The Role of Vitamin D and Vitamin D Receptor in Immunity to Leishmania major Infection

The association of 25(OH)D, interleukin-4, interleukin-5, and interleukin-13 levels with the burden of soil-transmitted helminth infection in stunted children aged 24-59 months

Soil-transmitted helminth (STH) among children aged 24-59 months is one cause of chronic infection that could lead to stunting. The association of 25(OH)D and immune responses during chronic infection in stunted populations has not yet been well established. An association study of case-control data was conducted in Bandung district from October 2019 to January 2023. Sociodemographic factors, stool samples, and serum levels of 25(OH)D, interleukin-4 (IL-4), interleukin-5 (IL-5), and interleukin-13 (IL-13) were assessed. Statistical analysis was performed to evaluate the prevalence and association of 25(OH)D, IL-4, IL-5, and IL-13 with the burden of STH infection in stunted children. In total, 401 stunted children were recruited. A higher burden of STH infection was found for lower levels of IL-5 (r = -0.477; p = 0.004) and IL-13 (r = -0.433; p = 0.028). Thus, 25(OH)D, IL-4, IL-5, and IL-13 play a role in the burden of STH infection.

Trends and Gaps in the Scientific Literature about the Effects of Nutritional Supplements on Canine Leishmaniosis

In canine leishmaniosis (CanL), complex interactions between the parasites and the immunological background of the host influence the clinical presentation and evolution of infection and disease. Therefore, the potential use of nutraceuticals as immunomodulatory agents becomes of considerable interest. Some biological principles, mainly derived from plants and referred to as plant-derived nutraceuticals, are considered as supplementation for Leishmania spp. infection. This study provides a systematic review regarding the use of nutraceuticals as a treatment using a text mining (TM) and topic analysis (TA) approach to identify dominant topics of nutritional supplements in leishmaniosis-based research, summarize the temporal trend in topics, interpret the evolution within the last century and highlight any possible research gaps. Scopus® database was screened to select 18 records. Findings revealed an increasing trend in research records since 1994. TM identified terms with the highest weighted frequency and TA highlighted the main research areas, namely "Nutraceutical supports and their anti-inflammatory/antioxidant properties", "AHCC and nucleotides in CanL", "Vit. D3 and Leishmaniosis", "Functional food effects and Leishmaniosis" and "Extract effects and Leishmaniosis". Despite the existing academic interest, there are only a few studies on this issue so far, which reveals a gap in the literature that should be filled.

The Possible Role of Selected Vitamins and Minerals in the Therapeutic Outcomes of Leishmaniasis

Leishmaniasis is a protozoal disease declared as an endemic in areas suffering from severe malnutrition and poverty. The factors associated with poverty like low income, ecological factors, and malnutrition cause disruption in immunity and host defense increasing risk of infection. Altered resistance to infection and host susceptibility are associated with low micronutrient levels in undernourished patients. Malnutrition has been recognized as a poor predictive marker for leishmaniasis, in particular the deficiency of trace elements like zinc, iron, and vitamin A, B, C, D which has a prominent function in the regulation of innate and adaptive immunity, cell proliferation, human physiology, etc. Malnourishment can exacerbate host sensitivity and pathophysiologic intensity to infection in variety of ways, whereas infection can enhance underlying poor nutrition or enhance host vulnerability and sandfly's urge to attack specific hosts. The intensity of leishmaniasis can be influenced by body mass and micronutrient availability in the blood. Vitamin D, C, zinc, and iron are proved effective in inhibiting the growth of leishmaniasis in both amastigote or promastigote forms, either directly or by acting as precursor for a pathway which inhibits the parasite growth. This article elucidates a new perception to the crucial role of micronutrients and their probable role in the therapeutic outcomes of leishmaniasis. Since there is requirement of novel drugs to fight drug resistance and relapse of leishmaniasis, this article may pave way to understand the importance of micronutrients and their role in therapeutic outcomes of leishmaniasis.

Brief communication: Vitamin D serum levels in American tegumentary leishmaniasis from an endemic area in Northeast Brazil

INTRODUCTION

The pathogenesis of cutaneous and mucosal leishmaniasis is associated with different immune responses. Vitamin D may modulate the immune system. Here we evaluate the association of vitamin D levels with the severity of the clinical forms of cutaneous and mucosal leishmaniasis.

METHODS

We conducted an observational study evaluating the association between vitamin D levels, disease severity and therapeutic response in patients with cutaneous and mucosal leishmaniasis. Additionally, we conducted a cross-sectional study to compare vitamin D levels in patients with leishmaniasis and healthy subjects. Hypovitaminosis D was defined as a serum level of 25 (OH) D < 30 ng/mL.

RESULTS

In patients with leishmaniasis, vitamin D serum levels were 38.5 ± 11.54 ng/mL, and 37.5 ± 10.43 ng/mL in healthy subjects The prevalence of hypovitaminosis D was 23.3% and 20.0%, respectively (p = 0.72). There was no correlation between vitamin D serum levels, disease severity, and healing time in the mucosal leishmaniasis group.

CONCLUSION

Vitamin D levels are not associated with neither susceptibility nor severity of tegumentary leishmaniasis.

Single nucleotide polymorphisms in genes involved in immune responses and outcome of tegumentary leishmaniasis

Leishmaniases are neglected tropical diseases with a broad clinical spectrum. Tegumentary leishmaniasis (TL) is a disease caused by different Leishmania species, transmitted by phlebotomine sand flies and distributed worldwide. TL can present a cutaneous (CL) or mucocutaneous (MCL) clinical form depending on factors inherent to the parasite, the host and the vector. Polymorphisms in the immune response genes are host genetic factors that influence the pathogenesis or control of leishmaniasis. Single nucleotide polymorphisms (SNPs) in immune genes have been evaluated in several countries where leishmaniasis is endemic. In this review, we report studies on SNPs in several immune genes that might be associated with susceptibility or resistance to TL. We summarize studies from around the world and in Brazil, highlight the difficulties of these studies and future analyses needed to enhance our knowledge regarding host genetic factors in TL. Understanding the genetic characteristics of the host that facilitate resistance or susceptibility to leishmaniasis can contribute to the development of immunotherapy schedules for this disease. The current treatment methods are toxic, and no human vaccine is available.

Vitamins A and D and Zinc Affect the Leshmanicidal Activity of Canine Spleen Leukocytes

Canine leishmaniasis (CanL) is a chronic disease caused by Leishmania infantum, and the limitations of the current treatments have encouraged new alternatives, such as the use of immunomodulatory nutrients. The objective of this study was to determine the serum levels of vitamin A (retinol), vitamin D (25(OH)VD3), and zinc (Zn) in dogs with CanL and the effect of in vitro supplementation with the respective active forms ATRA, 1,25(OH)2VD3, and SZn on spleen leukocyte cultures. Serum retinol, 25(OH)VD3, and Zn were determined by HPLC, ELISA, and ICP-MS, respectively. Spleen leukocyte cultures were used for the detection of NO and ROS by flow cytometry; the IFN-γ, TNF-α, and IL-10 levels were determined by ELISA; and the parasite load was determined by microscopy. We detected low serum levels of retinol and Zn and high levels of 25(OH)VD3 in the CanL group. The in vitro supplementation of CanL spleen leukocytes with ATRA, 1,25(OH)2VD3, and SZn, in addition to a soluble leishmania antigen (SLA) treatment, increased the NO and ROS levels, while the treatments with only ATRA and SZn increased the TNF-a levels. Increased IL-10 and IFN-g levels were observed with the addition of SLA to the medium, although the addition of the three nutrients led to a reduction of the IL-10 levels, and the addition of 1,25(OH)2VD3 and SZn led to a reduction of IFN-g. A supplementation with 1,25(OH)2VD3 and SZn reduced the parasite load but only in the absence of SLA. We suggest that the nutrients we tested are involved in the leishmanicidal mechanism, showing a potential for investigation in future studies.

Vitamin d and leishmaniasis: Neither seasonal nor risk factor in canine host but potential adjuvant treatment through cbd103 expression

Vitamin D (VitD) deficiency has been shown to be a risk factor for a plethora of disorders. We have shown that dogs with clinical leishmaniasis presented lower VitD serum levels than non-infected dogs, and even lower than those with asymptomatic infection. However, if VitD deficiency is a risk factor to develop clinical leishmaniasis remains to be answered. It is also unknown if VitD participates in Leishmania control. First, we retrospectively analysed VitD concentration in serum samples from 36 healthy dogs collected in different periods of the year concluding that there isn't a seasonal variation of this vitamin in dogs. We also included 9 dogs with clinical leishmaniasis and 10 non-infected healthy dogs, in which we measured VitD levels at the beginning of the study, when all dogs were negative for serology and qPCR, and 1 year later. Whereas non-infected dogs showed no change in VitD levels along the study, those developing clinical leishmaniasis showed a significant VitD reduction at the end of the study (35%). When we compared VitD concentration between the two groups at the beginning of the study, no differences were detected (43.6 (38-59) ng/mL, P = 0.962). Furthermore, an in vitro model using a canine macrophage cell line proved that adding active VitD leads to a significant reduction in L. infantum load (31.4%). Analyzing expression of genes related to VitD pathway on primary canine monocytes, we showed that CBD103 expression was significantly enhanced after 1,25(OH)2D addition. Our results show that VitD concentration is neither seasonal nor a risk factor for developing canine leishmaniasis, but it diminishes with the onset of clinical disease suggesting a role in parasitic control. Our in vitro results corroborate this hypothesis and point out that VitD regulates infection through CBD103 expression. These results open the possibility for studies testing VitD as an adjuvant in leishmaniasis therapy.

Micronutrient levels and their effects on the prognosis of visceral leishmaniasis treatment, a prospective cohort study

BACKGROUND

Micronutrients are minerals and vitamins and they are essential for normal physiological activities. The objectives of the study were to describe the progress and determinants of micronutrient levels and to assess the effects of micronutrients in the treatment outcome of kalazar.

METHODS

A prospective cohort study design was used. The data were collected using patient interviews, measuring anthropometric indicators, and collecting laboratory samples. The blood samples were collected at five different periods during the leishmaniasis treatments: before starting anti-leishmaniasis treatments, in the first week, in the second week, in the third week, and in the 4th week of anti-leishmaniasis treatments. Descriptive statistics were used to describe the profile of patients and to compare the treatment success rate. The generalized estimating equation was used to identify the determinants of serum micronutrients.

RESULTS

The mean age of the patients were 32.88 years [SD (standard deviation) ±15.95]. Male constitute 62.3% of the patients and problematic alcohol use was present in 11.5% of the patients. The serum zinc level of visceral leishmaniasis patients was affected by alcohol (B - 2.7 [95% CI: - 4.01 - -1.5]), DDS (B 9.75 [95% CI: 7.71-11.79]), family size (B -1.63 [95% CI: - 2.68 - -0.58]), HIV (B -2.95 [95% CI: - 4.97 - -0.92]), and sex (B - 1.28 [95% CI: - 2.5 - -0.07]). The serum iron level of visceral leishmaniasis patients was affected by alcohol (B 7.6 [95% CI: 5.86-9.35]), family size (B -5.14 [95% CI: - 7.01 - -3.28]), malaria (B -12.69 [95% CI: - 14.53 - -10.87]), Hookworm (- 4.48 [- 6.82 - -2.14]), chronic diseases (B -7.44 [95% CI: - 9.75 - -5.13]), and HIV (B -5.51 [95% CI: - 8.23 - -2.78]). The serum selenium level of visceral leishmaniasis patient was affected by HIV (B -18.1 [95% CI: - 20.63 - -15.58]) and family size (B -11.36 [95% CI: - 13.02 - -9.7]). The iodine level of visceral leishmaniasis patient was affected by HIV (B -38.02 [95% CI: - 41.98 - -34.06]), DDS (B 25 .84 [95% CI: 22.57-29.1]), smoking (B -12.34 [95% CI: - 15.98 - -8.7]), chronic illness (B -5.14 [95% CI: - 7.82 - -2.46]), and regular physical exercise (B 5.82 [95% CI: 0.39-11.26]). The serum vitamin D level of visceral leishmaniasis patient was affected by HIV (B -9.43 [95% CI: - 10.92 - -7.94]), DDS (B 16.24 [95% CI: 14.89-17.58]), malaria (B -0.61 [95% CI: - 3.37 - -3.37]), and family size (B -1.15 [95% CI: - 2.03 - -0.28]). The serum vitamin A level of visceral leishmaniasis patient was affected by residence (B 0.81 [95% CI: 0.08-1.54]), BMI (B 1.52 [95% CI: 0.42-2.6]), DDS (B 1.62 [95% CI: 0.36-2.88]), family size (B -5.03 [95% CI: - 5.83 - -4.22]), HIV (B -2.89 [95% CI: - 4.44 - -1.34]),MUAC (B 0.86 [95% CI: 0.52-1.21]), and age (B 0.09 [95% CI: 0.07-0.12]).

CONCLUSION

The micronutrient levels of visceral leishmaniasis patients were significantly lower. The anti-leishmaniasis treatment did not increase the serum micronutrient level of the patients.

Vitamin D increases killing of intracellular Leishmania amazonensis in vitro independently of macrophage oxidative mechanisms

Vitamin D has been reported to activate macrophage microbicidal mechanisms by inducing the production of antimicrobial peptides and nitric oxide (NO), but conversely has been shown to contribute to a greater susceptibility to Leishmania amazonensis infection in mice. Thus, this study aimed to evaluate the role of vitamin D during intracellular infection with L. amazonensis by examining its effect on macrophage oxidative mechanisms and parasite survival in vitro. Vitamins D2 and D3 significantly inhibited promastigote and amastigote growth in vitro. Vitamin D3 was not able to induce NO and reactive oxygen species (ROS) production in uninfected macrophages or macrophages infected with L. amazonensis. In addition, vitamin D3 in combination with interferon (IFN)-γ did not enhance amastigote killing and in fact, significantly reduced NO and ROS production when compared with the effect of IFN-γ alone. In this study, we demonstrated that vitamin D directly reduces parasite growth in infected macrophages (approximately 50-60% at 50 μm) but this effect is independent of the activation of macrophage oxidative mechanisms. These findings will contribute to a better understanding of the role of vitamin D in cutaneous leishmaniasis.

Serum 25-hydroxyvitamin D level and vitamin D receptor (VDR) polymorphisms in patients infected with Leishmania tropica: a case control study

Leishmania, an obligate intracellular parasite is eliminated by a strong Th-1 host response. As Vitamin D metabolism and its receptor activity are important factors in human native immune system against some microorganisms, we hypothesized that VDR gene polymorphisms and concentration of Vitamin D might have effect on incidence of cutaneous leishmaniasis. The aim of this study was to investigate the association between VDR gene polymorphism and/or the serum vitamin D level and leishmaniasis in the infected patients in comparison to the healthy individuals. In this case-control study, the BsmI, FokI and Taq1 polymorphisms in the VDR gene and serum levels of vitamin D were studied in Iranian infected with Leishmania tropica (n = 50) and healthy controls using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and Electrochemiluminescence methods respectively. Data were statistically analyzed using SPSS software, Chi square and ANOVA tests. The results of this study showed that despite the relatively higher frequency of BsmI-BB, FokI-FF and TaqI-Tt than Non BsmI-BB, Non FokI-FF and Non TaqI-Tt in the patients compared with the healthy individuals, the differences were not statistically significant (P > 0.05). Based on our findings, the relationship between the VDR polymorphism, the serum concentration of 25-hydroxyvitamin D and the susceptibility to Leishmania tropica infection, remains unclear requiring further in-depth studies. However, for better interpretation, it is necessary to consider factors such as the size of the sample examined and the other alleles of VDR, including ApaI.

IL-15 enhances the capacity of primary human macrophages to control Leishmania braziliensis infection by IL-32/vitamin D dependent and independent pathways

How human macrophages can control the intracellular infection with Leishmania is not completely understood. IL-15 and IL-32 are cytokines produced by monocytes/macrophages that can induce antimicrobial mechanisms. Here, we evaluated the effects of recombinant human IL-15 (rhIL-15) on primary human macrophage infection and response to L. braziliensis. Priming with rhIL-15 reduced the phagocytosis of L. braziliensis and increased the killing of the parasites in monocyte-derived macrophages from healthy donors. rhIL-15 induced TNFα and IL-32 in uninfected cells. After infection, the high levels of rhIL-15-induced TNFα and IL-32 were maintained. In addition, there was an increase of NO and an inhibition of the parasite-induced IL-10 production. Inhibition of NO reversed the leishmanicidal effects of rhIL-15. Although rhIL-15 did not increase L. braziliensis-induced reactive oxygen intermediates (ROS) production, inhibition of ROS reversed the control of infection induced by rhIL-15. Treatment of the cells with rhIL-32γ increased microbicidal capacity of macrophages in the presence of high levels of vitamin D (25D3), but not in low concentrations of this vitamin. rhIL-15 together with rhIL-32 lead to the highest control of the L. braziliensis infection in high concentrations of vitamin D. In this condition, NO and ROS mediated rhIL-32γ effects on microbicidal activity. The data showed that priming of human macrophages with rhIL-15 or rhIL-32γ results in the control of L. braziliensis infection through induction of NO and ROS. In addition, rhIL-32γ appears to synergize with rhIL-15 for the control of L. braziliensis infection in a vitamin D-dependent manner.

Vitamins (A&D) and Isoprenoid (Chenodeoxycholic acid) molecules are accompanied by Th1 immunostimulatory response and therapeutic cure in vivo: possible antileishmanial drugs

Investigation of immune modulatory anti-leishmanial molecules is now being strongly encouraged to overcome the immunosuppression manifested during visceral leishmaniasis (VL), resistance, toxicity and high cost associated with conventional therapeutics. In the present study, we explored the protective efficacy of vitamin D₃, retinoic acid and isoprenoid chenodeoxycholic acid (CDCA) combinations against L. donovani infected BALB/c mice. We also probed the immune modulatory response (Th1 & Th2 cytokines) and infection dynamics following experimental infections with drug treated animals. Our results indicate that Vit.D₃/RA and CDCA/RA combination treatment led to significant inhibition of parasite load on days 21 and 28 post treatment. Furthermore, there was a marked inhibition of Th2 type immune responses in IL-4, IL-5 and polarization of Th1 biased immunity along with upregulation of IL-1, IFN-γ, and TNF-α levels on day 28 post treatment. In addition, mice treated with Vit.D₃/RA and CDCA/RA demonstrates here that splenic histological recovery against the virulent challenge of L. donovani by day 28 was comparable to control group. The conclusions derived from this study suggests that a combination of vitamin A, D₃ and isoprenoids may have a potential immunomodulatory therapeutic role against leishmaniasis.

Dietary Vitamin D3 Deficiency Increases Resistance to Leishmania (Leishmania) amazonensis Infection in Mice

The leishmaniases are a group of diseases caused by Leishmania parasites, which have different clinical manifestations. Leishmania (Leishmania) amazonensis is endemic in South America and causes cutaneous leishmaniasis (CL), which can evolve into a diffuse form, characterized by an anergic immune response. Since the leishmaniases mainly affect poor populations, it is important to understand the involvement of immunonutrition, how the immune system is modulated by dietary nutrients and the effect this has on Leishmania infection. Vitamin D3 (VitD) is an immunonutrient obtained from diet or endogenously synthesized, which suppresses Th1 and Th17 responses by favoring T helper (Th) 2 and regulatory T cell (Treg) generation. Based on these findings, this study aims to evaluate dietary VitD influence on L. (L.) amazonensis experimental infection in C57BL/6 and BALB/c mice. Thus, C57BL/6 and BALB/c VitD deficient (VDD) mice were generated through dietary VitD restriction 45 days prior to infection. Both strains of VDD mice showed a more controlled lesion development compared to mice on a regular diet (Ctrl). There were no differences in serum levels of anti-Leishmania IgG1 and IgG2a, but there was a decrease in IgE levels in BALB/c VDD mice. Although CD4⁺ T cell number was not changed, the CD4⁺ IFN-y⁺ T cell population was increased in both absolute number and percentage in C57BL/6 and BALB/c VDD mice compared to Ctrl mice. There was also no difference in IL-4 and IL-17 production, however, there was reduction of IL-10 production in VDD mice. Together, our data indicate that VitD contributes to murine cutaneous leishmaniasis susceptibility and that the Th1 cell population may be related to the resistance of VDD mice to L. (L.) amazonensis infection.

Macrophage nuclear receptors: Emerging key players in infectious diseases

Nuclear receptors (NRs) are ligand-activated transcription factors that are expressed in a variety of cells, including macrophages. For decades, NRs have been therapeutic targets because their activity can be pharmacologically modulated by specific ligands and small molecule inhibitors. NRs regulate a variety of processes, including those intersecting metabolic and immune functions, and have been studied in regard to various autoimmune diseases. However, the complex roles of NRs in host response to infection are only recently being investigated. The NRs peroxisome proliferator-activated receptor γ (PPARγ) and liver X receptors (LXRs) have been most studied in the context of infectious diseases; however, recent work has also linked xenobiotic pregnane X receptors (PXRs), vitamin D receptor (VDR), REV-ERBα, the nuclear receptor 4A (NR4A) family, farnesoid X receptors (FXRs), and estrogen-related receptors (ERRs) to macrophage responses to pathogens. Pharmacological inhibition or antagonism of certain NRs can greatly influence overall disease outcome, and NRs that are protective against some diseases can lead to susceptibility to others. Targeting NRs as a novel host-directed treatment approach to infectious diseases appears to be a viable option, considering that these transcription factors play a pivotal role in macrophage lipid metabolism, cholesterol efflux, inflammatory responses, apoptosis, and production of antimicrobial byproducts. In the current review, we discuss recent findings concerning the role of NRs in infectious diseases with an emphasis on PPARγ and LXR, the two most studied. We also highlight newer work on the activity of emerging NRs during infection.

Impact of Childhood Malnutrition on Host Defense and Infection

The global impact of childhood malnutrition is staggering. The synergism between malnutrition and infection contributes substantially to childhood morbidity and mortality. Anthropometric indicators of malnutrition are associated with the increased risk and severity of infections caused by many pathogens, including viruses, bacteria, protozoa, and helminths. Since childhood malnutrition commonly involves the inadequate intake of protein and calories, with superimposed micronutrient deficiencies, the causal factors involved in impaired host defense are usually not defined. This review focuses on literature related to impaired host defense and the risk of infection in primary childhood malnutrition. Particular attention is given to longitudinal and prospective cohort human studies and studies of experimental animal models that address causal, mechanistic relationships between malnutrition and host defense. Protein and micronutrient deficiencies impact the hematopoietic and lymphoid organs and compromise both innate and adaptive immune functions. Malnutrition-related changes in intestinal microbiota contribute to growth faltering and dysregulated inflammation and immune function. Although substantial progress has been made in understanding the malnutrition-infection synergism, critical gaps in our understanding remain. We highlight the need for mechanistic studies that can lead to targeted interventions to improve host defense and reduce the morbidity and mortality of infectious diseases in this vulnerable population.

Cutaneous Manifestations of Human and Murine Leishmaniasis

The leishmaniases are diseases caused by pathogenic protozoan parasites of the genus Leishmania. Infections are initiated when a sand fly vector inoculates Leishmania parasites into the skin of a mammalian host. Leishmania causes a spectrum of inflammatory cutaneous disease manifestations. The type of cutaneous pathology is determined in part by the infecting Leishmania species, but also by a combination of inflammatory and anti-inflammatory host immune response factors resulting in different clinical outcomes. This review discusses the distinct cutaneous syndromes described in humans, and current knowledge of the inflammatory responses associated with divergent cutaneous pathologic responses to different Leishmania species. The contribution of key hematopoietic cells in experimental cutaneous leishmaniasis in mouse models are also reviewed and compared with those observed during human infection. We hypothesize that local skin events influence the ensuing adaptive immune response to Leishmania spp. infections, and that the balance between inflammatory and regulatory factors induced by infection are critical for determining cutaneous pathology and outcome of infection.

Canine Leishmaniasis Progression is Associated with Vitamin D Deficiency

The relationship between vitamin D deficiency and the risk of suffering from a plethora of health disorders, ranging from autoimmune processes to infectious diseases has been widely described. Nonetheless, the potential role of vitamin D in visceral leishmaniasis remains uncharacterized. In the Mediterranean basin, where the dog is leishmania’s main peri-domestic reservoir, control measures against the canine disease have shown beneficial effects on the incidence of human leishmaniasis. In this study, we measured the vitamin D levels in serum samples from a cohort of 68 healthy and disease dogs from a highly endemic area and we have also studied the relationship of these levels with parasitological and immunological parameters. The sick dogs presented significantly lower (P < 0.001) vitamin D levels (19.6 ng/mL) than their non-infected (31.8 ng/mL) and the asymptomatic counterparts (29.6 ng/mL). In addition, vitamin D deficiency correlated with several parameters linked to leishmaniasis progression. However, there was no correlation between vitamin D levels and the Leishmania-specific cellular immune response. Moreover, both the leishmanin skin test and the IFN-γ levels displayed negative correlations with serological, parasitological and clinical signs. Further studies to determine the functional role of vitamin D on the progression and control of canine leishmaniasis are needed.

Evaluation of VDR gene polymorphisms in Trypanosoma cruzi infection and chronic Chagasic cardiomyopathy

Vitamin D is an important modulator of the immune response. It acts over several immune cell types where the Vitamin D receptor (VDR) is expressed. Due to the high relevance of this signaling pathway, several studies have investigated the possible influence of genes involved in the metabolism of Vitamin D and its receptor in different human diseases. Here, we analyzed whether four single-nucleotide polymorphisms of the VDR gene (rs731236, rs7975232, rs1544410 and rs2228570) are involved in the susceptibility to infection by Trypanosoma cruzi and/or to chronic Chagas cardiomyopathy (CCC) in a Colombian endemic population for this parasite. Our results showed that the rs2228570*A allele is associated with CCC development (P = 4.46E-03, OR = 1.51). In summary, the data presented in this report suggest that variation within the VDR gene may affect the immune response against T. cruzi, increasing the probability of cardiac complications in infected individuals.

Role of vitamin D in cytotoxic T lymphocyte immunity to pathogens and cancer

The discovery of vitamin D receptor (VDR) expression in immune cells has opened up a new area of research into immunoregulation by vitamin D, a niche that is distinct from its classical role in skeletal health. Today, about three decades since this discovery, numerous cellular and molecular targets of vitamin D in the immune system have been delineated. Moreover, strong clinical associations between vitamin D status and the incidence/severity of many immune-regulated disorders (e.g. infectious diseases, cancers and autoimmunity) have prompted the idea of using vitamin D supplementation to manipulate disease outcome. While much is known about the effects of vitamin D on innate immune responses and helper T (T(H)) cell immunity, there has been relatively limited progress on the frontier of cytotoxic T lymphocyte (CTL) immunity--an arm of host cellular adaptive immunity that is crucial for the control of such intracellular pathogens as human immunodeficiency virus (HIV), tuberculosis (TB), malaria, and hepatitis C virus (HCV). In this review, we discuss the strong historical and clinical link between vitamin D and infectious diseases that involves cytotoxic T lymphocyte (CTL) immunity, present our current understanding as well as critical knowledge gaps in the realm of vitamin D regulation of host CTL responses, and highlight potential regulatory connections between vitamin D and effector and memory CD8 T cell differentiation events during infections.

Vitamin D every day to keep the infection away?

Within the last decade, vitamin D has emerged as a central regulator of host defense against infections. In this regard, vitamin D triggers effective antimicrobial pathways against bacterial, fungal and viral pathogens in cells of the human innate immune system. However, vitamin D also mediates potent tolerogenic effects: it is generally believed that vitamin D attenuates inflammation and acquired immunity, and thus potentially limits collateral tissue damage. Nevertheless, several studies indicate that vitamin D promotes aspects of acquired host defense. Clinically, vitamin D deficiency has been associated with an increased risk for various infectious diseases in epidemiological studies; yet, robust data from controlled trials investigating the use of vitamin D as a preventive or therapeutic agent are missing. In this review, we summarize the current knowledge regarding the effect of vitamin D on innate and acquired host defense, and speculate on the difficulties to translate the available molecular medicine data into practical therapeutic or preventive recommendations.

The role of vitamin D in the control of Leishmania infection

Vitamin D has been described as an essential element for maintaining the homeostasis of mineral content in the body and bone architecture. However, our view of the physiological functions of this micronutrient has radically changed, owing to the vast number of properties, not calcium-related, mediated by its nuclear receptor. This receptor has been found in a variety of cells, including the immune cells, where many of the functions performed by vitamin D are related to inflammation. Although the effect of vitamin D has been widely studied in many diseases caused by viruses or bacteria, very little is known about its role in parasitic diseases, such as leishmaniasis, which is a vector-borne disease caused by different species of the intracellular parasite Leishmania spp. This disease occurs as a spectrum of different clinical syndromes, all of them characterized by a large amount of tissue damage, sometimes leading to necrosis. Owing to the involvement of vitamin D in inflammation and wound healing, its role in leishmaniasis must be relevant, and could be used as an adjuvant for the control of this parasitic disease, opening a possibility for a therapeutic application.

Association of Taq I, Fok I and Apa I polymorphisms in Vitamin D Receptor (VDR) gene with leprosy

BACKGROUND

Vitamin D Receptor (VDR) is a transacting transcription factor which mediates immunomodulatory function and plays a key role in innate and adaptive immune responses through its ligand and polymorphisms in VDR gene may affect its regulatory function.

OBJECTIVE

To investigate the association of three VDR gene polymorphisms (TaqI rs731236, FokI rs2228570 and ApaI rs7975232) with leprosy.

METHODS

The study group includes 404 participants of which 222 were leprosy patients (paucibacillary=87, multibacillary=135) and 182 healthy controls. Genotyping was done using PCR-RFLP technique. Statistical analysis was performed using SNP Stats and PLINK software.

RESULTS

The VDR FokI (rs2228570) ff genotype, ApaI (rs7975232) AA, Aa genotype and haplotype T-f-a, T-F-A were positively associated with leprosy when compared to healthy controls.

CONCLUSION

The two variants at Fok and Apa positions in VDR gene are significantly associated with leprosy. Genotypes at FokI (ff), ApaI (aa) and haplotype (T-F-a, T-f-a) may contribute to the risk of developing leprosy by altering VDR phenotype/levels subsequently modulation of immune response.

Vitamin D and inflammatory diseases

Beyond its critical function in calcium homeostasis, vitamin D has recently been found to play an important role in the modulation of the immune/inflammation system via regulating the production of inflammatory cytokines and inhibiting the proliferation of proinflammatory cells, both of which are crucial for the pathogenesis of inflammatory diseases. Several studies have associated lower vitamin D status with increased risk and unfavorable outcome of acute infections. Vitamin D supplementation bolsters clinical responses to acute infection. Moreover, chronic inflammatory diseases, such as atherosclerosis-related cardiovascular disease, asthma, inflammatory bowel disease, chronic kidney disease, nonalcoholic fatty liver disease, and others, tend to have lower vitamin D status, which may play a pleiotropic role in the pathogenesis of the diseases. In this article, we review recent epidemiological and interventional studies of vitamin D in various inflammatory diseases. The potential mechanisms of vitamin D in regulating immune/inflammatory responses in inflammatory diseases are also discussed.

A transcriptomic network identified in uninfected macrophages responding to inflammation controls intracellular pathogen survival

Intracellular pathogens modulate host cell function to promote their survival. However, in vitro infection studies do not account for the impact of host-derived inflammatory signals. Examining the response of liver-resident macrophages (Kupffer cells) in mice infected with the parasite Leishmania donovani, we identified a transcriptomic network operating in uninfected Kupffer cells exposed to inflammation but absent from Kupffer cells from the same animal that contained intracellular Leishmania. To test the hypothesis that regulated expression of genes within this transcriptomic network might impact parasite survival, we pharmacologically perturbed the activity of retinoid X receptor alpha (RXRα), a key hub within this network, and showed that this intervention enhanced the innate resistance of Kupffer cells to Leishmania infection. Our results illustrate a broadly applicable strategy for understanding the host response to infection in vivo and identify Rxra as the hub of a gene network controlling antileishmanial resistance.

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Leishmania infection rapidly activates infected and uninfected Kupffer cells in mice

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Transcriptomics of inflamed and infected KC uncover distinct and overlapping networks

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A network centered on RXRα is uniquely activated in inflammation-exposed uninfected KCs

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Manipulation of RXRα function leads to a reduction in early parasite burden

The vitamin D receptor turns off chronically activated T cells

T cell proliferation and T helper (TH ) cells that make IL-17 (TH 17 cells) and IFN-γ (TH 1 cells) have been shown to be inhibited by 1,25(OH)2 D3 . Previous work has shown that immune-mediated diseases, where TH 1 and TH 17 cells are pathogenic, are ameliorated with 1,25(OH)2 D3 treatment. Paradoxically, infectious diseases that require TH 1 and TH 17 responses for host resistance are unaffected by 1,25(OH)2 D3 treatment. Resting T cells are not responsive to vitamin D because they do not express the vitamin D receptor (VDR) until late after activation. T cells activated following an infection help clear the infection, and since the antigen is eliminated, vitamin D is not needed to dampen the immune response. Conversely, in immune-mediated disease, there is chronic T cell activation, and in this scenario, vitamin D and 1,25(OH)2 D3 are critical for inhibiting T cell proliferation and cytokine production. Vitamin D is a late regulator of T cell function and acts to turn off T cells. This paper will review these data.

Post kala-azar dermal leishmaniasis: an unresolved mystery

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Sodium antimony gluconate contributes towards the pathogenesis of PKDL.

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UV light plays a pivotal role in the development of PKDL.

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Development of PKDL can be viewed as a reinfection or activation of latent Leishmania parasites.

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PKDL can be resolved by mounting an effective tissue-specific memory T cell response.

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Host genetic factors play a contributory role.

Post kala-azar dermal leishmaniasis (PKDL), a cutaneous sequela of visceral leishmaniasis (VL), develops in some patients alongside but more commonly after apparent cure from VL. In view of the pivotal role of PKDL patients in the transmission of VL, here we review clinical, epidemiological, parasitological, and immunological perspectives of this disease, focusing on five hypotheses to explain the development of PKDL: (i) the role of antimonial drugs; (ii) UV-induced skin damage; (iii) reinfection; (iv) organ specific failure of memory T cell responses; and (v) genetic susceptibility of the host. This review will enable researchers and clinicians to explore the unresolved mystery of PKDL and provide a framework for future application of ‘omic’ approaches for the control and eventual elimination of VL.

Effect of 1,25(OH)2D3 on BALB/c mice infected with Leishmania mexicana

The most active metabolite of vitamin D, 1,25(OH)2D3 is a steroid hormone implicated in a wide range of cell functions such as differentiation, proliferation and apoptosis. Leishmania mexicana causes two kinds of cutaneous leishmaniasis: localized or diffuse. In this work we explored the effect of treatment of 1,25(OH)2D3 on a susceptible leishmaniasis mice model. A significant reduction in the lesion size was found in animals treated with 1,25(OH)2D3. Well preserved tissue and presence of large numbers of eosinophils and fibroblasts was found in the group treated with 1,25(OH)2D3. By contrast, destroyed epidermis was observed with large amount of neutrophils and epithelioid macrophages, on infected groups without 1,25(OH)2D3 treatment. The production of pro-inflammatory cytokines in mice infected and treated with 1,25(OH)2D3 was lower than the animals infected without 1,25(OH)2D3 treatment. Interestingly, there were no differences in the number of parasites in both groups. Finally, the amount of collagen was higher in animals with treatment compare with animals without 1,25(OH)2D3 treatment. In summary, mice treated with 1,25 (OH) 2D3 reflect a healing process without elimination of L. mexicana.

Testing in mice the hypothesis that melanin is protective in malaria infections

Malaria has had the largest impact of any infectious disease on shaping the human genome, exerting enormous selective pressure on genes that improve survival in severe malaria infections. Modern humans originated in Africa and lost skin melanization as they migrated to temperate regions of the globe. Although it is well documented that loss of melanization improved cutaneous Vitamin D synthesis, melanin plays an evolutionary ancient role in insect immunity to malaria and in some instances melanin has been implicated to play an immunoregulatory role in vertebrates. Thus, we tested the hypothesis that melanization may be protective in malaria infections using mouse models. Congenic C57BL/6 mice that differed only in the gene encoding tyrosinase, a key enzyme in the synthesis of melanin, showed no difference in the clinical course of infection by Plasmodium yoelii 17XL, that causes severe anemia, Plasmodium berghei ANKA, that causes severe cerebral malaria or Plasmodium chabaudi AS that causes uncomplicated chronic disease. Moreover, neither genetic deficiencies in vitamin D synthesis nor vitamin D supplementation had an effect on survival in cerebral malaria. Taken together, these results indicate that neither melanin nor vitamin D production improve survival in severe malaria.