Cell type-specific differences in β-glucan recognition and signalling in porcine innate immune cells

GFPBW1, a β-glucan from Grifola frondosa as vaccine adjuvant: APCs activation and maturation

Adjuvants for vaccines with characteristics of improving adaptive immunity particularly via leverage of antigen presenting cells (APCs) are currently lacking. In a previous work we obtained a new soluble 300 kDa homogeneous β-glucan named GFPBW1 from the fruit bodies of Granola frondosa. GFPBW1 could activate macrophages by targeting dendritic cell associated C-type lectin 1 (Dectin-1)/Syk/NF-κB signaling to achieve antitumour effects. In this study the adjuvant effects of GFPBW1 were explored with OVA-antigen and B16-OVA tumor model. We showed that GFPBW1 (5, 50, 500 μg/mL) dose-dependently promoted activation and maturation of APCs in vitro by increasing CD80, CD86 and MHC II expression. We immunized female mice with OVA in combination with GFPBW1 (50 or 300 μg) twice with an interval of two weeks. GFPBW1 markedly and dose-dependently increased OVA-specific antibody titers of different subtypes including IgG1, IgG2a, IgG2b and IgG3, suggesting that it could serve as an adjuvant for both Th1 and Th2 type immune responses. Furthermore, GFPBW1 in combination with aluminum significantly increased the titers of OVA-specific IgG2a and IgG2b, but not those of IgG1, suggesting that GFPBW1 could be used as a co-adjuvant of aluminum to compensate for Th1 deficiency. For mice immunized with OVA plus GFPBW1, no obvious pathological injury was observed in either major organs or injection sites, and no abnormalities were noted for any of the hematological parameters. When GFPBW1 served as an adjuvant in the B16-OVA cancer vaccine models, it could accomplish entire tumor suppression with preventive vaccines, and enhance antitumour efficacy with therapeutic vaccines. Differentially expressed genes were found to be enriched in antigen processing process, specifically increased tumor infiltration of DCs, B1 cells and plasma cells in the OVA plus GFPBW1 group, in accordance with its activation and maturation function of APCs. Collectively, this study systematically describes the properties of GFPBW1 as a novel potent and safe adjuvant and highlights its great potential in vaccine development.

Enhancement of systemic virus-specific T lymphocyte responses in pigs supplemented with algae-derived β-glucan

Algae-derived β-glucan has been widely used as a feed additive in the swine industry. The supplementation of β-glucan aims to improve growth performance and modulate the immunity of pigs. However, the potential effects of supplementing β-glucan from algae on immune responses in pigs-specifically antigen-specific immunity-must be determined. In this study, the effects of algae-derived β-glucan supplementation on growth performance, virus neutralising antibody and virus-specific T lymphocytes responses were investigated in pigs. Piglets (n=112 per treatment) were assigned to three treatments including non-supplemented group (control), β-glucan 100 g/ton supplemented group (BG100), and β-glucan 200 g/ton supplemented group (BG200). In this study, production performance of pigs was not found to be different between the experimental groups. Pigs supplemented with β-glucan exhibited high levels of classical swine fever virus (CSFV)-specific producing T lymphocytes and neutralising antibody titer, compared to the control group. Interestingly, supplementation of β-glucan significantly enhanced porcine reproductive and respiratory syndrome virus (PRRSV)-specific interferon-gamma (IFN-γ) producing T lymphocytes, including CD4+, CD8+, and CD4+CD8+ T lymphocyte subpopulations. Moreover, PRRS modified live vaccine (MLV) viremia was reduced in earlier for β-glucan-supplemented pigs compared to the control group. The findings indicate that the algae-derived β-glucan possesses biological potential as an immunomodulatory substance to enhance antiviral immunity, which may contribute to disease resistance in pigs.

Receptor basis of biological activity of polysaccharides

Polysaccharides, the most diverse forms of organic molecules in nature, exhibit a large number of different biological activities, such as immunomodulatory, radioprotective, antioxidant, regenerative, metabolic, signaling, antitumor, and anticoagulant. The reaction of cells to a polysaccharide is determined by its specific interaction with receptors present on the cell surface, the type of cells, and their condition. The effect of many polysaccharides depends non-linearly on their concentration. The same polysaccharide in different conditions can have very different effects on cells and organisms, up to the opposite; therefore, when conducting studies of the biological activity of polysaccharides, both for the purpose of developing new drugs or approaches to the treatment of patients, and in order to clarify the features of intracellular processes, information about already known research results is needed. There is a lot of scattered data on the biological activities of polysaccharides, but there are few reviews that would consider natural polysaccharides from various sources and possible molecular mechanisms of their action. The purpose of this review is to present the main results published at different times in order to facilitate the search for information necessary for conducting relevant studies.

Role of Dectin-1 in immune response of macrophages induced by Fonsecaea monophora wild strain and melanin-deficient mutant strain

Chromoblastomycosis is a chronic granulomatous subcutaneous fungal disease caused mainly by Fonsecaea monophora in southern China. Melanin is an important virulence factor in wild strain (Mel+), and the strains lack of the polyketide synthase gene is a melanin-deficient mutant strain (Mel-). We investigated the effect of melanin in F. monophora on Dectin-1 receptor-mediated immune responses in macrophages. Conidia and tiny hyphae of Mel+ and Mel- were co-cultured with THP-1 macrophages expressing normal or low levels of Dectin-1. Compare the killing rate, phagocytosis rate, and expression levels of the inflammatory cytokines tumour necrosis factor-α, interleukin-1β, interleukin-6, and nitric oxide in each group. The results showed that the killing rate, phagocytosis rate, and pro-inflammatory factor levels of Mel+ infected macrophages with normal expression of Dectin-1 were lower than those of Mel-. And the knockdown of Dectin-1 inhibited the phagocytic rate, killing rate, and proinflammatory factor expression in macrophages infected with Mel+ and Mel-. And there was no significant difference in the above indexes between Mel+ and Mel- groups in Dectin-1 knockdown macrophages. In summary, the study reveals that melanin of F. monophora inhibits the immune response effect of the host by hindering its binding to Dectin-1 on the surface of macrophage, which may lead to persistent fungal infections.

β-Glucans in particulate and solubilized forms elicit varied immunomodulatory and apoptosis effects in teleost macrophages in a dosedependent manner

β-Glucans are a group of heterogeneous glucose polymers that possess immunomodulatory activities. The complex nature of their structures, uncertainty regarding the doses, and variable immune effects pose a challenge to comprehensive understanding. In this study, we investigated the immune responses and apoptosis effects in Nile tilapia (Oreochromis niloticus) head kidney macrophages (MФ) upon exposure to two β-Glucans (Paramylon and Laminarin) at low and high doses. Our results demonstrate that Paramylon elicits more robust immune responses than Laminarin, albeit with a dose-limiting effect. We also observed that the high-dose Paramylon induces apoptosis, whereas no such effect was detected in Laminarin treatment. Mechanistically, high-dose Paramylon activates the intrinsic apoptosis pathway, with significantly up-regulation of intrinsic apoptosis-related genes and impaired mitochondrial function. On the other hand, Laminarin triggers metabolic reprogramming in MФ, resulting in the enrichment of the metabolite α-Ketoglutarate, which protects the MФ from apoptosis. Overall, our findings highlight the importance of identifying the optimal dose range for β-Glucans, based on sources or structures, to achieve maximal immunomodulatory effects. These results have important implications for the design and optimization of β-Glucans-based drugs or adjuvants in immunotherapies.

Porcine Macrophage Markers and Populations: An Update

Besides its importance as a livestock species, pig is increasingly being used as an animal model for biomedical research. Macrophages play critical roles in immunity to pathogens, tissue development, homeostasis and tissue repair. These cells are also primary targets for replication of viruses such as African swine fever virus, classical swine fever virus, and porcine respiratory and reproductive syndrome virus, which can cause huge economic losses to the pig industry. In this article, we review the current status of knowledge on porcine macrophages, starting by reviewing the markers available for their phenotypical characterization and following with the characteristics of the main macrophage populations described in different organs, as well as the effect of polarization conditions on their phenotype and function. We will also review available cell lines suitable for studies on the biology of porcine macrophages and their interaction with pathogens.

Immunomodulatory Effect and Biological Significance of β-Glucans

β-glucan, one of the homopolysaccharides composed of D-glucose, exists widely in cereals and microorganisms and possesses various biological activities, including anti-inflammatory, antioxidant, and anti-tumor properties. More recently, there has been mounting proof that β-glucan functions as a physiologically active "biological response modulator (BRM)", promoting dendritic cell maturation, cytokine secretion, and regulating adaptive immune responses-all of which are directly connected with β-glucan-regulated glucan receptors. This review focuses on the sources, structures, immune regulation, and receptor recognition mechanisms of β-glucan.

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.

Effect of dietary β-glucan on intestinal microbial diversity and Salmonella vaccine immunogenicity and efficacy in pigs

Alternatives to antibiotics to improve animal performance, limit the negative impact of infectious disease, and/or reduce colonization with foodborne pathogens is a major focus of animal agricultural research. β-glucans, a generally-recognized-as-safe (GRAS) product derived from various sources, are used in swine and can serve as both a prebiotic and/or stimulant of the immune system given the expression of β-glucan receptors on immune cells. When supplied in the diet of nursery pigs, it is unclear how dietary additives, particularly those known to modulate immune status, impact immunogenicity and efficacy of mucosal-delivered vaccines. Salmonellosis is one of the most common bacterial foodborne infections in the United States, and consumption of contaminated pork is a major source of human infection. Reduction of foodborne Salmonella in pigs via vaccination is one strategy to reduce contamination risk and subsequently reduce human disease. We examined the ability of dietary β-glucan to modulate fecal microbial diversity, and immunogenicity and efficacy of a mucosally-delivered, live-attenuated Salmonella vaccine during the nursery period. While dietaryβ-glucan did modulate fecal alpha diversity, it did not alter the induction of peripheral Salmonella-specific IFN-γ secreting Tcells or Salmonella-specific IgA in oral fluids. In addition, vaccination reduced Salmonella enterica serovar Typhimurium fecal shedding and tissue colonization. Overall, addition of β-glucan to the nursery diet of pigs impacted the microbiota but did not alter mucosal vaccine immunogenicity and efficacy.

Beta-glucan enhanced immune response to Newcastle disease vaccine and changed mRNA expression of spleen in chickens

The present study was performed to investigate the effect of oral administration of β-glucan (G70), a product obtained from the cell wall of yeast, on Newcastle disease virus (NDV)-specific hemagglutination inhibition (HI) titers, lymphocyte proliferation, and the role of T lymphocyte subpopulations in chickens treated with live NDV vaccine. In addition, the influence of β-glucan on splenic gene expression was investigated by transcriptome sequencing. The results revealed that the supplementation of β-glucan boosted the titer of serum NDV HI increased the NDV stimulation index of lymphocytes in peripheral blood and intestinal tract, and promoted the differentiation of T lymphocytes into CD4⁺ T cells. The RNA sequencing (RNA-seq) analysis demonstrated that G70 upregulated the mRNA expressions related to G-protein coupled receptor and MHC class I polypeptide, and downregulated the mRNA expressions related to cathelicidin and beta-defensin. The immunomodulatory effect of G70 might function through mitogen-activated protein kinase signaling pathway. To sum up, G70 could boost the immunological efficacy of live NDV vaccine in chickens and could be applied as a potential adjuvant candidate in the poultry industry.

Feeding a whole-cell inactivated Pichia guilliermondii yeast to gestating and lactating sows in a commercial production system

A total of 606 sows (PIC 1050) and their progeny (PIC 1050 × 280) were used to determine if feeding gestating and lactating sows a proprietary strain of Pichia guilliermondii as a whole-cell inactivated yeast product (WCY; CitriStim, ADM Animal Nutrition, Quincy, IL) improves sow and litter performance in a commercial production system. Once confirmed pregnant at d 35 post-breeding pregnancy check, sows were fed a basal gestation control (CON) diet (0.55% SID lysine) or the control diet fortified with 0.15% of the WCY replacing corn in the CON diet. Dietary treatments were also fed in lactation (1.05% SID lysine) once sows were moved into farrowing crates on approximately d 112 of gestation until weaning. Sows supplemented with WCY in gestation and lactation had increased total born piglets by 0.45 pigs (P < 0.04), piglets born alive (14.27 vs. 13.85; P < 0.04), and, therefore, heavier born alive litter weights (P < 0.001) compared to CON fed sows. A greater post cross-foster litter size (P < 0.001) meant that litter size at weaning was increased by 0.54 pigs when sows were fed WCY compared to CON (P < 0.001). However, litter weaning weights and 21-d adjusted litter weaning weights were similar (P > 0.158), although numerically greater, for WCY fed sows. Pigs from CON fed sows were 0.35 kg heavier at weaning compared to pigs from WCY fed sows (P < 0.001). This increase in weaning weight of pigs from CON fed sows is partially explained by their 0.93 d longer lactation (P < 0.001) and may also be due to the smaller litter size throughout lactation. The percent of litters treated for scours decreased from 38.3 to 14.2% when sows were fed WCY (P < 0.001). The distribution of birth and weaning weights was not impacted (P > 0.2461) by treatment. In conclusion, feeding gestating and lactating sows a proprietary strain of Pichia guilliermondii as a whole-cell inactivated yeast product increased the number of pigs born and weaned, and decreased the prevalence of scours during lactation.

Exopolysaccharide from the yeast Papiliotrema terrestris PT22AV for skin wound healing

INTRODUCTION

Exopolysaccharides (EPSs) are high-value functional biomaterials mainly produced by bacteria and fungi, with nutraceutical, therapeutic and industrial potentials.

OBJECTIVES

This study sought to characterize and assess the biological properties of the EPS produced by the yeast Papiliotrema terrestris PT22AV.

METHODS

After extracting the yeast's DNA and its molecular identification, the EPS from P. terrestris PT22AV strain was extracted and its physicochemical properties (structural, morphological, monosaccharide composition and molecular weight) were characterized. The EPS's in vitro biological activities and in vivo wound healing potential were also evaluated.

RESULTS

The obtained EPS was water-soluble and revealed an average molecular weight (M_w) of 202 kDa. Mannose and glucose with 97% and 3% molar percentages, respectively, constituted the EPS. In vitro antibacterial activity analysis of the extracted EPS exhibited antibacterial activity (>80%) against Escherichia coli, Staphylococcus aureus, and Staphylococcus epidermidis at a concentration of 2 mg/mL. The EPS showed cytocompatibility against the human fibroblast and macrophage cell lines and the animal studies showed a dose-dependent wound healing capacity of the EPS with higher wound closure at 10 mg/mL compared to negative and positive control after 14 days.

CONCLUSION

The EPS from P. terrestris PT22AV could serve as a promising source of biocompatible macromolecules with potential for skin wound healing.

Immunomodulatory activity of β-glucan polysaccharides isolated from different species of mushroom - A potential treatment for inflammatory lung conditions

Acute respiratory distress syndrome (ARDS) is the most common form of acute severe hypoxemic respiratory failure in the critically ill with a hospital mortality of 40%. Alveolar inflammation is one of the hallmarks for this disease. β-Glucans are polysaccharides isolated from a variety of natural sources including mushrooms, with documented immune modulating properties. To investigate the immunomodulatory activity of β-glucans and their potential as a treatment for ARDS, we isolated and measured glucan-rich polysaccharides from seven species of mushrooms. We used three models of in-vitro injury in THP-1 macrophages, Peripheral blood mononuclear cells (CD14+) (PMBCs) isolated from healthy volunteers and lung epithelial cell lines. We observed variance between β-glucan content in extracts isolated from seven mushroom species. The extracts with the highest β-glucan content found was Lentinus edodes which contained 70% w/w and Hypsizygus tessellatus which contained 80% w/w with low levels of α-glucan. The extracts had the ability to induce secretion of up to 4000 pg/mL of the inflammatory cytokine IL-6, and up to 5000 pg/mL and 500 pg/mL of the anti-inflammatory cytokines IL-22 and IL-10, respectively, at a concentration of 1 mg/mL in THP-1 macrophages. In the presence of cytokine injury, IL-8 was reduced from 15,000 pg/mL to as low as 10,000 pg/mL in THP-1 macrophages. After insult with LPS, phagocytosis dropped from 70-90% to as low 10% in CD14+ PBMCs. After LPS insult CCL8 relative gene expression was reduced, and IL-10 relative gene expression increased from 50 to 250-fold in THP-1 macrophages. In lung epithelial cells, both A549 and BEAS-2B after IL-1β insult, IL-8 levels dropped from 10,000 pg/mL to as low as 6000 pg/mL. TNF-α levels dropped 10-fold from 100 pg/mL to just below 10 pg/mL. These results demonstrate the therapeutic potential of β-glucans in inflammatory lung conditions. Findings also advance bio-based research that connects green innovation with One Health applications for the betterment of society.

The phagocytic receptors of β-glucan

Phagocytosis is a cellular process maintaining tissue balance and plays an essential role in initiating the innate immune response. The process of phagocytosis was triggered by the binding of pathogen-associated molecular patterns (PAMP) with their cell surface receptors on the phagocytes. These receptors not only perform phagocytic functions, but also bridge the gap between extracellular and intracellular communication, leading to signal transduction and the production of inflammatory mediators, which are crucial for clearing the invading pathogens and maintaining cell homeostasis. For the past few years, the application of β-glucan comes down to immunoregulation and anti-tumor territory. As a well-known PAMP, β-glucan is one of the most abundant polysaccharides in nature. By binding to specific receptors on immune cells and activating intracellular signal transduction pathways, it causes phagocytosis and promotes the release of cytokines. Further retrieval and straightening out literature related to β-glucan phagocytic receptors will help better elucidate their immunomodulatory functions. This review attempts to summarize physicochemical properties and specific processes involved in β-glucan induced phagocytosis, its phagocytic receptors, and cascade events triggered by β-glucan at the cellular and molecular levels.

Dectin-1-Mediated Production of Pro-Inflammatory Cytokines Induced by Yeast β-Glucans in Bovine Monocytes

Yeast-derived products containing β-glucans have long been used as feed supplements in domesticated animals in an attempt to increase immunity. β-glucans are mainly recognized by the cell surface receptor CLEC7A, also designated Dectin-1. Although the immune mechanisms elicited through Dectin-1 activation have been studied in detail in mice and humans, they are poorly understood in other species. Here, we evaluated the response of bovine monocytes to soluble and particulate purified β-glucans, and also to Zymosan. Our results show that particulate, but not soluble β-glucans, can upregulate the surface expression of costimulatory molecules CD80 and CD86 on bovine monocytes. In addition, stimulated cells increased production of IL-8 and of TNF, IL1B, and IL6 mRNA expression, in a dose-dependent manner, which correlated positively with CLEC7A gene expression. Production of IL-8 and TNF expression decreased significantly after CLEC7A knockdown using two different pairs of siRNAs. Overall, we demonstrated here that bovine monocytes respond to particulate β-glucans, through Dectin-1, by increasing the expression of pro-inflammatory cytokines. Our data support further studies in cattle on the induction of trained immunity using dietary β-glucans.

β-Glucan-Induced IL-10 Secretion by Monocytes Triggers Porcine NK Cell Cytotoxicity

Beta-glucans are naturally occurring polysaccharides present in cell walls of fungi, yeast, bacteria, cereals, seaweed, and algae. These microbe-associated molecular patterns (MAMPs) possess immunomodulatory properties. In human, it has been suggested that NK cells can be activated by β-glucans. Here, we aimed to elucidate whether β-glucans modulate porcine NK cell responses in vitro and if so, how these effects are mediated. We investigated the effect of two β-glucans, Macrogard and Curdlan, which differ in solubility and structure. Direct addition of β-glucans to purified porcine NK cells did not affect cytotoxicity of these cells against K562 target cells. However, when using PBMC instead of purified NK cells, β-glucan addition significantly increased NK cell-mediated cytotoxicity. This effect depended on factors secreted by CD14+ monocytes upon β-glucan priming. Further analysis showed that monocytes secrete TNF-α, IL-6, and IL-10 upon β-glucan addition. Of these, IL-10 turned out to play a critical role in β-glucan-triggered NK cell cytotoxicity, since depletion of IL-10 completely abrogated the β-glucan-induced increase in cytotoxicity. Furthermore, addition of recombinant IL-10 to purified NK cells was sufficient to enhance cytotoxicity. In conclusion, we show that β-glucans trigger IL-10 secretion by porcine monocytes, which in turn leads to increased NK cell cytotoxicity, and thereby identify IL-10 as a potent stimulus of porcine NK cell cytotoxicity.

Yarrowia lipolytica N6-glucan protects goat leukocytes against Escherichia coli by enhancing phagocytosis and immune signaling pathway genes

Immunostimulant and protective effects of Yarrowia lipolytica glucans against important pathogens, such as Escherichia coli, have not been investigated in goats and other ruminants. This study aimed to characterize Y. lipolytica N6-glucan (Yl-glucan) and its possible role in immunological signaling pathway activation and immunoprotection against E. coli in goat leukocytes. Characterization analyses showed that Y. lipolytica content had a mix of β and α-D-glucans, molecular weight of 3301.53 kDa and low solubility after the heat treatment. The stimulation of goat leukocytes with Yl-glucan induced protection against E. coli challenge. Remarkably, Yl-glucan and E. coli interaction increased gene expression of dectin-1 and TLR-2 receptors, signaling pathway Syk/NFκB, and cytokines, such as TNF-α and IL-10. As a consequence of signaling activation, phagocytosis, and nitric oxide production enhanced killing of pathogens. Altogether, Y. lipolytica-glucan demonstrated to possess an immunoprotective potential against E. coli through innate immune response modulation in goat leukocytes.

Ferumoxytol-β-glucan Inhibits Melanoma Growth via Interacting with Dectin-1 to Polarize Macrophages into M1 Phenotype

Background: Regulating the polarization of macrophages to antitumor M1 macrophages is a promising strategy for overcoming the immunosuppression of the tumor microenvironment for cancer therapy. Ferumoxytol (FMT) can not only serve as a drug deliver agent but also exerts anti-tumor activity. β-glucan has immuno-modulating properties to prevent tumor growth. Thus, a nanocomposite of FMT surface-coated with β-glucan (FMT-β-glucan) was prepared to explore its effect on tumor suppression. Methods: Male B16F10 melanoma mouse model was established to explore the antitumor effect of FMT-β-glucan. The viability and apoptotic rates of B16F10 cells were detected by cell counting kit-8 and Annexin-V/PI experiments. The levels of M1 markers were quantified by quantitative reverse transcription-polymerase chain reaction and enzyme linked immunosorbent assay. Phagocytic activity and intracellular reactive oxygen species (ROS) in macrophages were evaluated by the neutral red uptake assay and flow cytometry, respectively. Small interfering RNA (siRNA) transfection was applied to knock down the Dectin-1 gene in RAW 264.7 cells. Results: FMT-β-glucan suppressed tumor growth to a greater extent and induced higher infiltration of M1 macrophages than the combination of FMT and β-glucan (FMT+β-glucan) in vivo. In vitro, supernatant from FMT-β-glucan-treated RAW 264.7 cells led to lower cell viability and induced more apoptosis of B16F10 cells than that from the FMT+β-glucan group. Moreover, FMT-β-glucan boosted the expression of M1 type markers, and increased phagocytic activity and ROS in RAW 264.7 cells. Further research indicated that FMT-β-glucan treatment promoted the level of Dectin-1 on the surface of RAW 264.7 cells and that knockdown of Dectin-1 abrogated the phosphorylation levels of several components in MAPK and NF-κB signaling. Conclusion: The nanocomposite FMT-β-glucan suppressed melanoma growth by inducing the M1 macrophage-activated tumor microenvironment.

β-Glucan Metabolic and Immunomodulatory Properties and Potential for Clinical Application

β-glucans are complex polysaccharides that are found in several plants and foods, including mushrooms. β-glucans display an array of potentially therapeutic properties. β-glucans have metabolic and gastro-intestinal effects, modulating the gut microbiome, altering lipid and glucose metabolism, reducing cholesterol, leading to their investigation as potential therapies for metabolic syndrome, obesity and diet regulation, gastrointestinal conditions such as irritable bowel, and to reduce cardiovascular and diabetes risk. β-glucans also have immune-modulating effects, leading to their investigation as adjuvant agents for cancers (solid and haematological malignancies), for immune-mediated conditions (e.g., allergic rhinitis, respiratory infections), and to enhance wound healing. The therapeutic potential of β-glucans is evidenced by the fact that two glucan isolates were licensed as drugs in Japan as immune-adjuvant therapy for cancer in 1980. Significant challenges exist to further clinical testing and translation of β-glucans. The diverse range of conditions for which β-glucans are in clinical testing underlines the incomplete understanding of the diverse mechanisms of action of β-glucans, a key knowledge gap. Furthermore, important differences appear to exist in the effects of apparently similar β-glucan preparations, which may be due to differences in sources and extraction procedures, another poorly understood issue. This review will describe the biology, potential mechanisms of action and key therapeutic targets being investigated in clinical trials of β-glucans and identify and discuss the key challenges to successful translation of this intriguing potential therapeutic.

Conjugation of β-glucans on heat-stable enterotoxin (ST) to enhance the immunogenic response in mouse leucocytes

Enterotoxigenic Escherichia coli (ETEC) is an important diarrhea-causing pathogen for humans. Heat-stable enterotoxin (ST) plays a crucial role in triggering diarrhea and ETEC pathogenesis. However, ST is a small peptide that lacks immunogenic activity itself but becomes immunogenic when it is coupled to a carrier molecule. In this study, the β-glucans (BG) from yeasts have been used to test their immunomodulatory activity and adjuvant effect on the properties of ST. This study aimed to synthesize and characterize a conjugate of yeast-derived β-glucan with the ST enterotoxin (BG-ST) and evaluate the antigenic and antioxidant activities in mouse splenocytes. Fourier transform infrared spectroscopy and scanning electron microscopy analysis showed new bands and changes in morphology, respectively, confirming ST was successfully coupled to beta glucan. Additionally, according to the enzyme-linked immunosorbent assay (ELISA), conjugation efficiency was almost 90%. Cellular viability, phagocytic cell proportion, and respiratory burst enhanced splenocytes stimulated by BG-ST. In addition, nitric oxide production and antioxidant enzymes increased in cells stimulated with BG-ST, BG and ST. In conclusion, the results revealed the successful conjugation of β-glucan with ST peptide enhancing immune and antioxidant parameters to a greater extent than their individual components.

Dietary supplementation of beta-glucan-rich molasses yeast powder on antibody response to swine fever virus and hematology of starter-grower pigs

This research investigated the impact of dietary beta-glucan-rich molasses yeast powder (MYP) supplementation on the antibody response to swine fever virus (Titer) and hematology of starter-grower pig. Sixteen cross pigs (30 kg body weight) were equally split into four groups; each group with four replicates and fed four dietary treatments that consisted of basal diets (control) and the basal diets added with 2.5, 5.0, and 7.5% MYP. Feed and water were consumed ad libitum for 44 days. Feed intake (FI), MYP intake (MYPI), beta-glucan intake (BGI), and Mannan-oligosaccharide intake (MOSI) were recorded daily. Titer was evaluated after 15 (Titer15) and 30 (Titer30) days after vaccination, while hematology was analyzed at the end of the experiment. The results indicated that it was unchangeable for ADFI (P > 0.05). No impacts were observed on hematological variables and Titer15 in MYP fed pigs (P > 0.05). However, supplementation with 7.5% MYP increased platelet count (PC) and Titer30 (P < 0.01), but decreased hematocrit (Hct) (P < 0.05). Titer 30 and titer 15 were linked to MYPI, BGI, and MOSI (P < 0.05). Based on the study, feeding starter-grower pigs diets supplemented with 7.5% MYP might enhance the antibody response to swine fever virus 30 days after vaccination, and it has a potential role in the application in prevention of swine fever virus disease.

Development of Fish Immunity and the Role of β-Glucan in Immune Responses

Administration of β-glucans through various routes, including immersion, dietary inclusion, or injection, have been found to stimulate various facets of immune responses, such as resistance to infections and resistance to environmental stress. β-Glucans used as an immunomodulatory food supplement have been found beneficial in eliciting immunity in commercial aquaculture. Despite extensive research involving more than 3000 published studies, knowledge of the receptors involved in recognition of β-glucans, their downstream signaling, and overall mechanisms of action is still lacking. The aim of this review is to summarize and discuss what is currently known about of the use of β-glucans in fish.

The anti-inflammatory effects of low- and high-molecular-weight beta-glucans from Agrobacterium sp. ZX09 in LPS-induced weaned piglets

The physicochemical characteristics of beta-glucans determine the immune responses of the intestines and whole body. It is hypothesized that glucans with different molecular weights have diverse modes of action on LPS-mediated immune activity. This study aimed to verify the immune-modulatory effects of two types of beta-glucans in LPS-induced weaned piglets. The results indicated that dietary beta-glucan supplementation could prevent losses in body weight gain caused by LPS challenge. Supplementation with different molecular weights of beta-glucans decreased the production of IL-1β and TNF-α and increased IL-10 production, which is likely associated with key factors such as TLR4 and NF-κB. High-molecular-weight beta-glucans seemed to have a strong functional capacity to modulate the innate immune response through the Dectin-1 receptor. Therefore, the results indicate that supplementing piglets with Agrobacterium sp. ZX09 beta-glucans inhibits LPS-mediated depression in the growth performance and plays a protective role during LPS challenge possibly via the Dectin-1 receptor and the TLR4/NF-κB pathway. The results reveal the potential therapeutic activity of purified Agrobacterium sp. ZX09 beta-glucan following experimental LPS infusion.

Paeonol promotes the phagocytic ability of macrophages through confining HMGB1 to the nucleus

Phagocytosis is a basic immune response to the pathogens invading. Immunosuppression may occur in diseases like sepsis and cancer, and cause a low phagocytic ability of phagocytes. High mobility group protein B1 (HMGB1) is a DNA chaperone which is closely related to the phagocytosis. Nonetheless, its influence on phagocytosis is still controversial. We found that paeonol could inhibit the translocation of HMGB1 from the nucleus to the cytoplasm, it may have an impact on phagocytosis. In the present study, we performed in vivo and in vitro experiments to investigate the influence of paeonol on phagocytosis. Zymosan was used to test the phagocytic function of macrophages. Our results showed that paeonol promotes the phagocytosis of macrophages through confining HMGB1 to the nucleus. Through interacting with P53, the nuclear HMGB1 keep it in the nucleus and decrease the negative influence of P53 on the phosphorylation of Focal Adhesion Kinase (FAK). The increasing of phosphorylated FAK promotes the formation of pseudopod and enhances the phagocytic ability of macrophages.

Differential induction of innate memory in porcine monocytes by -glucan or bacillus Calmette-Guerin

Innate immunomodulation via induction of innate memory is one mechanism to alter the host’s innate immune response to reduce or prevent disease. Microbial products modulate innate responses with immediate and lasting effects. Innate memory is characterized by enhanced (training) or depressed (tolerance) innate immune responses, including pro-inflammatory cytokine production, to secondary exposure following a priming event. To investigate the ability of β-glucans and bacillus Calmette-Guerin to induce innate training or tolerance in pig cells, porcine monocytes were cultured with priming agonist (β-glucans or bacillus Calmette-Guerin) then re-stimulated 5 d later with a heterologous microbial agonist to determine induction of innate memory. Priming with β-glucan from Saccharomyces cerevisiae depressed IL-1β and TNF-α cytokine responses to re-stimulation with LPS, indicative of a tolerized state. However, bacillus Calmette-Guerin priming induced a trained state in porcine monocytes, as LPS re-stimulation enhanced IL-1β and TNF-α gene expression and protein production. We present the first evidence of innate memory in pig monocytes, with bacillus Calmette-Guerin (training) or Saccharomyces cerevisiae β-glucan (tolerance). Induction of a trained or tolerized state in vitro is a first step to identify agonists to alter the innate immune system at the animal level with the intent of enhancing disease resistance.

C-Type Lectins in Veterinary Species: Recent Advancements and Applications

C-type lectins (CTLs), a superfamily of glycan-binding receptors, play a pivotal role in the host defense against pathogens and the maintenance of immune homeostasis of higher animals and humans. CTLs in innate immunity serve as pattern recognition receptors and often bind to glycan structures in damage- and pathogen-associated molecular patterns. While CTLs are found throughout the whole animal kingdom, their ligand specificities and downstream signaling have mainly been studied in humans and in model organisms such as mice. In this review, recent advancements in CTL research in veterinary species as well as potential applications of CTL targeting in veterinary medicine are outlined.

Beta-glucan's varying structure characteristics modulate survival and immune-related genes expression from Vibrio harveyi-infected Artemia franciscana in gnotobiotic conditions

β-Glucans have long been used as an immunostimulant in aquaculture. However, the relationship of its structure to its immunomodulatory properties are poorly understood. In this study, the particle size and chemical structure of β-glucans extracted from wild-type strain of baker's yeast (Saccharomyces cerevisiae) and its null-mutant yeasts Gas1 were characterised. Using Sigma β-glucan as a reference, the immunomodulatory properties of these polysaccharides in the germ-free Artemia franciscana model system in the presence of Vibrio harveyi bacterial challenge were investigated. The survival of the A. franciscana nauplii, upon challenge with V. harveyi, was significantly higher in all three glucan-treated groups compared to the control. The glucan Gas1 with a lower degree of branching and shorter side chain length had the most prominent V. harveyi-protective effects. The particle size did not affect the nauplii survival when challenged with V. harveyi. Results also showed that the salutary effect of the tested glucans was associated with the upregulation of innate immune genes such as lipopolysaccharide and β-1,3-glucan-binding protein (lgbp), high mobility group box protein (hmgb), and prophenoloxidase (proPO). Interestingly, the up-regulation of superoxidase dismutase (sod) and glutathione-s-transferase (gst) was only observed in Gas1 treated group, indicating that Gas1 could function to induce higher reactive oxygen species and stronger immunomodulatory function in A. franciscana, and therefore higher survival rate. The expression of heat shock protein 70 (hsp70), peroxinectin (pxn), and down syndrome cell adhesion molecule (dscam) remain unaltered in response to glucan treatment. Taken together, this study provides insights into the structure-function relationship of β-glucan and the results confirmed that β-glucan can be an effective immunostimulant in aquaculture, especially the Gas1 glucan.

Immune activation of murine RAW264.7 macrophages by sonicated and alkalized paramylon from Euglena gracilis

BACKGROUND

Euglena is a new super health food resource that is rich in the natural polysaccharide paramylon, a linear β-1,3-glucan with various biological activities including activity on the immune system in different cell lines and animals. Despite these reports, the immune regulation mechanism of paramylon is still unclear.

RESULTS

We investigate the signaling pathways paramylon impacts in immune macrophages. In RAW264.7 macrophages, sonicated and alkalized paramylon oligomers up-regulated inducible nitric oxide synthase (iNOS) and increased secretion of nitric oxide (NO), interleukin (IL)-6 and tumor necrosis factor (TNF)-α, in a concentration-dependent manner. In addition, paramylon activated the nuclear factor-κB(NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways and inhibiting these pathways attenuated the paramylon-induced secretion of the above immune-mediators.

CONCLUSIONS

These results demonstrate that Euglena gracilis paramylon modulates the immune system via activation of the NF-κB and MAPK signaling pathways and thus has potential therapeutic benefits.

Innate Immunomodulation in Food Animals: Evidence for Trained Immunity?

Antimicrobial resistance (AMR) is a significant problem in health care, animal health, and food safety. To limit AMR, there is a need for alternatives to antibiotics to enhance disease resistance and support judicious antibiotic usage in animals and humans. Immunomodulation is a promising strategy to enhance disease resistance without antibiotics in food animals. One rapidly evolving field of immunomodulation is innate memory in which innate immune cells undergo epigenetic changes of chromatin remodeling and metabolic reprogramming upon a priming event that results in either enhanced or suppressed responsiveness to secondary stimuli (training or tolerance, respectively). Exposure to live agents such as bacille Calmette-Guerin (BCG) or microbe-derived products such as LPS or yeast cell wall ß-glucans can reprogram or "train" the innate immune system. Over the last decade, significant advancements increased our understanding of innate training in humans and rodent models, and strategies are being developed to specifically target or regulate innate memory. In veterinary species, the concept of enhancing the innate immune system is not new; however, there are few available studies which have purposefully investigated innate training as it has been defined in human literature. The development of targeted approaches to engage innate training in food animals, with the practical goal of enhancing the capacity to limit disease without the use of antibiotics, is an area which deserves attention. In this review, we provide an overview of innate immunomodulation and memory, and the mechanisms which regulate this long-term functional reprogramming in other animals (e.g., humans, rodents). We focus on studies describing innate training, or similar phenomenon (often referred to as heterologous or non-specific protection), in cattle, sheep, goats, swine, poultry, and fish species; and discuss the potential benefits and shortcomings of engaging innate training for enhancing disease resistance.

Nuclear HMGB1 promotes the phagocytic ability of macrophages

Phagocytosis is a basic immune response to the invasion of pathogens. High mobility group protein B1 (HMGB1) is a DNA chaperone that is associated with phagocytosis. However, its influence on phagocytosis is debated. In the present study, HMGB1-mutant, HMGB1-overexpressing and HMGB1-silenced RAW264.7 cells were constructed. In addition, HMGB1 conditional knockout mice were constructed to determine the influence of HMGB1 on phagocytosis. Lipopolysaccharide (LPS) was used to stimulate the translocation of HMGB1 from the nucleus to the cytoplasm. Zymosan particles were used to test the phagocytic function of the macrophages. Our results showed that the accumulation of HMGB1 in the nucleus enhances the phagocytic function of the macrophages. By interacting with P53, nuclear HMGB1 may remain in the nucleus and decrease the negative influence of P53 on the phosphorylation of focal adhesion kinase (FAK). The increase in phosphorylated FAK promotes the formation of pseudopods and enhances the phagocytic ability of macrophages.

Structure-Functional Activity Relationship of β-Glucans From the Perspective of Immunomodulation: A Mini-Review

β-Glucans are a heterogeneous group of glucose polymers with a common structure comprising a main chain of β-(1,3) and/or β-(1,4)-glucopyranosyl units, along with side chains with various branches and lengths. β-Glucans initiate immune responses via immune cells, which become activated by the binding of the polymer to specific receptors. However, β-glucans from different sources also differ in their structure, conformation, physical properties, binding affinity to receptors, and thus biological functions. The mechanisms behind this are not fully understood. This mini-review provides a comprehensive and up-to-date commentary on the relationship between β-glucans' structure and function in relation to their use for immunomodulation.

Glucan particles as suitable carriers for the natural anti-inflammatory compounds curcumin and diplacone - Evaluation in an ex vivo model

Natural compounds offer a wide spectrum of potential active substances, but often they have a poor bioavailability. To increase the bioavailability and bioactivity of the natural anti-inflammatory molecules curcumin and diplacone, we used glucan particles (GPs), hollow shells from Saccharomyces cerevisiae composed mainly of β-1,3-d-glucan. Their indigestibility and relative stability in the gut combined with their immunomodulatory effects makes them promising carriers for such compounds. This study aimed to determine how curcumin and diplacone, either alone or incorporated in GPs, affect the immunomodulatory activity of the latter by assessing the respiratory burst response and the secretion of pro-inflammatory cytokines by primary porcine innate immune cells. Incorporating curcumin and diplacone into GPs by controlled evaporation of the organic solvent substantially reduced the respiratory burst response mediated by GPs. Incorporated curcumin in GPs also reduced GPs mediated secretion of IL-1β and TNF-α by innate immune cells. The obtained results indicate a potentially beneficial effect of the incorporation of curcumin or diplacone into GPs against inflammation.

Effects of omega-3 fatty acids on immune, health and growth variables in veal calves

Under the present intensive rearing conditions, calves face a series of stressors and multiple pathogens often necessitating antimicrobial use. Multiple feed additives are currently explored for their ability to prevent disease and limit the use of antimicrobials. Supplementation of the polyunsaturated long chain n-3 fatty acids eicosapentaenoic (EPA) and docohexaenoic (DHA) from marine origin has been proposed as a strategy to improve immune function and prevent excessive inflammation reactions. The aim of this randomized clinical trial was to explore the effects of n-3 fatty acids (PUFAs) used as feed supplement on health, production and immune variables in a veal calf setting. One hundred-seventy calves were randomly assigned to 3 treatment groups: microalgae (MA, n = 57, 2.5 g DHA/animal/day), fish oil (FO, n = 57, 2.5 g EPA + DHA/animal/day)] and a control group (CON, n = 56). Average daily gain (ADG), bodyweight at 12 weeks on feed and slaughter weight were determined. Health monitoring consisted of recording of clinical signs and repeated thoracic ultrasonography. After 5, 8 and 11 weeks of supplementation, the function of neutrophils, monocytes and peripheral blood mononuclear cells (PBMCs) was evaluated ex vivo by measuring reactive oxygen species (ROS) production by neutrophils and monocytes and proliferation of and cytokine release by PBMCs. Under the field conditions of this study, dietary supplementation of MA and FO showed very limited immunomodulatory effects. Feeding MA led to increased ROS production by neutrophils, Estimate (E) = 0.38, Standard Error (SE) = 0.14; P < 0.05, compared to the control calves after 5 weeks of in-feed supplementation. FO reduced IL-6 secretion E= -0.29, SE= 0.11; P < 0.05 compared to MA treated animals after 11 weeks on feed. Health and production variables were unaffected by treatments. The doses of EPA and DHA used in this study did not cause immunomodulatory changes in highly stressed calves to such an extent that this led to better health or growth of animals.

Effects of glycerol-esters of saturated short- and medium chain fatty acids on immune, health and growth variables in veal calves

In veal and dairy beef production systems, Holstein bull calves experience many stressors and excessive pathogen exposure, necessitating the use of antimicrobials for welfare and production reasons. The aim of this randomized clinical trial was to explore the effects of esterified fatty acids used as feed supplement on health, production and immune variables in veal calves. Different glycerol-esters of fatty acids were used: short chain fatty acid (SCFA)-based glycerol-mono- (C4) and tributyrate (C4), and medium chain fatty acid (MCFA)-based glycerol-monocaprylate/monocaprinate (C8/C10) and glycerol-monolaurate (C12) in two different doses. One hundred sixty eight calves (2-to 4-week-old) were randomly assigned to 6 treatment groups; tributyrate (0.5 g/animal/day); monobutyrate (1 g/animal/day); low C8/C10 (7 g/animal/day) and high C8/C10 (10 g/animal/day); low C12 (4 g/animal/day) and high C12 (6 g/animal/day) and a control group (CON). Duration of in-feed supplementation was 14 weeks. Average daily gain, bodyweight at 14 weeks on feed and slaughter weight were determined. Health monitoring consisted of clinical signs and repeated thoracic ultrasonography. After 4, 8 and 12 weeks of supplementation, the function of neutrophils, monocytes and peripheral blood mononuclear cells (PBMCs) was evaluated ex vivo by measuring reactive oxygen species (ROS) production by neutrophils and monocytes, proliferation of and cytokine release by PBMCs. Study power was based upon ROS production by neutrophils and treatment groups were too limited to detect significant differences in growth and health variables. Glycerol-ester supplementation resulted in different effects on immune cell function, depending on the type and dose of the glycerol-ester as well as duration of supplementation. Our main findings were increased secretion of interleukin IL-17A by PBMCs at 4 weeks of feed supplementation in high C8/C10 (P< 0.01), low C12 (P < 0.01) and monobutyrate (P< 0.01) groups, combined with decreased ROS production in neutrophils (P < 0.001) and monocytes (P < 0.05) in the high C8/C10 and monocytes (P < 0.05) in low C12 groups compared to the control animals. After 12 weeks on feed, ROS production by neutrophils (P < 0.001) and monocytes (P < 0.01) of monobutyrate and by monocytes (P < 0.01) of tributyrate groups was decreased compared to control calves. In summary, supplementation of glycerol-esters of MCFAs resulted in immune-modulatory effects, which did not manifest themselves in improved health and growth of calves under the conditions and limitations of this study. Especially doses of high C8/C10 and low C12 show potential to promote an early, robust pro-inflammatory response with diminished ROS production. This might be beneficial for clearance of pathogens in young calves in periods of stress and high pathogen load.

Paramylon, a Potent Immunomodulator from WZSL Mutant of Euglena gracilis

β-glucans, heterogeneous glucose polymers present in many organisms, have the capability to activate the innate immune system. Efficacy of activation depends on purity of the compound, molecular structure, polymerization degree, and source. One of the purest forms of crystallized β-(1–3)-glucan present in nature is the paramylon extracted from the WZSL non-chloroplastic mutant of Euglena gracilis, which can be processed to produce linear nanofibers capable of interacting with specific receptors present on cell membranes. The effects of these nanofibers, already investigated on plants, animals, and humans, will be analyzed.

Randomized field trial on the effects of body weight and short transport on stress and immune variables in 2- to 4-week-old dairy calves

Background

Whether underweight calves respond differently to transport stress, enhancing their disease risk, is currently unknown.

Objective

To determine the effects of low body weight and transport stress on immune variables.

Animals

Twenty‐one 2‐ to 4‐week‐old male Holstein calves, housed on a commercial farm.

Methods

Randomized clinical trial. Full factorial design with 4 treatment groups: low body weight (≤46 kg)/no transport (LOWCON); low body weight/transport (LOWTRANS); normal body weight (>46 kg)/no transport (NORMCON), and normal body weight/transport (NORMTRANS). Transport duration was 2 hours.

Results

Transport significantly increased serum cortisol concentration (77.8 μg/mL; 95% confidence interval [CI], 37.8‐131.6; P < .001), interleukin (IL)‐17A (344.9 pg/mL; 95% CI, 32.2‐556.5; P = .04), and tumor necrosis factor‐α (TNF‐α) (218.2 pg/mL; 95% CI, 32.5‐368.3; P = .03) production after lipopolysaccharide (LPS) stimulation. Body weight did not affect any of the studied variables. However, the interaction of transport and body weight was significant. LOWTRANS calves showed increased monocyte count (2.0 × 10⁹/L; 95% CI, 0.6‐4.2; P < .05) and interleukin IL‐17A production (106.0 pg/mL; 95% CI, 4.2‐306.9; P = .03) compared to normal weight calves and increased TNF‐α production (275.6 pg/mL; 95% CI, 2.6‐463.0; P = .02) compared to LOWCON calves in unstimulated peripheral blood mononuclear cells (PBMCs) after transport.

Conclusion and Clinical Importance

These findings contribute to our understanding of increased disease susceptibility of underweight calves when transported. Gamma globulin concentration was identified as important interfering factor in studies on immune variables in neonatal calves.

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.

Sterigmatomyces halophilus β-glucan improves the immune response and bacterial resistance in Pacific red snapper (Lutjanus peru) peripheral blood leucocytes: In vitro study

β-Glucans are naturally occurring polysaccharides that are produced by bacteria, fungi and yeast. They are considered immunostimulants in fish acting on non-specific defense mechanism. Yeast-derived glucans from cell wall (Sterigmatomyces halophilus, β-Gluc/Sh) have been used for this purpose in this study. Therefore, an in vitro assay using peripheral blood leucocytes (PBLs) from Pacific red snapper was performed to evaluate the stimulant effects of β-Gluc/Sh and zymosan A (positive control) for 12 and 24 h and after bacterial challenge with Aeromonas hydrophila at 24 h. In addition, structural characterization of this marine yeast glucan was performed by proton nuclear magnetic resonance (NMR) revealing structures containing (1-6)-branched (1-3)-β-D-glucan. PBLs responded positively to β-Gluc/Sh where cell viability was higher than 80%. After challenge, β-Gluc/Sh was able to inhibit cytotoxicity caused by A. hydrophila, highlighting that the PBLs incubated with β-Gluc/Sh significantly increased the non-specific immune response, such as phagocytic activity, respiratory burst, nitric oxide and peroxidase activities followed by an increase in superoxide dismutase and catalase activities after 12 and 24 h post-stimulation and after challenge with the pathogen. Regarding induction of antioxidant gene expression, it was more pronounced in stimulated β-Gluc/Sh leucocytes compared to other groups at all experimental times of the trial and after bacterial challenge. Indeed, our results clearly showed the ability of leucocytes to strongly react to β-Gluc/Sh with an increase in cytokine gene expression, particularly the IL-1β, IL-10 and IL-17 genes. These results confirm that S. halophilus yeast-derived β-glucan, isolated from an extreme marine environment, is beneficial for increasing innate immune response and enhancing resistance against A. hydrophila in vitro.

Immunostimulant effects and potential application of β-glucans derived from marine yeast Debaryomyces hansenii in goat peripheral blood leucocytes

Debaryomyces hansenii has been described to be effective probiotic and immunostimulatory marine yeast in fish. Nonetheless, to the best of our knowledge, it has been not assayed in ruminants. This study attempts to describe the immunostimulatory effects of its β-glucan content through in vitro assays using goat peripheral blood leukocytes at 24 h of stimulation. The structural characterization of yeast glucans by proton nuclear magnetic resonance indicated structures containing (1-6)-branched (1-3)-β-D-glucan. In vitro assays using peripheral blood leukocytes stimulated with β-glucans derived from three D. hansenii strains and zymosan revealed that β-glucans significantly increased cell immune parameters, such as phagocytic ability, reactive oxygen species production (respiratory burst), peroxidase activity and nitric oxide production. Antioxidant enzymes revealed an increase in superoxide dismutase and catalase activities in leukocytes stimulated with yeast β-glucans. This study revealed that yeast β-glucans were able to activate dectin-1 mRNA gene expression in leukocytes. The TLR4 gene expression was up-regulated in leukocytes after stimulation with yeast β-glucans. In conclusion, β-glucans were able to modulate the immune system by promoting cell viability, phagocytic activity, antioxidant immune response and immune-related gene expression in leukocytes. Therefore, β-glucans derived from Debaryomyces hansenii should be considered a potential immunostimulant for goat production systems.

Immunomodulatory potential of β-glucan as supportive treatment in porcine rotavirus enteritis

A non-blinded randomized clinical trial was conducted to assess the immunomodulatory potential of β-glucan (BG) in piglet diarrhoea associated with type A rotavirus infection. A total of 12 rotavirus-infected diarrheic piglets were randomly divided into two groups: wherein six rotavirus-infected piglets were treated with supportive treatment (ST) and other six rotavirus-infected piglets were treated with BG along with ST (ST-BG). Simultaneously, six healthy piglets were also included in the study which served as control. In rotavirus-infected piglets, marked increase of Intestinal Fatty Acid Binding Protein-2 (I-FABP2), nitric oxide (NOx), Interferon-γ (IFN-γ) concentrations and decrease of immunoglobulin G (IgG) were noticed compared to healthy piglets. The faecal consistency and dehydration scores were significantly higher in rotavirus-infected piglets than healthy piglets. The ST-BG treatment progressively reduced the I-FABP2 and increased the IgG concentrations over the time in rotavirus-infected piglets compared to piglets received only ST. A pronounced enhancement of NOx and IFN-γ concentrations was observed initially on day 3 and thereafter the values reduced on day 5 in ST-BG treated piglets in comparison to piglets which received only ST. Additionally, ST-BG treatment significantly reduced faecal consistency and dehydration scores on day 3 compared to ST in rotavirus-infected piglets. These findings point that BG represents a potential additional therapeutic option to improve the health condition and reduce the piglet mortality from rotavirus associated diarrhoea where porcine rotavirus vaccine is not available.

Duality of β-glucan microparticles: antigen carrier and immunostimulants

Designing efficient recombinant mucosal vaccines against enteric diseases is still a major challenge. Mucosal delivery of recombinant vaccines requires encapsulation in potent immunostimulatory particles to induce an efficient immune response. This paper evaluates the capacity of β-glucan microparticles (GPs) as antigen vehicles and characterizes their immune-stimulatory effects. The relevant infectious antigen FedF was chosen to be loaded inside the microparticles. The incorporation of FedF inside the particles was highly efficient (roughly 85%) and occurred without antigen degradation. In addition, these GPs have immunostimulatory effects as well, demonstrated by the strong reactive oxygen species (ROS) production by porcine neutrophils upon their recognition. Although antigen-loaded GPs still induce ROS production, antigen loading decreases this production by neutrophils for reasons yet unknown. However, these antigen-loaded GPs are still able to bind their specific β-glucan receptor, demonstrated by blocking complement receptor 3, which is the major β-glucan receptor on porcine neutrophils. The dual character of these particles is confirmed by a T-cell proliferation assay. FedF-loaded particles induce a significantly higher FedF-specific T-cell proliferation than soluble FedF. Taken together, these results show that GPs are efficient antigen carriers with immune-stimulatory properties.

Euglena gracilis paramylon activates human lymphocytes by upregulating pro-inflammatory factors

The aim of this study was to verify the activation details and products of human lymphomonocytes, stimulated by different β-glucans, that is Euglena paramylon, MacroGard^®, and lipopolysaccharide. We investigated the gene expression of inflammation-related cytokines and mediators, transactivation of relevant transcription factors, and phagocytosis role in cell-glucan interactions, by means of RT-PCR, immunocytochemistry, and colorimetric assay. Our results show that sonicated and alkalized paramylon upregulates pro-inflammatory factors (NO, TNF-α, IL-6, and COX-2) in lymphomonocytes. A clear demonstration of this upregulation is the increased transactivation of NF-kB visualized by immunofluorescence microscopy. Phagocytosis assay showed that internalization is not a mandatory step for signaling cascade to be triggered, since immune activity is not present in the lymphomonocytes that have internalized paramylon granules and particulate MacroGard^®. Moreover, the response of Euglena β-glucan-activated lymphomonocytes is much greater than that induced by commercially used β-glucans such as MacroGard^®. Our in vitro results indicate that linear fibrous Euglena β-glucan, obtained by sonication and alkaline treatment can act as safe and effective coadjutant of the innate immune system response.

Polymorphisms of the immune-modulating receptor dectin-1 in pigs: their functional influence and distribution in pig populations

Dectin-1, a C-type lectin receptor that recognizes fungal β-glucans, is involved in antifungal immunity and the regulation of intestinal immune homeostasis. Dectin-1 is involved in both synthesis and maturation of interleukin-1β, a key pro-inflammatory cytokine in immunity. Here, we assessed the genetic diversity in the gene encoding dectin-1 (CLEC7A) within various pig populations and examined the influence of these polymorphisms on the two different signaling pathways after ligand recognition. An amino-acid polymorphism located in the carbohydrate-recognition domain, leucine to serine at position 138 (L138S), which occurred exclusively in Japanese wild boars at low frequency, significantly increased NF-κB induction but not caspase-8 activity after stimulation with zymosan. In contrast, other amino-acid polymorphisms present at comparatively high frequency in commercial pig populations had little influence on ligand recognition. These results suggest that functionally neutral polymorphisms in dectin-1 are widespread in pig populations.

Muscle wound healing in rainbow trout (Oncorhynchus mykiss)

We followed the progression of healing of deep excisional biopsy punch wounds over the course of 365 days in rainbow trout (Oncorhynchus mykiss) by monitoring visual wound healing and gene expression in the healing muscle at regular intervals (1, 3, 7, 14, 38 and 100 days post-wounding). In addition, we performed muscle texture analysis one year after wound infliction. The selected genes have all previously been investigated in relation to vertebrate wound healing, but only few specifically in fish. The selected genes were interleukin (IL)-1β, IL-6, transforming growth factor (TGF)-β1 and -β3, matrix metalloproteinase (MMP) -9 and -13, inducible nitric oxide synthase (iNOS), fibronectin (FN), tenascin-C (TN-C), prolyl 4-hydroxylase α1-chain (P4Hα1), lysyl oxidase (LOX), collagen type I α1-chain (ColIα1), CD41 and CD163. Wound healing progressed slowly in the presented study, which is at least partially due to the low temperature of about 8.5 °C during the first 100 days. The inflammation phase lasted more than 14 days, and the genes relating to production and remodeling of new extracellular matrix (ECM) exhibited a delayed but prolonged upregulation starting 1-2 weeks post-wounding and lasting until at least 100 days post-wounding. The gene expression patterns and histology reveal limited capacity for muscle regeneration in rainbow trout, and muscle texture analyses one year after wound infliction confirm that wounds heal with fibrosis. At 100 dpw epidermis had fully regenerated, and dermis partially regenerated. Scales had not regenerated even after one year. CD163 is a marker of "wound healing"-type M2c macrophages in mammals. M2 macrophage markers are as yet poorly described in fish. The pattern of CD163 expression in the present study is consistent with the expected timing of presence of M2c macrophages in the wound. CD163 may thus potentially prove a valuable marker of M2 macrophages - or a subset hereof - in fish. We subjected a group of fish to bathing in an immunomodulatory β-glucan product during wound healing, but found this to have very limited effect on wound healing in contrast to a previously published study on common carp.