diseases with high cathelicidin peptide levels. Injection of cathelicidin peptides promoted the formation of thrombosis, whereas deletion of cathelicidin inhibited thrombosis in vivo. These results suggest that cathelicidin antimicrobial peptide LL-37 is elevated during SARS-CoV-2 infection, which may induce hypercoagulation in COVID-19 patients by activating coagulation factors.

Vitamin D-induced LL-37 modulates innate immune responses of human primary macrophages during DENV-2 infection

Epidemics of dengue, an acute and potentially severe disease caused by mosquito-borne dengue virus (DENV), pose a major challenge to clinicians and health care services across the sub(tropics). Severe disease onset is associated with a dysregulated inflammatory response to the virus and there are currently no drugs to alleviate disease symptoms. LL-37 is a potent antimicrobial peptide with a wide range of immunoregulatory properties. In this study, we assessed the effect of LL-37 on DENV-2-induced responses in human monocyte-derived macrophages (MDMs). We show that simultaneous exposure of exogenous LL-37 and DENV-2 resulted in reduced replication of the virus in MDMs, while the addition of LL-37 post-exposure to DENV-2 did not. Interestingly, the latter condition reduced the production of IL-6 and increased the expression of genes involved in virus sensing and antiviral response. Finally, we demonstrate that low endogenous levels and limited production of LL-37 in MDMs in response to DENV-2 infection can be increased by differentiating MDMs in the presence of Vitamin D (VitD3). Taken together, this study demonstrates that in addition to its antimicrobial properties, LL-37 has immunomodulatory properties in the curse of DENV infection and its production can be increased by VitD3.

Biological Functions and Applications of Antimicrobial Peptides

Abstract:

Despite antimicrobial resistance, which is attributed to the misuse of broad-spectrum antibiotics, antibiotics can indiscriminately kill pathogenic and beneficial microorganisms. These events disrupt the delicate microbial balance in both humans and animals, leading to secondary infections and other negative effects. Antimicrobial peptides (AMPs) are functional natural biopolymers in plants and animals. Due to their excellent antimicrobial activities and absence of microbial resistance, AMPs have attracted enormous research attention. We reviewed the antibacterial, antifungal, antiviral, antiparasitic, as well as antitumor properties of AMPs and research progress on AMPs. In addition, we highlighted various recommendations and potential research areas for their progress and challenges in practical applications.

Vitamin D, infections and immunity

Vitamin D, best known for its role in skeletal health, has emerged as a key regulator of innate immune responses to microbial threat. In immune cells such as macrophages, expression of CYP27B1, the 25-hydroxyvitamin D 1α-hydroxylase, is induced by immune-specific inputs, leading to local production of hormonal 1,25-dihydroxyvitamin D (1,25D) at sites of infection, which in turn directly induces the expression of genes encoding antimicrobial peptides. Vitamin D signaling is active upstream and downstream of pattern recognition receptors, which promote front-line innate immune responses. Moreover, 1,25D stimulates autophagy, which has emerged as a mechanism critical for control of intracellular pathogens such as M. tuberculosis. Strong laboratory and epidemiological evidence links vitamin D deficiency to increased rates of conditions such as dental caries, as well as inflammatory bowel diseases arising from dysregulation of innate immune handling intestinal flora. 1,25D is also active in signaling cascades that promote antiviral innate immunity; 1,25D-induced expression of the antimicrobial peptide CAMP/LL37, originally characterized for its antibacterial properties, is a key component of antiviral responses. Poor vitamin D status is associated with greater susceptibility to viral infections, including those of the respiratory tract. Although the severity of the COVID-19 pandemic has been alleviated in some areas by the arrival of vaccines, it remains important to identify therapeutic interventions that reduce disease severity and mortality, and accelerate recovery. This review outlines of our current knowledge of the mechanisms of action of vitamin D signaling in the innate immune system. It also provides an assessment of the therapeutic potential of vitamin D supplementation in infectious diseases, including an up-to-date analysis of the putative benefits of vitamin D supplementation in the ongoing COVID-19 crisis.

Exploring the Immune-Boosting Functions of Vitamins and Minerals as Nutritional Food Bioactive Compounds: A Comprehensive Review

Food components have long been recognized to play a fundamental role in the growth and development of the human body, conferring protective functionalities against foreign matter that can be severe public health problems. Micronutrients such as vitamins and minerals are essential to the human body, and individuals must meet their daily requirements through dietary sources. Micronutrients act as immunomodulators and protect the host immune response, thus preventing immune evasion by pathogenic organisms. Several experimental investigations have been undertaken to appraise the immunomodulatory functions of vitamins and minerals. Based on these experimental findings, this review describes the immune-boosting functionalities of micronutrients and the mechanisms of action through which these functions are mediated. Deficiencies of vitamins and minerals in plasma concentrations can lead to a reduction in the performance of the immune system functioning, representing a key contributor to unfavorable immunological states. This review provides a descriptive overview of the characteristics of the immune system and the utilization of micronutrients (vitamins and minerals) in preventative strategies designed to reduce morbidity and mortality among patients suffering from immune invasions or autoimmune disorders.

Vitamin D Inhibits IL-6 Pro-Atherothrombotic Effects in Human Endothelial Cells: A Potential Mechanism for Protection against COVID-19 Infection?

BACKGROUND

Thrombosis with cardiovascular involvement is a crucial complication in COVID-19 infection. COVID-19 infects the host by the angiotensin converting enzyme-2 receptor (ACE2r), which is expressed in endothelial cells too. Thus, COVID-related thrombotic events might be due to endothelial dysfunction. IL-6 is one of the main cytokines involved in the COVID-19 inflammatory storm. Some evidence indicates that Vitamin D (VitD) has a protective role in COVID-19 patients, but the molecular mechanisms involved are still debated. Thus, we investigated the effect of VitD on Tissue Factor and adhesion molecules (CAMs) in IL-6-stimulated endothelial cells (HUVEC). Moreover, we evaluated levels of the ACE2r gene and proteins. Finally, we studied the modulation of NF-kB and STAT3 pathways.

METHODS

HUVEC cultivated in VitD-enriched medium were stimulated with IL-6 (0.5 ng/mL). The TF gene (RT-PCR), protein (Western blot), surface expression (FACS) and procoagulant activity (FXa generation assay) were measured. Similarly, CAMs soluble values (ELISA) and ACE2r (RT-PCR and Western blot) levels were assessed. NF-kB and STAT3 modulation (Western blot) were also investigated.

RESULTS

VitD significantly reduced TF expression at both gene and protein levels as well as TF-procoagulant activity in IL-6-treated HUVEC. Similar effects were observed for CAMs and ACE2r expression. IL-6 modulates these effects by regulating NF-κB and STAT3 pathways.

CONCLUSIONS

IL-6 induces endothelial dysfunction with TF and CAMs expression via upregulation of ACE2r. VitD prevented these IL-6 deleterious effects. Thus, it might be speculated that this is one of the hypothetical mechanism(s) by which VitD exerts its beneficial effects in COVID-19 infection.

Emerging Roles of Vitamin D-Induced Antimicrobial Peptides in Antiviral Innate Immunity

Vitamin D deficiency, characterized by low circulating levels of calcifediol (25-hydroxyvitamin D, 25D) has been linked to increased risk of infections of bacterial and viral origin. Innate immune cells produce hormonal calcitriol (1,25-dihydroxyvitamin D, 1,25D) locally from circulating calcifediol in response to pathogen threat and an immune-specific cytokine network. Calcitriol regulates gene expression through its binding to the vitamin D receptor (VDR), a ligand-regulated transcription factor. The hormone-bound VDR induces the transcription of genes integral to innate immunity including pattern recognition receptors, cytokines, and most importantly antimicrobial peptides (AMPs). Transcription of the human AMP genes β-defensin 2/defensin-β4 (HBD2/DEFB4) and cathelicidin antimicrobial peptide (CAMP) is stimulated by the VDR bound to promoter-proximal vitamin D response elements. HDB2/DEFB4 and the active form of CAMP, the peptide LL-37, which form amphipathic secondary structures, were initially characterized for their antibacterial actively. Notably, calcitriol signaling induces secretion of antibacterial activity in vitro and in vivo, and low circulating levels of calcifediol are associated with diverse indications characterized by impaired antibacterial immunity such as dental caries and urinary tract infections. However, recent work has also provided evidence that the same AMPs are components of 1,25D-induced antiviral responses, including those against the etiological agent of the COVID-19 pandemic, the SARS-CoV2 coronavirus. This review surveys the evidence for 1,25D-induced antimicrobial activity in vitro and in vivo in humans and presents our current understanding of the potential mechanisms by which CAMP and HBD2/DEFB4 contribute to antiviral immunity.

Utilizing the Potential of Antimicrobial Peptide LL-37 for Combating SARS-COV- 2 Viral Load in Saliva: an In Silico Analysis

Limiting the spread of virus during the recent pandemic outbreak was a major challenge. Viral loads in saliva, nasopharyngeal and oropharyngeal swabs were the major cause for droplet transmission and aerosols. Saliva being the major contributor for the presence of viral load is the major key factor; various mouthwashes and their combination were analyzed and utilized in health care centers to hamper the spread of virus and decrease viral load. The compositions of these mouthwashes to an extent affected the viral load and thereby transmission, but there is always a scope for other protocols which may provide better results. Here we evaluated the potential of antimicrobial peptide LL-37 in decreasing the viral load of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) through an in silico work and evidence from other studies. This narrative review highlighted a brief nonsystematic methodology to include the selected articles for discussion. Accessible electronic databases (Medline, Scopus, Web of Science, SciELO, and PubMed) were used to find studies that reported the salivary viral load of SARS-CoV-2 published between December 2019 and June 2021. The following keywords were utilized for brief searching of the databases: "saliva," "viral load," and "SARS-CoV-2." Articles in English language, in vitro cell-line studies, ex vivo studies, and clinical trials explaining the viral load of SARS-CoV-2 in saliva and strategies to decrease viral load were included in this review. The search was complemented by manual searching of the reference lists of included articles and performing a citation search for any additional reviews. The antiviral potential of cationic host defense peptide LL-37 was evaluated using computational approaches providing in silico evidence. The analysis of docking studies and the display of positive interfacial hydrophobicity of LL-37 resulting in disruption of COVID-19 viral membrane elucidate the fact that LL-37 could be effective against all variants of SARS-CoV-2. Further experimental studies would be needed to confirm the binding of the receptor-binding domain with LL-37. The possibility of using it in many forms further to decrease the viral load by disrupting the viral membrane is seen.

Associations of 25 Hydroxyvitamin D and High Sensitivity C-reactive Protein Levels in Early Life

Vitamin D deficiency and elevated high sensitivity C-reactive protein (hs-CRP) have been associated with several health outcomes, but knowledge on early life trajectories and association between 25 hydroxyvitamin D (25(OH)D) and hs-CRP is lacking. We investigated the association between longitudinal measurements of 25(OH)D and hs-CRP, respectively, from pregnancy to childhood and throughout childhood in two Danish mother–child cohorts—the COPSAC₂₀₁₀ and COPSAC₂₀₀₀. In COPSAC₂₀₁₀, there was an association between 25(OH)D concentrations at week 24 in pregnancy and at age 6 months in childhood (n = 633): estimate (95% CI); 0.114 (0.041;0.187), p = 0.002, and between 25(OH)D at age 6 months and 6 years (n = 475): 0.155 (0.083;0.228), p < 0.001. This was also demonstrated in the COPSAC₂₀₀₀ cohort between 25(OH)D concentrations in cord blood and at age 4 years (n = 188): 0.294 (0.127;0.461), p < 0.001 and at age 6 months and 4 years (n = 264): 0.260 (0.133;0.388), p < 0.001. In COPSAC₂₀₀₀, we also found an association between hs-CRP at age 6 months and 12 years in childhood (n = 232): 0.183 (0.076;0.289), p < 0.001. Finally, we found a negative association between the cross-sectional measurements of 25(OH)D and hs-CRP at age 6 months (n = 613) in COPSAC₂₀₁₀: −0.004 (−0.008;−0.0004), p = 0.030, but this was not replicated in COPSAC₂₀₀₀. In this study, we found evidence of associations across timepoints of 25(OH)D concentrations from mid-pregnancy to infancy and through childhood and associations between hs-CRP levels during childhood, although with weak correlations. We also found a negative cross-sectional association between 25(OH)D and hs-CRP concentrations in COPSAC₂₀₁₀ proposing a role of vitamin D in systemic low-grade inflammation, though this association was not present in COPSAC₂₀₀₀.

Vitamin D Actions: The Lung Is a Major Target for Vitamin D, FGF23, and Klotho

Vitamin D is well known for its role as a calcium regulator and in maintenance of phosphate homeostasis in musculoskeletal health, and fibroblast growth factor 23 (FGF23) and its coreceptor α-klotho are known for their roles as regulators of serum phosphate levels. However, apart from these classical actions, recent data point out a relevant role of vitamin D and FGF23/klotho in lung health. The expression of the vitamin D receptor by different cell types in the lung and the fact that those cells respond to vitamin D or can locally produce vitamin D indicate that the lung represents a target for vitamin D actions. Similarly, the presence of the four FGF receptor isoforms in the lung and the ability of FGF23 to stimulate pulmonary cells support the concept that the lung is a target for FGF23 actions, whereas the contribution of klotho is still undetermined. This review will give an overview on how vitamin D or FGF23/klotho may act on the lung and interfere positively or negatively with lung health. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Are Host Defense Peptides and Their Derivatives Ready to be Part of the Treatment of the Next Coronavirus Pandemic?

The term host defense peptides arose at the beginning to refer to those peptides that are part of the host's immunity. Because of their broad antimicrobial capacity and immunomodulatory activity, nowadays, they emerge as a hope to combat resistant multi-drug microorganisms and emerging viruses, such as the case of coronaviruses. Since the beginning of this century, coronaviruses have been part of different outbreaks and a pandemic, and they will be surely part of the next pandemics, this review analyses whether these peptides and their derivatives are ready to be part of the treatment of the next coronavirus pandemic.

Experimental Antiviral Therapeutic Studies for Human Rhinovirus Infections

Rhinovirus infection is common and usually causes mild, self-limiting upper respiratory tract symptoms. Rhinoviruses can cause exacerbation of chronic respiratory diseases, such as asthma or chronic obstructive pulmonary disease, leading to a significant burden of morbidity and mortality. There has been a great deal of progress in efforts to understand the immunological basis of rhinovirus infection. However, despite a number of in vitro and in vivo attempts, there have been no effective treatments developed. This review article summarises the up to date virological and immunological understanding of these infections. We discuss the challenges researchers face, and key solutions, in their work to investigate potential therapies including in vivo rhinovirus challenge studies. Finally, we explore past and present experimental therapeutic strategies employed in the treatment of rhinovirus infections and highlight promising areas of future work.

Role of ACE 2 and Vitamin D: The Two Players in Global Fight against COVID-19 Pandemic

The global pandemic of coronavirus disease 2019 (COVID-19) has spread across the borders, gaining attention from both health care professional and researchers to understand the mode of entry and actions induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), its causative agent in the human body. The role of angiotensin-converting enzyme–2 (ACE2) in facilitating the entry of the virus in the host cell by binding to it is similar to SARS-CoV-1, the causative agent for severe acute respiratory syndrome (SARS) which emerged in 2003. Besides the role of ACE2 as a molecular target for the virus, the review displays the potential benefits of ACE2 enzyme and various agents that modify its activity in curbing the effects of the deadly virus, thus unfolding a dual character of ACE2 in the current pandemic. As evident by the differences in the susceptibility toward viral infection in children and geriatric population, it must be noted that the older population has limited ACE2 levels and greater infection risk, whereas the situation is reversed in the case of the pediatric population, demonstrating the defensive character of ACE2 in the latter, despite acting as receptor target for SARS-CoV-2. Also, the upregulation of ACE2 levels by estrogen has indicated greater resistance to infection in females than in the male human population. ACE2 is a carboxypeptidase, which degrades angiotensin II and counteracts its actions to protect against cardiovascular risks associated with the virus. Another contribution of this enzyme is supported by the role of circulating soluble ACE2, which acts as a receptor to bind the virus but does not mediate its actions, therefore blocking its interaction to membrane-bound ACE2 receptors. The review also shares the enhanced risks of developing COVID-19 infection by using ACE inhibitors and ARBs. However, both these agents have been reported to upregulate ACE2 levels; yet, adequate evidence regarding their role is quite inconsistent in human studies. Furthermore, the role of vitamin D has been highlighted in regulating the immune system of the body through renin-angiotensin-aldosterone system (RAAS) inhibition, by downregulating host cell receptor expression to prevent virus attachment. Besides, vitamin D also acts through several other mechanisms like upregulating antimicrobial peptides, fighting against the proinflammatory milieu created by the invading virus, and interfering with the viral replication cycle as well as calcitriol-mediated blockage of CREB protein. Hypovitaminosis D is attributed to elevated risks of acute respiratory distress syndrome (ARDS), lung damage, and cardiovascular disorders, further increasing the severity of COVID-19 infection.

Cathelicidin antimicrobial peptides suppress EV71 infection via regulating antiviral response and inhibiting viral binding

Cathelicidin antimicrobial peptides (human LL-37 and mouse CRAMP) are mainly virucidal to enveloped virus. However, the effects and relative mechanisms of LL-37 and CRAMP on non-enveloped virus are elusive. We herein found that CRAMP expression was significantly up-regulated post non-enveloped Enterovirus 71 (EV71) infection in different tissues of newborn ICR mice, while EV71 replication gradually declined post CRAMP up-regulation, indicating the antiviral potential of cathelicidin against EV71. In vitro antiviral assay showed that LL-37 and CRAMP markedly reduced cytopathic effects (CPE), intracellular viral RNA copy numbers, viral VP1 protein levels, and extracellular virons in U251 cells post EV71 infection, indicating that LL-37 and CRAMP significantly inhibited EV71 replication. Mechanism of action assay showed that LL-37 and CRAMP were not virucidal to EV71, but markedly regulated antiviral immune response in U251 cells. Co-incubation of LL-37 or CRAMP with U251 cells markedly increased the basal interferon-β (IFN-β) expression and interferon regulatory transcription factor 3 (IRF3) phosphorylation, modestly enhanced IFN-β production and IRF3 phosphorylation upon EV71 infection, and significantly reduced interleukin-6 (IL-6) production and p38 mitogen-activated protein kinase (MAPK) activation post EV71 infection. Additionally, LL-37 and CRAMP directly inhibited viral binding to U251 cells. Collectively, LL-37 and CRAMP markedly inhibited EV71 replication via regulating antiviral response and inhibiting viral binding, providing potent candidates for peptide drug development against EV71 infection.

Vitamin D Modulation of the Innate Immune Response to Paediatric Respiratory Pathogens Associated with Acute Lower Respiratory Infections

Vitamin D is an essential component of immune function and childhood deficiency is associated with an increased risk of acute lower respiratory infections (ALRIs). Globally, the leading childhood respiratory pathogens are Streptococcus pneumoniae, respiratory syncytial virus and the influenza virus. There is a growing body of evidence describing the innate immunomodulatory properties of vitamin D during challenge with respiratory pathogens, but recent systematic and unbiased synthesis of data is lacking, and future research directions are unclear. We therefore conducted a systematic PubMed literature search using the terms “vitamin D” and “Streptococcus pneumoniae” or “Respiratory Syncytial Virus” or “Influenza”. A priori inclusion criteria restricted the review to in vitro studies investigating the effect of vitamin D metabolites on human innate immune cells (primary, differentiated or immortalised) in response to stimulation with the specified respiratory pathogens. Eleven studies met our criteria. Despite some heterogeneity across pathogens and innate cell types, vitamin D modulated pathogen recognition receptor (PRRs: Toll-like receptor 2 (TLR2), TLR4, TLR7 and nucleotide-binding oligomerisation domain-containing protein 2 (NOD2)) expression; increased antimicrobial peptide expression (LL-37, human neutrophil peptide (HNP) 1-3 and β-defensin); modulated autophagosome production reducing apoptosis; and modulated production of inflammatory cytokines (Interleukin (IL) -1β, tumour necrosis factor-α (TNF-α), interferon-ɣ (IFN-ɣ), IL-12p70, IFN-β, Regulated on Activation, Normal T cell Expressed (RANTES), IL-10) and chemokines (IL-8 and C-X-C motif chemokine ligand 10 (CXCL10)). Differential modulation of PRRs and IL-1β was reported across immune cell types; however, this may be due to the experimental design. None of the studies specifically focused on immune responses in cells derived from children. In summary, vitamin D promotes a balanced immune response, potentially enhancing pathogen sensing and clearance and restricting pathogen induced inflammatory dysregulation. This is likely to be important in controlling both ALRIs and the immunopathology associated with poorer outcomes and progression to chronic lung diseases. Many unknowns remain and further investigation is required to clarify the nuances in vitamin D mediated immune responses by pathogen and immune cell type and to determine whether these in vitro findings translate into enhanced immunity and reduced ALRI in the paediatric clinical setting.

Covid-19 Susceptibility and Severity Might be Modified by Vitamin D Status: Theoretical and Practical Considerations

Background:

The recently identified SARS-CoV-2 coronavirus has resulted in the Covid-19 pandemic with severe morbidity and high mortality, particularly in certain sections of the population. The co-morbidity patterns associated with adverse outcomes are multiple and complex and there is emerging epidemiological, nutritional and molecular biological evidence that an inadequate vitamin D status is a contributing factor.

Objective:

The aim was to review the role of vitamin D in immune function with particular reference to the mechanisms whereby it supports immune efficiency, host protection and immune modulation. The evidence for the possible benefit of vitamin D supplementation to ameliorate the severity of respiratory infection by SARS-CoV-2 and other pathogens was also reviewed with a view to making a recommendation.

Methods:

PubMed, MEDLINE and Google Scholar were searched using the terms: Covid-19, coronavirus, SARS-CoV-2, vitamin D, calcitriol, deficiency, adaptive immunity, innate immunity, ventilation, critical care, intensive care, acute respiratory distress syndrome, cytokine storm, respiratory viruses, respiratory tract infection, respiratory syncytial virus, influenza, supplementation. Papers for inclusion were selected on the basis of relevance and quality.

Findings:

Vitamin D insufficiency is widespread in many parts of the world. Vitamin D is needed for normal protective and surveillance immune function and there is evidence that deficiency increases the risk of some respiratory infections, probably including Covid-19. By binding with dedicated receptors on immune cells vitamin D influences several strands of immune function, including the production of anti-microbial peptides and several cytokines that promote an appropriate immune response. Vitamin D supplementation probably reduces the risk of respiratory infection, with persuasive biological, epidemiological and observational evidence for possible benefit against Covid-19.

Conclusion:

Despite the lack of direct evidence specific to Covid-19 a cogent theoretical case can be made for giving adults from selected groups, and arguably all adults, routine supplementation with vitamin D to improve immune efficiency and reduce the incidence and severity of respiratory infections. This could be particularly important in sections of the population with a high prevalence of vitamin D insufficiency. Targeted research is required to provide firm evidence to guide practice.

Preventing the development of severe COVID-19 by modifying immunothrombosis

BACKGROUND

COVID-19-associated acute respiratory distress syndrome (ARDS) is associated with significant morbidity and high levels of mortality. This paper describes the processes involved in the pathophysiology of COVID-19 from the initial infection and subsequent destruction of type II alveolar epithelial cells by SARS-CoV-2 and culminating in the development of ARDS.

MAIN BODY

The activation of alveolar cells and alveolar macrophages leads to the release of large quantities of proinflammatory cytokines and chemokines and their translocation into the pulmonary vasculature. The presence of these inflammatory mediators in the vascular compartment leads to the activation of vascular endothelial cells platelets and neutrophils and the subsequent formation of platelet neutrophil complexes. These complexes in concert with activated endothelial cells interact to create a state of immunothrombosis. The consequence of immunothrombosis include hypercoagulation, accelerating inflammation, fibrin deposition, migration of neutrophil extracellular traps (NETs) producing neutrophils into the alveolar apace, activation of the NLRP3 inflammazome, increased alveolar macrophage destruction and massive tissue damage by pyroptosis and necroptosis Therapeutic combinations aimed at ameliorating immunothrombosis and preventing the development of severe COVID-19 are discussed in detail.

Perspective: Vitamin D deficiency and COVID-19 severity - plausibly linked by latitude, ethnicity, impacts on cytokines, ACE2 and thrombosis

BACKGROUND

SARS-CoV-2 coronavirus infection ranges from asymptomatic through to fatal COVID-19 characterized by a 'cytokine storm' and lung failure. Vitamin D deficiency has been postulated as a determinant of severity.

OBJECTIVES

To review the evidence relevant to vitamin D and COVID-19.

METHODS

Narrative review.

RESULTS

Regression modelling shows that more northerly countries in the Northern Hemisphere are currently (May 2020) showing relatively high COVID-19 mortality, with an estimated 4.4% increase in mortality for each 1 degree latitude north of 28 degrees North (P = 0.031) after adjustment for age of population. This supports a role for ultraviolet B acting via vitamin D synthesis. Factors associated with worse COVID-19 prognosis include old age, ethnicity, male sex, obesity, diabetes and hypertension and these also associate with deficiency of vitamin D or its response. Vitamin D deficiency is also linked to severity of childhood respiratory illness. Experimentally, vitamin D increases the ratio of angiotensin-converting enzyme 2 (ACE2) to ACE, thus increasing angiotensin II hydrolysis and reducing subsequent inflammatory cytokine response to pathogens and lung injury.

CONCLUSIONS

Substantial evidence supports a link between vitamin D deficiency and COVID-19 severity but it is all indirect. Community-based placebo-controlled trials of vitamin D supplementation may be difficult. Further evidence could come from study of COVID-19 outcomes in large cohorts with information on prescribing data for vitamin D supplementation or assay of serum unbound 25(OH) vitamin D levels. Meanwhile, vitamin D supplementation should be strongly advised for people likely to be deficient.

Could SARS-CoV-2-induced lung injury be attenuated by vitamin D?

A novel coronavirus (severe acute respiratory syndrome coronavirus 2, SARS-CoV-2) has been confirmed as having the capacity to transmit from humans to humans, causing acute respiratory distress syndrome (ARDS) and acute lung injury. Angiotensin converting enzyme-2 (ACE2) is known to be expressed on type II pneumocytes. As a counter-regulatory arm of the renin-angiotensin system (RAS), ACE2 plays critical roles in the pathogenesis of ARDS and acute lung injury. The affinity of the spike protein receptor binding domain (RBD) of SARS-CoV-2 for human ACE2 (hACE2) largely determines the degree of clinical symptoms after infection by SARS-CoV-2. Previous studies have shown that regulating the ACE2/RAS system is effective in the treatment of severe acute respiratory syndrome coronavirus (SARS-CoV)-induced ARDS and acute lung injury. Since ACE2 is the host cell receptor for both SARS-CoV-2 and SARS-CoV, regulating the ACE2/RAS system may alleviate ARDS and acute lung injury caused by SARS-CoV-2 as well as SARS-CoV. Vitamin D was found to affect ACE2, the target of SARS-CoV-2; therefore, we propose that vitamin D might alleviate ARDS and acute lung injury induced by SARS-CoV-2 by modulating ACE2.

Investigating the Potential for Ultraviolet Light to Modulate Morbidity and Mortality From COVID-19: A Narrative Review and Update

During the COVID-19 (coronavirus disease of 2019) pandemic, researchers have been seeking low-cost and accessible means of providing protection from its harms, particularly for at-risk individuals such as those with cardiovascular disease, diabetes and obesity. One possible way is via safe sun exposure, and/or dietary supplementation with induced beneficial mediators (e.g., vitamin D). In this narrative review, we provide rationale and updated evidence on the potential benefits and harms of sun exposure and ultraviolet (UV) light that may impact COVID-19. We review recent studies that provide new evidence for any benefits (or otherwise) of UV light, sun exposure, and the induced mediators, vitamin D and nitric oxide, and their potential to modulate morbidity and mortality induced by infection with SARS-CoV-2 (severe acute respiratory disease coronavirus-2). We identified substantial interest in this research area, with many commentaries and reviews already published; however, most of these have focused on vitamin D, with less consideration of UV light (or sun exposure) or other mediators such as nitric oxide. Data collected to-date suggest that ambient levels of both UVA and UVB may be beneficial for reducing severity or mortality due to COVID-19, with some inconsistent findings. Currently unresolved are the nature of the associations between blood 25-hydroxyvitamin D and COVID-19 measures, with more prospective data needed that better consider lifestyle factors, such as physical activity and personal sun exposure levels. Another short-coming has been a lack of measurement of sun exposure, and its potential to influence COVID-19 outcomes. We also discuss possible mechanisms by which sun exposure, UV light and induced mediators could affect COVID-19 morbidity and mortality, by focusing on likely effects on viral pathogenesis, immunity and inflammation, and potential cardiometabolic protective mechanisms. Finally, we explore potential issues including the impacts of exposure to high dose UV radiation on COVID-19 and vaccination, and effective and safe doses for vitamin D supplementation.

Vitamin D and COVID-19: evidence and recommendations for supplementation

Vitamin D is a hormone that acts on many genes expressed by immune cells. Evidence linking vitamin D deficiency with COVID-19 severity is circumstantial but considerable-links with ethnicity, obesity, institutionalization; latitude and ultraviolet exposure; increased lung damage in experimental models; associations with COVID-19 severity in hospitalized patients. Vitamin D deficiency is common but readily preventable by supplementation that is very safe and cheap. A target blood level of at least 50 nmol l-1, as indicated by the US National Academy of Medicine and by the European Food Safety Authority, is supported by evidence. This would require supplementation with 800 IU/day (not 400 IU/day as currently recommended in UK) to bring most people up to target. Randomized placebo-controlled trials of vitamin D in the community are unlikely to complete until spring 2021-although we note the positive results from Spain of a randomized trial of 25-hydroxyvitamin D3 (25(OH)D3 or calcifediol) in hospitalized patients. We urge UK and other governments to recommend vitamin D supplementation at 800-1000 IU/day for all, making it clear that this is to help optimize immune health and not solely for bone and muscle health. This should be mandated for prescription in care homes, prisons and other institutions where people are likely to have been indoors for much of the summer. Adults likely to be deficient should consider taking a higher dose, e.g. 4000 IU/day for the first four weeks before reducing to 800 IU-1000 IU/day. People admitted to the hospital with COVID-19 should have their vitamin D status checked and/or supplemented and consideration should be given to testing high-dose calcifediol in the RECOVERY trial. We feel this should be pursued with great urgency. Vitamin D levels in the UK will be falling from October onwards as we head into winter. There seems nothing to lose and potentially much to gain.

Immunomodulatory Role of the Antimicrobial LL-37 Peptide in Autoimmune Diseases and Viral Infections

Antimicrobial peptides (AMPs) are produced by neutrophils, monocytes, and macrophages, as well as epithelial cells, and are an essential component of innate immunity system against infection, including several viral infections. AMPs, in particular the cathelicidin LL-37, also exert numerous immunomodulatory activities by inducing cytokine production and attracting and regulating the activity of immune cells. AMPs are scarcely expressed in normal skin, but their expression increases when skin is injured by external factors, such as trauma, inflammation, or infection. LL-37 complexed to self-DNA acts as autoantigen in psoriasis and lupus erythematosus (LE), where it also induces production of interferon by plasmocytoid dendritic cells and thus initiates a cascade of autocrine and paracrine processes, leading to a disease state. In these disorders, epidermal keratinocytes express high amounts of AMPs, which can lead to uncontrolled inflammation. Similarly, LL-37 had several favorable and unfavorable roles in virus replication and disease pathogenesis. Targeting the antiviral and immunomodulatory functions of LL-37 opens a new approach to limit virus dissemination and the progression of disease.

Childhood asthma heterogeneity at the era of precision medicine: Modulating the immune response or the microbiota for the management of asthma attack

Exacerbations are a main characteristic of asthma. In childhood, the risk is increasing with severity. Exacerbations are a strong phenotypic marker, particularly of severe and therapy-resistant asthma. These early-life events may influence the evolution and be involved in lung function decline. In children, asthma attacks are facilitated by exposure to allergens and pollutants, but are mainly triggered by microbial agents. Multiple studies have assessed immune responses to viruses, and to a lesser extend bacteria, during asthma exacerbation. Research has identified impairment of innate immune responses in children, related to altered pathogen recognition, interferon release, or anti-viral response. Influence of this host-microbiota dialog on the adaptive immune response may be crucial, leading to the development of biased T helper (Th)2 inflammation. These dynamic interactions may impact the presentations of asthma attacks, and have long-term consequences. The aim of this review is to synthesize studies exploring immune mechanisms impairment against viruses and bacteria promoting asthma attacks in children. The potential influence of the nature of infectious agents and/or preexisting microbiota on the development of exacerbation is also addressed. We then discuss our understanding of how these diverse host-microbiota interactions in children may account for the heterogeneity of endotypes and clinical presentations. Finally, improving the knowledge of the pathophysiological processes induced by infections has led to offer new opportunities for the development of preventive or curative therapeutics for acute asthma. A better definition of asthma endotypes associated with precision medicine might lead to substantial progress in the management of severe childhood asthma.

Vitamin D in Prevention and Treatment of COVID-19: Current Perspective and Future Prospects

Vitamin D deficiency (VDD) partly explains geographical differences in COVID-19 susceptibility, severity, and mortality. VDD among African-Americans, diabetics, hypertensive, and aged populations possibly explain the higher death rate, aggravated by cocooning. Vitamin D is pleiotropic, mediating bone metabolism, calcium homeostasis, and immune functions, whereas VDD is associated with inflammatory reactions and immune dysfunction, predisposing individuals to severe infections. Vitamin D modulates innate and adaptive immunity via the expression of genes that code antimicrobial peptides (AMPs). And the expression of cluster of differentiation (CD)14, the co-receptor for epidermal toll-like receptor (TLR)4. AMPs stimulate TLR2 in macrophages, increasing the conversion of vitamin D into its active form by cytochrome P450 27B1. Antiviral properties of vitamin D-induced AMPs can shift the polarization of the adaptive immune response from helper T cells (Th)1 to the more regulatory Th2 responses that suppress immune over-reactivity by preventing cytokine storm, which is already demonstrated during the Spanish flu episode. Vitamin D induces antiviral effects by both direct and indirect mechanisms via AMPs, immunomodulation, the interplay between major cellular and viral elements, induction of autophagy and apoptosis, variation of genetic and epigenetic factors. The crosstalk between vitamin D and intracellular signaling pathways may operate as a primary regulatory action on viral gene transcription. VDD may increase the likelihood of infection with enveloped viruses, including retrovirus, hepatitis, and dengue. Global data correlates severe VDD with COVID-19 associated coagulopathy, disrupted immune response and mortality, reduced platelet count, and prolonged prothrombin time, suggesting benefits from supplementation.Key teaching pointsVitamin D induces antiviral effects by direct and indirect mechanisms via AMPs, immunomodulation, induction of autophagy, etc.Epidemiology of VDD partly explains geographical differences in COVID-19 susceptibility, severity, and mortality.Global data correlates severe VDD with COVID-19 associated coagulopathy, disrupted immune response and mortality, reduced platelet count, and prolonged prothrombin time, together suggesting benefits from supplementation.Many clinical trials are underway globally to delineate the role of vitamin D in both prevention and treatment of COVID-19.

Vitamin and mineral supplementation for β-thalassemia during COVID-19 pandemic

AIM

Low levels of immune-related micronutrients have been identified in β-thalassemia samples. Moreover, the excess amount of iron, contributing to oxidative stress in the pathogenesis of the disease, alters the immune system in β-thalassemia, which is important during the COVID-19 pandemic.

MATERIALS & METHODS

Searches of PUBMED and EMBASE were conducted to identify the level and supplementation of micronutrients in β-thalassemia, published from 2001-May 2020.

RESULTS

The review found six observational and five interventional studies supporting the importance of supplementing vitamins and minerals among patients with β-thalassemia.

CONCLUSION

Supplementation of immune-related vitamins and minerals might bring benefits to the immune system, especially in reducing oxidative stress in β-thalassemia.

Early Nutritional Interventions with Zinc, Selenium and Vitamin D for Raising Anti-Viral Resistance Against Progressive COVID-19

OBJECTIVES

The novel coronavirus infection (COVID-19) conveys a serious threat globally to health and economy because of a lack of vaccines and specific treatments. A common factor for conditions that predispose for serious progress is a low-grade inflammation, e.g., as seen in metabolic syndrome, diabetes, and heart failure, to which micronutrient deficiencies may contribute. The aim of the present article was to explore the usefulness of early micronutrient intervention, with focus on zinc, selenium, and vitamin D, to relieve escalation of COVID-19.

METHODS

We conducted an online search for articles published in the period 2010-2020 on zinc, selenium, and vitamin D, and corona and related virus infections.

RESULTS

There were a few studies providing direct evidence on associations between zinc, selenium, and vitamin D, and COVID-19. Adequate supply of zinc, selenium, and vitamin D is essential for resistance to other viral infections, immune function, and reduced inflammation. Hence, it is suggested that nutrition intervention securing an adequate status might protect against the novel coronavirus SARS-CoV-2 (Severe Acute Respiratory Syndrome - coronavirus-2) and mitigate the course of COVID-19.

CONCLUSION

We recommended initiation of adequate supplementation in high-risk areas and/or soon after the time of suspected infection with SARS-CoV-2. Subjects in high-risk groups should have high priority as regards this nutritive adjuvant therapy, which should be started prior to administration of specific and supportive medical measures.

Impact of the Local Inflammatory Environment on Mucosal Vitamin D Metabolism and Signaling in Chronic Inflammatory Lung Diseases

Vitamin D plays an active role in the modulation of innate and adaptive immune responses as well as in the protection against respiratory pathogens. Evidence for this immunomodulatory and protective role is derived from observational studies showing an association between vitamin D deficiency, chronic airway diseases and respiratory infections, and is supported by a range of experimental studies using cell culture and animal models. Furthermore, recent intervention studies have now shown that vitamin D supplementation reduces exacerbation rates in vitamin D-deficient patients with chronic obstructive pulmonary disease (COPD) or asthma and decreases the incidence of acute respiratory tract infections. The active vitamin D metabolite, 1,25-dihydroxy-vitamin D (1,25(OH)₂D), is known to contribute to the integrity of the mucosal barrier, promote killing of pathogens (via the induction of antimicrobial peptides), and to modulate inflammation and immune responses. These mechanisms may partly explain its protective role against infections and exacerbations in COPD and asthma patients. The respiratory mucosa is an important site of local 1,25(OH)₂D synthesis, degradation and signaling, a process that can be affected by exposure to inflammatory mediators. As a consequence, mucosal inflammation and other disease-associated factors, as observed in e.g., COPD and asthma, may modulate the protective actions of 1,25(OH)₂D. Here, we discuss the potential consequences of various disease-associated processes such as inflammation and exposure to pathogens and inhaled toxicants on vitamin D metabolism and local responses to 1,25(OH)₂D in both immune- and epithelial cells. We furthermore discuss potential consequences of disturbed local levels of 25(OH)D and 1,25(OH)₂D for chronic lung diseases. Additional insight into the relationship between disease-associated mechanisms and local effects of 1,25(OH)₂D is expected to contribute to the design of future strategies aimed at improving local levels of 1,25(OH)₂D and signaling in chronic inflammatory lung diseases.

Antiviral and Immunomodulatory Properties of Antimicrobial Peptides Produced by Human Keratinocytes

Keratinocytes, the main cells of the epidermis, are the first site of replication as well as the first line of defense against many viruses such as arboviruses, enteroviruses, herpes viruses, human papillomaviruses, or vaccinia virus. During viral replication, these cells can sense virus associated molecular patterns leading to the initiation of an innate immune response composed of pro-inflammatory cytokines, chemokines, and antimicrobial peptides. Human keratinocytes produce and secrete at least nine antimicrobial peptides: human cathelicidin LL-37, types 1–4 human β-defensins, S100 peptides such as psoriasin (S100A7), calprotectin (S100A8/9) and koebnerisin (S100A15), and RNase 7. These peptides can exert direct antiviral effects on the viral particle or its replication cycle, and indirect antiviral activity, by modulating the host immune response. The purpose of this review is to summarize current knowledge of antiviral and immunomodulatory properties of human keratinocyte antimicrobial peptides.

Controversial Effects of Vitamin D and Related Genes on Viral Infections, Pathogenesis, and Treatment Outcomes

Vitamin D (VD) plays an essential role in mineral homeostasis and bone remodeling. A number of different VD-related genes (VDRG) are required for the metabolic activation of VD and the subsequent induction of its target genes. They include a set of genes that encode for VD-binding protein, metabolic enzymes, and the VD receptor. In addition to its well-characterized skeletal function, the immunoregulatory activities of VD and the related polymorphisms of VDRG have been reported and linked to its therapeutic and preventive actions for the control of several viral diseases. However, in regards to their roles in the progression of viral diseases, inconsistent and, in some cases, contradictory results also exist. To resolve this discrepancy, I conducted an extensive literature search by using relevant keywords on the PubMed website. Based on the volume of hit papers related to a certain viral infection, I summarized and compared the effects of VD and VDRG polymorphism on the infection, pathogenesis, and treatment outcomes of clinically important viral diseases. They include viral hepatitis, respiratory viral infections, acquired immunodeficiency syndrome (AIDS), and other viral diseases, which are caused by herpesviruses, dengue virus, rotavirus, and human papillomavirus. This review will provide the most current information on the nutritional and clinical utilization of VD and VDRG in the management of the key viral diseases. This information should be valuable not only to nutritionists but also to clinicians who wish to provide evidence-based recommendations on the use of VD to virally infected patients.

Citrullination Alters the Antiviral and Immunomodulatory Activities of the Human Cathelicidin LL-37 During Rhinovirus Infection

Human rhinoviruses (HRV) are the most common cause of viral respiratory tract infections. While normally mild and self-limiting in healthy adults, HRV infections are associated with bronchiolitis in infants, pneumonia in immunocompromised patients, and exacerbations of asthma and COPD. The human cathelicidin LL-37 is a host defense peptide (HDP) with broad immunomodulatory and antimicrobial activities that has direct antiviral effects against HRV. However, LL-37 is known to be susceptible to the enzymatic activity of peptidyl arginine deiminases (PAD), and exposure of the peptide to these enzymes results in the conversion of positively charged arginines to neutral citrullines (citrullination). Here, we demonstrate that citrullination of LL-37 reduced its direct antiviral activity against HRV. Furthermore, while the anti-rhinovirus activity of LL-37 results in dampened epithelial cell inflammatory responses, citrullination of the peptide, and a loss in antiviral activity, ameliorates this effect. This study also demonstrates that HRV infection upregulates PAD2 protein expression, and increases levels of protein citrullination, including histone H3, in human bronchial epithelial cells. Increased PADI gene expression and HDP citrullination during infection may represent a novel viral evasion mechanism, likely applicable to a wide range of pathogens, and should therefore be considered in the design of therapeutic peptide derivatives.

Targeting Vitamin D Deficiency to Limit Exacerbations in Respiratory Diseases: Utopia or Strategy With Potential?

Patients with respiratory diseases such as cystic fibrosis, chronic obstructive pulmonary disease, or asthma often experience an acute worsening of respiratory symptoms, termed exacerbations. Although the course of exacerbations is disease specific, they are mostly triggered by a respiratory infection. Exacerbations often require hospitalization and are an important cause of mortality. Treatments of exacerbations aim to minimize the negative impact and to prevent subsequent events. Despite many existing therapy options, many patients do not benefit from therapy and suffer from recurrent events. Vitamin D deficiency is a worldwide problem and is extremely prevalent in these patients. Vitamin D, known for its calcemic effects, also has immunomodulatory and anti-infectious actions and can therefore be a possible agent to treat or prevent exacerbations. This review will focus on vitamin D as a potential candidate to treat or prevent exacerbations in CF, COPD, and asthma.

Antiviral Activities of Human Host Defense Peptides

Peptides with broad-spectrum antimicrobial activity are found widely expressed throughout nature. As they participate in a number of different aspects of innate immunity in mammals, they have been termed Host Defense Peptides (HDPs). Due to their common structural features, including an amphipathic structure and cationic charge, they have been widely shown to interact with and disrupt microbial membranes. Thus, it is not surprising that human HDPs have activity against enveloped viruses as well as bacteria and fungi. However, these peptides also exhibit activity against a wide range of non-enveloped viruses as well, acting at a number of different steps in viral infection. This review focuses on the activity of human host defense peptides, including alpha- and beta-defensins and the sole human cathelicidin, LL-37, against both enveloped and non-enveloped viruses. The broad spectrum of antiviral activity of these peptides, both in vitro and in vivo suggest that they play an important role in the innate antiviral defense against viral infections. Furthermore, the literature suggests that they may be developed into antiviral therapeutic agents.

Lung allograft donors with excessive alcohol use have increased levels of human antimicrobial peptide LL-37

The relatively low long-term survival rate of lung transplant recipients as compared to other organ recipients serves as an impetus to identify potential lung dysfunction as early as possible. There is an association between donor heavy alcohol use and acute lung injury in the lung allograft after transplant, known as primary graft dysfunction. Excessive alcohol use (EAU) can induce pulmonary immune dysregulation in response to an infection. Antimicrobial peptides (AMPs) are an important component of the innate immune response to pulmonary infections, but the impact of EAU on AMPs in the allograft lung has not been evaluated. Our hypothesis is that specific lung AMPs, LL-37, α-defensin-1,2,3, and β-defensin-2, are dysregulated in the lungs from organ donors who had EAU. In this prospective observational investigation, we measured AMPs via ELISA and inflammatory cytokines via multiplex bead array, in bronchoalveolar lavage (BAL) fluid of lung allograft donors, comparing results based on their alcohol consumption. LL-37 levels in lung donors with EAU were found to be increased compared to nondrinker (ND) donors [median 7.7 ng/mL (IQR 4.1-37.0) vs. 2.3 ng/mL (IQR 1.1-7.9), p = 0.004], whereas α-defensins-1,2,3 were decreased only in the presence of an infection in donors with EAU compared to ND donors [median 2.2 ng/mL (IQR 1.6-2.4) vs. 3.2 ng/mL (IQR 2.3-3.8), p = 0.049]. There was no difference in β-defensin-2 levels. Gene expression levels of these AMPs were not different. Elevated levels of CXCL8 were noted in bronchial washings of donors with EAU compared to ND donors, [median 4372 pg/mL (IQR 3352-13180) vs. 867.3 pg/mL (IQR 163.6-3675), p = 0.04], suggesting a potentially heightened inflammatory response. At 1 month post-transplant, LL-37 and CXCL8 levels are decreased compared to levels at time of transplant. In lung donors with EAU, LL-37 and α-defensins-1,2,3 dysregulated levels in the presence of an infection may be a harbinger of dysfunction of the lungs through the transplant process.

Human Antimicrobial Peptides as Therapeutics for Viral Infections

Successful in vivo infection following pathogen entry requires the evasion and subversion of multiple immunological barriers. Antimicrobial peptides (AMPs) are one of the first immune pathways upregulated during infection by multiple pathogens, in multiple organs in vivo. In humans, there are many classes of AMPs exhibiting broad antimicrobial activities, with defensins and the human cathelicidin LL-37 being the best studied examples. Whereas historically the efficacy and therapeutic potential of AMPs against bacterial infection has been the primary focus of research, recent studies have begun to elucidate the antiviral properties of AMPs as well as their role in regulation of inflammation and chemoattraction. AMPs as therapeutic tools seem especially promising against emerging infectious viral pathogens for which no approved vaccines or treatments are currently available, such as dengue virus (DENV) and Zika virus (ZIKV). In this review, we summarize recent studies elucidating the efficacy and diverse mechanisms of action of various classes of AMPs against multiple viral pathogens, as well as the potential use of human AMPs in novel antiviral therapeutic strategies.

Lung disease and vitamin D levels in cystic fibrosis infants and preschoolers

INTRODUCTION

Vitamin D acts on the immune system and lung response. Patients with cystic fibrosis (CF) may be deficient in this vitamin. The aims of the study were to evaluate vitamin D levels and severity of lung disease in infants and preschoolers diagnosed with CF, and to compare them to a group of children without pancreatic insufficiency (PI).

METHODS

Patients with CF up to 4 years old were included, and compared to an age-matched group of children without diagnosis of CF. CF group had medical records and High Resolution Thorax Computed Tomography (HRCCT) evaluated in order to verify the severity of lung disease. Information on demographic data, sun exposure habits, supplemental vitamin D therapy, and on the season at the time of vitamin D sampling were collected for both groups.

RESULTS

This study included 45 patients in the CF group and 102 in the non-CF group, with no differences in age (P = 0.327) between them. There was no association between vitamin D levels and markers of lung disease in the CF group. The non-CF group had lower daily sun exposure (P = 0.034), and lower supplementation than the CF group (P < 0.001). Supplementation and seasonality were the determinant variables for vitamin D levels, which were lower for non-supplemented children and for assessments during fall/winter.

CONCLUSION

There was no association between lung disease severity and vitamin D levels in CF group. Supplementation and seasonality were associated to higher vitamin levels.