Novel aggregate structure adjuvants modulate lymphocyte proliferation and Th1 and Th2 cytokine profiles in ovalbumin immunized mice

The steroidal alkaloids α-tomatine and tomatidine: Panorama of their mode of action and pharmacological properties

The steroidal glycoalkaloid α-tomatine (αTM) and its aglycone tomatidine (TD) are abundant in the skin of unripe green tomato and present in tomato leaves and flowers. They mainly serve as defensive agents to protect the plant against infections by insects, bacteria, parasites, viruses, and fungi. In addition, the two products display a range of pharmacological properties potentially useful to treat various human diseases. We have analyzed all known pharmacological activities of αTM and TD, and the corresponding molecular targets and pathways impacted by these two steroidal alkaloids. In experimental models, αTM displays anticancer effects, particularly strong against androgen-independent prostate cancer, as well as robust antifungal effects. αTM is a potent cholesterol binder, useful as a vaccine adjuvant to improve delivery of protein antigens or therapeutic oligonucleotides. TD is a much less cytotoxic compound, able to restrict the spread of certain viruses (such as dengue, chikungunya and porcine epidemic diarrhea viruses) and to provide cardio and neuro-protective effects toward human cells. Both αTM and TD exhibit marked anti-inflammatory activities. They proceed through multiple signaling pathways and protein targets, including the sterol C24 methyltransferase Erg6 and vitamin D receptor, both directly targeted by TD. αTM is a powerful regulator of the NFkB/ERK signaling pathway implicated in various diseases. Collectively, the analysis shed light on the multitargeted action of αTM/TD and their usefulness as chemo-preventive or chemotherapeutic agents. A novel medicinal application for αTM is proposed.

Toxicity And Surface Modification Of Dendrimers: A Critical Review

As compared to other nano polymers, dendrimers have novel three dimensional, synthetic hyperbranched, nano-polymeric structures. The characteristic of these supramolecular dendritic structures has a high degree of significant surface as well as core functionality in the transportation of drugs for targeted therapy, specifically in host-guest response, gene transfer therapy and imaging of biological systems. However, there are conflicting shreds of evidence regarding biological safety and dendrimers toxicity due to their positive charge at the surface. It includes cytotoxicity, hemolytic toxicity, haematological toxicity, immunogenicity and in vivo toxicity. Therefore to resolve these problems surface modification of the dendrimer group is one of the methods. From that point, this review involves different strategies which reduce the toxicity and improve the biocompatibility of different types of dendrimers. From that viewpoint, we broaden the structural and safe characteristics of the dendrimers in the biomedical and pharmaceutical fields.

Antioxidants in Potatoes: A Functional View on One of the Major Food Crops Worldwide

With a growing world population, accelerating climate changes, and limited arable land, it is critical to focus on plant-based resources for sustainable food production. In addition, plants are a cornucopia for secondary metabolites, of which many have robust antioxidative capacities and are beneficial for human health. Potato is one of the major food crops worldwide, and is recognized by the United Nations as an excellent food source for an increasing world population. Potato tubers are rich in a plethora of antioxidants with an array of health-promoting effects. This review article provides a detailed overview about the biosynthesis, chemical and health-promoting properties of the most abundant antioxidants in potato tubers, including several vitamins, carotenoids and phenylpropanoids. The dietary contribution of diverse commercial and primitive cultivars are detailed and document that potato contributes much more than just complex carbohydrates to the diet. Finally, the review provides insights into the current and future potential of potato-based systems as tools and resources for healthy and sustainable food production.

Glycoalkaloids: Structure, Properties, and Interactions with Model Membrane Systems

The glycoalkaloids which are secondary metabolites from plants have proven to be of significant interest for their biological properties both in terms of their roles in plant biology and the effects they exhibit when ingested by humans. The main feature of the action of glycoalkaloids is their strong binding to 3β-hydroxysterols, such as cholesterol, to form complexes with the consequence that membrane structure is significantly perturbed, and leakage or release of contents inside cells or liposomes becomes possible. The glycoalkaloids have been studied for their ability to inhibit the growth of cancer cells and in other roles such as vaccine adjuvants and as synergistic agents when combined with other therapeutics. The glycoalkaloids have rich and complex physical behavior when interacting with model membranes for which many aspects are yet to be understood. This review introduces the general properties of glycoalkaloids and aspects of their behavior, and then summarizes their effects against model membrane systems. While there are many glycoalkaloids that have been identified, most physical or biological studies have focused on the readily available ones from tomatoes (α-tomatine), potatoes (α-chaconine and α-solanine), and eggplant (α-solamargine and α-solasonine).

Assessment of interactions of efavirenz solid drug nanoparticles with human immunological and haematological systems

Background

Recent work has developed solid drug nanoparticles (SDNs) of efavirenz that have been demonstrated, preclinically, improved oral bioavailability and the potential to enable up to a 50% dose reduction, and is currently being studied in a healthy volunteer clinical trial. Other SDN formulations are being studied for parenteral administration, either as intramuscular long-acting formulations, or for direct administration intravenously. The interaction of nanoparticles with the immunological and haematological systems can be a major barrier to successful translation but has been understudied for SDN formulations. Here we have conducted a preclinical evaluation of efavirenz SDN to assess their potential interaction with these systems. Platelet aggregation and activation, plasma coagulation, haemolysis, complement activation, T cell functionality and phenotype, monocyte derived macrophage functionality, and NK cell function were assessed in primary healthy volunteer samples treated with either aqueous efavirenz or efavirenz SDN.

Results

Efavirenz SDNs were shown not to interfere with any of the systems studied in terms of immunostimulation nor immunosuppression. Although efavirenz aqueous solution was shown to cause significant haemolysis ex vivo, efavirenz SDNs did not. No other interaction with haematological systems was observed. Efavirenz SDNs have been demonstrated to be immunologically and haematologically inert in the utilised assays.

Conclusions

Taken collectively, along with the recent observation that lopinavir SDN formulations did not impact immunological responses, these data indicate that this type of nanoformulation does not elicit immunological consequences seen with other types of nanomaterial. The methodologies presented here provide a framework for pre-emptive preclinical characterisation of nanoparticle safety.

Electronic supplementary material

The online version of this article (10.1186/s12951-018-0349-y) contains supplementary material, which is available to authorized users.

Determining the relationship between nanoparticle characteristics and immunotoxicity: key challenges and approaches

The growing wealth of information regarding the influence that physicochemical characteristics play on nanoparticle biocompatibility and safety is allowing improved design and rationale for their development and preclinical assessment. Accurate and appropriate measurement of these characteristics accompanied by informed toxicological assessment is a necessity for the development of safe and effective nanomedicines. While particle type, formulation and mode of administration dictate the individual causes for concern through development, the benefits of nanoformulation for treatment of the diseased state are great. Here we have proposed certain considerations and suggestions, which could lead to better-informed preclinical assessment of nanomaterials for nanomedicine, as well as how this information can and should be extrapolated to the physiological state of the end user.

Cytokines as biomarkers of nanoparticle immunotoxicity

Nanoscale objects, whether of biologic origin or synthetically created, are being developed into devices for a variety of bionanotechnology diagnostic and pharmaceutical applications. However, the potential immunotoxicity of these nanomaterials and mechanisms by which they may induce adverse reactions have not received sufficient attention. Nanomaterials, depending on their characteristics and compositions, can interact with the immune system in several ways and either enhance or suppress immune system function. Cytokines perform pleiotropic functions to mediate and regulate the immune response and are generally recognized as biomarkers of immunotoxicity. While the specificity and validity of certain cytokines as markers of adverse immune response has been established for chemicals, small and macromolecular drugs, research on their applicability for predicting and monitoring the immunotoxicity of engineered nanomaterials is still ongoing. The goal of this review is to provide guidelines as to important cytokines that can be utilized for evaluating the immunotoxicity of nanomaterials and to highlight the role of those cytokines in mediating adverse reactions, which is of particular importance for the clinical development of nanopharmaceuticals and other nanotechnology-based products. Importantly, the rational design of nanomaterials of low immunotoxicity will be discussed, focusing on synthetic nanodevices, with emphasis on both the nanoparticle-forming materials and the embedded cargoes.

A long-term comparison of the influence of organic and conventional crop management practices on the content of the glycoalkaloid α-tomatine in tomatoes

BACKGROUND

α-Tomatine, synthesized by Lycopersicon and some Solanum species, is a steroidal glycoalkaloid which functions to protect against pathogens and insects. Although glycoalkaloids are generally considered toxic, α-tomatine appears to be well tolerated in humans. α-Tomatine has numerous potential health benefits including the ability to inhibit cancer cell growth in in vitro studies. α-Tomatine is influenced by numerous agronomic factors including fertilization and nitrogen availability. Herein, the levels of α-tomatine were compared in dried tomato samples (Lycopersicon esculentum L. cv. Halley 3155) produced in organic and conventional cropping systems that had been archived over the period from 1994 to 2004 from the Long Term Research on Agricultural Systems project (LTRAS) at UC Davis.

RESULTS

The α-tomatine levels of tomatoes in both cropping systems ranged from 4.29 to 111.85 µg g(-1) dry weight. Mean levels of α-tomatine were significantly higher in the organically grown tomatoes than conventional ones (P < 0.001). In the organic management system, α-tomatine content was also significantly (P < 0.001) different between cropping years, suggesting that other influencing factors such as environmental conditions also affect α-tomatine content in tomato.

CONCLUSIONS

The organically produced tomatoes had higher average α-tomatine content than their conventional counterpart over the 10-year study. Significant annual variability in the α-tomatine content in tomatoes was also observed and suggests that environmental factors, external to nitrogen fertilization, influence α-tomatine content in tomatoes.

Challenges for nanoparticle characterization

The Food and Drug Administration (FDA) and pharmaceutical industry have used standards to assess material biocompatibility, immunotoxicity, purity, and sterility (as well as many other properties) for several decades. Nanoparticle developers and manufacturers leverage well-established methods as much as possible. However, the unique properties of nanomaterials often interfere with standardized protocols, giving false-positive or false-negative results. This chapter provides details of some of the problems which can arise during the characterization of nanoparticle samples. Additionally, we discuss ways to identify, avoid, and resolve such interference, with emphasis on the use of inhibition and enhancement controls.

Tomatine adjuvantation of protective immunity to a major pre-erythrocytic vaccine candidate of malaria is mediated via CD8+ T cell release of IFN-gamma

The glycoalkaloid tomatine, derived from the wild tomato, can act as a powerful adjuvant to elicit an antigen-specific cell-mediated immune response to the circumsporozoite (CS) protein, a major pre-erythrocytic stage malaria vaccine candidate antigen. Using a defined MHC-class-I-restricted CS epitope in a Plasmodium berghei rodent model, antigen-specific cytotoxic T lymphocyte activity and IFN-γ secretion ex vivo were both significantly enhanced compared to responses detected from similarly stimulated splenocytes from naive and tomatine-saline-immunized mice. Further, through lymphocyte depletion it is demonstrated that antigen-specific IFN-γ is produced exclusively by the CD8⁺ T cell subset. We conclude that the processing of the P. berghei CS peptide as an exogenous antigen and its presentation via MHC class I molecules to CD8⁺ T cells leads to an immune response that is an in vitro correlate of protection against pre-erythrocytic malaria. Further characterization of tomatine as an adjuvant in malaria vaccine development is indicated.

Dendrimers for vaccine and immunostimulatory uses. A review

Dendrimers are well-defined (monodisperse) synthetic globular polymers with a range of interesting chemical and biological properties. Chemical properties include the presence of multiple accessible surface functional groups that can be used for coupling biologically relevant molecules and methods that allow for precise heterofunctionalization of surface groups. Biologically, dendrimers are highly biocompatible and have predictable biodistribution and cell membrane interacting characteristics determined by their size and surface charge. Dendrimers have optimal characteristics to fill the need for efficient immunostimulating compounds (adjuvants) that can increase the efficiency of vaccines, as dendrimers can provide molecularly defined multivalent scaffolds to produce highly defined conjugates with small molecule immunostimulators and/or antigens. The review gives an overview on the use of dendrimers as molecularly defined carriers/presenters of small antigens, including constructs that have built-in immunostimulatory (adjuvant) properties, and as stand-alone adjuvants that can be mixed with antigens to provide efficient vaccine formulations. These approaches allow the preparation of molecularly defined vaccines with highly predictable and specific properties and enable knowledge-based vaccine design substituting the traditional empirically based approaches for vaccine development and production.

Alpha-tomatine inactivates PI3K/Akt and ERK signaling pathways in human lung adenocarcinoma A549 cells: effect on metastasis

This study first investigates the anti-metastatic effect of alpha-tomatine in the human lung adenocarcinoma cell line: A549. In this study, we first noted alpha-tomatine inhibited A549 cells invasion and migration by wound-healing assay and Boyden chamber assay. The data also showed alpha-tomatine could inhibit phosphorylation of Akt and extracellular signal-regulated kinase 1 and 2 (ERK1/2), which is involved in the up-regulating matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9) or urokinase-type plasminogen activator (u-PA), whereas it did not affect phosphorylation of c-Jun N-terminal kinase (JNK) and p38. Next, alpha-tomatine significantly decreased the nuclear levels of nuclear factor kappa B (NF-kappaB), c-Fos, and c-Jun. Also, treating A549 cells with alpha-tomatine also leads to a dose-dependent inhibition on the binding abilities of NF-kappaB and activator protein-1 (AP-1). Further, the treatment of inhibitors specific for PI3K (Wortmannin) or ERK (U0126) to A549 cells could cause reduced activities of MMP-2, MMP-9, and u-PA. These results showed alpha-tomatine could inhibit the metastatic ability of A549 cells by reducing MMP-2, MMP-9, and u-PA activities through suppressing phosphoinositide 3-kinase/Akt (PI3K/Akt) or ERK1/2 signaling pathway and inhibition NF-kappaB or AP-1 binding activities. These findings proved alpha-tomatine might be an anti-metastatic agent against human lung adenocarcinoma.

Immunoinformatics: an overview of computational tools and techniques for understanding immune function

In recent years, there has been a rapid expansion in the application of information technology to biological data. Although the use of information science techniques is less common for the discipline of immunology, this field has seen great strides in recent years. This review addresses why in silico modeling is needed in immunology research, highlights some of the major areas of research and suggests what may be important for the future of immunoinformatics.

Immunological properties of engineered nanomaterials

Most research on the toxicology of nanomaterials has focused on the effects of nanoparticles that enter the body accidentally. There has been much less research on the toxicology of nanoparticles that are used for biomedical applications, such as drug delivery or imaging, in which the nanoparticles are deliberately placed in the body. Moreover, there are no harmonized standards for assessing the toxicity of nanoparticles to the immune system (immunotoxicity). Here we review recent research on immunotoxicity, along with data on a range of nanotechnology-based drugs that are at different stages in the approval process. Research shows that nanoparticles can stimulate and/or suppress the immune responses, and that their compatibility with the immune system is largely determined by their surface chemistry. Modifying these factors can significantly reduce the immunotoxicity of nanoparticles and make them useful platforms for drug delivery.

GRA1 protein vaccine confers better immune response compared to codon-optimized GRA1 DNA vaccine

The present study evaluates immunogenicity and protection potency of a codon-optimized GRA1 DNA vaccine, wild type GRA1 DNA vaccine and an adjuvanted recombinant GRA1 protein vaccine candidate in BALB/c mice against lethal toxoplasmosis. Of the three GRA1 vaccines tested, the recombinant GRA1 protein vaccine results reveal significant increase in immune response and prolonged survival against acute toxoplasmosis compared to DNA vaccinations. Immune response and protection conferred by codon-optimized GRA1 DNA vaccine was slightly better than wild type GRA1 DNA vaccine.

Tomato is a highly effective vehicle for expression and oral immunization with Norwalk virus capsid protein

Norwalk virus (NV) is an important agent of epidemic gastroenteritis, and an oral subunit vaccine shows potential for protection. Recombinant Norwalk virus (rNV) capsid protein expressed in plants assembles virus-like particles (VLPs) that are orally immunogenic in mice and humans. In this article we examine rNV expression in tomato and potato using a plant-optimized gene, and test the immunogenicity of dried tomato fruit and potato tuber fed to mice. The synthetic gene increased rNV expression fourfold in tomato and potato plants, which assembled VLP. Four doses of 0.4 g freeze-dried tomato fruit containing 64 microg rNV (40 microg VLPs) induced NV-specific serum IgG and mucosal IgA in > or = 80% of mice, while doses of 0.8 g elicited systemic and mucosal antibody responses in all mice. Feedings of 1 g freeze-dried potato tuber containing 120 microg rNV (90 microg VLPs) were required to produce 100% responsiveness. Oxidation of phenolic compounds upon rehydration of dried tuber caused significant VLP instability, thus decreasing immunogenicity. Air-dried tomato fruit stimulated stronger immune responses than freeze-dried fruit of the same mass, perhaps by limiting the destruction of plant cell matrix and membrane systems that occurs with freeze-drying. Thus, rNV in dried transgenic tomato fruit was a more potent immunogen than that in dried potato tubers, based on the total VLPs ingested. These findings support the use of stabilized, dried tomato fruit for oral delivery of subunit vaccines.

Transgenic expression of bean alpha-amylase inhibitor in peas results in altered structure and immunogenicity

The development of modern gene technologies allows for the expression of recombinant proteins in non-native hosts. Diversity in translational and post-translational modification pathways between species could potentially lead to discrete changes in the molecular architecture of the expressed protein and subsequent cellular function and antigenicity. Here, we show that transgenic expression of a plant protein (alpha-amylase inhibitor-1 from the common bean (Phaseolus vulgaris L. cv. Tendergreen)) in a non-native host (transgenic pea (Pisum sativum L.)) led to the synthesis of a structurally modified form of this inhibitor. Employing models of inflammation, we demonstrated in mice that consumption of the modified alphaAI and not the native form predisposed to antigen-specific CD4+ Th2-type inflammation. Furthermore, consumption of the modified alphaAI concurrently with other heterogeneous proteins promoted immunological cross priming, which then elicited specific immunoreactivity of these proteins. Thus, transgenic expression of non-native proteins in plants may lead to the synthesis of structural variants possessing altered immunogenicity.

The immunogenicity-enhancing effect of emulsion vaccine adjuvants is independent of the dispersion type and antigen release rate--a revisit of the role of the hydrophile-lipophile balance (HLB) value

Effective antigen delivery is one of the most important issues in vaccine development. It has been suggested that adjuvant action results from a depot effect by prolonging the duration of the interaction between antigen and cells, and thus is related to the antigen-releasing properties of emulsion adjuvants. The objective of this study was to investigate the effect of the dispersion properties of emulsion-type vaccine adjuvants on the immune response with the aim of optimizing vaccine adjuvant formulation. Emulsion-type adjuvants with various dispersion properties of either the oil-in-water or water-in-oil type were prepared using emulsifiers with various hydrophilic-hydrophobic balance (HLB) values. The physicochemical properties of the emulsions, including the conductivity and viscosity, and antigen release rates were then determined. Cell death induced by the vaccine adjuvants was examined in EL4 cells by Annexin V/propidium iodide (PI) staining and flow cytometric analysis. Mice were immunized with or without the adjuvants and the immunogenicity-enhancing effect of the adjuvants determined by measuring antibody production using an enzyme linked immunosorbent assay. The conductivity, viscosity, and antigen release rates varied widely among emulsions containing emulsifiers with different HLB values. However, the magnitude of the antigen-specific antibody response was similar in most emulsions adjuvants containing Spans or Tweens. L121-adjuvant, the control adjuvant inducing the strongest apoptosis in vitro, was shown to stimulate the highest antibody response in vivo. The results obtained in this study indicate that the immunogenicity-enhancing effect of emulsion adjuvants is independent of the dispersion type and the antigen release rate of the vaccine delivery system.

The apoptotic and necrotic effects of tomatine adjuvant

Tomatine adjuvant, consisting of tomatine, n-octyl-beta-d-glucopyranoside (OGP), phosphatidylethanolamine and cholesterol is unique in that when combined with soluble protein antigen it elicits a cytotoxic T lymphocyte (CTL) response in immunized animals. The mechanisms underlying this property are unknown. In an attempt to understand how tomatine activates cellular immunity, we examined its potential to induce apoptosis. Thus in the present study, cell death of EL4 thymoma cells induced by whole adjuvant and the surface-active components in the formulation was examined. Cytotoxicity was monitored using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] and lactate dehydrogenase release assays, apoptosis and necrosis were quantified by flow cytometry using Annexin V and propidium iodide staining, and morphology was examined by Hoechst 33342 staining. Flow cytometric analysis demonstrated the appearance of the sub-G1 phase in cells treated with these agents and Annexin V/PI staining showed that all three agents induced both apoptosis and necrosis in EL4 cells in a concentration-dependent manner. Tomatine was effective at much lower concentrations than OGP, suggesting that the majority of the effect of whole adjuvant could be attributed to this component. Microscopic examination of EL4 cells after treatment with these agents revealed morphological features of apoptosis, including chromatin condensation and DNA fragmentation. Pretreatment with zVAD-fmk did not block cell death induced by these agents, showing that tomatine adjuvant-induced EL4 cell apoptosis is caspase-independent.

Cell death induced by vaccine adjuvants containing surfactants

Many vaccine adjuvants contain surface-active agents, but the immunological roles played by these components have been essentially ignored. The objective of this study was to examine possible apoptotic and necrotic effects of the surface-active agents, Pluronic L121 and Tween 80, which are components of L121-adjuvant (a formulation we synthesized with the aim of representing several commercially produced adjuvants), on EL4 lymphoma cells. Cell viability and cytolytic effects were analyzed using the MTT and LDH release assays, and the distribution of cells in different stages of the cell cycle after treatment with these agents was analyzed by propidium iodide (PI) staining and flow cytometry. L121-adjuvant was shown to induce cell cycle arrest and inhibit cell proliferation. Treatment of EL4 cells with surface-active agents resulted in a concentration-dependent increase in the apoptotic/necrotic cell populations. Fluorescence microscopy using Hoechst 33342 staining demonstrated chromosome condensation and DNA fragmentation in cells treated with surfactants or adjuvant. The apoptotic and necrotic effects of vaccine adjuvant containing surface-active agents were confirmed by Annexin V/propidium iodide staining and flow cytometric analysis. Pretreatment of EL4 cells with zVAD-fmk, a broad range caspase inhibitor, partially prevented apoptosis induced by Pluronic L121, but did not prevent the cell death induced by Tween 80 or L121-adjuvant. These findings suggested that Tween 80 and L121-adjuvant induced apoptosis in EL4 cells via a "non-classical" caspase-independent pathway. Results presented in this study suggest mechanisms of elicitation of CD8(+), class I-restricted CTL response by soluble antigens mediated by the vaccine adjuvant containing surface-active agents.

Immunobiology of the Tomatine adjuvant

Soluble or sub-unit protein vaccines alone are incapable of generating antigen-specific cellular immune responses. This failure can be attributed to the manner in which the immune system processes antigen; endogenous antigens are cycled through the MHC class I pathway to stimulate CD8+ restricted responses and exogenous antigens are processed through the MHC class II pathway to generate humoral immunity. Traditionally sub-unit vaccines have been formulated with adjuvants to enhance immunogenicity, however in the last decade a number of adjuvants have been developed that effectively stimulate the generation of both humoral and cellular immune responses, although the manner in which they exert their effects has not been investigated. Here we describe Tomatine, a glycoalkaloid based adjuvant, capable of stimulating potent antigen-specific humoral and cellular immune responses that contribute to protection against malaria, Francisella tularensis and regression of experimental tumors. Using in vivo models we investigated the manner in which cellular immune responses were generated by Tomatine. We established that Tomatine did not require either lymph node or splenic macrophages to generate cytotoxic T lymphocytes (CTL) and delivered soluble protein into a pathway not dependant on the machinery of the classical MHC class I pathway. We also observed that at the molecular level Tomatine required both CD80 and CD86 costimulation to engender antigen-specific cellular immunity.

Differential requirements for CTL generation by novel immunostimulants: APC tropism, use of the TAP-independent processing pathway, and dependency on CD80/CD86 costimulation

A major drawback of subunit vaccines is their inability to generate cytolytic T lymphocytes (CTL), a deficit attributed to segregation of the class I and class II antigen-processing pathways. We sought to understand processes involved in CTL induction by three proprietary adjuvants: Tomatine, PROVAX, and a synthesized glycolipid (Glc-N-(8/16), Glycolipid). We used in vivo models to investigate antigen uptake, macrophage involvement, TAP-independent processing, and costimulatory molecule dependencies. Glycolipid required splenic and lymph node macrophages, whereas Tomatine generated CTL independently of either macrophage population. In contrast, PROVAX showed partial macrophage requirements. Immunized TAP knockout mice revealed that ovalbumin (OVA)-Tomatine and OVA-PROVAX, but not OVA-Glycolipid, generate class I-peptide complexes. All three immunostimulants also elicited CD86-dependent TH1 cytokine responses.

Analysis of the role of vaccine adjuvants in modulating dendritic cell activation and antigen presentation in vitro

We have studied the effects of adjuvant formulations on the activation and antigen-presenting functions of bone marrow-derived dendritic cells (DCs). While LPS could induce high-level expression of MHC Class II and co-stimulator molecules on DCs, it did not enhance antigen presentation to co-stimulation independent DO11.GFP T hybridoma cells. In contrast, alum, NISV and PLGA formulations failed to activate DCs, but NISV and PLGA could enhance antigen-presentation efficiency by 10-100-fold. Irrespective of the previously described antigen release characteristics of each adjuvant, antigen presentation peaked at 6h and waned thereafter for all formulations. Given the importance of DCs in the activation of nai;ve T cell responses, these studies suggest that as yet undefined pathways of DC activation in vivo may underlie the activity of alum, PLGA and NISV adjuvants. Furthermore, as NISV and PLGA do not appear to act as slow-release systems in DCs, the ability of these particulate systems to induce high levels of antigen presentation by DCs probably has a more significant role in their adjuvant activity.

Effect of feeding solanidine, solasodine and tomatidine to non-pregnant and pregnant mice

The aglycone forms of three steroidal glycoalkaloids-solanidine (derived by hydrolytic removal of the carbohydrate side chain from the potato glycoalkaloids alpha-chaconine and alpha-solanine), solasodine (derived from solasonine in eggplants) and tomatidine (derived from alpha-tomatine in tomatoes)-were evaluated for their effects on liver weight increase (hepatomegaly) in non-pregnant and pregnant mice and on fecundity in pregnant mice fed for 14 days on a diet containing 2.4 mmol/kg of aglycone. In non-pregnant mice, observed ratios of % liver weights to body weights (%LW/BWs) were significantly greater than those of the control values as follows (all values in % vs matched controls+/-S.D.): solanidine, 25.5+/-13.2; solasodine 16.8+/-12.0; and tomatidine, 6.0+/-7.1. The corresponding increases in pregnant mice were: solanidine, 5.3+/-10.7; solasodine, 33.1+/-15.1; tomatidine, 8.4+/-9.1. For pregnant mice (a) body weight gains were less with the algycones than with controls: solanidine, -36.1+/-14.5; solasodine, -17.9+/-14.3; tomatidine, -11.9+/-18.1; (b) litter weights were less than controls: solanidine, -27.0+/-17.1; solasodine, -15.5+/-16.8; tomatidine, no difference; (c) the %LTW/BW ratio was less than that of the controls and was significant only for solasodine, -8.7+/-13.7; and (d) the average weight of the fetuses was less than the controls: solanidine, -11.2+/-15.2; solasodine, -11.4+/-9.4; tomatidine, no difference. Abortion of fetuses occurred in five of 24 pregnant mice on the solanidine and none on the other diets. To obtain evidence for possible mechanisms of the observed in vivo effects, the four glycoalkaloids (alpha-chaconine, alpha-solanine, solasonine and alpha-tomatine) mentioned above and the aglycones solanidine and tomatidine were also evaluated in in vitro assays for estrogenic activity. Only solanidine at 10 microM concentration exhibited an increase in the MCF-7 human breast cancer cell proliferation assay. Generally, the biological effects of solanidine differ from those of the parent potato glycoalkaloids. Possible mechanisms of these effects and the implication of the results for food safety and plant physiology are discussed.

The ultrastructure of tomatine adjuvant

The tomatine adjuvant, consisting of tomatine, n-octyl-beta-D-glucopyranoside, phosphatidylethanolamine, cholesterol, and ovalbumin, has recently been shown to potentiate the immunogenicity of protein antigen and elicit cytotoxic T-lymphocyte responses in immunized animals. The physicochemical properties of tomatine adjuvant have not been characterized. The aim of this study was to examine the microstructure of this complex formulation, as directly related to its physicochemical properties. To elucidate the micromorphology of this system, the tomatine adjuvant was separated by isopycnic ultracentrifugation, followed by freeze fracturing and examination by transmission and scanning electron microscopy. The adjuvant mixture was shown to be composed of several micro- and nano-structures. The major fraction obtained from isopycnic separation was shown to consist of flaky needle-like microcrystals, approximately 80-160 nm in width and 2-4 microm in length. The tomatine crystals alone in 0.9% NaCl, on the other hand, were shown to be elongated hollow tubular crystals of hundreds of nanometers up to a few microns in length, along which n-octyl-beta-glucopyranoside was speculated to serve as a seeding microtemplate for gel crystallization of protein complexes. Indented marks within the gel phase were observed in the freeze fractured replicas of the adjuvant, suggesting that protein complexes may have been crystallized or precipitated within the gels. Several other forms of micro- and nano-structures were also observed, showing multiple-dispersion features with gel characteristics. The presence of gel crystalline and multiple-dispersed phases is postulated to contribute to the sustained immunopotentiation effect of tomatine adjuvant.

Tomato glycoalkaloids: role in the plant and in the diet

Tomatoes, a major food source for humans, accumulate a variety of secondary metabolites including phenolic compounds, phytoalexins, protease inhibitors, and glycoalkaloids. These metabolites protect against adverse effects of hosts of predators including fungi, bacteria, viruses, and insects. Because glycoalkaloids are reported to be involved in host-plant resistance, on the one hand, and to have a variety of pharmacological and nutritional properties in animals and humans, on the other, a need exists to develop a better understanding of the role of these compounds both in the plant and in the diet. To contribute to this effort, this integrated review presents data on the history, composition, and nutrition of tomatoes, with special focus on the assessment of the chemistry, analysis, composition, nutrition, microbiology, and pharmacology of the tomato glycoalkaloids comprising alpha-tomatine and dehydrotomatine; their content in different parts of the tomato plant, in processed tomato products, and in wild and transgenic tomatoes; their biosynthesis, inheritance, metabolism, and catabolism; plant-microbe relationships with fungi, bacteria, viruses, insects, and worms; interactions with ergosterol and cholesterol; disruption of cell membranes; tomatine-induced tomatinases, pantothenate synthetase, steroid hydroxylases, and cytokines; and inhibition of acetylcholinesterase. Also covered are tomato-human pathogen relationships and tomatine-induced lowering of plasma cholesterol and triglycerides and enhancement of the immune system. Further research needs in each of these areas are suggested. The overlapping aspects are discussed in terms of general concepts for a better understanding of the impact of tomato glycoalkaloids in the plant in general and in food in particular. Such an understanding can lead to the creation of improved tomatoes and to improved practices on the farm and in the consumption of tomatoes.

Influence of adjuvant-active peptidoglycan monomer on specific T cell responses in mice

Peptidoglycan monomer (PGM) originating from Brevibacterium divaricatum is a non-toxic, non-pyrogenic, water-soluble immunostimulator. It potentiates humoral immune response to ovalbumin (OVA) in mice upregulating both immunoglobulin (IgG) 1 and IgG2a antibody subclasses. This study concerns the influence of PGM on T cell activation and cytokine networks in response to OVA. OVA-specific proliferative response as well as interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) secretion in lymph node cell cultures of immunised mice were studied. Due to pharmacokinetic properties of PGM, namely its fast metabolism and excretion, special emphasis was on choosing the appropriate time for lymph node removal and duration of cell cultivation for each cytokine. PGM treatment in addition to OVA resulted in an increase of lymph node cellularity, stimulation of OVA-specific IFN-gamma and IL-4 production as well as of OVA-specific proliferative response. Results demonstrate that PGM stimulated both Th1 and Th2 subpopulations.

A DNA vaccine against foot-and-mouth disease elicits an immune response in swine which is enhanced by co-administration with interleukin-2

A plasmid DNA vaccine candidate (pCEIS) encoding two foot-and-mouth disease virus (FMDV) VP1 epitopes (amino acid residues 141-160 and 200-213) has been demonstrated to have the ability to elicit both FMDV-specific T cell proliferation and neutralizing antibody against FMD in swine. In this study, the efficiency of the pCEIS DNA vaccine when administrated by intramuscularly injection in swine was confirmed, and the immunogenicity of the pCEIS vaccine candidate was found to be enhanced through co-administration with a newly constructed plasmid (pIL2S) encoding the swine interleukin-2 (IL-2) cDNA. The expression of the pIL2S plasmid was driven by a CMV promotor provided by a pcDNA3.1 vector. Swine IL-2 cDNA was cloned by RT-PCR from swine spleen cells. The pIL2S plasmid was expressed in COS-7 cells after 24 and 96h of transfection in vitro. In an animal trial, results from T cell proliferation assay indicated that the stimulation index (SI) in response to stimulation of FMDV proteins in the swine groups injected with pCEIS plus pIL2S (SI ranging from 9.9 to 15.5) were significantly higher than that with pCEIS alone (SI ranging from 3.3 to 6.6). However, there was no significant difference in FMDV-neutralizing antibody level detected in these two swine groups. Mouse protection tests (MPTs) showed that the blood sera from immunized swine injected with either pCEIS alone or pCEIS plus pIL2S were able to protect suckling mice from FMDV challenge, with protection levels ranging from 10(1) to 10(2) lethal dose 50 (LD(50)) M. In a direct FMDV challenge, all swines immunized with either pCEIS plus pIL2S or with pCEIS alone were challenged with 50LD(50)S (50 x lethal dosage in swine) of FMDV. The animals were fully protected (100%) from the FMD viral challenge. These results suggest that co-administration of the plasmids, pCEIS and pIL2S, enhances of the immunogenicity of the pCEIS DNA vaccine candidate, and both intramuscular injection of pCEIS alone and co-administration of the vaccine candidate with pIL2S can protect the swine from direct FMD challenge.

Potentiation by a novel alkaloid glycoside adjuvant of a protective cytotoxic T cell immune response specific for a preerythrocytic malaria vaccine candidate antigen

We have recently demonstrated that the novel glycoalkaloid tomatine, derived from leaves of the wild tomato Lycopersicon pimpinellifolium, can act as a powerful adjuvant for the elicitation of antigen-specific CD8+ T cell responses. Here, we have extended our previous investigation with the model antigen ovalbumin to an established malaria infection system in mice and evaluated the cellular immune response to a major preerythrocytic stage malaria vaccine candidate antigen when administered with tomatine. The defined MHC H-2kd class I-binding 9-mer peptide (amino acids 252-260) from Plasmodium berghei circumsporozoite (CS) protein was prepared with tomatine to form a molecular aggregate formulation and this used to immunise BALB/c (H-2kd) mice. Antigen-specific IFN-gamma secretion and cytotoxic T lymphocyte activity in vitro were both significantly enhanced compared to responses detected from similarly stimulated splenocytes from naive and tomatine-saline-immunised control mice. Moreover, when challenged with P. berghei sporozoites, mice immunised with the CS 9-mer-tomatine preparation had a significantly delayed onset of erythrocytic infection compared to controls. The data presented validate the use of tomatine to potentiate a cellular immune response to antigenic stimulus by testing in an important biologically relevant system. Specifically, the processing of the P. berghei CS 9-mer as an exogenous antigen and its presentation via MHC class I molecules to CD8+ T cells led to an immune response that is an in vitro correlate of protection against preerythrocytic malaria. This was confirmed by the protective capacity of the 9-mer-tomatine combination upon in vivo immunisation. These findings merit further work to optimise the use of tomatine as an adjuvant in malaria vaccine development.

A systematic approach to vaccine complexity using an automaton model of the cellular and humoral immune system. I. Viral characteristics and polarized responses

A modern approach to vaccination faces the compound complexity of microorganism behavior and immune response triggering and regulation. Since computational modeling can yield useful guidelines for biological experimentation, we have used IMMSIM(3), a cellular automaton model for simulating humoral- and cell-mediated responses, to explore a wide range of virus-host relations. Sixty-four virtual viruses were generated by an assortment of speed of growth, infectivity level and lethal load. The outcome of the infections, as influenced by the immune response and the bolstering of cures, obtained by vaccine presensitization are illustrated in this first article. The results of the in machina experiments allow us to relate the success rate of responses to certain combinations of viral parameters and by freezing one or the other branch, and to determine that some viruses are more susceptible to humoral, and others to cellular responses, depending either on single parameters or combinations thereof. This finding allows prediction of which infection may be susceptible to polarized ((Th)(1)>Th(2) and Th(1)<Th(2)) responses and will eventually help designing vaccines whose action relies on antagonizing both the specificity and the behavior of the invader. A second, not lesser, result of this study is the finding that humoral and cellular responses, while cooperating, towards the cure of the infected body, also show significant patterns of competition and mutual thwarting.

Cutaneous vaccination: the skin as an immunologically active tissue and the challenge of antigen delivery

Vaccination is one of the major achievements of modern medicine. As a result of vaccination, diseases such as polio and measles have been controlled and small pox has been eradicated. However, despite these successes there are still many microbial diseases that cause tremendous suffering because there is no vaccine or the vaccines available are inadequate. In addition, even if vaccines were available for all infectious diseases there is no guarantee that people would use them routinely. One of the major impediments to ensuring vaccine efficacy and compliance is that of delivery. Presently most vaccines are given by intramuscular administration. Unfortunately this is often traumatic, especially in infants. Thus, if it was possible to replace intramuscular immunization by mucosal (oral/intranasal) or transdermal delivery it may be possible to both enhance mucosal immunity as well as improve overall compliance rates. The transdermal route has been used by the pharmaceutical industry for the delivery of various low molecular weight drugs. Some of the approaches used for smaller compounds may also have potential for delivery of either protein or polynucleotide vaccines. However, there is a greater challenge to delivering large molecular weight molecules through the skin due to size, charge and other physicochemical properties. This review will describe the recent advances that have been made in dermal and topical delivery as related to vaccines.