Duality of β-glucan microparticles: antigen carrier and immunostimulants

Bioinspired yeast-based β-glucan system for oral drug delivery

Oral drug delivery is the preferred route of drug administration for patients, especially those who need long-term medication. Recently, bioinspired drug delivery systems have emerged for the oral delivery of various therapeutics. Among them, the yeast-based β-glucan system is a novel and promising platform, for oral administration that can overcome the biological barriers of the harsh gastrointestinal environment. Remarkably, the yeast-based β-glucan system not only protects the drug through the harsh gastrointestinal environment but also achieves targeted therapeutic effects by specifically recognizing immune cells, especially macrophages. Otherwise, it exhibits immunomodulatory properties. Based on the pleasant characteristics of the yeast-based β-glucan system, they are widely used in various macrophage-related diseases for oral administration. In this review, we introduced the structure and function of yeast-based β-glucan. Subsequently, we further summarized the current preparation methods of yeast-based β-glucan carriers and the strategies for preparing yeast-based β-glucan drug delivery systems. In addition, we focus on discussing the applications of β-glucan drug delivery systems in various diseases. Finally, the current challenges and future perspectives of the β-glucan drug delivery system are introduced.

Optimal Extraction and Deproteinization Method for Mannoprotein Purification from Kluyveromyces marxianus

Background

Mannoproteins, mannose-glycosylated proteins, play an important role in biological processes and have various applications in industries. Several methods have been already used for the extraction of mannoproteins from yeast cell-wall. The aim of this study was to evaluate the extraction and deproteinization of mannan oligosaccharide from the Kluyveromyces (K.) marxianus mannoprotein.

Methods

To acquire crude mannan oligosaccharides, K. marxianus mannoproteins were deproteinized by the Sevage, trichloroacetic acid, and hydrochloric acid (HCL) methods. Total nitrogen, crude protein content, fat, carbohydrate and ash content were measured according to the monograph prepared by the meeting of the Joint FAO/WHO Expert Committee and standard. Mannan oligosaccharide loss, percentage of deproteinization, and chemical composition of the product were assessed to check the proficiency of different methods.

Results

Highly purified (95.4%) mannan oligosaccharide with the highest deproteinization (97.33 ± 0.4%) and mannan oligosaccharide loss (25.1 ± 0.6%) were obtained following HCl method.

Conclusion

HCl, was the most appropriate deproteinization method for the removal of impurities. This preliminary data will support future studies to design scale-up procedures.

Sustainable production and pharmaceutical applications of β-glucan from microbial sources

β-glucans are a large class of complex polysaccharides found in abundant sources. Our dietary sources of β-glucans are cereals that include oats and barley, and non-cereal sources can consist of mushrooms, microalgae, bacteria, and seaweeds. There is substantial clinical interest in β-glucans; as they can be used for a variety of diseases including cancer and cardiovascular conditions. Suitable sources of β-glucans for biopharmaceutical applications include bacteria, microalgae, mycelium, and yeast. Environmental factors including culture medium can influence the biomass and ultimately β-glucan content. Therefore, cultivation conditions for the above organisms can be controlled for sustainable enhanced production of β-glucans. This review discusses the various sources of β-glucans and their cultivation conditions that may be optimised to exploit sustainable production. Finally, this article discusses the immune-modulatory potential of β-glucans from these sources.

Beta glucan as an immune stimulant in tumor microenvironment - Insight into lessons and promises from past decade

Cancer is characterized by a perturbed immune landscape. Inside tumor microenvironment, immune system is reprogrammed to facilitate tumor growth and survival rather than eliminating it. This immune evasive mechanism needs to be reversed to normal for effective anticancer therapeutic strategy. Immunotherapy has emerged as a novel strategy for redeployment of immune cells against cancer. However, they suffer in their efficacy, response rate and side effects. This necessitated us to turn toward natural repertoires which can act as a substitute to conventional immunotherapeutics. Beta glucan, a polysaccharide derived from mushroom, serves the role of immunomodulator inside tumor microenvironment. It acts as pathogen associated molecular pattern and bind to various pattern recognition receptors expressed on surface of immune cells thereby facilitating their activation and crosstalk. This result in resurgence of suppressed immune surveillance in the tumor milieu. In this review, we highlight in brief the advances and limitation of cancer immunotherapy. Alongside, we have discussed the detailed mechanistic principle and recent advances underlying restoration of immune functionality by beta glucan.

Oral organic nanovaccines against bacterial and viral diseases

Vaccines have saved millions of humans and animals from deadly diseases. Many vaccines are still under development to fight against lethal diseases. Indeed, subunit vaccines are a versatile approach with several advantageous attributes, but they lack strong immunogenicity. Nanotechnology is an avenue to vaccine development because nanoparticles may serve as nanocarriers and adjuvants, which are critical aspects for oral vaccines. This review provides an update of oral organic nanovaccines, describing suitable nanomaterials for oral vaccine design and recent (last five-year view) oral nanovaccine developments to fight against those principal pathogens causing human and animal diseases.

Carboxymethyl-β-glucan/chitosan nanoparticles: new thermostable and efficient carriers for antigen delivery

In the last few decades, nanotechnology has emerged as an important tool aimed at enhancing the immune response against modern antigens. Nanocarriers designed specifically for this purpose have been shown to provide protection, stability, and controlled release properties to proteins, peptides, and polynucleotide-based antigens. Polysaccharides are particularly interesting biomaterials for the construction of these nanocarriers given their wide distribution among pathogens, which facilitates their recognition by antigen-presenting cells (APCs). In this work, we focused on an immunostimulant beta-glucan derivative, carboxymethyl-β-glucan, to prepare a novel nanocarrier in combination with chitosan. The resulting carboxymethyl-β-glucan/chitosan nanoparticles exhibited adequate physicochemical properties and an important protein association efficiency, with ovalbumin as a model compound. Moreover, thermostability was achieved through the optimization of a lyophilized form of the antigen-loaded nanoparticles, which remained stable for up to 1 month at 40 ºC. Biodistribution studies in mice showed an efficient drainage of the nanoparticles to the nearest lymph node following subcutaneous injection, and a significant co-localization with dendritic cells. Additionally, subcutaneous immunization of mice with a single dose of the ovalbumin-loaded nanoparticles led to induced T cell proliferation and antibody responses, comparable to those achieved with alum-adsorbed ovalbumin. These results illustrate the potential of these novel nanocarriers in vaccination.

Engineering a sustained release vaccine with a pathogen-mimicking manner for robust and durable immune responses

Sustained release vaccine carriers can facilitate an increased interaction time between the antigen and immune system to strengthen immune responses, but their promotion on adaptive immune responses, especially cellular immunity, are still unfavorable. Herein, we report a sustained antigen delivery vector, which carries abundant antigens, a nucleic acid adjuvant and pathogen-associated molecular patterns to simulate a natural pathogen to reinforce immune responses. Specifically, murine colorectal cancer cells MC38 lysate and Toll-like receptor 9 agonist CpG are loaded into yeast derived β-glucan particles (GPs). After vaccination, these particles can form a vaccine depot that continuously release the antigen similar to the traditional aluminum hydroxide gel, but recruit more immune cells and induce more cytokine secretion at the injection site. Stronger antibody responses, Th1 and Th17 biased cellular immunity and immune memory are achieved compared with aluminum hydroxide gel. More importantly, treatment with these particles significantly suppress tumor growth in a therapeutic tumor model. This work shed light on the efficacy of combining sustained antigen release with pathogen-mimicking manner in vaccine design.

Advances in Oral Subunit Vaccine Design

Many pathogens invade the host at the intestinal surface. To protect against these enteropathogens, the induction of intestinal secretory IgA (SIgA) responses is paramount. While systemic vaccination provides strong systemic immune responses, oral vaccination is the most efficient way to trigger protective SIgA responses. However, the development of oral vaccines, especially oral subunit vaccines, is challenging due to mechanisms inherent to the gut. Oral vaccines need to survive the harsh environment in the gastrointestinal tract, characterized by low pH and intestinal proteases and need to reach the gut-associated lymphoid tissues, which are protected by chemical and physical barriers that prevent efficient uptake. Furthermore, they need to surmount default tolerogenic responses present in the gut, resulting in suppression of immunity or tolerance. Several strategies have been developed to tackle these hurdles, such as delivery systems that protect vaccine antigens from degradation, strong mucosal adjuvants that induce robust immune responses and targeting approaches that aim to selectively deliver vaccine antigens towards specific immune cell populations. In this review, we discuss recent advances in oral vaccine design to enable the induction of robust gut immunity and highlight that the development of next generation oral subunit vaccines will require approaches that combines these solutions.

Mushrooms and immunity

In the wide field of nutraceuticals, the effects of mushrooms on immunity, cancer and including autoimmunity have been proposed for centuries but in recent years a growing interest has led scientists to elucidate which specific compounds have bioactive properties and through which mechanisms. Glucans and specific proteins are responsible for most of the biological effects of mushrooms, particularly in terms of immunomodulatory and anti-tumor results. Proteins with bioactive effects include lectins, fungal immunomodulatory proteins (FIPs), ribosome inactivating proteins (RIPs), ribonucleases, laccases, among others. At the present status of knowledge, numerous studies have been performed on cell lines and murine models while only a few clinical trials have been conducted. As in most cases of dietary components, the multitude of variables implicated in the final effect and an inadequate standardization are expected to affect the observed differences, thus making the available evidence insufficient to justify the treatment of human diseases with mushrooms extracts. We will herein provide a comprehensive review and critically discussion the biochemical changes induced by different mushroom compounds as observed in in vitro studies, particularly on macrophages, dendritic cells, T cells, and NK cells, compared to in vivo and human studies. Additional effects are represented by lipids which constitute a minor part of mushrooms but may have a role in reducing serum cholesterol levels or phenols acting as antioxidant and reducing agents. Human studies provide a minority of available data, as well illustrated by a placebo-controlled study of athletes treated with β-glucan from Pleurotus ostreatus. Variables influencing study outcomes include different mushrooms strains, growing conditions, developmental stage, part of mushroom used, extraction method, and storage conditions. We foresee that future rigorous research will be needed to determine the potential of mushroom compounds for human health to reproduce the effects of some compounds such as lentinan which a metaanalysis demonstrated to increase the efficacy of chemotherapy in the treatment of lung cancer and in the improvement of the patients quality of life.

Composites of yeast glucan particles and curcumin lead to improvement of dextran sulfate sodium-induced acute bowel inflammation in rats

The goal of this work was to assess the usability of yeast glucan particles (GPs) as carriers for curcumin and determine the beneficial effect of a pharmacological composite of curcumin in GPs on dextran sulfate sodium induced colitis in rats. The assessment of the anti-inflammatory effect of particular substances was evaluated on the basis of the calculated disease activity index and by assessment of cytokines and enzymes from the gut tissue - tumor necrosis factor α (TNF-α), transforming growth factor β1, interleukin (IL)-1β, IL-6, IL-10, IL-17, catalase, superoxide dismutase 2, myeloperoxidase (MPO), and matrix metalloproteinase 9. Composites of GPs with incorporated curcumin showed promising results with the capability to lower symptoms of colitis and significantly decrease the production of pro-inflammatory cytokines TNF-α, IL-1β, IL-6, and the activity of MPO, as well. The anti-inflammatory effect of the composites was greater than those of pure GPs or curcumin.

Carbohydrate Conjugates in Vaccine Developments

Vaccines are powerful tools that can activate the immune system for protection against various diseases. As carbohydrates can play important roles in immune recognition, they have been widely applied in vaccine development. Carbohydrate antigens have been investigated in vaccines against various pathogenic microbes and cancer. Polysaccharides such as dextran and β-glucan can serve as smart vaccine carriers for efficient antigen delivery to immune cells. Some glycolipids, such as galactosylceramide and monophosphoryl lipid A, are strong immune stimulators, which have been studied as vaccine adjuvants. In this review, we focus on the current advances in applying carbohydrates as vaccine delivery carriers and adjuvants. We will discuss the examples that involve chemical modifications of the carbohydrates for effective antigen delivery, as well as covalent antigen-carbohydrate conjugates for enhanced immune responses.

β-glucan as a new tool in vaccine development

Vaccination constitutes one of the major breakthroughs in human medicine. At the same time, development of more immunogenic vaccine alternatives to using aluminium-based adjuvants is one of the most important phases of vaccination development. Among different sources of carbohydrate polymers, including plants, microbes and synthetic sources tested, glucans were found to be the most promising vaccine adjuvant, as they alone stimulate various immune reactions including antibody production without any negative side effects. The use of glucan particles as a delivery system is a viable option based on the documented efficient antigen loading and receptor-targeted uptake in antigen-presenting cells. In addition to particles, soluble glucans can be used as novel hydrogels or as direct immunocyte-targeting delivery systems employing novel complexes with oligodeoxynucleotides. This review focuses on recent advances in glucan-based vaccine development from glucan-based conjugates to a glucan-based delivery and adjuvant platform.

Biomimetic and bioinspired strategies for oral drug delivery

Oral drug delivery remains the most preferred approach due to its multiple advantages. Recently there has been increasing interest in the development of advanced vehicles for oral delivery of different therapeutics. Among them, biomimetic and bioinspired strategies are emerging as novel approaches that are promising for addressing biological barriers encountered by traditional drug delivery systems. Herein we provide a state-of-the-art review on the current progress of biomimetic particulate oral delivery systems. Different biomimetic nanoparticles used for oral drug delivery are first discussed, mainly including ligand/antibody-functionalized nanoparticles, transporter-mediated nanoplatforms, and nanoscale extracellular vesicles. Then we describe bacteria-derived biomimetic systems, with respect to oral delivery of therapeutic proteins or antigens. Subsequently, yeast-derived oral delivery systems, based on either chemical engineering or bioengineering approaches are discussed, with emphasis on the treatment of inflammatory diseases and cancer as well as oral vaccination. Finally, bioengineered plant cells are introduced for oral delivery of biological agents. A future perspective is also provided to highlight the existing challenges and possible resolution toward clinical translation of currently developed biomimetic oral therapies.

Curcumin encapsulation in yeast glucan particles promotes its anti-inflammatory potential in vitro

Glucan particles (GPs) from Saccharomyces cerevisiae are hollow shells that are composed mainly of β-1,3-d-glucan, which has demonstrated immunomodulatory and anti-inflammatory potential both in vitro and in vivo. Curcumin is a natural hydrophobic phenolic compound, which possesses a significant anti-inflammatory effect and is used as supportive therapy in the treatment of many inflammatory diseases. The aim of this study is to evaluate the possible synergic effect and other benefits of the co-application of GPs and curcumin in the form of pharmaceutical composites. GP/curcumin composites were prepared using controlled evaporation of the organic solvent and their anti-oxidative effect and anti-inflammatory potential were tested on THP1‑XBlue™‑MD2‑CD14 human monocytes cell line. The anti-oxidative effect was measured on pyocyanin-stimulated cells in vitro and the NF-κB/AP-1 signaling pathway on lipopolysaccharide pre-treated monocytes was chosen for anti-inflammatory assays. The secretion of pro-inflammatory cytokines TNF-α and IL-1β was evaluated as well. Results mostly showed a pro-oxidative activity of empty GPs, however, pharmaceutical composites demonstrated an anti-oxidative effect. The activity of NF-κB/AP-1 was substantially decreased by the tested GP/curcumin composites, which also caused the attenuation of cytokines secretion. The obtained results indicate a beneficial effect of the incorporation of curcumin into GPs.

Glucan and Mannan-Two Peas in a Pod

In recent decades, various polysaccharides isolated from algae, mushrooms, yeast, and higher plants have attracted serious attention in the area of nutrition and medicine. The reasons include their low toxicity, rare negative side effects, relatively low price, and broad spectrum of therapeutic actions. The two most and best-studied polysaccharides are mannan and glucan. This review focused on their biological properties.

Glucan Particles Are a Powerful Adjuvant for the HBsAg, Favoring Antiviral Immunity

The lack of vaccine adjuvants that are able to induce robust T cell responses fosters the search for more powerful options. Pathogen-like particles are a promising approach. The adjuvant activity of pathogen-like particles is highly influenced by size and surface composition. This study aimed to evaluate the adjuvant potential of two different β-glucan-based particles, blend chitosan/β-glucan particles (ChiGluPs), which are positively charged and have mean size of 1276 nm, and neutral yeast-derived glucan particles (GPs), with a mean size of 3 μm. Additionally, chitosan particles (ChiPs) were used to understand the effect of β-glucan addition (ChiGluPs). Mouse spleen cells responded through the production of either TNF-α or RANTES, following in vitro stimulation with particles containing either β-glucan (ChiGluPs and GPs) or chitosan (ChiGluPs and ChiPs). Human monocytes responded to all particles through TNF-α secretion. Subcutaneous vaccination of mice with the hepatitis B surface antigen (HBsAg) showed increased serum IgG for all particles compared to HBsAg alone (435-, 4500-, or 2500-fold increase for either ChiPs, ChiGluPs, or GPs). Interestingly, only GPs elicited the secretion of HBsAg-specific Th1, Th2, Th9, Th17, Th22, and Treg-related cytokines. This study demonstrates, for the first time, that GPs can have a significant role against the hepatitis B virus by favoring antiviral immunity.

The scale-up cultivation of Candida utilis in waste potato juice water with glycerol affects biomass and β(1,3)/(1,6)-glucan characteristic and yield

New ideas on production of yeast origin β-glucan preparations for industrial application are attracting interest considering market development of that high-value functional polysaccharide. Sellecting an efficient yeast producer and designing culture conditions are a prerequisite for obtaining high yield of β-glucan. The aim of this study was to describe at the first time the influence of the mode of cultivation (shake-flasks and batch fermentation) and time of culture on characteristic and yield of biomass and β(1,3)/(1,6)-glucan preparations of Candida utilis ATCC 9950 after cultivation in medium based on waste potato juice water supplemented with 10% of glycerol. After shake-flask culture, the biomass was characterized by higher protein content (app. 26.5%) compared to 19% after batch fermentation while the cultivation on a biofermentor scale promoted polysaccharides biosynthesis. The highest output of purified β(1,3)/(1,6)-glucan preparation (5.3 g_d.w./L), containing app. 85% of that polysaccharide, was found after 48 h cultivation in biofermentor. Batch fermentation promoted biosynthesis of alkali-insoluble β(1,3)/(1,6)-glucan fraction, decreasing the content of β(1,6)-glucan. The yield of β(1,3)/(1,6)-glucan synthesis was 0.063 (g/g glycerol), while the productivity of that polysaccharide reached 0.094 (g/L/h). Longer batch fermentation (72 h) resulted in reduction of production efficiency of β-glucan preparation under studied conditions. The results of the study provide a new efficient biotechnological solution to produce high-value β-glucan preparations of C. utilis origin based on valorization of agro-waste potato juice water with glycerol.

β-glucans as potential immunoadjuvants: A review on the adjuvanticity, structure-activity relationship and receptor recognition properties

β-glucans, a group of polysaccharides exist in many organism species such as mushrooms, yeasts, oats, barley, seaweed, but not mammalians, have a variety of biological activities and applications in drugs and other healthcare products. In recent years, β-glucans have been studied as adjuvants in anti-infection vaccines as well as immunomodulators in anti-cancer immunotherapy. β-glucans can regulate immune responses when administered alone and can connect innate and adaptive immunity to improve immunogenicity of vaccines. When β-glucans act as immunostimulants or adjuvants, a set of receptors have been revealed to recognize β-glucans, including dectin-1, complement receptor 3 (CR3), CD5, lactosylceramide, and so on. Therefore, this review is mainly focused on the application of β-glucans as immune adjuvants, the receptors of β-glucans, as well as their structure and activity relationship which will benefit future research of β-glucans.

Modification of the cell wall structure of Saccharomyces cerevisiae strains during cultivation on waste potato juice water and glycerol towards biosynthesis of functional polysaccharides

Changes in cell wall structure of four strains of Sacccharomyces cerevisiae species (brewer's, baker's and probiotic yeast) after culturing on deproteinated potato juice water (DPJW) with diverse addition of glycerol and different pH were investigated. It allowed to select conditions intensifying biosynthesis of β(1,3)/(1,6)-glucan and mannoproteins of cell walls of tested strains. Yeast cell wall structural polysaccharides show biological activity and technological usability in food industry but also decide about therapeutic properties of yeast biomass. The highest increase in the thickness of walls (by about 100%) and β-glucan layer (by about 120%) was stated after cultivation of S. cerevisiae R9 brewer's yeast in DPJW supplemented with 5 and 10% (w/v) of glycerol and pH 7.0 while S. cerevisiae var. boulardi PAN yeast synthesized by ab. 70% thicker β-glucan layer when the pH of growth medium was equal to 5.0. The cells of brewer's yeast (S. cerevisiae R9), probiotic (S. cerevisiae CNCM 1-745) and baker's (S. cerevisiae 102) intensified the ratio of mannoproteins in the structure of cell walls cultivated in mediums supplemented with above 15% of glycerol what point out the protective action of glycoprotein's under osmotic stress conditions. The study confirms at the first time the possibility of using agro-industrial waste in biosynthesis of functional polysaccharides of S. cerevisiae cell wall. It could be an new advantage in production of yeast biomass with therapeutic properties or β-glucan preparation as a novel food ingredient.

The Pseudorabies Virus Glycoprotein gE/gI Complex Suppresses Type I Interferon Production by Plasmacytoid Dendritic Cells

Plasmacytoid dendritic cells (pDC) play a central role in the antiviral immune response, both in the innate response and in shaping the adaptive response, mainly because of their ability to produce massive amounts of type I interferon (TI-IFN). Here, we report that cells infected with the live attenuated Bartha vaccine strain of porcine alphaherpesvirus pseudorabies virus (PRV) trigger a dramatically increased TI-IFN response by porcine primary pDC compared to cells infected with wild-type PRV strains (Becker and Kaplan). Since Bartha is one of the relatively few examples of a highly successful alphaherpesvirus vaccine, identification of factors that may contribute to its efficacy may provide insights for the rational design of other alphaherpesvirus vaccines. The Bartha vaccine genome displays several mutations compared to the genome of wild-type PRV strains, including a large deletion in the unique short (US) region, encompassing the glycoprotein E (gE), gI, US9, and US2 genes. Using recombinant PRV Becker strains harboring the entire Bartha US deletion or single mutations in the four affected US genes, we demonstrate that the absence of the viral gE/gI complex contributes to the observed increased IFN-α response. Furthermore, we show that the absence of gE leads to an enhanced extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation in pDC, which correlates with a higher TI-IFN production by pDC. In conclusion, the PRV Bartha vaccine strain triggers strongly increased TI-IFN production by porcine pDC. Our data further indicate that the gE/gI glycoprotein complex suppresses TI-IFN production by pDC, which represents the first alphaherpesvirus factor that suppresses pDC activity.IMPORTANCE Several alphaherpesviruses, including herpes simpex virus, still lack effective vaccines. However, the highly successful Bartha vaccine has contributed substantially to eradication of the porcine alphaherpesvirus pseudorabies virus (PRV) in several countries. The impact of Bartha on the immune response is still poorly understood. Type I interferon (TI-IFN)-producing plasmacytoid dendritic cells (pDC) may play an important role in vaccine development. Here, we show that Bartha elicits a dramatically increased type I interferon (TI-IFN) response in primary porcine pDC compared to wild-type strains. In addition, we found that the gE/gI complex, which is absent in Bartha, inhibits the pDC TI-IFN response. This is the first description of an immune cell type that is differentially affected by Bartha versus wild-type PRV and is the first report describing an alphaherpesvirus protein that inhibits the TI-IFN response by pDC. These data may therefore contribute to the rational design of other alphaherpesvirus vaccines.