Acemannan purified from Aloe vera induces phenotypic and functional maturation of immature dendritic cells

Hybrid crystalline bioparticles with nanochannels encapsulating acemannan from Aloe vera: Structure and interaction with lipid membranes

Smart nanocarrier-based bioactive delivery systems are a current focus in nanomedicine for allowing and boosting diverse disease treatments. In this context, the design of hybrid lipid-polymer particles can provide structure-sensitive features for tailored, triggered, and stimuli-responsive devices. In this work, we introduce hybrid cubosomes that have been surface-modified with a complex of chitosan-N-arginine and alginate, making them pH-responsive. We achieved high-efficiency encapsulation of acemannan, a bioactive polysaccharide from Aloe vera, within the nanochannels of the bioparticle crystalline structure and demonstrated its controlled release under pH conditions mimicking the gastric and intestinal environments. Furthermore, an acemannan-induced phase transition from Im3m cubic symmetry to inverse hexagonal HII phase enhances the bioactive delivery by compressing the lattice spacing of the cubosome water nanochannels, facilitating the expulsion of the encapsulated solution. We also explored the bioparticle interaction with membranes of varying curvatures, revealing thermodynamically driven affinity towards high-curvature lipid membranes and inducing morphological transformations in giant unilamellar vesicles. These findings underscore the potential of these structure-responsive, membrane-active smart bioparticles for applications such as pH-triggered drug delivery platforms for the gastrointestinal tract, and as modulators and promoters of cellular internalization.

New opportunities and perspectives on biosynthesis and bioactivities of secondary metabolites from Aloe vera

Historically, the genus Aloe has been an indispensable part of both traditional and modern medicine. Decades of intensive research have unveiled the major bioactive secondary metabolites of this plant. Recent pandemic outbreaks have revitalized curiosity in aloe metabolites, as they have proven pharmacokinetic profiles and repurposable chemical space. However, the structural complexity of these metabolites has hindered scientific advances in the chemical synthesis of these compounds. Multi-omics research interventions have transformed aloe research by providing insights into the biosynthesis of many of these compounds, for example, aloesone, aloenin, noreugenin, aloin, saponins, and carotenoids. Here, we summarize the biological activities of major aloe secondary metabolites with a focus on their mechanism of action. We also highlight the recent advances in decoding the aloe metabolite biosynthetic pathways and enzymatic machinery linked with these pathways. Proof-of-concept studies on in vitro, whole-cell, and microbial synthesis of aloe compounds have also been briefed. Research initiatives on the structural modification of various aloe metabolites to expand their chemical space and activity are detailed. Further, the technological limitations, patent status, and prospects of aloe secondary metabolites in biomedicine have been discussed.

An Aloe-Based Composition Constituting Polysaccharides and Polyphenols Protected Mice against D-Galactose-Induced Immunosenescence

A decline in immune response, exhibited in the form of immunosenescence and inflammaging, is an age-associated disturbance of the immune system known to predispose the elderly to a greater susceptibility to infection and poor vaccine response. Polysaccharides and polyphenols from botanicals are known for their immune modulation effects. Here we evaluated a standardized mushroom-based composition, UP360, from Aloe barbadensis, Poria cocos, and Rosmarinus officinalis, as a natural nutritional supplement for a balanced immune response in an accelerated aging mouse model. Immunosenescence was induced by continual subcutaneous injection of D-galactose (D-gal) at a dose of 500 mg/kg/day to CD-1 mice. UP360 was administered at oral doses of 200 and 400 mg/kg to the mice starting on the 5th week of D-gal injection. The study lasted for a total of 9 weeks. All mice were given a quadrivalent influenza vaccine at 3 µg/animal via intramuscular injection 14 days before the end of the study. A group of D-gal-treated mice treated at 400 mg/kg/day UP360 was kept without vaccination. Whole blood, serum, spleen homogenate, and thymus tissues were used for analysis. UP360 was found to improve the immune response as evidenced by stimulation of innate and adaptive immune responses, increase antioxidant capacity as reflected by augmented SOD and Nrf2, and preserve vital immune organs, such as the thymus, from aging-associated damage. The findings depicted in this report show the effect of the composition in activating and maintaining homeostasis of the immune system both during active infections and as a preventive measure to help prime the immune system. These data warrant further clinical study to explore the potential application of the mushroom-based composition as an adjunct nutritional supplement for a balanced immune response.

A Bidens pilosa L. Non-Polar Extract Modulates the Polarization of Human Macrophages and Dendritic Cells into an Anti-Inflammatory Phenotype

Different communities around the world traditionally use Bidens pilosa L. for medicinal purposes, mainly for its anti-inflammatory, antinociceptive, and antioxidant properties; it is used as an ingredient in teas or herbal medicines for the treatment of pain, inflammation, and immunological disorders. Several studies have been conducted that prove the immunomodulatory properties of this plant; however, it is not known whether the immunomodulatory properties of B. pilosa are mediated by its ability to modulate antigen-presenting cells (APCs) such as macrophages (MØs) and dendritic cells (DCs) (through polarization or the maturation state, respectively). Different polar and non-polar extracts and fractions were prepared from the aerial part of B. pilosa. Their cytotoxic and immunomodulatory effects were first tested on human peripheral blood mononuclear cells (PBMCs) and phytohemagglutinin (PHA)-stimulated PBMCs, respectively, via an MTT assay. Then, the non-cytotoxic plant extracts and fractions that showed the highest immunomodulatory activity were selected to evaluate their effects on human MØ polarization and DC maturation (cell surface phenotype and cytokine secretion) through multiparametric flow cytometry. Finally, the chemical compounds of the B. pilosa extract that showed the most significant immunomodulatory effects on human APCs were identified using gas chromatography coupled with mass spectrometry. The petroleum ether extract and the ethyl acetate and hydroalcoholic fractions obtained from B. pilosa showed low cytotoxicity and modulated the PHA-stimulated proliferation of PBMCs. Furthermore, the B. pilosa petroleum ether extract induced M2 polarization or a hybrid M1/M2 phenotype in MØs and a semi-mature status in DCs, regardless of exposure to a maturation stimulus. The immunomodulatory activity of the non-polar (petroleum ether) extract of B. pilosa on human PBMC proliferation, M2 polarization of MØs, and semi-mature status in DCs might be attributed to the low-medium polarity components in the extract, such as phytosterol terpenes and fatty acid esters.

Rapid increase in immune surveillance and expression of NKT and γδT cell activation markers after consuming a nutraceutical supplement containing Aloe vera gel, extracts of Poria cocos and rosemary. A randomized placebo-controlled cross-over trial

GOAL

To evaluate the acute impact of a nutraceutical blend on immune surveillance.

STUDY DESIGN

A randomized, double-blind, placebo-controlled, cross-over trial was conducted in 11 healthy subjects. Blood samples were taken immediately before and at 1, 2, and 3 hours after consuming placebo or 500 mg of UP360, which is a blend of botanicals from Aloe vera, Poria cocos, and rosemary (APR extract). Immunophenotyping and flow cytometry quantified numbers of monocytes, NK cells, NKT cells, CD8+ cytotoxic T cells, γδT cells, and total T cells, and expression of CD25 and CD69 activation markers. Plasma was tested for cytokines, chemokines, growth factors, and enzymatic activity of superoxide dismutase and catalase.

RESULTS

Compared to the placebo, consumption of APR extract triggered rapid increases in chemokine levels starting at 1 hour, including IP-10 (P<0.05) and MCP-1 (P<0.1), which peaked at 2 hours (P<0.01) and 3 hours (P<0.05), respectively. The stem cell-mobilizing growth factor G-CSF increased at 2 hours (P<0.05). Increased immune surveillance involved a transient effect for monocytes at 1 hour, followed by NKT cells, CD8+ cytotoxic T cells, and γδT cells at 2-3 hours. Increased immune cell alertness was seen at 1 hour by increased CD25 expression on monocytes (P<0.01), NKT cells (P<0.01), and T cells (P<0.05). NKT cells showed upregulation of CD69 at 2 hours (P<0.01). Increased enzymatic activity was seen at 2 hours for the antioxidant enzymes superoxide dismutase (P<0.05) and catalase (P<0.01).

CONCLUSION

Consumption of APR extract triggered acute changes to chemokine levels. In addition, immune alertness was increased via the expression of activation markers on multiple types of innate immune cells, followed by increased immune surveillance and antioxidant protection. This suggests a beneficial enhancement of natural immune surveillance, likely via a combination of gut-mediated cytokine release and vagus nerve communication, in combination with cellular protection from oxidative stress.

A New Biomaterial Derived from Aloe vera-Acemannan from Basic Studies to Clinical Application

Aloe vera is a kind of herb rich in polysaccharides. Acemannan (AC) is considered to be a natural polysaccharide with good biodegradability and biocompatibility extracted from Aloe vera and has a wide range of applications in the biomedical field due to excellent immunomodulatory, antiviral, antitumor, and tissue regeneration effects. In recent years, clinical case reports on the application of AC as a novel biomedical material in tissue regenerative medicine have emerged; it is mainly used in bone tissue engineering, pulp-dentin complex regeneration engineering, and soft tissue repair, among other operations. In addition, multiple studies have proved that the new composite products formed by the combination of AC and other compounds have excellent biological and physical properties and have broader research prospects. This paper introduces the preparation process, surface structure, and application forms of AC; summarizes the influence of acetyl functional group content in AC on its functions; and provides a detailed review of the functional properties, laboratory studies, clinical cutting-edge applications, and combined applications of AC. Finally, the current application status of AC from basic research to clinical treatment is analyzed and its prospects are discussed.

Potential of methacrylated acemannan for exerting antioxidant-, cell proliferation-, and cell migration-inducing activities in vitro

BACKGROUND

Acemannan is an acetylated polysaccharide of Aloe vera extract with antimicrobial, antitumor, antiviral, and antioxidant activities. This study aims to optimize the synthesis of acemannan from methacrylate powder using a simple method and characterize it for potential use as a wound-healing agent.

METHODS

Acemannan was purified from methacrylated acemannan and characterized using high-performance liquid chromatography (HPLC), Fourier-transform infrared spectroscopy (FTIR), and ¹H-nuclear magnetic resonance (NMR). 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assays were performed to investigate the antioxidant activity of acemannan and its effects on cell proliferation and oxidative stress damage, respectively. Further, a migration assay was conducted to determine the wound healing properties of acemannan.

RESULTS

We successfully optimized the synthesis of acemannan from methacrylate powder using a simple method. Our results demonstrated that methacrylated acemannan was identified as a polysaccharide with an acetylation degree similar to that in A. vera, with the FTIR revealing peaks at 1739.94 cm^-1 (C = O stretching vibration), 1370 cm^-1 (deformation of the H-C-OH bonds), and 1370 cm^-1 (C-O-C asymmetric stretching vibration); ¹H NMR showed an acetylation degree of 1.202. The DPPH results showed the highest antioxidant activity of acemannan with a 45% radical clearance rate, compared to malvidin, CoQ10, and water. Moreover, 2000 µg/mL acemannan showed the most optimal concentration for inducing cell proliferation, while 5 µg/mL acemannan induced the highest cell migration after 3 h. In addition, MTT assay findings showed that after 24 h, acemannan treatment successfully recovered cell damage due to H₂O₂ pre-treatment.

CONCLUSION

Our study provides a suitable technique for effective acemannan production and presents acemannan as a potential agent for use in accelerating wound healing through its antioxidant properties, as well as cell proliferation- and migration-inducing activities.

Immunopathological studies on Escherichia coli infected broiler chickens fed on Aloe vera leaf extract

Escherichia coli infection is the major bacterial disease affecting the poultry industry and the continuous use of antibiotics in poultry farming has resulted in antibiotic resistance. So this study was planned to evaluate the use of an ecologically safe alternative to fight against infections. The leaf gel of the Aloe vera plant was selected based on its antibacterial activity assessed in in-vitro tests. The objective of the present study was to evaluate the effect of A. vera leaf extract supplementation on the severity of clinical signs and pathological lesions, mortality rate, levels of antioxidant enzymes, and immune response in experimentally E. coli-infected broiler chicks. Broiler chicks were supplemented with aqueous Aloe vera Leaf (AVL) extract @ 20 ml per liter of water from day one of age. After seven days of age, they were experimentally infected with E. coli O78 @ 10⁷ CFU/0.5 ml intraperitoneally. Blood was collected at weekly intervals up to 28 days and assayed for antioxidant enzyme assays, and humoral and cellular immune response. The birds were observed daily for clinical signs and mortality. Dead birds were examined for gross lesions and representative tissues were processed for histopathology. The activities of antioxidants, Glutathione reductase (GR), and Glutathione-S-Transferase (GST) were significantly higher than the control infected group. The E. coli-specific antibody titer and Lymphocyte stimulation Index were comparatively higher in the AVL extract-supplemented infected group as compared to the control infected group. No considerable change was noted in the severity of clinical signs and pathological lesions, and mortality. Thus, Aloe vera Leaf gel extract enhanced the antioxidant activities and cellular immune responses of infected broiler chicks to combat this infection.

Growth performance, feed utilization, hematological parameters, and histological features of Nile tilapia (Oreochromis niloticus) fed diets with supplementary herbal extracts under prolonged water exchange

Nile tilapia is known for its relative tolerance to some biotic and abiotic stressors. However, long-period water exchange may impair the health status and, thereby, the growth performance and feed utilization. In this regard, using herbal extracts may help to relieve the adverse impacts of low water quality on the productivity of this fish species. A 100-day feeding trial was designed to examine the effects of dietary supplements of Aloe vera leaves (AVE), and chamomile flowers, Matricaria chamomilla (CFE) extracts on water quality, growth performance, and well-being of Nile tilapia. Fish (3.95±0.05 g, n=1200) were distributed into five groups (15 fiberglass tanks, 2 m3) under a water exchange rate of 20% every two days for standard control (T0) without herbal supplements. In groups (T1, T2, T3, and T4), a long period water exchange period of 50% every month, wherein T1 (stressed control), T2, T3, and T4 groups were fed a diet supplemented with 0% herbal extract, 1% AVE, 1% CFE and 0.5% AVE +0.5% CFE, respectively. Results showed that feeding on a T2 diet exhibited a clear improvement under a long period of water exchange stress, and it is almost similar to their counterparts under normal conditions (T0) in terms of specific growth rate, survival rate, feed intake, feed conversion ratio, and protein efficiency ratio. Moreover, the lowest levels of aspartate aminotransferase were obtained with T2 and T0. In addition, the highest white blood cell count and hemoglobin values were recorded with group T0, followed by T2, and T4, while no significant difference between T3 and T1. Fish under stressed conditions without herbal extracts (T1) showed the lowest performance and survival rate compared to T0 and T2 groups. In conclusion, feeding diet supplied with 1% A. vera extract to stressed fish restored their performance and well-being to the level of their counterparts under normal conditions.

Extraction, purification, structural characterization, and gut microbiota relationship of polysaccharides: A review

Intestinal dysbiosis is one of the major causes of the occurrence of metabolic syndromes, such as obesity, diabetes, nonalcoholic fatty liver disease, and cardiovascular diseases. Polysaccharide-based microbial therapeutic strategies have excellent potential in the treatment of metabolic syndromes, but the underlying regulatory mechanisms remain elusive. Identification of the internal regulatory mechanism of the gut microbiome and the interaction mechanisms involving bacteria and the host are essential to achieve precise control of the gut microbiome and obtain valuable clinical data. Polysaccharides cannot be directly digested; the behavior in the intestinal tract is considered a "bridge" between microbiota and host communication. To provide a relatively comprehensive reference for researchers in the field, we will discuss the polysaccharide extraction and purification processes and chemical and structural characteristics, focusing on the polysaccharides in gut microbiota through the immune system, gut-liver axis, gut-brain axis, energy axis interactions, and potential applications.

Utilization of Aloe Compounds in Combatting Viral Diseases

Plants contain underutilized resources of compounds that can be employed to combat viral diseases. Aloe vera (L.) Burm. f. (syn. Aloe barbadensis Mill.) has a long history of use in traditional medicine, and A. vera extracts have been reported to possess a huge breadth of pharmacological activities. Here, we discuss the potential of A. vera compounds as antivirals and immunomodulators for the treatment of viral diseases. In particular, we highlight the use of aloe emodin and acemannan as lead compounds that should be considered for further development in the management and prevention of viral diseases. Given the immunomodulatory capacity of A. vera compounds, especially those found in Aloe gel, we also put forward the idea that these compounds should be considered as adjuvants for viral vaccines. Lastly, we present some of the current limitations to the clinical applications of compounds from Aloe, especially from A. vera.

In vitro and in vivo anti-Cryptosporidium and anti-inflammatory effects of Aloe vera gel in dexamethasone immunosuppressed mice

Cryptosporidiosis has been considered as a serious diarrheal disease, especially in immunodeficient patients, where they failed to clear the infection leading to several consequences of infection (i.e death). The role of cell mediated immunity in clearing the infection was demonstrated by the increased susceptibility of HIV/AIDS patients to infection. To date, no specific treatment has been proven for cryptosporidiosis in immunodeficient patients. The study aimed to evaluate the efficacy of Aloe vera gel for the treatment of cryptosporidiosis in immunocompetent and dexamethasone immunosuppressed mice in comparison to that of nitazoxanide. Mice were orally administrated with Aloe vera gel, in a daily dose of 250 mg/L in drinking water, for 14 consecutive days post infection. Parasitological, molecular and immunological measurements were recorded on the 7th, 14th, 21st and 32nd days post infection. Our in vitro results showed that 250 mg/L of prepared gel achieved the highest parasitic reduction. The body weights of Aloe vera treated mice on the 21st and 32nd day post infection, either in immunocompetent or immunosuppressed groups, were nearly the same as those of their corresponding control groups. Aloe vera gel succeeded in clearing cryptosporidiosis with a percent reduction of 100% in immunocompetent mice and 99.67% in immunosuppressed mice. The anti-inflammatory effect of Aloe vera reduced the levels of IFN-γ, IL-4, -6 and -17. The success of Aloe vera gel, in clearing cryptosporidiosis in immunosuppressed mice, was obvious either from the reduction of Cryptosporidium DNA or the oocysts in stool samples; and from the improvement of histopathological sections.

Pharmacodynamics of Aloe vera and acemannan in therapeutic applications for skin, digestion, and immunomodulation

Scientific studies of Aloe vera have tentatively explained therapeutic claims from a mechanistic perspective. Furthermore, in vitro outcomes demonstrate that the breakage of acemannan chains into smaller fragments enhances biological effects. These fragments can intravenously boost vaccine efficacy or entrain the immune system to attack cancer cells by mannose receptor agonism of macrophage or dendritic cells. With oral consumption, epithelialisation also occurs at injured sites in the small intestine or colon. The main advantage of dietary acemannan is the attenuation of the digestive process, increasing satiety, and slowing the release of sugars from starches. In the colon, acemannan is digested by microbes into short-chain fatty acids that are absorbed and augment the sensation of satiety and confer a host of other health benefits. In topical applications, an acemannan/chitosan combination accelerates the closure of wounds by promoting granular tissue formation, which creates a barrier between macrophages or neutrophils and the wound dressing. This causes M2 polarisation, reversal of inflammation, and acceleration of the re-epithelialisation process. This review summarises and explains the current pharmacodynamic paradigm in the context of acemannan in topical, oral, and intravenous applications. However, due to contradictory results in the literature, further research is required to provide scientific evidence to confirm or nullify these claims.

Development of Broad-Spectrum Antiviral Agents-Inspiration from Immunomodulatory Natural Products

Developing broad-spectrum antiviral drugs remains an important issue as viral infections continue to threaten public health. Host-directed therapy is a method that focuses on potential targets in host cells or the body, instead of viral proteins. Its antiviral effects are achieved by disturbing the life cycles of pathogens or modulating immunity. In this review, we focus on the development of broad-spectrum antiviral drugs that enhance the immune response. Some natural products present antiviral effects mediated by enhancing immunity, and their structures and mechanisms are summarized here. Natural products with immunomodulatory effects are also discussed, although their antiviral effects remain unknown. Given the power of immunity and the feasibility of host-directed therapy, we argue that both of these categories of natural products provide clues that may be beneficial for the discovery of broad-spectrum antiviral drugs.

Molecular mechanisms and associated cell signalling pathways underlying the anticancer properties of phytochemical compounds from Aloe species (Review)

Naturally occurring components from various species of Aloe have been used as traditional folk medicine since the ancient times. Over the last few decades, the therapeutic effects of extracts and phytochemical compounds obtained from Aloe vera have been proven in preclinical and clinical studies. Recently, compounds from other Aloe species apart from Aloe vera have been investigated for the treatment of different diseases, with a particular focus on cancer. In the present review, the effects of phytochemical compounds obtained from different Aloe species are discussed, with a specific focus on the effects on cell signalling in cancer and normal cells, and their selectivity and efficacy. This information will be useful for the application of Aloe-derived compounds as therapeutic agents, either alone or in combination with other standard drugs for cancer treatment.

Immunobiology and Application of Aloe Vera-Based Scaffolds in Tissue Engineering

Aloe vera (AV), a succulent plant belonging to the Liliaceae family, has been widely used for biomedical and pharmaceutical application. Its popularity stems from several of its bioactive components that have anti-oxidant, anti-microbial, anti-inflammatory and even immunomodulatory effects. Given such unique multi-modal biological impact, AV has been considered as a biomaterial for regenerative medicine and tissue engineering applications, where tissue repair and neo-angiogenesis are vital. This review outlines the growing scientific evidence that demonstrates the advantage of AV as tissue engineering scaffolds. We particularly highlight the recent advances in the application of AV-based scaffolds. From a tissue engineering perspective, it is pivotal that the implanted scaffolds strike an appropriate foreign body response to be well-accepted in the body without complications. Herein, we highlight the key cellular processes that regulate the foreign body response to implanted scaffolds and underline the immunomodulatory effects incurred by AV on the innate and adaptive system. Given that AV has several beneficial components, we discuss the importance of delving deeper into uncovering its action mechanism and thereby improving material design strategies for better tissue engineering constructs for biomedical applications.

Carrot Pomace Polysaccharide (CPP) Improves Influenza Vaccine Efficacy in Immunosuppressed Mice via Dendritic Cell Activation

Despite the advancements in vaccination research and practices, influenza viruses remain a global health concern. Inducing a robust immune response by vaccination is especially challenging in the elderly, the immunocompromised, and persons with chronic illnesses. Polysaccharides derived from food may act as a safe and readily accessible means to boost the immune system during vaccination. In this study, we investigated whether crude polysaccharides derived from carrot pomace (CPP) could stimulate innate immune cell function and promote influenza vaccine immunogenicity. In bone marrow-derived dendritic cells (BMDCs), CPP increased the fraction of CD11c+MHCII+ cells and the expression of co-stimulatory molecules CD40 and CD80, indicative of enhanced maturation and activation. Functionally, CPP-treated BMDCs promoted inflammatory cytokine production in splenic lymphocytes. In a mouse model of immunosuppression induced by cyclophosphamide, animals given CPP before and after an influenza vaccine challenge showed increased frequencies of dendritic cells and natural killer cells in the spleen, in addition to the recovery of vaccine-specific antibody titers. Moreover, innate myeloid cells in CPP-fed mice showed evidence of phenotypic modification via markedly enhanced interleukin(IL)-12 and interferon(IFN)-γ production in response to lipopolysaccharide(LPS) stimulation ex vivo. Our findings suggest that the administration of carrot pomace polysaccharides can significantly enhance the efficacy of influenza vaccination.

Adjuvanticity of Processed Aloe vera gel for Influenza Vaccination in Mice

The effectiveness of current influenza vaccines is considered suboptimal, and 1 way to improve the vaccines is using adjuvants. However, the current pool of adjuvants used in influenza vaccination is limited due to safety concerns. Aloe vera, or aloe, has been shown to have immunomodulatory functions and to be safe for oral intake. In this study, we explored the potential of orally administered processed Aloe vera gel (PAG) as an adjuvant for influenza vaccines in C57BL/6 mice. We first evaluated its adjuvanticity with a split-type pandemic H1N1 (pH1N1) Ag by subjecting the mice to lethal homologous influenza challenge. Oral PAG administration with the pH1N1 Ag increased survival rates in mice to levels similar to those of alum and MF59, which are currently used as adjuvants in influenza vaccine formulations. Similarly, oral PAG administration improved the survival of mice immunized with a commercial trivalent influenza vaccine against lethal homologous and heterologous virus challenge. PAG also increased hemagglutination inhibition and virus neutralization Ab titers against homologous and heterologous influenza strains following immunization with the split-type pH1N1 Ag or the commercial trivalent vaccine. Therefore, this study demonstrates that PAG may potentially be used as an adjuvant for influenza vaccines.

Extraction, Purification, Structural Characteristics, Biological Activities and Pharmacological Applications of Acemannan, a Polysaccharide from Aloe vera: A Review

Aloe vera is a medicinal plant species of the genus Aloe with a long history of usage around the world. Acemannan, considered one of the main bioactive polysaccharides of Aloe vera, possesses immunoregulation, anti-cancer, anti-oxidation, wound healing and bone proliferation promotion, neuroprotection, and intestinal health promotion activities, among others. In this review, recent advancements in the extraction, purification, structural characteristics and biological activities of acemannan from Aloe vera were summarized. Among these advancements, the structural characteristics of purified polysaccharides were reviewed in detail. Meanwhile, the biological activities of acemannan from Aloe vera determined by in vivo, in vitro and clinical experiments are summarized, and possible mechanisms of these bioactivities were discussed. Moreover, the latest research progress on the use of acemannan in dentistry and wound healing was also summarized in details. The structure-activity relationships of acemannan and its medical applications were discussed. Finally, new perspectives for future research work on acemannan were proposed. In conclusion, this review summarizes the extraction, purification, structural characteristics, biological activities and pharmacological applications of acemannan, and provides information for the industrial production and possible applications in dentistry and wound healing in the future.

Aloe polysaccharide protects skin cells from UVB irradiation through Keap1/Nrf2/ARE signal pathway

The aim of this study was to investigate if aloe polysaccharide (AP) has the repairing effect on ultraviolet b (UVB) injured nerve cells. The study applied BALB/c female mice as animal model, and NFG-activated PC12 cells as cell model of skin nerve. The cell viability was detected by MTT assay, and cell apoptosis was detected by TUNEL (TdT-mediated dUTP nick-end labeling) and Annexin-V/PI assay, and cell-cycle status in different groups were observed via flow cytometry (FCM). Enzyme-linked immunosorbent assay (ELISA) was applied to analyze oxidative stress and anti-oxidative ability in each group. Real-time PCR and western blot were used to detect the expression levels of Bax, Bcl-2, Caspase-3, Cyclin D1, Keap1, Nrf2, GCLC, and GSTP1. The results showed obvious inhibition of cell viability and cell-cycle progression and promotion of cell apoptosis by UVB irradiation through inducing oxidative stress. In AP treated groups, cell viability and proliferation could be markedly improved and cell apoptosis inhibited with higher anti-oxidative capability and up-regulated expression of Keap1, Nrf2, GCLC, and GSTP1. It suggested that AP was able to repair UVB induced injury on NGF activated skin neural cell PC12, probably through Keap1/Nrf2/ARE signal pathway.

Aloe Polysaccharides Inhibit Influenza A Virus Infection-A Promising Natural Anti-flu Drug

Influenza A virus causes periodic outbreaks and seriously threatens human health. The drug-resistant mutants have shown an epidemic trend because of the abuse of chemical drugs. Aloe polysaccharides (APS) extracted from Aloe vera leaves have evident effects on the therapy of virus infection. However, the activity of APS in anti-influenza virus has yet to be investigated. Here, we refined polysaccharides from A. vera leaf. In vitro test revealed that APS could inhibit the replication of a H1N1 subtype influenza virus, and the most obvious inhibitory effect was observed in the viral adsorption period. Transmission electron microscopy indicated that APS directly interacted with influenza virus particles. Experiments on PR8 (H1N1) virus infection in mice demonstrated that APS considerably ameliorated the clinical symptoms and the lung damage of the infected mice, and significantly reduced the virus loads and mortality. Our findings provided a theoretical basis for the development of novel natural anti-influenza agents.

Immunomodulatory effect of Stinging nettle (Urtica dioica) and Aloe vera (Aloe barbadensis) in broiler chickens

A study was conducted to identify the immunomodulatory effect of Stinging nettle (Urtica dioica) and Aloe vera (Aloe barbadensis) in broiler chicken. A total of 240 birds were divided into 4 treatment groups with 4 replications in each group, each replication containing 15 birds. Treatments were comprised of no Nettle and Aloe vera (T₀); Nettle 5% (T₁), Aloe vera @5 ml/lit drinking water (T₂) and Nettle 5% and Aloe vera @5 ml/lit drinking water (T₃). The study was conducted under a randomized design. The immunomodulating effect was evaluated by measuring antibody titer against NDV vaccine; and by estimating the albumin, globulin and total protein upto 40 days of age. The effect on liver was estimated by measuring liver enzymes alanine aminotransferase (ALT). The hypoglycemic effect was estimated by measuring glucose level in the serum, and morphological changes in the spleen and bursa were estimated by measuring the ratio score of the respective organs to the body weight. Throughout the experiment, the value for HI titer, albumin, globulin, total protein, spleen weight ratio score, bursa weight ratio score, liver function test and blood glucose of all treatment group were non significant (p > 0.05) except for albumin on 10th day, globulin on 0th day, total protein on 0th day and ratio score of spleen were found to be significant (p ≤ 0.05) at 30 days in all treatment compared to control group. Histopathology of spleen and bursa appeared normal in all treatment and control groups. Result thus suggests that nettle and Aloe vera have non-significant immunomodulatory effects.

Beneficial Effects of Prebiotic Saccharomyces cerevisiae Mannan on Allergic Asthma Mouse Models

One of the unmet needs for asthma management is a new therapeutic agent with both anti-inflammatory and anti-smooth muscle (ASM) remodeling effects. The mannose receptor (MR) family plays an important role in allergen uptake and processing of major allergens Der p 1 and Fel d 1. We have previously reported that ASM cells express a mannose receptor (ASM-MR) and that mannan derived from Saccharomyces cerevisiae (SC-MN) inhibits mannosyl-rich lysosomal hydrolase-induced bovine ASM cell proliferation. Using a humanized transgenic mouse strain (huASM-MRC2) expressing the human MRC2 receptor in a SM tissue-specific manner, we have demonstrated that ASM hyperplasia/hypertrophy can occur as early as 15 days after allergen challenge in this mouse model and this phenomenon is preventable with SC-MN treatment. This proof-of-concept study would facilitate future development of a potential asthma therapeutic agent with dual function of anti-inflammatory and anti-smooth muscle remodeling effects.

Advances on Bioactive Polysaccharides from Medicinal Plants

In recent decades, the polysaccharides from the medicinal plants have attracted a lot of attention due to their significant bioactivities, such as anti-tumor activity, antioxidant activity, anticoagulant activity, antidiabetic activity, radioprotection effect, anti-viral activity, hypolipidemic and immunomodulatory activities, which make them suitable for medicinal applications. Previous studies have also shown that medicinal plant polysaccharides are non-toxic and show no side effects. Based on these encouraging observations, most researches have been focusing on the isolation and identification of polysaccharides, as well as their bioactivities. A large number of bioactive polysaccharides with different structural features and biological effects from medicinal plants have been purified and characterized. This review provides a comprehensive summary of the most recent developments in physiochemical, structural features and biological activities of bioactive polysaccharides from a number of important medicinal plants, such as polysaccharides from Astragalus membranaceus, Dendrobium plants, Bupleurum, Cactus fruits, Acanthopanax senticosus, Angelica sinensis (Oliv.) Diels, Aloe barbadensis Miller, and Dimocarpus longan Lour. Moreover, the paper has also been focused on the applications of bioactive polysaccharides for medicinal applications. Recent studies have provided evidence that polysaccharides from medicinal plants can play a vital role in bioactivities. The contents and data will serve as a useful reference material for further investigation, production, and application of these polysaccharides in functional foods and therapeutic agents.

Acemannan increases NF-κB/DNA binding and IL-6/-8 expression by selectively binding Toll-like receptor-5 in human gingival fibroblasts

Acemannan, an acetylated polymannose from Aloe vera, has immunomodulatory effects. We investigated whether acemannan induces IL-6 and -8 expression and NF-κB/DNA binding in human gingival fibroblasts. IL-6 and -8 expression levels were assessed via RT-PCR and ELISA. The NF-κB p50/p65-DNA binding was determined. The structures of acemannan mono-pentamers and Toll-like receptor 5 (TLR5) were simulated. The binding energies between acemannan and TLR5 were identified. We found that acemannan significantly stimulated IL-6/-8 expression at both the mRNA and protein level and significantly increased p50/DNA binding. Preincubation with an anti-TLR5 neutralizing antibody abolished acemannan-induced IL-6/-8 expression and p50/DNA binding, and co-incubation of acemannan with Bay11-7082, a specific NF- κB inhibitor, abolished IL-6/-8 expression. The computer modeling indicated that monomeric/dimeric single stranded acemannan molecules interacted with the TLR5 flagellin recognition sites with a high binding affinity. We conclude that acemannan induces IL-6/-8 expression, and p50/DNA binding in gingival fibroblasts, at least partly, via a TLR5/NF-κB-dependent signaling pathway. Furthermore, acemannan selectively binds with TLR5 ectodomain flagellin recognition sites.

Co-adjuvant effects of plant polysaccharide and propolis on chickens inoculated with Bordetella avium inactivated vaccine

Taishan Pinus massoniana pollen polysaccharide (TPPPS), propolis (PP) and aloe polysaccharide (AP), used as adjuvants, have been proven to possess immunity-enhancing functions. However, their collaborative immunomodulatory effects are largely unknown. To determine which combination can induce the best effects, the three adjuvants were separately or conjointly added into Bordetella avium inactivated vaccines to investigate their co-adjuvant effects on vaccinated chickens. We found that, among all six adjuvant-treated vaccine inoculated groups (TPPPS, PP, AP, TPPPS-PP, PP-AP and TPPPS-AP), the chickens inoculated with TPPPS, PP or TPPPS-PP adjuvant vaccines showed significantly higher levels of antibody titre, cytokine, lymphocyte transformation and peripheral blood T-lymphocyte count than those of non-adjuvant vaccine inoculated groups (P < 0.05), indicating the good immune-enhancing effects of TPPPS and PP. The TPPPS-PP group showed the highest levels of antibody titres and interleukin-2 (IL-2) at 14-28 days post the first inoculation (dpi), lymphocyte transformation rates (LTRs) at 14-35 dpi, CD4(+) T-lymphocyte counts at 14-42 dpi, and CD8(+) T-lymphocyte counts at 28 dpi. The results revealed that B. avium inactivated vaccine used conjointly with TPPPS and PP induced the strongest humoral and cellular immune responses. Thus, there was a synergistic effect between TPPPS and PP on enhancing immunity, which suggests that they can be used as a novel adjuvant formulation for the development of poultry vaccines.

Influence of drinking water containing Aloe vera (Aloe barbadensis Miller) gel on growth performance, intestinal microflora, and humoral immune responses of broilers

Aim:

The risk of bacteria resistance to specific antibiotics possibly by continuous subtherapeutical administration of antibiotic growth promoters (AGPs) in poultry feed led to a ban on the use of AGP in poultry production. As a result of this ban, alternative substances for poultry growth promotion and disease prevention are being investigated, among which phytogenic and herbal products have received increased attention as natural additives because they have been accepted by consumers as natural additives. The effect of water supplementation of Aloe vera (AV) as an AGP substitute on performance, intestinal microflora, and immune responses of broilers.

Materials and Methods:

The five experimental treatments were allocated to four replicates. The following treatments were applied (1) a basal broiler diet (C) and normal drinking water, (2) 0.5% AV gel in drinking water, (3) 0.75% AV gel in drinking water, (4) 1% AV gel in drinking water, and (5) diet C supplemented with flavophospholipol at 4.5 mg/kg and drinking normal water. Vaccines against influenza disease and sheep red blood cell (SRBC) were administrated to immunological stimuli. The populations of Lactobacilli spp. and coliforms were enumerated in ileum.

Results:

Body weight of broilers supplemented with different levels of AV increased compared with control group (p<0.05). Birds supplemented with antibiotic had the best feed-to-gain ratio (F:G) in different periods. Supplementation of 0.5% and 0.75% AV improved F: G entire experimental period compared with control group (p<0.05). Coliform bacteria were reduced in broilers supplemented with different levels of AV or antibiotic (p<0.05). The Lactobacilli spp. population in birds supplemented with 0.75%, 1% AV or antibiotic significantly was higher than other groups (p<0.05). Supplementation with 1% AV led to greater antibody titers against SRBC compared with other groups (p<0.05).

Conclusion:

These findings demonstrated a possibility of supplementing broiler drinking water with 1% AV gel as an alternative for AGP substitution.

Prevention of azoxymethane/dextran sodium sulfate-induced mouse colon carcinogenesis by processed Aloe vera gel

The preventive effect of a processed Aloe vera gel (PAG) on colon carcinogenesis was examined using an azoxymethane (AOM)-initiated and dextran sodium sulfate (DSS)-promoted mouse colon carcinogenesis model. Oral administration of PAG (200, or 400mg/kg/day) significantly reduced the multiplicity of colonic adenomas and adenocarcinomas compared with the AOM/DSS only-treated mice. In the mice treated with 400mg/kg of PAG, adenoma and adenocarcinoma development was reduced to 80% and 60%, respectively, compared to 100% in the PAG-untreated AOM/DSS-treated mice. Western blot analysis using colon extracts showed that PAG reduced the activation of nuclear factor kappa B (NF-κB), resulting in the inhibition of inducible nitric oxide synthase and cyclooxygenase-2 expression. PAG appeared to inhibit the NF-κB activation through the activation of peroxisome proliferator-activated receptor gamma. PAG also inhibited the expression and phosphorylation of signal transducer and activator of transcription 3, which is known to connect inflammation and cancer. In addition, PAG inhibited cell cycle progression-inducing cellular factors, such as extracellular signal-regulated kinases 1/2, cyclin-dependent kinase 4, and cyclin D1. On the other hand, PAG increased the expression of Caudal-related homeobox transcription factor 2, which is known to be a tumor suppressor in colorectal cancer. These findings show that PAG suppresses colitis-related colon carcinogenesis by inhibiting both chronic inflammation and cell cycle progression in the colon.

Effects of Aloe barbadensis Mill. extract (AVH200®) on human blood T cell activity in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Aloe barbadensis Mill. (Aloe vera) is a widely used medicinal plant well reputed for its diverse therapeutic applications. It has been used for thousands of years in folk medicine to treat various conditions and the Aloe vera gel has been reported to possess anti-inflammatory as well as immunostimulatory and immunomodulatory properties. However, the mode of action is still unclear.

AIM OF THE STUDY

The aim of this study was determine the effects of two well-defined A. barbadensis Mill. extracts AVH200® and AVE200 on human blood T cells in vitro.

MATERIALS AND METHODS

Peripheral blood mononuclear cells (PBMC) from healthy donors were stimulated polyclonally in the presence or absence of AVH200® and AVE200. The T cell phenotype was investigated by flow cytometry, cell proliferation was determined by CFSE dye and thymidine assay, respectively and cytokine secretion was determined by MSD® Multi-Spot Assay system and ELISA.

RESULTS

The presence of AVH200® resulted in a reduced expression of CD25 among CD3(+) T cells and suppression of T cell proliferation in a dose dependent manner. Furthermore, AVH200® reduced the expression of CD28 on CD3(+) T cells. AVH200® also reduced the secretion of IL-2, IFN-γ and IL-17A in PBMC cultures. The AVH200® dose dependent reduction in T cell activation and proliferation recorded in the cell cultures was not due to apoptosis or cell death. Additionally, AVH200® was found to be more effective as compared to AVE200 in reducing T cell activation and proliferation.

CONCLUSION

AVH200® has the potential to reduce the activation, proliferation and cytokine secretion of healthy human blood T cells. Our study suggests that AVH200® has a suppressive effect on human blood T cells in vitro.

Review of Clinical Pharmacology of Aloe vera L. in the Treatment of Psoriasis

Aloe vera L., is a plant used worldwide as folk remedy for the treatment of various ailments, including skin disorders. Its gel is present in cosmetics, medicinal products and food supplements. Psoriasis, an immune-mediated chronic inflammatory disease, involving mainly the skin, affects about the 2-3% of general population. Conventional pharmacological treatments for psoriasis can have limited effectiveness and can cause adverse reactions. For this reason often psoriatic patients look for alternative treatments based on natural products containing Aloe vera. We conducted a systematic review of clinical trials assessing effectiveness and safety of aloe for the treatment of psoriasis. Clinical studies published in English were considered; a total of four clinical trials met inclusion criteria. Studies were also evaluated by using the Jadad scale and Consort Statement in Reporting Clinical trials of Herbal Medicine Intervention. Quality and methodological accuracy of considered studies varied considerably, and some crucial information to reproduce clinical results was missing. We conclude that administration of aloe as cutaneous treatment is generally well tolerated, as no serious side effects were reported. Results on the effectiveness of Aloe vera are contradictory; our analysis reveals the presence of methodological gaps preventing to reach final conclusions.

Processed Aloe vera gel ameliorates cyclophosphamide-induced immunotoxicity

The effects of processed Aloe vera gel (PAG) on cyclophosphamide (CP)-induced immunotoxicity were examined in mice. Intraperitoneal injection of CP significantly reduced the total number of lymphocytes and erythrocytes in the blood. Oral administration of PAG quickly restored CP-induced lymphopenia and erythropenia in a dose-dependent manner. The reversal of CP-induced hematotoxicity by PAG was mediated by the functional preservation of Peyer’s patch cells. Peyer’s patch cells isolated from CP-treated mice, which were administered PAG, produced higher levels of T helper 1 cytokines and colony-stimulating factors (CSF) in response to concanavalin A stimulation as compared with those isolated from CP-treated control mice. PAG-derived polysaccharides directly activated Peyer’s patch cells isolated from normal mice to produce cytokines including interleukin (IL)-6, IL-12, interferon-γ, granulocyte-CSF, and granulocyte-macrophage-CSF. The cytokines produced by polysaccharide-stimulated Peyer’s patch cells had potent proliferation-inducing activity on mouse bone marrow cells. In addition, oral administration of PAG restored IgA secretion in the intestine after CP treatment. These results indicated that PAG could be an effective immunomodulator and that it could prevent CP-induced immunotoxic side effects.

Acemannan, an Extracted Polysaccharide from Aloe vera: A Literature Review

In this review, the composition, actions, and clinical applications of acemannan in medicine and its effectiveness as an adjunct in the treatment of diseases are presented. An electronic literature search was performed up to January 2014 for studies and research presenting data to validate the efficacy of acemannan. A total of 50 titles, abstracts and full-text studies were selected and reviewed. Acemannan has various medicinal properties like osteogenic, anti-inflammatory, and antibacterial, which accelerate healing of lesions. Also, acemannan is known to have antiviral and antitumor activities in vivo through activation of immune responses. It was concluded that Aloe vera has immense potential as a therapeutic agent. Even though the plant is a promising herb with various clinical applications in medicine and dentistry, more clinical research needs to be undertaken to validate and explain the action of acemannan in healing, so that it can be established in the field of medicine and a more precise understanding of the biological activities of these is required to develop Aloe vera as a pharmaceutical source.

Oral administration of Aloe vera gel, anti-microbial and anti-inflammatory herbal remedy, stimulates cell-mediated immunity and antibody production in a mouse model

Introduction

Aloe vera (L.) Burm. f. (Aloe barbadensis Mill) Liliaceae, succulent plant native to northern Africa, is presently cultivated in many regions of the world. Traditionally, its inner part of parenchyma, which contains aloe gel, was used for the treatment of minor wounds, inflammatory skin disorders, thermal and radiation burns and to alleviate chronic osteoarthritis pain. It also possesses some antimicrobial activity. Now, aloe gel is also increasingly consumed as a dietary supplement. Some data suggest its immunomodulatory properties.

The aim of the study

The aim of the study was to evaluate the influence of orally administered aloe gel on some parameters of cellular and humoral immunity viz. mitogen-induced proliferation of splenic lymphocytes and their chemokinetic activity, and anti-sheep red blood cells (SRBC) antibody production in Balb/c mice.

Results

Daily treatment of mice for 14 and 21 days with 50 µl or 150 µl of aloe gel dose resulted in enhanced chemokinetic activity and stronger response of their splenic lymphocytes to mitogen PHA and enhancement of anti-SRBC antibody production.

Resiquimod, a TLR7/8 agonist, promotes differentiation of myeloid-derived suppressor cells into macrophages and dendritic cells

Myeloid-derived suppressor cells (MDSCs) accumulate in cancer patients and tumor-bearing mice, subsequently suppressing the host immune system. MDSCs represent a group of immature myeloid cells expressing CD11b and Gr-1. Here, we show that a Toll-like receptor (TLR) agonist, resiquimod, which binds to TLR7 and TLR8, induces the differentiation of MDSCs into mature myeloid cells. MDSCs were isolated from mice bearing mammary carcinoma 4T1 cells, and the purified MDSCs were cultured in the presence of resiquimod for 5 days. Phenotypic analysis showed that the resiquimod-treated MDSCs differentiated into F4/80⁺ macrophages and CD11c⁺/I-A(d⁺) dendritic cells. Functional analysis showed that the MDSCs also lost their suppressive activity on T cells. Resiquimod-treated MDSCs significantly enhanced the proliferation of T cells that were treated with anti-CD3 and anti-CD28 monoclonal antibodies. These results show that resiquimod induces the differentiation of MDSCs into macrophages and dendritic cells, and also suggest that resiquimod may improve cancer immunotherapy by reducing immunosuppressive MDSCs.

Applications of polymeric adjuvants in studying autoimmune responses and vaccination against infectious diseases

Polymers as an adjuvant are capable of enhancing the vaccine potential against various infectious diseases and also are being used to study the actual autoimmune responses using self-antigen(s) without involving any major immune deviation. Several natural polysaccharides and their derivatives originating from microbes and plants have been tested for their adjuvant potential. Similarly, numerous synthetic polymers including polyelectrolytes, polyesters, polyanhydrides, non-ionic block copolymers and external stimuli responsive polymers have demonstrated adjuvant capacity using different antigens. Adjuvant potential of these polymers mainly depends on their solubility, molecular weight, degree of branching and the conformation of polymeric backbone. These polymers have the ability not only to activate humoral but also cellular immune responses in the host. The depot effect, which involves slow release of antigen over a long duration of time, using different forms (particulate, solution and gel) of polymers, and enhances the co-stimulatory signals for optimal immune activation, is the underlying principle of their adjuvant properties. Possibly, polymers may also interact and activate various toll-like receptors and inflammasomes, thus involving several innate immune system players in the ensuing immune response. Biocompatibility, biodegradability, easy production and purification, and non-toxic properties of most of the polymers make them attractive candidates for substituting conventional adjuvants that have undesirable effects in the host.

Preliminary trial of aloe vera gruel on HIV infection

BACKGROUND

Ten (10) young women diagnosed with human immunodeficiency virus (HIV) infection in the Wesley Guild Hospital Ilesa, a unit of Obafemi Awolowo University Teaching Hospital, Ile Ife, Osun State, Nigeria who did not meet the national criteria for the use of antiretroviral drugs were managed with 30-40 mL of aloe vera (Aloe barbadensis miller) gruel daily.

METHODS

Their CD4 counts, general improvement, and physical well-being (including weight gain) were monitored over a 1-year period. The findings were compared with those of 20 age- matched controls who were on antiretroviral drugs. One (1) patient who reacted badly to antiretroviral drug switched over to aloe vera.

RESULTS

The average weight gain among those on aloe vera was 4.7 kg compared to 4.8 kg by those on antiretroviral drug (p=0.916). The average rise in CD4 count among them was 153.7 cells/μL compared to 238.85 cells/μL among the controls (p=0.087). There was no significant side effect(s) in either group except in the 1 patient who switched over from antiretroviral drugs to aloe vera gruel.

CONCLUSIONS

These preliminary data suggest that consumption of aloe vera may be of help to HIV-infected individuals in the tropics, given its availability and inexpensiveness.

Nanoliposomes of L-lysine-conjugated poly(aspartic acid) Increase the Generation and Function of Bone Marrow-derived Dendritic Cells

Background

Biodegradable polymers have increasingly been recognized for various biological applications in recent years. Here we examined the immunostimulatory activities of the novel poly(aspartic acid) conjugated with L-lysine (PLA).

Methods

PLA was synthesized by conjugating L-lysine to aspartic acid polymer. PLA-nanoliposomes (PLA-NLs) were prepared from PLA using a microfluidizer. The immunostimulatory activities of PLA-NLs were examined in mouse bone marrow-derived dendritic cells (BM-DCs).

Results

PLA-NLs increased the number of BM-DCs when added to cultures of GM-CSF-induced DC generation on day 4 after the initiation of cultures. Examination of the phenotypic properties showed that BM-DCs generated in the presence of PLA-NLs are more mature in terms of the expression of MHC class II molecules and major co-stimulatory molecules than BM-DCs generated in the absence of PLA-NLs. In addition, the BM-DCs exhibited enhanced capability to produce cytokines, such as IL-6, IL-12, TNF-α and IL-1β. Allogeneic mixed lymphocyte reactions also confirmed that the BMDCs were more stimulatory on allogeneic T cells. PLA- NL also induced further growth of immature BM-DCs that were harvested on day 8.

Conclusion

These results show that PLA-NLs induce the generation and functional activities of BM-DCs, and suggest that PLA-NLs could be immunostimulating agents that target DCs.

Carbohydrate-based immune adjuvants

The role for adjuvants in human vaccines has been a matter of vigorous scientific debate, with the field hindered by the fact that for over 80 years, aluminum salts were the only adjuvants approved for human use. To this day, alum-based adjuvants, alone or combined with additional immune activators, remain the only adjuvants approved for use in the USA. This situation has not been helped by the fact that the mechanism of action of most adjuvants has been poorly understood. A relative lack of resources and funding for adjuvant development has only helped to maintain alum's relative monopoly. To seriously challenge alum's supremacy a new adjuvant has many major hurdles to overcome, not least being alum's simplicity, tolerability, safety record and minimal cost. Carbohydrate structures play critical roles in immune system function and carbohydrates also have the virtue of a strong safety and tolerability record. A number of carbohydrate compounds from plant, bacterial, yeast and synthetic sources have emerged as promising vaccine adjuvant candidates. Carbohydrates are readily biodegradable and therefore unlikely to cause problems of long-term tissue deposits seen with alum adjuvants. Above all, the Holy Grail of human adjuvant development is to identify a compound that combines potent vaccine enhancement with maximum tolerability and safety. This has proved to be a tough challenge for many adjuvant contenders. Nevertheless, carbohydrate-based compounds have many favorable properties that could place them in a unique position to challenge alum's monopoly over human vaccine usage.