The dsRNA isolated from Escherichia coli infected with the MS2 bacteriophage induces the production of interferons

Viral infections pose a significant threat to public health, and the production of interferons represents one of the most critical antiviral innate immune responses of the host. Consequently, the screening and identification of compounds or reagents that induce interferon production are of paramount importance. This study commenced with the cultivation of host bacterium 15,597, followed by the infection of Escherichia coli with the MS2 bacteriophage. Utilizing the J2 capture technique, a class of dsRNA mixtures (MS2+15,597) was isolated from the E. coli infected with the MS2 bacteriophage. Subsequent investigations were conducted on the immunostimulatory activity of the MS2+15,597 mixture. The results indicated that the dsRNA mixtures (MS2+15,597) extracted from E. coli infected with the MS2 bacteriophage possess the capability to activate innate immunity, thereby inducing the production of interferon-β. These dsRNA mixtures can activate the RIG-I and TLR3 pattern recognition receptors, stimulating the expression of interferon stimulatory factors 3/7, which in turn triggers the NF-κB signaling pathway, culminating in the cellular production of interferon-β to achieve antiviral effects. This study offers novel insights and strategies for the development of broad-spectrum antiviral drugs, potentially providing new modalities for future antiviral therapies.

The immunostimulatory activity of sea spray aerosols: bacteria and endotoxins activate TLR4, TLR2/6, NF-κB and IRF in human cells

Frequent exposure to sea spray aerosols (SSA) containing marine microorganisms and bioactive compounds may influence human health. However, little is known about potential immunostimulation by SSA exposure. This study focuses on the effects of marine bacteria and endotoxins in SSA on several receptors and transcription factors known to play a key role in the human innate immune system. SSA samples were collected in the field (Ostend, Belgium) or generated in the lab using a marine aerosol reference tank (MART). Samples were characterized by their sodium contents, total bacterial counts, and endotoxin concentrations. Human reporter cells were exposed to SSA to investigate the activation of toll-like receptor 4 (TLR4) in HEK-Blue hTLR4 cells and TLR2/6 in HEK-Blue hTLR2/6 cells, as well as the activation of nuclear factor kappa B (NF-κB) and interferon regulatory factors (IRF) in THP1-Dual monocytes. These responses were then correlated to the total bacterial counts and endotoxin concentrations to explore dose-effect relationships. Field SSA contained from 3.0 × 103 to 6.0 × 105 bacteria/m3 air (averaging 2.0 ± 1.9 × 105 bacteria/m3 air) and an endotoxin concentration ranging from 7 to 1217 EU/m3 air (averaging 389 ± 434 EU/m3 air). In contrast, MART SSA exhibited elevated levels of total bacterial count (from 2.0 × 105 to 2.4 × 106, averaging 7.3 ± 5.5 × 105 cells/m3 air) and endotoxin concentration from 536 to 2191 (averaging 1310 ± 513 EU/m3 air). SSA samples differentially activated TLR4, TLR2/6, NF-κB and IRF. These immune responses correlated dose-dependently with the total bacterial counts, endotoxin levels, or both. This study sheds light on the immunostimulatory potential of SSA and its underlying mechanisms, highlighting the need for further research to deepen our understanding of the health implications of SSA exposure.

Structural and functional characteristics of pectins from three cultivars of apple (Malus pumila Mill.) pomaces

This study aimed to investigate the chemical composition, structural properties, and biological properties of pectin polysaccharides (AP-FS, AP-QG, and AP-HG) isolated from different varieties of apple pomace. Based on the methylation and nuclear magnetic resonance analyses, the structure of AP-FS was determined to be composed of an α-1,4-linked homogalacturonan backbone that exhibited high levels of O-6 methylation. All pectins exhibit potent inhibitory activity against human colon cancer and human liver cancer cells, along with immunostimulatory effects. Among them, AP-FS exhibited the highest activity level. Finally, we further investigated the underlying mechanism behind the effect of AP-FS on RAW 264.7 cells using proteomics analysis. Our findings revealed that AP-FS triggers RAW 264.7 macrophage activation via NOD-like receptor (NLR), NF-κB, and mitogen-activated protein kinase (MAPK) signaling pathways. Therefore, our research contributes to a better understanding of the structure-function relationship among apple pectins, and AP-FS has the potential to be applied to dietary supplements targeting immunomodulation.

Fermentation enrichment, structural characterization and immunostimulatory effects of β-glucan from Quinoa

We developed an efficient mixed-strain co-fermentation method to increase the yield of quinoa β-glucan (Q+). Using a 1:1 mass ratio of highly active dry yeast and Streptococcus thermophilus, solid-to-liquid ratio of 1:12 (g/mL), inoculum size of 3.8 % (mass fraction), fermentation at 32 °C for 27 h, we achieved the highest β-glucan yield of (11.13 ± 0.80)%, representing remarkable 100.18 % increase in yield compared to quinoa β-glucan(Q-) extracted using hot water. The structure of Q+ and Q- were confirmed through Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (NMR) spectroscopies. Q+ contained 41.66 % β-glucan, 3.93 % protein, 2.12 % uronic acid; Q- contained 37.21 % β-glucan, 11.49 % protein, and 1.73 % uronic acid. The average molecular weight of Q+(75.37 kDa) was lower than that of Q- (94.47 kDa). Both Q+ and Q- promote RAW264.7 cell proliferation without displaying toxicity. They stimulate RAW264.7 cells through the NF-κB and MAPK signaling pathways, primarily inducing NO and pro-inflammatory cytokines by upregulating CD40 expression. Notably, Q+ exhibited stronger immunostimulatory activity compared to Q-. In summary, the fermentation enrichment method yields higher content of quinoa β-glucan with increased purity and stronger immunostimulatory properties. Further study of its bioimmunological activity and structure-activity relationship may contribute to the development of new immunostimulants.

Protective efficacy of recombinant Toxoplasma gondii dense granule protein 15 against toxoplasmosis in C57BL/6 mice

Toxoplasma gondii is a pervasive protozoan parasite that is responsible for significant zoonoses. A wide array of vaccines using different effector molecules of T. gondii have been studied worldwide to control toxoplasmosis. None of the existing vaccines are sufficiently effective to confer protective immunity. Among the different Toxoplasma-derived effector molecules, T. gondii dense granule protein 15 from the type II strain (GRA15 (II)) was recently characterized as an immunomodulatory molecule that induced host immunity via NF-κB. Therefore, we assessed the immunostimulatory and protective efficacy of recombinant GRA15 (II) (rGRA15) against T. gondii infection in a C57BL/6 mouse model. We observed that rGRA15 treatment increased the production of IL-12p40 from mouse peritoneal macrophages in vitro. Immunization of mice with rGRA15 induced the production of anti-TgGRA15-specific IgG, IgG1 and IgG2c antibodies. The rGRA15-sensitized spleen cells from mice inoculated with the same antigen strongly promoted spleen cell proliferation and IFN-γ production. Immunization with rGRA15 significantly enhanced the survival rate of mice and dramatically decreased parasite burden in mice challenged with the Pru (type II) strain. These results suggested that rGRA15 triggered humoral and cellular immune responses to control infection. However, all of the immunized mice died when challenged with the GRA15-deficient Pru strain or the RH (type I) strain. These results suggest that GRA15 (II)-dependent immunity plays a crucial role in protection against challenge infection with the type II strain of T. gondii. This study is the first report to show GRA15 (II) as a recombinant vaccine antigen against Toxoplasma infection.

Preparation of β-1,3-glucan mimics via modification of polymer backbone, and evaluation of cytokine production using the polymer library in immune activation

β-1,3-Glucans possess therapeutic potential owing to their ability to exhibit immunostimulating activity. β-1,3-Glucans, isolated from various organisms, differ in their chemical structures, molecular weight, and branching degree, potentially forming particulate, helix, or random coil conformations in water. Therefore, this study used synthesized β-1,3-glucan mimic polymers to investigate the difference in binding affinity for dectin-1 and induced cytokine productions based on polymer structures. The β-1,3-glucan mimic polymers were synthesized using β-1,3-glucan tetrasaccharyl monomer, with subsequent modifications to the polymer backbones through the introduction of hydrogen or a hydroxy group. Polymers with different structures in both ligands and polymer backbones were utilized to comprehensively investigate their binding affinity to dectin-1 and cytokine-inducing in macrophages. Hydroxylated polymers exhibited a high binding affinity for dectin-1, similar to that of schizophyllan, whereas the polymer composed of only saccharyl monomers did not bind to dectin-1. Further, when administered to macrophage RAW264 cells, polymers with branched and hydrophobic polymer backbones exhibited strong cytokine-inducing activities. Moreover, the results revealed that the essential factors for cytokine induction include the branches of β-1,3-glucans, high (tens of thousands) molecular weights, and hydrophobicity. The results suggests that artificial polymers comprising these factors exhibit immunostimulating activity and could be developed as therapeutic agents.

Isolation and absolute configuration of alkylpyridine alkaloids from the marine sponge Hippospongia lachne

Marine sponges are well known as prolific producers of structurally diverse molecules with valuable pharmacological potential. As part of our ongoing program to discover bioactive compounds from marine sponges collected from the Xisha Islands in the South China Sea, a chemical study on the specimens of Hippospongia lachne was conducted. As a result, eight undescribed compounds, including four zwitterionic alkylpyridinium salts, hippospondines A-D (1-4), and four 3-alkylpyridine alkaloids, hippospondines E (5), F (6), and (±)-hippospondine G (7), were isolated from the marine sponge H. lachne, together with one known 3-alkylpyridine alkaloid (8). The undescribed structures were elucidated by HRESIMS, NMR, DP4+ and CP3 probability analysis, and the Snatzke's method. Hippospondines A-D (1-4) represent the rare example of inner salt type alkylpyridinium alkaloid with a farnesyl moiety. Compounds 1-3 and 8 were subjected to cytotoxic and lymphocyte proliferation assays. Compound 3 exhibited a weak promotion effect on the ConA-induced T lymphocyte proliferation.

Angelica gigas polysaccharide induces CR3-mediated macrophage activation and the cytotoxicity of natural killer cells against HCT-116 cells via NF-κB and MAPK signaling pathways

Angelica gigas (A. gigas) is traditional medicinal herb that mainly exists in Korea and northeastern China. There have been relatively few studies conducted thus far on its polysaccharides and their bioactivities. We purified and described a novel water-soluble polysaccharide derived from A. gigas and investigated its immunoenhancing properties. The basic components of crude and purified polysaccharides (F1 and F2) were total sugar (41.07% - 70.55%), protein (1.12-10.33%), sulfate (2.9-5.5%), and uronic acids (0.5-31.05%) in total content. Our results demonstrated that the crude and fractions' molecular weights (Mw) varied from 42.2 to 285.2 × 103 g/mol. As the most effective polysaccharide, F2 significantly stimulated RAW264.7 cells to release nitric oxide (NO) and express several cytokines. Furthermore, F2 increased the expression of tumor necrosis factor-α (TNF-α), interferon-gamma (IFN-ɣ), natural killer cytotoxicity receptors (NKp44), and granzyme-B in NK-92 cells and enhanced the cytotoxicity against HCT-116 cells. In our experiments, we found that F2 stimulated RAW264.7 cells and NK-92 cells via MAPK and NF-κB pathways. The monosaccharide and methylation analysis of the high immunostimulant F2 polysaccharide findings revealed that the polysaccharide was primarily composed of 1 → 4, 1 → 6, 1 → 3, 6, 1 → 3 and 1 → 3, 4, 6 galactopyranose residues, 1 → 3 arabinofuranose residues, 1 → 4 glucopyranose residues. These results demonstrated that the F2 polysaccharide of A. gigas which possesses potential immunostimulatory attributes, could be used to create a novel functional food.

Dictyophora indusiata polysaccharide mediates priming of the NLRP3 inflammasome activation via TLR4/ NF-κB signaling pathway to exert immunostimulatory effects

Dictyophora indusiata, commonly known as bamboo fungus, is a type of edible mushroom that is highly popular worldwide for its rich flavor and nutritional value. It is also recognized for its pharmaceutical efficacy, with medicinal benefits attributed to its consumption. One of the most important components of Dictyophora indusiata is polysaccharide, which has been acknowledged as a promising regulator of biological response due to its immunostimulatory and anti-inflammatory properties. However, the specific roles of polysaccharide in modulating the NOD-like receptor protein 3 (NLRP3) inflammasome activation within macrophages remain relatively under-researched. To investigate this further, the mechanism by which Dictyophora indusiata polysaccharide (DIP) exerts its immunostimulatory activity in RAW 264.7 macrophages was analyzed. Results indicated that DIP has the potential to facilitate the priming of NLRP3 inflammasome activation by enhancing TLR4 expression, phosphorylation of IκB-α, and nuclear translocation of NF-κB p65 subunit. It was noted that DIP was unable to mediate the second step of NLRP3 inflammasome activation. The findings of this study provide compelling evidence that DIP has immunomodulatory effects by modulating the NLRP3 inflammasome in RAW264.7 macrophages.

The traditional use, structure, and immunostimulatory activity of bioactive polysaccharides from traditional Chinese root medicines: A review

As research on traditional Chinese medicine (TCM) has expanded, our understanding of the role it can have in controlling the immune system has increased. Polysaccharides from medicinal plants exhibit numerous beneficial therapeutic properties, presumably owing to their modulation of innate immunity and macrophage function. Numerous studies have demonstrated the multiple ways whereby certain polysaccharides can affect the immune system. In addition to stimulating immune cells, such as T cells, B lymphocytes, macrophages, and natural killer cells, polysaccharides stimulate complements and increase cytokine secretion. The biological functions of polysaccharides are directly correlated with their structures. This paper summarizes the sources, TCM uses, extraction and purification methods, structural characterization, in vitro and in vivo immune activities, and underlying molecular mechanisms of TCM root polysaccharides. Moreover, the structure-activity relationships of TCM root polysaccharides are emphasized and discussed. This review can provide a scientific basis for the research and industrial utilization of TCM root polysaccharides.

Cnidium officinale polysaccharide enhanced RAW 264.7 cells activation and NK-92 cells cytotoxicity against colon cancer via NF-κB and MAPKs signaling pathways

In this study, Cnidium officinale-derived polysaccharides were isolated and investigated for their immune enhancing and anticancer activities. The isolated crude and its fractions, such as F1 and F2, contain carbohydrates (51.3-63.1%), sulfates (5.4-5.8%), proteins (1.5-7.1%), and uronic acids (2.1-26.9%). The molecular weight (Mw) of the polysaccharides ranged from 59.9 to 429.0 × 103 g/mol. The immunostimulatory activity of the polysaccharides was tested on RAW 264.7 cells, and the results showed that the F2 treatment notably enhanced pro-inflammatory activity in RAW 264.7 cells by increasing NO production and the expression of various cytokines. Furthermore, the influence of polysaccharide treatment on natural killer cells (NK-92) anticancer activities was investigated using a colon cancer cell line (HCT-116). Crude polysaccharide and its fractions showed no direct cytotoxicity to NK-92 and HCT-116 cells. However, the treatment of F2 showed an enhancement of NK-92 cells cytotoxicity against HCT-116 cells by upregulating the mRNA expression of IFN-γ, TNF-α, NKGp44, and granzyme-B. The western blot results showed that the induced RAW 264.7 cells activation and NK-92 cells cytotoxicity occur via NF-κB and MAPK signaling pathways. Overall, C. officinale-derived polysaccharides show potential as immunotherapeutic agents capable of enhancing pro-inflammatory macrophage signaling and activating NK-92 cells; thus, they could be useful for biomedical applications.

Water-extractable polysaccharide fraction PNE-P1 from Pinus koraiensis pine nut: Structural features and immunostimulatory activity

The polysaccharide fraction PNE-P1 was isolated from hot water extract (PNE) of the defatted meal of pine nuts (Pinus koraiensis) using DEAE-cellulose column chromatography. This fraction had three components of molecular masses 1251, 616, and 303 g/mol consisting mainly of arabinose, xylose, and galacturonic acid at a molar ratio of 2:1.6:1. Structural analysis with FTIR/Raman, methylation and GC-MS, and NMR revealed that PNE-P1 is a cell wall polysaccharide complex including arabinan, heteroxylan, homogalacturonan (HM) and rhamnogalacturonan I (RG-I) parts. Being nontoxic to RAW 264.7 macrophages in the concentration range of 10-200 μg/mL, PNE-P1 promoted proliferation of these cells, significantly induced the secretion of proinflammatory cytokines (TNF-α and IL-6) and chemokines (RANTES and MIP-1α) and enhanced the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and nitric oxide (NO). PNE-P1 also markedly induced macrophage-mediated phagocytosis of apoptotic Jurkat T cells. These results demonstrate that pine nuts Pinus koraiensis contain a complex of water-soluble plant cell wall polysaccharides, which can stimulate innate immunity by potentiating macrophage function.

Averrhoa carambola L. fruit and stem metabolites profiling and immunostimulatory action mechanisms against cyclosporine induced toxic effects in rat model as analyzed using UHPLC/MS-MS-based chemometrics and bioassays

The Averrhoa carambola L. tree encompasses a myriad of phytochemicals contributing to its nutritional and health benefits. The current study aims at investigating the A. carambola L. the metabolite profile grown in tropical and temperate regions represented by fruit and stem, for the first time using UPLC/MS-based molecular networking and chemometrics. Asides, assessment of the immunostimulatory effect of ripe fruit and stem, was compared in relation to metabolite fingerprints. Eighty metabolites were identified, 8 of which are first-time to be reported including 3 dihydrochalcone-C-glycosides, 4 flavonoids, and one phenolic. Multivariate data analysis revealed dihydrochalcones as origin-discriminating metabolites between temperate and tropical grown fruits. Further, an in vivo immunomodulatory assay in a cyclosporine A-induced rat model revealed a potential immune-enhancing effect as manifested by down-regulation of inflammatory markers (IL-6, INF-γ, IL-1, TLR4, and ESR) concurrent with the up-regulation of CD4 level and the CD4/CD8 ratio. Moreover, both extracts suppressed elevation of liver and kidney functions in serum as well as reduction in oxidative stress with concurrent increased levels of T-protein, albumin, globulin, and A/G ratio. This study pinpoints differences in secondary metabolite profiles amongst A. carambola L. accessions from different origins and organ type and its immunomodulatory action mechanisms.

Anti-inflammatory activity of bupropion through immunomodulation of the macrophages

Depression might manifest itself with a chronic inflammation in different tissues and organs independent of the central nervous system. Psoriasis, Crohn's disease, and fibromyalgia are among these disorders accompanying the depression. The treatment options for these conditions are a combination of the anti-depressants and anti-inflammatory agents. Bupropion has been widely utilized as an anti-depressant. It has been preferred among the patients with Crohn's disease and psoriasis due to its anti-inflammatory role, as well. In this study, we aimed to decipher its target in the immune system. Macrophages were activated in the presence of LPS and increasing concentrations of the bupropion. TNF-α, IL-6, GM-CSF, and IL-12p40 cytokines' production levels were measured by ELISA to compare it to the control groups. These cytokines have been associated with the aggressive inflammation in different tissues. Moreover, p38 and PI3K proteins' phosphorylated levels were measured to examine whether bupropion acts through these pathways or not. Our results suggest that bupropion had anti-inflammatory action on the activated macrophages and its mechanism of action was partially dependent on p38 but independent of PI3K pathways.

Immunostimulatory activity and safety evaluation of Bordetella bronchiseptica-derived lipopolysaccharide, a new vaccine adjuvant candidate

Adjuvants are used to elicit strong immune responses for vaccines that show poor immunogenicity. Previously, we demonstrated that a sonicated bacterin of Bordetella bronchiseptica can be used as a safe adjuvant that enhances the antigen-presenting capability of dendritic cells (DCs). In this study, we purified the lipopolysaccharide (LPS) of B. bronchiseptica (Bb-LPS) and investigated its immunogenic effects on DCs compared to those of Escherichia coli O26:B6 (O26)-derived LPS (O26-LPS), a positive control. Bb-LPS was purified using an LPS extraction kit. Limulus amebocyte lysate assay was performed to determine the optimal concentration of Bb-LPS and O26-LPS for treatment. Bb-LPS increased the metabolic activity of DCs at a concentration of 0 to 250 EU/mL, similar to that of O26-LPS. Bb-LPS significantly increased the expression level of CD40 and CD54, related to the immune responses of DCs. Bb-LPS enhanced the antigen-presenting capability of DCs and significantly increased the interferon-gamma/interleukin-4 ratio of CD4+ T cells co-cultured with DCs to 0.95 (p < 0.05). Moreover, Bb-LPS increased the production of pro-inflammatory cytokines in a safer manner than that obtained by O26-LPS. In vivo safety tests revealed that Bb-LPS was less toxic than O26-LPS in mice. This study demonstrated that Bb-LPS showed unique immune characteristics and immunogenic effects on the antigen-presenting capability of DCs, which differed from those of O26-LPS. This study provides valuable information for basic and clinical research for developing safe vaccine adjuvants.

Immunostimulatory Activity of Syneilesis palmata Leaves through Macrophage Activation and Macrophage Autophagy in Mouse Macrophages, RAW264.7 Cells

Syneilesis palmata (SP) is a traditional medicinal plant. SP has been reported to have anti-inflammatory, anticancer, and anti-human immunodeficiency virus (HIV) activities. However, there is currently no research available on the immunostimulatory activity of SP. Therefore, in this study, we report that S. palmata leaves (SPL) activate macrophages. Increased secretion of both immunostimulatory mediators and phagocytic activity was observed in SPL-treated RAW264.7 cells. However, this effect was reversed by the inhibition of TLR2/4. In addition, inhibition of p38 decreased the secretion of immunostimulatory mediators induced by SPL, and inhibition of TLR2/4 decreased the phosphorylation of p38 induced by SPL. SPL augmented p62/SQSTM1 and LC3-II expression. The increase in protein levels of p62/ SQSTM1 and LC3-II induced by SPL was decreased by the inhibition of TLR2/4. The results obtained from this study suggest that SPL activates macrophages via TLR2/4-dependent p38 activation and induces autophagy in macrophages via TLR2/4 stimulation.

Immunostimulatory activity of Lactococcus lactis LM1185 isolated from Hydrangea macrophylla

The lactic acid bacteria, Lactococcus lactis subsp. lactis LM1185 was isolated from Hydrangea macrophylla. Strain LM1185 showed 50.5% of acid tolerance at pH 2.5 for 2 h and 30.4% of 0.3% (w/v) bile salt tolerance for 24 h. The antioxidant activity of this strain was measured at 99.4% of 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activity. When RAW 264.7 macrophage cells were treated with strain LM1185, there was no observed cytotoxicity. This strain showed high nitric oxide production and mRNA expression levels of cytokines such as tumor necrosis factor-α and inducible nitric oxide synthase (iNOS). The nuclear factor-kB signaling pathway was activated by this strain resulting in the production of iNOS and cyclooxygenase-2 determined by western blotting. The present results indicated that L. lactis subsp. lactis LM1185 could be used as potential probiotics and may play a crucial role in the immunostimulatory effect on macrophages.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01199-5.

Structural analysis and prebiotic activity of exopolysaccharide produced by probiotic strain Bifidobacterium bifidum EPS DA-LAIM

Exopolysaccharide (EPS)-producing Bifidobacterium bifidum EPS DA-LAIM was isolated from healthy human feces, the structure of purified EPS from the strain was analyzed, and its prebiotic activity was evaluated. The EPS from B. bifidum EPS DA-LAIM is a glucomannan-type heteropolysaccharide with a molecular weight of 407-1007 kDa, and its structure comprises 2-mannosyl, 6-mannosyl, and 2,6-mannosyl residues. The purified EPS promoted the growth of representative lactic acid bacteria and bifidobacterial strains. Bifidobacterium bifidum EPS DA-LAIM increased nitric oxide production in RAW 264.7 macrophage cells, indicating its immunostimulatory activity. Bifidobacterium bifidum EPS DA-LAIM also exhibited high gastrointestinal tract tolerance, gut adhesion ability, and antioxidant activity. These results suggest that EPS from B. bifidum EPS DA-LAIM is a potentially useful prebiotic material, and B. bifidum EPS DA-LAIM could be applied as a probiotic candidate.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01213-w.

Evaluation and mechanism of immune enhancement effects of Pleurotus ferulae polysaccharides-gold nanoparticles

We previously demonstrated that Pleurotus ferulae polysaccharide (PFPS) promoted dendritic cell (DC) maturation through the TLR4 signaling pathway. To improve PFPS activity and bioavailability, gold nanoparticles with PFPS (PFPS-Au NPs) were synthesized. Of note, although the polysaccharide content of PFPS-Au NPs was only one tenth of PFPS, PFPS-Au NPs enhanced the immunostimulatory activities of PFPS in the maturation and function of dendritic cells (DCs) by TLR4 and NLRP3 signaling pathways, evidenced by stronger activation of the down-stream MAPK and NF-κB pathways and NLRP3 inflammasome pathway. More importantly, PFPS-Au NPs enhanced DC migration and murine immunity, particularly in type 1 T-helper cell responses. Moreover, the half-life of PFPS-Au NPs (2.217 ± 0.187 h) was longer than that of PFPS (1.39 ± 0.257 h) in the blood and the distribution of PFPS-Au NPs (19.8 %) in the spleen was significantly increased compared with PFPS (13.3 %), indicating the improved bioavailability in vivo. PFPS-Au NPs as an adjuvant promoted antigen-specific cellular immune responses to an HPV DC-based vaccine, which significantly inhibited the growth of TC-1 tumors in mice. All results suggest that the prepared Au NPs could enhance PFPS-immunostimulatory activity, which will pave the way for PFPS-Au NPs to be applied in clinical trials.

Probiotic Debaryomyces hansenii CBS 8339 yeast enhanced immune responses in mice

This study aimed to examine the effect of Debaryomyces hansenii CBS 8339 on innate immune responses in mice. Thirty BALB/c mice were randomly treated with phosphate buffered saline (PBS) (control) and two D. hansenii (Dh) doses: Dh 10ˆ6 CFU (colony forming units) and Dh 10ˆ8 CFU daily for 15 days. Spleen, blood, and gut samples were taken on days 7 and 15. Mouse splenocytes were isolated and challenged with Escherichia coli. Immunological assays and immune-related gene expressions were performed. Serum was obtained from blood for total IgA and IgG antibody titer determination. Gut samples were taken for yeast colonization assessment. Phagocytosis, respiratory burst activity, and nitric oxide production in mice were mainly enhanced (p < 0.05) upon 7 days of D. hansenii intake at a concentration of 10ˆ8 CFU before and after bacterial challenge. Moreover, oral D. hansenii in mice upregulated (p < 0.05) gene expression of pro-inflammatory cytokines (INF-γ, IL-6 and IL-1β) before or after E. coli challenge on day 7 but downregulated (p < 0.05) on day 15. Furthermore, total serum IgG and IgA titers were higher (p < 0.05) in Dh 10ˆ8 CFU at days 7 and 15, and only at day 7, respectively, than that in the other dose and control groups. Finally, D. hansenii was detected in the gut of mice that received the treatments, suggesting that yeast survived gastrointestinal transit. Altogether, a short period (7 days) of D. hansenii CBS 8339 oral delivery improved immune innate response on mice.

Effect of carrier molecular weight on physicochemical properties and the in vitro immune-stimulatory activity of the CpG-dextran conjugates

The effect of dextran molecular weight on the in vitro physicochemical and immune properties of cytosine-phosphate-guanine (CpG) oligodeoxynucleotide-amino-dextran conjugates is investigated. CpG-1668 was conjugated at the 3'-end to amino-dextran of differing molecular weight (20, 40, 70 or 110-kDa) via a stable bis-aryl hydrazone linkage. Conjugate formation was confirmed by agarose gel electrophoresis and dynamic light scattering measured the size and surface charge of conjugates. Uptake and immune-stimulatory activity of CpG-dextran by antigen-presenting cells was evaluated by flow cytometry and confocal microscopy. Degradation by DNase I was monitored by loss of the fluorescent signal from labelled CpG and changes in size and zeta potential. Hydrazone bond formation (UV 354 nm) showed on average four CpG molecules conjugated per polymer. CpG-dextran prepared from 20 or 40-kDa dextran had a size of 17 nm while 70 or 110-kDa was 30 nm. CpG-dextran was preferentially taken up by dendritic cells, followed by macrophages and then B-cells. Only the 20-kDa dextran conjugate significantly enhanced uptake by bone-marrow derived dendritic cells (BMDCs) compared to free CpG. Confocal microscopy showed that CpG and CpG-dextran accumulates in the endo-lysosomal compartment of BMDCs at 24 h. All conjugates upregulated activation markers (CD40, CD80 or CD86) of BMDCs to a similar level as for free CpG. CpG-dextran 40-kDa produced highest levels of cytokines (TNF-α, IL-6, and IL-12p70) secreted by BMDCs. Enzymatic protection assays showed that the conjugate made from dextran 20-kDa provided no protection for CpG while the higher molecular weight conjugates reduced degradation by DNase I. The 40-kDa dextran conjugate produced the greatest in vitro immune activity, this was due to the conjugate being relatively small in size for cell uptake while sufficiently large enough to protect CpG from nuclease attack. These in vitro studies identify the need to consider the molecular weight of the carrier in bioconjugate design.

Identification and immunological evaluation of novel TLR2 agonists through structural optimization of Diprovocim

As an important family member of Toll-like receptors (TLRs), TLR2 can recognize various pathogen-associated molecular patterns (PAMPs) such as bacteria and viral components. Accumulating evidence demonstrates that TLR2 agonists play a critical role in cancer immunotherapy and infectious diseases. Diprovocim is the most potent small molecule TLR2 agonist known, showing remarkably immune adjuvant activity in mice. However, the further clinical research and development of Diprovocim was hampered because of its structural complexity as well as high molecular weight. Here, we designed and synthesized 21 structurally simplified derivatives of Diprovocim, performed their TLR2 agonistic activities by HEK-Blue hTLR2 SEAP assay, and evaluated the toxicity in two human normal cell lines. Compounds B3-B4 and B9-B12 with excellent TLR2 agonistic activity were found through the structure-activity relationship study. Among them, diastereomer B10 and B12 substituted (S)-2-phenylcyclopropylamide side chain of Diprovocim with simple (R)- and (S)-n-butyl groups exhibited comparable TLR2 agonistic activities with EC₅₀ values of 35 nM and 39 nM, respectively. ELISA and western blot experiments on THP-1 cells showed that B10 and B12 displayed remarkable immunostimulatory activity in the release of various inflammatory cytokines through activating MyD88-dependent NF-κB and MAPK signaling pathways. Importantly, B10 and B12 have less structural complexity and better safety compared to Diprovocim, and the chiral center of right pyrrolidine ring has negligible influence on TLR2 activition. Our study provides simplified Diprovocim derivatives with high agonistic activity, providing a clue to further optimize Diprovocim.

Influence of ultrasound assisted metal-free Fenton reaction on the structural characteristic and immunostimulatory activity of a β-D-glucan isolated from Dictyophora indusiata

The present study aimed to evaluate the influence of ultrasound assisted H₂O₂/ascorbic acid reaction on the structural characteristic and immunostimulatory activity of a β-D-glucan isolated from D. indusiata, so as to reveal its potential structure-immunostimulatory activity relationship. A purified β-D-glucan, named as DP, was quickly isolated from D. indusiata, and further identified as a 1,3-β-D-glucan with 1,6-β-D-Glcp as branched chains, which exhibited a rigid rod chain conformation in 0.9 % (w/v) of NaCl solution. Furthermore, results showed that the primary structure of DP was overall stable after the degradation by ultrasound assisted H₂O₂/ascorbic acid reaction. However, the molar mass and chain conformation of DP obviously changed. In addition, DP and its degraded products exerted remarkable immunostimulatory activity in vitro and in vivo, which could activate the nuclear factor-κB (NF-κB) signaling pathway through toll-like receptor 4 (TLR4). Indeed, the immunostimulatory activity of DP was closely-correlated to its molar mass and chain conformation. An appropriate degradation of molar mass could promote its immunostimulatory activity. While the transformation of chain conformation from rigid rod to random coil could cause the significant decrease of its immunostimulatory activity. These findings are beneficial to better understanding the structure-immunostimulatory activity relationship of β-D-glucans from edible mushrooms.

Low molecular-weight polyguluronate phosphate: An immunostimulant by activating splenocyte/macrophage invitro and improving immune response invivo

The substituents and backbones are two main factors affecting immune activities of polysaccharides. In the present study, we firstly evaluated the immunostimulating effects of phosphorylated, sulfated, H-phosphonated and nitrated derivatives of low-molecular-weight polymannuronate (LPM) and polyguluronate (LPG) on splenocytes and peritoneal macrophages in vitro. The results showed that the phosphate group was the best substituent to enhance the immune activities, and LPG phosphate (LPGP) had much better activity than LPM phosphate (LPMP). Further studies showed that LPGP not only promoted the proliferation of mouse splenocytes in the presence of either LPS or Con A, but also acted as an excellent peritoneal macrophage activator to enhance the cell phagocytosis, energy metabolism, cytokines release and activities of intracellular enzymes. The studies in RAW264.7 cells revealed that LPGP activated the TBK1-IκBα-NF-κB and the TBK1-IRF3 pathway. Moreover, LPGP rescued the immune response in the Cyclophosphamide-treated mice in vivo. In conclusion, LPGP is a potential alginate-based biological response modifier (BRM).

Immunoregulatory activity of a low-molecular-weight heteropolysaccharide from Ganoderma leucocontextum fruiting bodies in vitro and in vivo

The chemical structure of GLP-1, a novel water-soluble heteropolysaccharide purified Ganoderma leucocontextum fruiting bodies, has been characterized in our previous study. This study aimed to investigate the immunostimulatory activity of GLP-1 in vitro and in vivo by using RAW264.7 macrophages and cyclophosphamide-induced immunosuppressed mice model. Results showed that GLP-1 was able to enhance phagocytic activity and promote the production of reactive oxygen species, nitric oxide, tumor necrosis factor-α, interleukin-6, and monocyte chemoattractant protein-1 in RAW264.7 macrophages. Moreover, GLP-1 could activate mitogen-activated protein kinase, phosphatidylinositol-3-kinase/protein kinase B, and nuclear factor-kappa B signaling pathways through toll-like receptor 2 and dectin-1 receptors. Furthermore, GLP-1 increased the thymus index, serum immunoglobulin levels, and percentage of CD3⁺ T lymphocytes in cyclophosphamide-induced immunosuppressed mice. These results demonstrated that GLP-1 possessed significant immunostimulatory effects in vivo and in vitro and could be developed as an effective immunomodulator for application in functional foods.

Isolation and identification of an arabinogalactan extracted from pistachio external hull: Assessment of immunostimulatory activity

This work studies the extraction and purification of a novel arabinogalactan from pistachio external hull. It was extracted with a simple method from pistachio hull which is considered as unexploited waste. Based on the results of sugar analysis by GC-FID, glycosidic linkage by GC-MS, NMR spectroscopy, and molecular weight by Size Exclusion Chromatography, pistachio hull water soluble polysaccharides (PHWSP) were identified as a type II arabinogalactan (AG), with characteristic terminally linked α-Araf, (α1 → 5)-Araf, (α1 → 3,5)-Araf, terminally linked β-Galp, (β1 → 6)-Galp, and (β1 → 3,6)-Galp. DEPT-135, HSQC, HMBC and COSY NMR data suggested the presence of (β1 → 3)-Galp mainly branched at O-6 with (β1 → 6)-Galp chains, α-Araf chains, and terminally linked α-Araf. These AG from pistachio external hulls showed in vitro stimulatory activity for B cells, suggesting their possible use as an immunological stimulant in nutraceutical and biomedical applications.

Structure, immunostimulatory activity, and the effect of ameliorating airway inflammation of polysaccharides from Pyrus sinkiangensis Yu

Purified acid polysaccharides PSAP-1 and PSAP-2 with apparent molecular weights of 64.6 and 38.9 kDa, respectively, were isolated from Pyrus sinkiangensis Yu. through combined techniques of ion-exchange and gel permeation chromatography. Both polysaccharides were composed of predominant amounts of GalA and small amounts of Ara, Rha, and Gal. They are deduced to be native pectin-type polysaccharides containing the HG backbone consisting of α-1,4-GalAp and methyl-esterified α-1,4-GalAp residues by IR, GC-MS and NMR spectra analyses. The immunoregulatory activity test showed that PSAP-1 and PSAP-2 could increase the cell viability and the release of NO, IL-6, and TNF-α on the RAW264.7 macrophage. It indicated that PSAP-1 and PSAP-2 could increase macrophage-mediated immunostimulatory activity. The airway inflammation test of antiasthmatic mice showed that PSAP-1 could decrease the contents of IL-4, IL-5, and IL-13 and the number of inflammatory cells in BALF and improve the pathological changes in lung tissue. PSAP-1 could also decrease the amount of mucus secreted by goblet cells and the expression levels of NF-κB p65, IκBα, IKK, ERK, JNK, P38, and Muc5ac mRNA and increase the expression levels of TLR2 and TLR4 mRNA in lung tissues. This suggested that PSAP-1 may resist airway inflammation in mice. PSAP-1 and PSAP-2 had potential clinical application value.

Enhanced immune response by vacuoles isolated from Saccharomyces cerevisiae in RAW 264.7 macrophages

Vacuoles are membrane vesicles in eukaryotic cells, the digestive system of cells that break down substances absorbed outside the cell and digest the useless components of the cell itself. Researches on anticancer and intractable diseases using vacuoles are being actively conducted. The practical application of the present study to animals requires the determination of the biocompatibility of vacuole. In the present study, we evaluated the effects of vacuoles isolated from Saccharomyces cerevisiae in RAW 264.7 cells. This showed a significant increase in the production of nitric oxide (NO) produced by macrophage activity. Using Reactive Oxygen Species (ROS) assay, we identified that ROS is increased in a manner dependent on vacuole concentration. Western blot analysis showed that vacuole concentration-dependently increased protein levels of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2). Therefore, iNOS expression was stimulated to induce NO production. In addition, pro-inflammatory cytokines levels promoted, such as interleukin (IL) 6 (IL-6) and tumor necrosis factor (TNF) α (TNF-α). In summary, vacuoles activate the immune response of macrophages by promoting the production of immune-mediated transporters NO, ROS, and pro-inflammatory cytokines.

Enhanced Immune Response by Vacuoles isolated from Saccharomyces cerevisiae in RAW 264.7 Macrophages

Vacuoles are membrane vesicles in eukaryotic cells, the digestive system of cells that break down substances absorbed outside the cell and digest the useless components of the cell itself. Researches on anti-cancer and intractable diseases using vacuoles are being actively conducted. The practical application of this study to animals requires the determination of the biocompatibility of vacuole. In the present study, we evaluated the effects of vacuoles isolated from S. cerevisiae in RAW264.7 cells. This showed a significant increase in the production of nitric oxide produced by macrophage activity. Using Reactive Oxygen Species (ROS) Assay, we identified that ROS is increased in a manner dependent on vacuole concentration. Western blot analysis showed that vacuole concentration-dependently increased protein levels of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2). Therefore, iNOS expression was stimulated to induce Nitric oxide (NO) production. In addition, pro-inflammatory cytokines levels promoted, such as interleukin 6 and tumor necrosis factor -α. In summary, vacuoles activate the immune response of macrophages by promoting the production of immune-mediated transporters NO, ROS, and pro-inflammatory cytokines.

Structural characterization of novel arabinoxylan and galactoarabinan from citron with potential antitumor and immunostimulatory activities

This study aimed to extract polysaccharides from citron and analyze their structures and potential bioactivities. Two novel polysaccharides CM-1 and CM-2 were purified from citron by DEAE-Sepharose Fast Flow and Sephadex G-100 column chromatography. Monosaccharide composition, linkage and NMR data were used to infer their sugar chains composition. The anti-breast cancer cells and immunoregulatory activities of CM-1 and CM-2 were investigated. Results indicated that CM-1 (Mw = 21,520 Da), composed of arabinose, xylose, mannose and glucose in a molar ratio of 10.78:11.53:1.00:1.70, was arabinoxylan (AX) with (1 → 4)-linked β-d-Xylp skeleton monosubstituted with α-l-Araf units at O-3 position. While CM-2 (Mw = 22,303 Da), composed of arabinose, mannose, glucose and galactose in a molar ratio of 25.46:1.45:1.00:6.57, was galactoarabinan (GA) with (1 → 5)-linked α-l-Araf backbone substituted by β-d-Galp units at O-2 and/or O-3 positions. Both polysaccharides exhibited potential inhibiting cancer and immunostimulatory activities in vitro, especially CM-1. These results provide a basis for further research on citron polysaccharides.

Structural characterization and immunostimulatory activity in vitro of a glycogen from sea urchin-Strongylocentyotus internedius

Sea urchin possesses both high nutritional and medicinal value. It contains diverse biological active polysaccharides. But there are few studies on its glycogen. In the current study, a glucan (MSGA) was separated from Strongylocentyotus internedius and purified by ion exchange and gel filtration column. Chemical analysis revealed that MSGA with 2.65 × 10⁷ Da is made up entirely of glucose. The analysis of methylation, NMR and mass spectrum demonstrated that MSGA is a highly branched glycogen with α-(1→4) linked gluconic backbone and branched at C-6 (one branch per five residues). In addition, MSGA showed good in vitro immunostimulatory activity via NF-κB and MAPKs pathways. It is considered that high degree of branching is necessary for its activity. However, the relationship between structure and immunostimulatory activity of natural glycogens is difficult to elucidate because the difference in their structural properties. Therefore, much more research is needed in this area.

Purification, structural characterization and immunostimulatory activity of polysaccharides from Umbilicaria esculenta

In this study, an active component UP1-1 was isolated from Chinese Huangshan Umbilicaria esculenta via hot water extraction and purified by anion-exchange and gel-filtration chromatography. UP1-1 mainly composed of galactose, mannose and glucose in a molar ratio of 0.8:1.0:4.6 with an average molecular weight of 281 kDa. Methylation analysis of UP1-1 revealed the major glycosidic bonds comprised 1,6-linked Glcp, 1,4-linked Glcp, t-linked Glcp, 1,3,6-linked Manp, 1,3-linked Galp, t-linked Galp at the ratio of 2.28:0.38:0.32:0.63:0.25:0.29. Structural analysis results revealed that the backbone of UP1-1 consisted of →6)-β-D-Glcp-(1→, →6)-β-D-Manp-(1→, →4)-β-D-Glcp-(1 → residues with side chains of →3)-β-D-Galp-(1→, β-D-Galp-(1 → and β-D-Glcp-(1 → branches located at O-3 position of →6)-β-D-Manp-(1→. Immunostimulatory activity tests showed that UP1-1 could promote the phagocytic activity and NO production of RAW 264.7 cells in a dose-dependent manner. UP1-1 could significantly improve the proliferation effect of RAW 264.7 cells at the concentration of 50 μg/mL. Thus, UP1-1 exerted good immunostimulatory activity, suggesting that UP1-1 has a great potential application in pharmacological industry.

Biopolymer production by halotolerant bacteria isolated from Caatinga biome

Saline environments are extreme habitats with a high diversity of microorganisms source of a myriad of biomolecules. These microorganisms are assigned as extremophiles recognized to be producers of new natural compounds, which can be synthesized by helping to survive under harshness and extreme conditions. In Brazil, in the saline and semi-arid region of Areia Branca (Caatinga biome), halotolerant bacteria (able to growth at high NaCl concentrations) were isolated from rhizosphere of native plants Blutaparon portulacoides and Spergularia sp. and their biopolymer production was studied. A total of 25 bacterial isolates were identified at genus level based on 16S rRNA gene sequence analysis. Isolates were mainly Gram-positive bacteria from Bacillaceae, Staphylococcaceae, Microbacteriaceae, and Bacillales XII incertae sedis families, affiliates to Bacillus, Staphylococcus, Curtobacterium, and Exiguobacterium genera, respectively. One of the Gram-negative isolates was identified as member of the Pseudomonadaceae family, genus Pseudomonas. All the identified strains were halotolerant bacteria with optimum growth at 0.6-2.0 M salt concentrations. Assays for biopolymer production showed that the halotolerant strains are a rich source of compounds as polyhydroxyalkanoates (PHA), biodegradable biopolymer, such as poly(3-hydroxybutyrate) (PHB) produced from low-cost substrates, and exopolysaccharides (EPS), such as hyaluronic acid (HA), metabolite of great interest to the cosmetic and pharmaceutical industry. Also, eight bacterial EPS extracts showed immunostimulatory activity, promising results that can be used in biomedical applications. Overall, our findings demonstrate that these biomolecules can be produced in culture medium with 0.6-2.0 M NaCl concentrations, relevant feature to avoid costly production processes. This is the first report of biopolymer-producing bacteria from a saline region of Caatinga biome that showed important biological activities.

Structural characterization and transcript-metabolite correlation network of immunostimulatory effects of sulfated polysaccharides from green alga Ulva pertusa

Three water-soluble polysaccharides (UPPs 1-3) were obtained from edible green alga Ulva pertusa. The chemico-physical analyses indicated that UPPs 1-3 possessed molecular weights of 376.7 kDa, 57.21 kDa, and 131.13 kDa, with sulfate contents of 26.01 ± 8.13%, 9.86 ± 3.24%, and 13.32 ± 6.56%, respectively, and composed of arabinose, galactose, glucose, xylose, galacturonic acid, glucuronic acid, and mannuronic acid, with different ratios. The in vitro studies revealed that UPP-1 showed significant effects on the proliferation and phagocytic activity of macrophage, release of nitric oxide, and secretion of cytokines (TNF-α and IL-6). The transcript-metabolite analysis of UPP-1 treated macrophage revealed 4747 differential genes (2416 up-regulated and 2331 down-regulated) and 94 differential metabolites (77 up-regulated and 17 down-regulated) that significantly co-mapped a transcript-metabolite correlation network of biosynthesis of amino acids, glycerophospholipid metabolism, and carbon metabolism. Thus, these findings provide a valuable foundation for the potential application of U. pertusa polysaccharides.

Structure, antioxidant and immunomodulatory activity of a polysaccharide extracted from Sacha inchi seeds

In this study, a novel water-soluble polysaccharide (PVLP-1) was extracted and purified from Sacha inchi (Plukenetia volubilis L.) seeds and the structure, antioxidant and immunomodulatory activity of PVLP-1 were investigated. PVLP-1 (144 kDa) consisted of glucose (69.76%), mannose (14.86%), arabinose (10.53%), galactose (2.42%), ribose (1.23%), rhamnose (0.27%) and xylose (0.93%). PVLP-1 displayed characteristic polysaccharide bands in Fourier transform NMR spectra and infrared. The primary structure of PVLP-1 was a heteropolysaccharide with a backbone of (1 → 6)-linked glucose, sidechains of (1 → 4)-linked mannose, (1 → 4)-linked glucose and (1 → 3, 6)-linked mannose and a residue unit of →1)-linked arabinose as revealed the methylation analysis. PVLP-1 possessed good water-holding capacity (WHC), oil-holding capacity (OHC) and antioxidant capacities. Besides, PVLP-1 induced the proliferation of RAW264.7 cell and enhanced the expression of inflammatory cytokines IL-6, TNF-alpha(TNF-α) and IL-1 beta (IL-1β). The present study indicated that PVLP-1 possessed immune-enhancing bioactivities and could be functional food or adjuvant drug to improve biological immunity of immunodeficiency diseases and hypoimmunity.

Structural characterization and immunostimulatory activity of polysaccharides from Pyrus sinkiangensis Yu

Two neutral polysaccharides (PSNP-1, 104.7 kDa; PSNP-2, 24.5 kDa) were isolated from the pulp of Pyrus sinkiangensis Yu. by using the combined techniques of ion-exchange and gel permeation chromatography. According to the IR, NMR spectra, monosaccharide composition, and methylation analyses, PSNP-1 was mainly composed of glucose and xylose residues, which form a typical xyloglucan. PSNP-2 contained an arabinan region composed of 1,5-linked Araf residues, a xyloglucan region that was mainly composed of t-, 1,2-linked Xylp, and 1,4-, 1,4,6-linked Glcp residues. PSNP-1 and PSNP-2 could stimulate the cell viability, NO release, and cytokine secretion (IL-6 and TNF-α) of RAW264.7 macrophages at the adosage of 250 μg/mL. It was suggested that PSNP-1 and PSNP-2 may increase macrophage-mediated immunostimulatory activity.

Isolation, purification, and structural characterization of polysaccharides from Atractylodis Macrocephalae Rhizoma and their immunostimulatory activity in RAW264.7 cells

Three water-soluble polysaccharides (AMAP-1, AMAP-2 and AMAP-3) were isolated and purified from Atractylodis Macrocephalae Rhizoma by using the combination of ion-exchange chromatography and gel permeation chromatography. The structures of the polysaccharides were characterized by chemical derivatization, HPGC, GC-MS, FT-IR, and NMR techniques. Structural analyses show that the three polysaccharides are pectin-type macromolecules consisting of homogalacturonan (HG) and rhamnogalacturonan type I (RG-I) regions in different ratios. Immunostimulatory assay highlighted that the RG-I-rich AMAP-1 and AMAP-2 with high molecular weights can stimulate RAW264.7 macrophages to release nitric oxide, but HG-rich AMAP-3 with a low molecular weight cannot. This finding suggests that the immune activity may be related to the side chains of the RG-I region, which provides a certain theoretical guidance for further exploring the structure-activity relationship. Meanwhile, AMAP-1 and AMAP-2, especially AMAP-2, from Atractylodis Macrocephalae Rhizoma show potential as immune adjuvants.

Isolation, purification, characterization and immunostimulatory activity of an exopolysaccharide produced by Lactobacillus pentosus LZ-R-17 isolated from Tibetan kefir

In this study, three strains of lactic acid bacteria isolated from Tibetan kefir grains, including two strains of Lactobacillus pentosus LZ-R-17 and L. helveticus LZ-R-5, and one strain of Lactococcus lactis subsp. lactis LZ-R-12. The ability of three strains to produce exopolysaccharide (EPS) was tested, and L. pentosus LZ-R-17 was found to have the highest EPS yield. One EPS (R-17-EPS) was isolated from the fermented milk by L. pentosus LZ-R-17 and purified by DEAE-52 anion exchange chromatography. Furthermore, R-17-EPS preliminary structure and macrophage immunomodulatory activity in vitro were investigated. On the basis of the analytical results of ultraviolet-visible spectrum, Fourier transform-infrared spectrum, monosaccharide composition analysis and one-dimensional and two-dimensional nuclear magnetic resonance (NMR) spectra, R-17-EPS was found to have an average molecular weight of 1.20 × 106 Da and was composed of galactose and glucose residues with a molar ratio of 1.00:3.15. NMR analysis revealed that the R-17-EPS was a linear hetero-galactoglucan containing repeating units of →2)-α-D-Galp-(1 → 4)-β-D-Glcp-(1 → 4)-β-D-Glcp-(1 → 4)-β-D-Glcp-(1→. In addition, R-17-EPS could effectively enhanced the proliferation, phagocytosis, nitric oxide and cytokines production of RAW264.7 cells, suggesting that R-17-EPS had potent immunostimulatory activity and could be explored as immunomodulator in functional food and/or medicine fields.

Effect of enzyme-assisted extraction on the physicochemical properties and bioactive potential of lotus leaf polysaccharides

Lotus leaf polysaccharides were extracted by enzyme-assisted extraction using α-amylase (LLEP-A), cellulose (LLEP-C), pectinase (LLEP-P) or protease (LLEP-PR). Their physicochemical properties and immunostimulatory activities were compared with those of hot-water extracted polysaccharides (LLWP). HPAEC-PDA and HPSEC-RI profiles indicated that variations in their molecular weight patterns and chemical compositions. Moreover, their effects on proliferation, phagocytic activity, and cytokine production in macrophages could be ordered as LLEP-P > LLEP-C > LLEP-A > LLWP > LLEP-PR, suggesting that LLEP-P by pectinase-assisted extraction was the most potent enhancer of macrophage activation. LLEP-P was further purified by gel filtration, and the main fraction (LLEP-P-І) was obtained to elucidate the structural and functional properties. LLEP-P-І (14.63 × 10³ g/mol) mainly consisted of rhamnose, arabinose, galactose, and galacturonic acid at molar percentages of 15.5:15.8:20.1:32.8. FT-IR spectra indicated the predominant acidic and esterified form, suggesting the pectic-like structure. Above all, LLEP-P-І exerted greater stimulation effects on NO and cytokines production and the phagocytic activity in macrophages. Transcriptome analysis also demonstrated that LLEP-P and LLEP-P-І could upregulate macrophage immune response genes, including cytokines, chemokines, and interferon via TLR and JAK-STAT signaling. Thus, these results suggest that pectinase application is most suitable to obtain immunostimulatory polysaccharides from lotus leaves.

Synthesis of β-1,3-glucan mimics by β-1,3-glucan trisaccharyl monomer polymerization

β-1,3-Glucans are important as immunostimulating agents in living organisms. The multivalent binding of β-1,3-glucans to dectin-1, a cell surface receptor, activates immunological defenses. To study artificial immunostimulating agents, glycopolymers carrying β-1,3-glucan trisaccharides as artificial ligands were synthesized. The β-1,3-glucan trisaccharide, defined as an active unit of β-1,3-glucan, was constructed from D-glucose by glycosylation. A norbornene group was introduced as a polymerizable group into the trisaccharide derivative at the aglycone. The prepared endo/exo norbornene stereoisomers of the monomers were separated by silica gel chromatography and identified by NMR spectroscopy and mass spectrometry. The synthesized glycosyl monomers were polymerized and copolymerized with norbornene using 2^nd generation Hoveyda-Grubbs catalyst, deprotected, and purified by gel filtration to prepare water-soluble glycopolymers of varied compositions and high molecular weights. These polymers will have the potential for multivalent binding to dectin-1 to activate immune response and facilitate studies to understand the binding mechanisms of β-1,3-glucans with dectin-1.

Structural characterization and immunostimulatory activity of a novel polysaccharide from green alga Caulerpa racemosa var peltata

A novel water-soluble polysaccharide (named CRVP-1) was successfully obtained from Caulerpa racemosa var peltata by hot-water extraction, ethanol precipitation, and column chromatography. The structure of CRVP-1 was characterized by HPGPC, HPAEC-PAD, FT-IR, GC-MS and NMR. The structural analysis indicated that CRVP-1 possessed a sulfate content of 25.8%±0.7% and was a heteropolysaccharide with an average molecular weight of 29.68kDa, and composed of mannose, galactose, glucose, galacturonic acid, and glucuronic acid with rates of 92.1%, 2.9%, 1.8%, 1.7% and 1.2%, respectively, owning a backbone structure of (1→6)-linked α-D-Manp residues with (1→4)-linked α-D-Manp and (1→2)-linked α-D-Manp residues and side chain that was consisted of (1→4)-linked β-D-Galp residues. The immunostimulatory assay revealed that CRVP-1 had significant effects on the proliferation of macrophage, production of NO and secretion of cytokines (TNF-α, IL-1β and IL-6). These findings provide a scientific basis for further utilization of polysaccharides from C. racemosa var peltata.

Structural characteristics of a red ginseng acidic polysaccharide rhamnogalacturonan I with immunostimulating activity from red ginseng

Background

Many researchers reported that the various immune activities of red ginseng are due to acid polysaccharides. But, the exact structural characteristics of the acidic polysaccharide in red ginseng have not been fully elucidated. Therefore, we isolated the acidic polysaccharide from red ginseng and characterized the structural property of the active moiety of this polysaccharide, which contributes to the immunostimulatory activity of red ginseng.

Methods

A polysaccharide (RGP-AP-I) was purified from red ginseng via size-exclusion chromatography using Sephadex G-100. Immunostimulatary activity of RGP-AP-I was investigated via anti-complementory and macrophage stimulatory activity. The structure of RGP-AP-I was characterized by HPLC, sugar composition, β-glucosyl Yariv reagent and methylation analysis.

Results

Peritoneal macrophages stimulated using RGP-AP-I significantly augmented the production of various cytokines such as interleukin (IL)-6, IL-12, and tumor necrosis factor (TNF)-α. The primary structure of RGP-AP-I was elucidated by assessing its sugar composition and methylation analysis. RGP-AP-I is a 96 kDa acidic polysaccharide, and comprises nine different monosaccharides, which mainly include sugars such as rhamnose (Rha, 9.5%), galacturonic acid (GalA, 18.4%), galactose (Gal, 30.4%), and arabinose (Ara, 35.0%). RGP-AP-I exhibited an considerable reaction with the β-glucosyl Yariv reagent, revealing the presence of arabino-β-3,6-galactan. Methylation analysis indicated that RGP-AP-I comprises 21 different glycosyl linkages, such as 3-, 4-, 6- and 3,6-linked Galp; 5-linked Araf; 2,4-linked Rhap; and 4-linked GalAp, which are characteristics of rhamnogalacturonan I (RG-I).

Conclusion

we assumed that the immunostimulatory activity of RGP-AP-I may be due to the RG-I structure, which comprises a main chain with a repeating linkage unit, [→2)-Rhap-(1→4)-GalAp-(1→] and three groups of side chains such as (1→5)-linked arabinan, (1→4)-linked galactan, and arabino-β-3,6-galactan, which branch at the C(O)4 positions of Rha residues in the main chain of RGP-AP-I.

Hydroxypropyltrimethyl ammonium chloride chitosan activates RAW 264.7 macrophages through the MAPK and JAK-STAT signaling pathways

Hydroxypropyltrimethyl ammonium chloride chitosan (HACC) is a water-soluble derivative of chitosan. To investigate the immunostimulatory effects of HACC, quaternized chitosans with different molecular weights were prepared and their effects on RAW 264.7 macrophages were compared. The results showed that HACC promoted nitric oxide (NO) production in a molecular weight- and dose-dependent manner. Lower molecular weight HACC was more active in promoting NO production. Furthermore, flow cytometry analysis showed that HACC significantly promoted the production of interleukin-6 and tumor necrosis factor-α. These results were further demonstrated by quantitive real-time reverse transcription polymerase chain reaction and western blot analysis. Moreover, western blotting revealed that HACC induced the phosphorylation of extracellular signal-regulated kinase, c-Jun N-terminal kinase, p38, and signal transducer and activator of transcription (STAT) proteins. In conclusion, HACC activated RAW 264.7 cells through the mitogen-activated protein kinases and Janus kinase/STAT pathways.

Effect of sulfation and partial hydrolysis of polysaccharides from Polygonatum sibiricum on immune-enhancement

The aqueous polysaccharide from Polygonatum sibiricum was extracted and fractionated using anion-exchange chromatography to obtain F₁ fraction. The F₁ was chemically sulfated and partially acid-hydrolyzed for the production of its over-sulfated (OS_1,2,3) and hydrolyzed (HP_1,2,3) derivatives, in which the sulfate content of OS_1,2,3 was 7.5-17.1%, and the M_w of HP_1,2,3 ranged from 18.2 × 10³ to 57.3 × 10³ g/mol. Considerable RAW264.7 cell activation was observed by HP_1,2,3 with NO production of 34.9, 44.3 and 42.7 μM, respectively, as well as the mRNA expression of cytokines (IL-1β, IL-6, IL-10 and IL-12). NK cell cytotoxicity against HT-29 cell was facilitated by OS_1,2,3 treatment with the increased gene expressions of INF-γ, Granzyme-B, perforin, NKG2D, and FasL. RAW264.7 cells appeared to be activated via MR and TLR4 mediated signaling pathway, but CR3 and TRL2 might play a main role in stimulating NK cells. Overall, the present study suggests the potential application of polysaccharides from P. sibiricum in functional foods and pharmacological industries.

Physicochemical properties, immunostimulatory activity of the Lachnum polysaccharide and polysaccharide-dipeptide conjugates

The physicochemical properties and the immunoregulatory actions in vitro of an exopolysaccharide from Lachnum (LEP) and its conjugation with a dipeptide (LEP-RH) were investigated aiming to improve their functional characteristics. The structure characteristic of the LEP and LEP-RH were determined via FT-IR and NMR. The physicochemical properties were evaluated by scanning electron microscopy (SEM), rheometer, and differential scanning calorimeter (DSC). SEM results showed that LEP-RH had a rough surface and relatively loose distribution that different from LEP. Rheological studies of LEP and LEP-RH at the same concentration indicated that LEP and LEP-RH have similar shear-thinning behaviors and gel-like structures, while LEP-RH has a better thermal stability than LEP. Bioassay results showed that treatment with the higher dosage (200 μg/mL) of LEP and LEP-RH stimulated the proliferation, cytokine secretion (IL-2, IL-6 and TNF-α) of RAW264.7 macrophages.

TO17: A teleost antimicrobial peptide that induces degradation of bacterial nucleic acids and inhibits bacterial infection in red drum, Sciaenops ocellatus

Tissue factor pathway inhibitor (TFPI)-1 is well known for its role as an inhibitor of blood coagulation. Several studies have demonstrated that the C-terminal peptides of TFPI-1 are active against a broad spectrum of microorganisms. In a previous study, we found that TO17 (with 17 amino acids), a TFPI-1 C-terminal peptide from red drum (Sciaenops ocellatus), was active against Edwardsiella tarda. In the present study, we investigated further the antimicrobial spectrum, action mode, as well as the immunostimulatory property of TO17. Our results showed that TO17 displayed antimicrobial activity against Staphylococcus aureus, Micrococcus luteus, Vibrio vulnificus, and infectious spleen and kidney necrosis virus, independent of host serum. Furthermore, the activity of TO17 was influenced by the length or type of amino acids at the N and C termini. During its interaction with V. vulnificus, TO17 exerted its antibacterial activity by destroying cell membrane integrity, penetrating the cytoplasm and inducing degradation of genomic DNA and total RNA. In addition, TO17 had no hemolytic activity against red drum blood cells. In vitro, TO17 enhanced production of nitric oxide and bactericidal activity of red drum macrophages. In vivo, administration of red drum with TO17 before bacterial infection significantly reduced pathogen dissemination and replication in tissues. These results indicate that TO17 is a broad-spectrum antimicrobial peptide with immunostimulatory properties and it has the potential to be used as an antimicrobial agent in aquaculture.

Immunostimulatory effects of sulfated chitosans on RAW 264.7 mouse macrophages via the activation of PI3K/Akt signaling pathway

To investigate the immunostimulatory effects of chitosan sulfates, we prepared α- and β-chitosan sulfates with different molecular weights and compared their immunostimulatory activities in RAW 264.7 macrophages. Results suggest that β-chitosan sulfates were more active than α-chitosan in promoting nitric oxide (NO) production. Further study show that β-chitosan sulfate significantly promoted the production of NO, prostaglandin E₂, tumor necrosis factor (TNF)-α, interleukin-6 and interleukin-1β at the levels of transcription and translation. Moreover, Western blots revealed that it induced the phosphorylation of p85 and Akt, and the nuclear translocation of p50/p65 and c-Fos/c-Jun. The luciferase activity of cells pretreated with β-chitosan sulfate further confirmed the nuclear translocation of p50/p65 and c-Fos/c-Jun. Determination of Toll-like receptor (TLR) 4 expression suggested that β-chitosan sulfate at least partly bound to TLR4. In conclusion, β-chitosan sulfates activate RAW 264.7 cells through the PI3K-Akt pathway, which is dependent on activator protein-1 and nuclear factor-κB activation.

Anthocyanins enriched purple tea exhibits antioxidant, immunostimulatory and anticancer activities

Purple coloured tea shoot clones have gained interest due to high content of anthocyanins in addition to catechins. Transcript expression of genes encoding anthocyanidin reductase (ANR), dihydroflavonol-4-reductase (DFR), anthocyanidin synthase (ANS), flavonol synthase (FLS) and leucoantho cyanidin reductase (LAR) enzymes in three new purple shoot tea clones compared with normal tea clone showed higher expression of CsDFR, CsANR, CsANS and lower expression of CsFLS and CsLAR in purple shoot clones compared to normal clone. Expression pattern supported high content of anthocyanins in purple tea. Four anthocyanins (AN_1-4) were isolated and characterized by UPLC-ESI-QToF-MS/MS from IHBT 269 clone which recorded highest total anthocyanins content. Cyanidin-3-O-β-d-(6-(E)-coumaroyl) glucopyranoside (AN₂) showed highest in vitro antioxidant activity (IC_50 DPPH = 25.27 ± 0.02 μg/mL and IC_50 ABTS = 10.71 ± 0.01 μg/mL). Anticancer and immunostimulatory activities of cyanidin-3-glucoside (AN₁), cyanidin-3-O-β-d-(6-(E)-coumaroyl) glucopyranoside (AN₂), delphinidin-3-O-β-d-(6-(E)-coumaroyl) glucopyranoside (AN₃), cyanidin-3-O-(2-O-β-xylopyranosyl-6-O-acetyl)-β-glucopyranoside (AN₄) and crude anthocyanin extract (AN₅) showed high therapeutic perspective. Anthocyanins AN_1-4 and crude extract AN₅ showed cytotoxicity on C-6 cancer cells and high relative fluorescence units (RFU) at 200 μg/mL suggesting promising apoptosis induction activity as well as influential immunostimulatory potential. Observations demonstrate potential of purple anthocyanins enriched tea clone for exploitation as a nutraceutical product.

Isolation, purification, structural analysis and immunostimulatory activity of water-soluble polysaccharides from Grifola Frondosa fruiting body

A new polysaccharide had been successfully isolated from maitake mushroom (Grifola Frondosa)-GFP. HPLC and Monosaccharide analysis showed that the average molecular weight of GFP was 155kDa and it was mainly composed of rhamnose, xylose, mannose, glucose, molar ratio of 1.00: 1.04: 1.11: 6.21. FTIR, methylation analysis and NMR were used to analyze the structural characterization of GFP. Structural analysis results revealed that its backbone consisted of (1→4)-linked methylation, Glcp residues were major structural polysaccharide GFP units, accounting of the polysaccharide backbone speculate GFP every→3)-Glcp-(1→and one→3,4)-Glcp-(1→connected interval with a small amount of 1→, 1→4, 1→6 glycosidic linkage. MTT assay showed that GFP could significantly improve the proliferation activity of RAW264.7 cells in a certain range of concentrations and time. Scanningelectro microscopy (SEM) results indicated that GFP could induce RAW264.7 cells activation. GFP could obviously increase the proliferation index and enhance the immunostimulatory activity such as the cytokine and chemokine production.

Structural elucidation and immunostimulatory activity of polysaccharide isolated by subcritical water extraction from Cordyceps militaris

Water-soluble polysaccharides were obtained from Cordyceps militaris (C. militaris) (CMP) by subcritical water extraction (SWE). Two polysaccharides fractions, CMP-W1 and CMP-S1, were isolated from CMP using DEAE-52 cellulose and Sephadex G-150 column chromatography. The structural characteristics of CMP-W1 and CMP-S1 were investigated. The results showed that the molecular weight of CMP-W1 and CMP-S1 are 3.66×105Da and 4.60×105Da, respectively, and both of them were heteropolysaccharides composed of d-mannose, d-glucose, d-galactose with the molar ratios of 2.84:1:1.29 and 2.05:1:1.09, respectively. FT-IR spectra analysis suggested that CMP-W1 and CMP-S1 belonged to pyranose form sugar and protein free. For immunostimulatory activity assay in vitro, CMP-W1 and CMP-S1 significantly promoted lymphatic spleen cell proliferation of mice. Therefore, the polysaccharides obtained from C. militaris by SWE can be used as potential natural immunostimulant in functional foods or medicine.