Sun-A Im

In vivo evidence of the immunomodulatory activity of orally administered Aloe vera gel

The gels of Aloe species contain immunomodulatory components such as aloctin A and acemannan. Most studies on these gels were performed in in vitro cell culture systems. Although several studies examined their immunomodulatory activity in vivo, the route of administration was intraperitoneal or intramuscular. Here, we evaluated the in vivo immunomodulatory activity of processed Aloe vera gel (PAG) in mice. Oral administration of PAG significantly reduced the growth of C. albicans in the spleen and kidney following intravenous injection of C. albicans in normal mice. PAG administration also reduced the growth of C. albicans in streptozotocin-induced diabetic mice. PAG administration did not increase ovalbumin (OVA)-specific cytotoxic T lymphocyte (CTL) generation in normal mice, but did increase it in high-fat-diet induced diabetic mice. These findings provide the first clear evidence for the immunomodulatory activity of orally administered Aloe vera gel.

Biodegradable nanoparticles containing TLR3 or TLR9 agonists together with antigen enhance MHC-restricted presentation of the antigen

The effects of intraphagosomal toll-like receptor (TLR) activation on the MHC-restricted presentation of exogenous antigen were examined in dendritic cells (DCs). For phagosomal targeting, nanoparticles containing both a TLR agonist and a model antigen, ovalbumin (OVA), were prepared using biodegradable polymer poly(D,L-lactic acid-co-glycolic acid) and were then opsonized with mouse IgG. After incubating mouse DCs with the nanoparticles, the efficacy of OVA peptide presentation was evaluated using OVA-specific CD8 and CD4 T cells. Inclusion of either the TLR3 agonist poly(I:C) or the TLR9 agonist CpG oligodeoxynucleotides (ODN) significantly increased and prolonged both MHC class I- and class II-restricted OVA presentation. Accordingly, the DCs that phagocytosed the nanoparticles containing poly(I:C) or CpG ODN together with OVA efficiently induced the proliferation of OVA-specific CD8 and CD4 T cells. The potency levels of poly(I:C) and CpG ODN in increasing the MHC-restricted presentation of the exogenous antigen appeared to be similar. A combination of the 2 TLR agonists was synergistic in increasing the MHC class I-restricted, but not the class II-restricted, presentation of exogenous antigen. These results show that IgG-opsonized biodegradable nanoparticles containing both intraphagosomal TLR agonists and antigens can be efficient carrier materials in inducing antigen-specific T cell responses.

Calcineurin Inhibitors Block MHC-Restricted Antigen Presentation In Vivo

APCs, like T cells, are affected by calcineurin inhibitors. In this study, we show that calcineurin inhibitors efficiently block MHC-restricted exogenous Ag presentation in vivo. Mice were injected with clinical doses of tacrolimus (FK-506) followed by soluble OVA, and dendritic cells (DCs) were isolated from lymph nodes and spleens. The efficacy of OVA peptide presentation by DCs was evaluated using OVA-specific CD8 and CD4 T cells. Tacrolimus inhibited both class I- and class II-restricted DC presentation of OVA to T cells. Tacrolimus also inhibited both class I- and class II-restricted presentation of OVA in peritoneal macrophages isolated from mice injected with tacrolimus followed by soluble OVA. Tacrolimus-treated peritoneal macrophages, however, were able to present synthetic OVA peptide, SIINFEKL. Inclusion of cyclosporine A to biodegradable microspheres containing OVA greatly reduced their capacity to induce OVA-specific CTL response in mice. These findings provide novel insight into the mode of action of calcineurin inhibitors and have important implications for clinical immunosuppression regimens.

Induction of Potent Antigen-specific Cytotoxic T Cell Response by PLGA-nanoparticles Containing Antigen and TLR Agonist

Previously we showed that biodegradable nanoparticles containing poly-IC or CpG oligodeoxynucleotide (ODN) together with ovalbumin (OVA) were efficient at inducing MHC-restricted presentation of OVA peptides in dendritic cells. The CTL-inducing activities of the nanoparticles were examined in the present study. Nanoparticles containing poly-IC or CpG ODN together with OVA were prepared using biodegradable polymer poly(D,L-lactic acid-co-glycolic acid), and then were opsonized with mouse IgG. The nanoparticles were injected into the tail vein of mice, and 7 days later the OVA-specific CTL activities were measured using an in vivo CTL assay. Immunization of mice with the nanoparticles containing poly-IC or CpG ODN together with OVA elicited potent OVA-specific CTL activity compared to those containing OVA only. In accordance with these results, nanoparticles containing poly-IC or CpG ODN together with OVA exerted potent antitumor activity in mice that were subcutaneously implanted with EG7.OVA tumor cells. These results show that encapsulation of poly-IC or CpG ODN together with antigen in biodegradable nanoparticles is an effective approach for the induction of potent antigen-specific CTL responses in vivo.

Cyclooxygenase Inhibitors, Aspirin and Ibuprofen, Inhibit MHC-restricted Antigen Presentation in Dendritic Cells

Background Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used to relieve pain, reduce fever and inhibit inflammation. NSAIDs function mainly through inhibition of cyclooxygenase (COX). Growing evidence suggests that NSAIDs also have immunomodulatory effects on T and B cells. Here we examined the effects of NSAIDs on the antigen presenting function of dendritic cells (DCs). Methods DCs were cultured in the presence of aspirin or ibuprofen, and then allowed to phagocytose biodegradable microspheres containing ovalbumin (OVA). After washing and fixing, the efficacy of OVA peptide presentation by DCs was evaluated using OVA-specific CD8 and CD4 T cells. Results Aspirin and ibuprofen at high concentrations inhibited both MHC class I and class II-restricted presentation of OVA in DCs. In addition, the DCs generated in the presence of low concentrations of the drugs exhibit a profoundly suppressed capability to present MHC-restricted antigens. Aspirin and ibuprofen did not inhibit the phagocytic activity of DCs, the expression level of total MHC molecules and co-stimulatory molecules on DCs. Ibuprofen rather increased the expression level of total MHC molecules and co-stimulatory molecules on DCs. Conclusion These results demonstrate that aspirin and ibuprofen inhibit the intracellular processing event of the phagocytosed antigen, and further suggest that prolonged administration of NSAIDs in high doses may impair the capability of DCs to present antigens in asiociation with MHC molecules.

Formulation and Characterization of Antigen-loaded PLGA Nanoparticles for Efficient Cross-priming of the Antigen

Background Nanoparticles (NPs) prepared from biodegradable polymers, such as poly (D,L-lactic acid-co-glycolic acid) (PLGA), have been studied as vehicles for the delivery of antigens to phagocytes. This paper describes the preparation of antigen-loaded PLGA-NPs for efficient cross-priming. Methods NPs containing a similar amount of ovalbumin (OVA) but different sizes were produced using a micromixer-based W/O/W solvent evaporation procedure, and the efficiency of the NPs to induce the cross-presentation of OVA peptides were examined in dendritic cells (DCs). Cellular uptake and biodistribution studies were performed using fluorescein isothiocyanate (FITC)-loaded NPs in mice. Results The NPs in the range of 1.1~1.4µm in size were the most and almost equally efficient in inducing the cross-presentation of OVA peptides via H-2Kb molecules. Cellular uptake and biodistribution studies showed that opsonization of the NPs with mouse IgG greatly increased the percentage of FITC-positive cells in the spleen and lymph nodes. The major cell type of FITC-positive cells in the spleen was macrophages, whereas that of lymph nodes was DCs. Conclusion These results show that IgG-opsonized PLGA-NPs with a mean size of 1.1µm would be the choice of biodegradable carriers for the targeted-delivery of protein antigens for cross-priming in vivo.

Dendritic cells process antigens encapsulated in a biodegradable polymer, poly(D,L-lactide-co-glycolide), via an alternate class I MHC processing pathway

Biodegradable nanospheres generated from a biocompatible polymer, poly(D,L-lactide-co-gly-colide) (PLGA), have been studied extensively as implantable reservoirs for sustained-release drug delivery. PLGA-nanospheres have also been studied as vehicles to deliver antigens to phagocytes. The intracellular processing pathway of antigens delivered to phagocytes by PLGA particles was studied in the present study. Ovalbumin (OVA) encapsulated with PLGA (OVA-nanosphere) was efficiently captured, processed and presented on class I major histocompatibility complex (MHC-I) by dendritic cells (DCs). The MHC-I processing of OVA-nano-spheres was resistant to lactacystin, a proteosome inhibitor, and brefeldin A, which blocks anterograde transport from the endoplasmic reticulum (ER) through the Golgi apparatus. Chloroquine, which inhibits phagolysosomal enzymes by increasing phagolysosomal pH, inhibited MHC-I processing of OVA-nanospheres. In addition, DCs generated from TAP-/- mice were markedly suppressed in MHC-I processing of OVA-nanospheres. These results demonstrate that DCs process phagocytosed OVA-nanospheres via a vacuolar alternate MHC-I pathway for presentation of OVA peptides to T lymphocytes.

Restoration of Electric Footshock-Induced Immunosuppression in Mice by Gynostemma pentaphyllum Components

The immunomodulatory effects of the ethanol extract of Gynostemma pentaphyllum (GP-EX) were examined in electric footshock (EFS)-stressed mice. The mice were orally administered various doses of GP-EX for 7 days before exposure to EFS (duration: 3 min, interval: 10 s, intensity: 2 mA) once a day from day 8 for 14 days with continuous daily feeding of GP-EX. Oral administration of GP-EX to mice prevented EFS stress-induced immunosuppression as determined by the lymphoid organ (thymus and spleen) weight and cellularity. In addition, oral administration of GP-EX restored EFS-suppressed functional properties of mature lymphocytes in terms of concanavalin A-induced proliferation of splenocytes and lipopolysaccharide-induced cytokine production (TNF-α, IL-1β). Furthermore, we found that mice that were orally administered with GP-EX generated much more potent ovalbumin-specific cytotoxic T lymphocyte responses upon intravenous ovalbumin injection compared to the untreated controls. These results demonstrate that oral administration of the ethanol extract of Gynostemma pentaphyllum could increase host defense in immunocompromised situations such as stress-induced immunosuppression.

Activation of Macrophages by Exopolysaccharide Produced by MK1 Bacterial Strain Isolated from Neungee Mushroom, Sarcodon aspratus

Background The MK1 strain, a novel bacterial isolate from soft-rotten tissue of the Neungee mushroom, produces copious amounts of exopolysaccharide (EPS) in a dextrose minimal medium. This study examined the molecular characteristics and immunomodulatory activity of MK1 EPS. Methods The EPS in the culture supernatant was purified by cold ethanol precipitation, and characterized by SDS-PAGE/silver staining and Bio-HPLC. The immunomodulatory activities of the EPS were examined using the mouse monocytic cell line, RAW 264.7 cells. Results The molecular weights of the purified EPS were rather heterogeneous, ranging from 10.6 to 55 kDa. The EPS was composed of glucose, rhamnose, mannose, galactose, and glucosamine at an approximate molar ratio of 1.00:0.8:0.71:0.29:0.21. EPS activated the RAW cells to produce cytokines, such as TNF-α and IL-1β, and nitric oxide (NO). EPS also induced the expression of co-stimulatory molecules, such as B7-1, B7-2 and ICAM-1, and increased the phagocytic activity. The macrophage-activating activity of EPS was not due to endotoxin contamination because the treatment of EPS with polymyin B did not reduce the macrophage-activating activity. Conclusion The EPS produced from the MK1 strain exerts macrophage-activating activity.

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.