All-trans retinoic acid biases immune response induced by DNA vaccine in a Th2 direction

The effect of calcitriol and all-trans retinoic acid on T-bet, IFN-γ, GATA3 and IL-4 genes expression in experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an immune-mediated inflammatory disease which affects the central nervous system (CNS). In the present study, the in vivo effects of ATRA, calcitriol, and their combinations on the expression of murine CD4+ T cell cytokines and their specific transcription factors in experimental autoimmune encephalomyelitis (EAE)-induced mice were explored. Thirty-two EAE induced inbred C57BL/6 female mice with an age ranged from 8 to 10 weeks were divided into four categories in a random manner. The first, second, and third groups received ATRA, calcitriol, ATRA+ calcitriol, respectively, and the fourth group received vehicle. The treatment started on the day prior to immunization and through the IP injections every other days for 21 days. The dosages of administration for calcitriol, ATRA, and calcitriol+ ATRA were 100 ng, 250 μg, and 50ng + 125 μg, respectively per mouse. An equal volume of excipient was administered for the vehicle group. T-bet, IFN-γ, GATA-3, and IL-4 genes expression were assessed in the splenocytes of EAE -induced mice. The expression of T-bet and IFN-γ genes in the splenocytes of ATRA, calcitriol and combination- treated mice were significantly reduced compared to vehicle group (p < 0.05). A significant decrease in T-bet expression was observed in the combination-treated group compared to the ATRA-treated group (p < 0.05). The expression of GATA3 and IL-4 genes was significantly increased in the ATRA-, calcitriol-, and combination-treated mice when compared with the control group (p < 0.05). Furthermore, the effect of calcitriol alone and in combination with ATRA was more considerable than that of ATRA alone. The nutraceutical approaches may be promising in the prevention and/or treatment of MS.

Potential role of nuclear receptor ligand all-trans retinoic acids in the treatment of fungal keratitis

Fungal keratitis (FK) is a worldwide visual impairment disease. This infectious fungus initiates the primary innate immune response and, later the adaptive immune response. The inflammatory process is related to a variety of immune cells, including macrophages, helper T cells, neutrophils, dendritic cells, and Treg cells, and is associated with proinflammatory, chemotactic and regulatory cytokines. All-trans retinoic acids (ATRA) have diverse immunomodulatory actions in a number of inflammatory and autoimmune conditions. These retinoids regulate the transcriptional levels of target genes through the activation of nuclear receptors. Retinoic acid receptor α (RAR α), retinoic acid receptor γ (RAR γ), and retinoid X receptor α (RXR α) are expressed in the cornea and immune cells. This paper summarizes new findings regarding ATRA in immune and inflammatory diseases and analyzes the perspective application of ATRA in FK.

Immunomodulatory properties of vitamins, flavonoids and plant oils and their potential as vaccine adjuvants and delivery systems

INTRODUCTION

During the past century, vaccinologists have attempted to mimic pathogens in their immune-enhancing capacity. This led to the development of life-saving vaccines based on live attenuated viruses, bacteria and toxoids. Hence, intense research in vaccine adjuvant discovery has focused on toll like receptors, mutant toxins and viral and bacterial vectors. Nutritive components such as vitamins and select polyphenols also possess immunomodulating properties without the potential toxic and adverse side effects of agents that mimic danger signals.

AREAS COVERED

This review pertains to immunomodulatory properties of nutritive components, that is vitamins A, C, D, E, flavonoids and plant oils, as potential vaccine adjuvants and delivery systems, covering Pubmed publication searches from 1980 through 2011.

EXPERT OPINION

This relatively unexplored field of the potential of nutritive components as vaccine adjuvants holds great promise to promote the development of effective and above all safe vaccines. Hence the future focus should be placed on enhancing their efficacy, mainly through novel approaches in designing structural derivatives, formulations, delivery systems and routes of administration. As safety has been the major issue in development of novel vaccines, this new approach will probably result in new discoveries in designing safe and effective vaccines.

A novel retinoic acid, catechin hydrate and mustard oil-based emulsion for enhanced cytokine and antibody responses against multiple strains of HIV-1 following mucosal and systemic vaccinations

Non-replicating protein- or DNA-based antigens generally require immune-enhancing adjuvants and delivery systems. It has been particularly difficult to raise antibodies against gp120 of HIV-1, which constitutes an important approach in HIV vaccine design. While almost all effort in adjuvant research has focused on mimicking the pathogens and the danger signals they engender in the host, relatively little effort has been spent on nutritive approaches. In this study, a new nutritive immune-enhancing delivery system (NIDS) composed of vitamin A, a polyphenol-flavonoid, catechin hydrate, and mustard oil was tested for its adjuvant effect in immune responses against the gp120 protein of HIV-1(CN54). Following a combination of two mucosal and two systemic vaccinations of mice, we found significant enhancement of both local and systemic antibodies as well as cytokine responses. These data have important implications for vaccine and adjuvant design against HIV-1 and other pathogens.

Human basophils activated by mast cell–derived IL-3 express retinaldehyde dehydrogenase-II and produce the immunoregulatory mediator retinoic acid

The vitamin A metabolite retinoic acid (RA) plays a fundamental role in cellular functions by activating nuclear receptors. Retinaldehyde dehydrogenase-II (RALDH2) creates localized RA gradients needed for proper embryonic development, but very little is known regarding its regulated expression in adults. Using a human ex vivo model of aller-gic inflammation by coincubating IgE receptor–activated mast cells (MCs) with blood basophils, we observed prominent induction of a protein that was identified as RALDH2 by mass spectroscopy. RALDH2 was selectively induced in basophils by MC-derived interleukin-3 (IL-3) involving PI3-kinase and NF-κB pathways. Importantly, neither constitutive nor inducible RALDH2 expression was detectable in any other human myeloid or lymphoid leukocyte, including dendritic cells. RA generated by RALDH2 in basophils modulates IL-3–induced gene expression in an autocrine manner, providing positive (CD25) as well as negative (granzyme B) regulation. It also acts in a paracrine fashion on T-helper cells promoting the expression of CD38 and α4/β7 integrins. Furthermore, RA derived from IL-3–activated basophils provides a novel mechanism of Th2 polarization. Thus, RA must be viewed as a tightly controlled basophil-derived mediator with a high potential for regulating diverse functions of immune and resident cells in allergic diseases and other Th2-type immune responses.

Combination of physical activity, nutrition, or other metabolic factors and vaccine response

A number of lifestyle factors that reduce cancer risk in the primary prevention setting may be potential new targets for use in combination with cancer vaccines. This review discusses the modulation of energy balance (physical activity, calorie restriction, and obesity prevention), and the supplementation with natural and synthetic analogs of vitamins A and E, as potential interventions for use in combination with cancer vaccines. Additionally, the pharmacologic manipulation of nutrient metabolism in the tumor microenvironment (e.g., arachidonic acid, arginine, tryptophan, and glucose metabolism) is discussed. This review includes a brief overview of the role of each agent in primary cancer prevention; outlines the effects of these agents on immune function, specifically adaptive and/or anti-tumor immune mechanisms, when known; and discusses the potential use of these interventions in combination with therapeutic cancer vaccines. Modulation of energy balance through exercise and strategies targeting nutrient metabolism in the tumor microenvironment represent the most promising interventions to partner with therapeutic cancer vaccines. Additionally, the use of vitamin E succinate and the retinoid X receptor-directed rexinoids in combination with cancer vaccines offer promise. In summary, a number of energy balance- and nutrition-related interventions are viable candidates for further study in combination with cancer vaccines.

Disease manifestations of canine distemper virus infection in ferrets are modulated by vitamin A status

The measles virus (MV) causes half a million childhood deaths annually. Vitamin A supplements significantly reduce measles-associated mortality and morbidity. The mechanisms whereby vitamin A acts against MV are not understood and currently there is no satisfactory small animal model for MV infection. We report on the development of a ferret model to study antiviral activity of vitamin A against canine distemper virus (CDV). CDV is closely related to MV at the molecular level and distemper in ferrets mimics measles in humans. We infected vitamin A-replete (control) and vitamin A-depleted ferrets with CDV and assessed the ability of high-dose vitamin A supplements to influence CDV disease. In control ferrets, CDV infection caused fever, rash, conjunctivitis, cough, coryza, and diarrhea. In contrast, control ferrets that were given 30 mg of vitamin A did not develop typical distemper after infection and exhibited only a mild rash. The supplement did not negatively affect ferret health and resulted in a 100% increase in serum and liver vitamin A concentrations. We also found that profound vitamin A deficiency is inducible in ferrets and can be rapidly reversed upon high-dose vitamin A supplementation. Vitamin A deficiency caused anorexia, diarrhea, cataracts, behavioral abnormalities, and ultimately death, with or without CDV infection. All ferrets that received vitamin A supplements, however, recovered uneventfully from CDV infection. These results replicate many aspects of the observations of vitamin A therapy in humans with measles and suggest that CDV infection in ferrets is an appropriate model for the study of the antiviral mechanism of vitamin A.

The distinct effects of three tandem repeats of C3d in the immune responses against tumor-associated antigen hCGbeta by DNA immunization

Several examples have shown that C3d3, when fused to a corresponding antigen, had a strong adjuvant effect on certain specific antibody production. In a previous study, we attempted to prove that this was the case of the human chorionic gonadotrophin beta chain (hCGbeta)-induced immunity following DNA vaccination. However, we found that C3d3 when fused to hCGbeta inhibited rather than enhanced the antigen-specific immune response. In the present study, using hCGbeta DNA vaccine preparations, we demonstrated that C3d3 inhibited the antigen-specific humoral antibody response and several other immune responses, such as the hCGbeta specific lymphoproliferation. Such inhibitory effects of C3d3 were not related to the expression level of the target protein, the gender of the test mice, or the vector used. Contrastingly, C3d3 fused with the envelope protein of hepatitis B virus (PreS2/S) used as a control system resulted in the enhancement of both humoral and cell-mediated antigen-specific immune responses against HBV-preS2/S, which was consistent with other groups' adjuvant-effect findings. We further showed that the mechanisms involved in the inhibitory effect of C3d3 might be possible due to impairing the function of antigen presenting B lymphocytes and reducing the expression of transcription factors (T-bet and GATA-3) and cytokine IL-4. Collectively, unlike its usual expected adjuvant function, the fusion of C3d3 with the tumor-associated antigen hCGbeta was found to inhibit both humoral and cell-mediated antigen-specific immune responses. These findings indicate that research concerning tumor immune escapes and vaccine designs require further extensive attention.

Vitamin A supplementation and retinoic acid treatment in the regulation of antibody responses in vivo

Vitamin A (VA, retinol) is essential for normal immune system maturation, but the effect of VA(1) on antibody production, the hallmark of successful vaccination, is still not well understood. In countries where VA deficiency is a public health problem, many children worldwide are now receiving VA along with immunizations against poliovirus, measles, diphtheria, pertussis, and tetanus. The primary goal has been to provide enough VA to protect against the development of VA deficiency for a period of 4-6 months. However, it is also possible that VA might promote the vaccine antibody response. Several community studies, generally of small size, have been conducted in children supplemented with VA at the time of immunization, as promoted by the World Health Organization/UNICEF. However, only a few studies have reported differences in antibody titers or seroconversion rates due to VA. However, VA status was not directly assessed, and in some communities children were often breast fed, another strategy for preventing VA deficiency. Some of the vaccines used induced a high rate of seroconversion, even without VA. In children likely to have been VA deficient, oral polio vaccine seroconversion rate was increased by VA. In animal models, where VA status was controlled and VA deficiency confirmed, the antibody response to T-cell-dependent (TD) and polysaccharide antigens was significantly reduced, congruent with other defects in innate and adaptive immunity. Moreover, the active metabolite of VA, retinoic acid (RA) can potentiate antibody production to TD antigens in normal adult and neonatal animals. We speculate that numerous animal studies have correctly identified VA deficiency as a risk factor for low antibody production. A lack of effect of VA in human studies could be due to a low rate of VA deficiency in the populations studied or low sample numbers. The ability to detect differences in antibody response may also depend on the vaccine-adjuvant combination used. Future studies of VA supplementation and immunization should include assessment of VA status and a sufficiently large sample size. It would also be worthwhile to test the effect of neonatal VA supplementation on the response to immunization given after 6 months to 1 year of age, as VA supplementation, by preventing the onset of VA deficiency, may improve the response to immunizations given later on.

All-trans retinoic acid negatively regulates cytotoxic activities of nature killer cell line 92

NK cells are key components of innate immune systems and their activities are regulated by cytokines and hormones. All-trans retinoic acid (ATRA), as a metabolite of vitamin A and an immunomodulatory hormone, plays an important role in regulating immune responses. In the present study, we investigated the effect of ATRA on human NK cell line NK92. We found that ATRA dose-dependently suppressed cytotoxic activities of NK92 cells without affecting their proliferation. To explore the mechanisms underlying the ATRA influence on NK92 cells, we examined the production of cytokines (TNF-alpha, IFN-gamma), gene expression of cytotoxic-associated molecules (perforin, granzyme B, nature killer receptors (NCRs), and NKG2D), and the activation of NF-kappaB pathways related with immune response. Our results demonstrated that ATRA suppressed NF-kappaB activity and prevented IkappaBalpha degradation in a dose-dependent way, inhibited IFN-gamma production and gene expression of granzyme B and NKp46. Our findings suggest that ATRA is a negative regulator of NK92 cell activation and may act as a potential regulator of anti-inflammatory functions in vivo.