Liposomal glycosphingolipids activate natural killer T cell-mediated immune responses through the endosomal pathway

Glycosphingolipids (GSLs) from Sphingomonas paucimobilis Increase the Efficacy of Liposome-Based Nanovaccine against Acinetobacter baumannii-Associated Pneumonia in Immunocompetent and Immunocompromised Mice

Due to the high propensity of drug resistance in Acinetobacter baumannii, the number of currently available therapeutic drugs has become very limited. Thus, it becomes incredibly important to prepare an effective vaccine formulation capable of eliciting an effective immune response against A. baumannii. In this study, we prepared a liposomal vaccine formulation bearing glycosphingolipids (GSLs) from Sphingomonas paucimobilis and loaded with the whole cell antigen (WCAgs-GSLs-liposomes) of A. baumannii. The immune-stimulating potential and prophylactic efficacy of WCAgs-GSLs-liposomes were compared with those of WCAgs-liposomes (without GSLs) or free WCAgs in both immunocompetent and immunodeficient mice. The efficacy of vaccine formulations was determined by analyzing antibody titer, cytokine levels, and survival studies in the immunized mice. The findings revealed that vaccination with WCAgs-GSLs-liposomes stimulated a greater secretion of antibodies and cytokines, higher lymphocyte proliferation, and increased expression of the co-stimulatory molecules. Anti-sera from WCAgs-GSLs-liposomes-immunized mice remarkably reduced the biofilm formation by A. baumannii. Most importantly, WCAgs-GSLs-liposomes-vaccinated mice demonstrated a higher defiance against the pathogen, as compared to the immunizations with WCAgs-liposomes (without GSLs) or free WCAgs. Immunocompetent mice immunized with WCAgs-GSLs-liposomes showed a 100% survival rate, while those immunized with WCAgs-liposomes exhibited a 60% survival rate. The protective effect of WCAgs-GSLs-liposomes was also found to be higher in immunocompromised mice, as the immunized mice showed a 50% survival rate, which was greater than the 20% survival rate of those immunized with WCAgs-liposomes. The survival data was also supported by the findings of bacterial load and histological analysis that substantiated the greatest prophylactic potential of the WCAgs-GSLs-liposomes. These findings recommend that WCAgs-GSLs-liposomes may be reckoned as a prospective vaccine to protect the persons against A. baumannii infection.

Role of NKT Cells during Viral Infection and the Development of NKT Cell-Based Nanovaccines

Natural killer T (NKT) cells, a small population of T cells, are capable of influencing a wide range of the immune cells, including T cells, B cells, dendritic cells and macrophages. In the present review, the antiviral role of the NKT cells and the strategies of viruses to evade the functioning of NKT cell have been illustrated. The nanoparticle-based formulations have superior immunoadjuvant potential by facilitating the efficient antigen processing and presentation that favorably elicits the antigen-specific immune response. Finally, the immunoadjuvant potential of the NKT cell ligand was explored in the development of antiviral vaccines. The use of an NKT cell-activating nanoparticle-based vaccine delivery system was supported in order to avoid the NKT cell anergy. The results from the animal and preclinical studies demonstrated that nanoparticle-incorporated NKT cell ligands may have potential implications as an immunoadjuvant in the formulation of an effective antiviral vaccine that is capable of eliciting the antigen-specific activation of the cell-mediated and humoral immune responses.

Formation of Food Grade Microemulsion with Rice Glycosphingolipids to Enhance the Oral Absorption of Coenzyme Q10

The purpose of this study is to examine the possible use of rice glycosphingolipids (RGSLs) as an emulsifier to form food grade microemulsions (mean particle size, 10-20 nm) and improve the absorption of CoQ10 with a poor solubility property by prepared emulsion. Because RGSLs could act as an auxiliary emulsifying agent, its addition to the surfactant/oil mixture decreased the emulsion's particle size. This suggests that RGSLs exist between the water and oil phases to decrease oil droplet size via reduced interfacial tension. CoQ10-loaded microemulsion was also successfully prepared with RGSLs and powdered after freeze-drying with a cryoprotectant. CoQ10's solubility in freeze-dried particles was dramatically improved compared to that of CoQ10 powder. Moreover, oral absorption of CoQ10 was significantly enhanced when administered via CoQ10-loaded microemulsion. The area under the plasma concentration-time curve for the microemulsion improved up to seven-fold compared to CoQ10 powder. The use of RGSLs could, therefore, be an effective processing technique for improving CoQ10's solubility and absorption.

Liposomal formulation of glycosphingolipids from Sphingomonas paucimobilis induces antitumour immunity in mice

Natural Killer T (NKT) cells play an important role in host's anti-tumour immune response. Glycosphingolipids (GSLs) isolated from Sphingomonas paucimobilis have the ability to stimulate NKT cells. In this study, the activity of free GSLs or GSLs-incorporated liposomes (glycosphingosomes) was investigated against dimethyl-α-benzanthracene (DMBA)-induced tumours in mice. The anti-tumour immunity of GSLs- or glycosphingosomes-loaded bone marrow-derived dendritic cells (BMDCs) was investigated in tumour-bearing mice. The Immunotherapeutic potential of co-administration of liposomal doxorubicin (Lip-Dox) and GSLs or glycosphingosomes was assessed by measuring cytokine levels and VEGF in the tumour tissues. Pretreatment with glycosphingosomes significantly delayed the frequency of tumour formation. Immunotherapy with glycosphingosomes-loaded BMDCs increased serum IFN-γ level and survival rate in mice. The effect of immunotherapy was dependent on effector functions of NK cells because the depletion of NK cells abolished the effects of immunotherapy. There was reduced tumour growth with low expression of VEGF in the group of mice treated with glycosphingosomes and Lip-Dox combination. Moreover, the splenocytes secreted higher levels of IFN-γ, IL-12 and lower TGF-β level. The results of this study indicate that glycosphingosomes can induce better antitumour immunity and may be considered a novel formulation in antitumour therapy.

Combination of glycosphingosomes and liposomal doxorubicin shows increased activity against dimethyl-α-benzanthracene-induced fibrosarcoma in mice

The present study aimed to assess the antitumor effect of glycosphingolipid-incorporated liposomes (glycosphingosomes) in combination with liposomal doxorubicin (Lip-Dox) in a mouse model of fibrosarcoma. Glycosphingosomes were prepared by incorporating glycosphingolipids isolated from Sphingomonas paucimobilis into the liposomes of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, cholesterol, and cardiolipin. Tumors were induced by administering dimethyl-α-benzanthracene, and tumor-bearing mice were treated with various formulations of Dox, including free Dox, Lip-Dox, or glycosphingosomes + Lip-Dox. Mice were observed for 90 days to monitor their survival and tumor size. Free Dox, but not Lip-Dox or a combination of glycosphingosomes and Lip-Dox, caused the substantial depletion of leukocytes and significantly increased the levels of lactate dehydrogenase and creatinine kinase in mice. Tumor-bearing mice treated with a combination of glycosphingosomes and Lip-Dox showed restricted tumor growth and increased survival when compared to those treated with free Dox or Lip-Dox. The results of the present study suggest that a combination of glycosphingosomes and Lip-Dox may prove to be very effective in the treatment of tumors.

Helicobacter pylori cholesteryl α-glucosides contribute to its pathogenicity and immune response by natural killer T cells

Approximately 10–15% of individuals infected with Helicobacter pylori will develop ulcer disease (gastric or duodenal ulcer), while most people infected with H. pylori will be asymptomatic. The majority of infected individuals remain asymptomatic partly due to the inhibition of synthesis of cholesteryl α-glucosides in H. pylori cell wall by α1,4-GlcNAc-capped mucin O-glycans, which are expressed in the deeper portion of gastric mucosa. However, it has not been determined how cholesteryl α-glucosyltransferase (αCgT), which forms cholesteryl α-glucosides, functions in the pathogenesis of H. pylori infection. Here, we show that the activity of αCgT from H. pylori clinical isolates is highly correlated with the degree of gastric atrophy. We investigated the role of cholesteryl α-glucosides in various aspects of the immune response. Phagocytosis and activation of dendritic cells were observed at similar degrees in the presence of wild-type H. pylori or variants harboring mutant forms of αCgT showing a range of enzymatic activity. However, cholesteryl α-glucosides were recognized by invariant natural killer T (iNKT) cells, eliciting an immune response in vitro and in vivo. Following inoculation of H. pylori harboring highly active αCgT into iNKT cell-deficient (Jα18^−/−) or wild-type mice, bacterial recovery significantly increased in Jα18^−/− compared to wild-type mice. Moreover, cytokine production characteristic of Th1 and Th2 cells dramatically decreased in Jα18^−/− compared to wild-type mice. These findings demonstrate that cholesteryl α-glucosides play critical roles in H. pylori-mediated gastric inflammation and precancerous atrophic gastritis.

Intracellular delivery of lipopolysaccharide induces effective Th1-immune responses independent of IL-12

Lipopolysaccharide (LPS) is responsible for many of the inflammatory responses and pathogenic effects of Gram-negative bacteria, however, it also induces protective immune responses. LPS induces the production of inflammatory cytokines such as TNF-α, IL-6, and IL-12 from dendritic cells (DCs) and macrophages. It is thought that IL-12 is required for one of the protective immune responses induced by LPS, the T helper 1 (Th1)-immune response, which include the production of IFN-γ from Th1cells and IgG2c class switching. Here, we clearly demonstrate that intracellular delivery of LPS by LPS-formulated liposomes (LPS-liposomes) does not induce the production of inflammatory cytokines from DCs, but enhances Th1-immune responses via type-I IFNs, independent of IL-12. Collectively, our results strongly suggest that LPS-liposomes can effectively induce Th1-immune responses without inducing unnecessary inflammation, and may be useful as an immune adjuvant to induce protective immunity.

Liposomal lipopolysaccharide initiates TRIF-dependent signaling pathway independent of CD14

Lipopolysaccharide (LPS) is recognized by CD14 with Toll-like receptor 4 (TLR4), and initiates 2 major pathways of TLR4 signaling, the MyD88-dependent and TRIF-dependent signaling pathways. The MyD88-dependent pathway induces inflammatory responses such as the production of TNF-α, IL-6, and IL-12 via the activation of NFκB and MAPK. The TRIF-dependent pathway induces the production of type-I IFN, and RANTES via the activation of IRF-3 and NFκB, and is also important for the induction of adaptive immune responses. CD14 plays a critical role in initiating the TRIF-dependent signaling pathway response to LPS, to support the internalization of LPS via endocytosis. Here, we clearly demonstrate that intracellular delivery of LPS by LPS-formulated liposomes (LPS-liposomes) initiate only TRIF-dependent signaling via clathrin-mediated endocytosis, independent of CD14. In fact, LPS-liposomes do not induce the production of TNF-α and IL-6 but induce RANTES production in peritoneal macrophages. Additionally, LPS-liposomes could induce adaptive immune responses effectively in CD14-deficient mice. Collectively, our results strongly suggest that LPS-liposomes are useful as a TRIF-dependent signaling-based immune adjuvant without inducing unnecessary inflammation.

Preparation and evaluation of lidocaine hydrochloride-loaded TAT-conjugated polymeric liposomes for transdermal delivery

Transactivation transcriptional activator (TAT) peptides were conjugated on the octadecyl-quaternized, lysine-modified chitosan to form polymeric liposomes (TAT-PLs) with cholesterol for improving transdermal delivery of local anesthetic lidocaine hydrochloride (LID). In this study, the LID loaded TAT-conjugated polymeric liposomes (LID-TAT-PLs) have been successfully prepared. LID-TAT-PLs were characterized by determination of their particle size, polydispersity, morphology, drug encapsulation efficiency, drug release behavior in vitro, and storage-stability. The skin permeation of LID-TAT-PLs was examined using a Franz diffusion cell mounted with depilated mouse skin in vitro, and penetration of TAT-PLs was visualized by confocal laser scanning microscopy (CLSM). The results showed that LID-TAT-PLs were spherical in solution, with substantially smaller mean diameter (154.7±10.7 nm), higher encapsulation efficiency (80.05±2.64%) and better stability in contrast to conventional liposomes (CLs). From the in vitro skin permeation results, transdermal flux of LID-TAT-PLs was approximately 4.17 and 1.75 times higher than that of LID solution and LID CLs (P<0.05). CLSM studies also confirmed that TAT-PLs reached viable layers of the skin. Hence, the results indicate that LID-TAT-PLs are effective and potential alternative for the LID transdermal formulation.

Optimization on preparation condition of epimedium polysaccharide liposome and evaluation of its adjuvant activity

The aim of this strategy was to investigate whether the adjuvant activity of epimedium polysaccharide (EPS) could be further enhanced after encapsulated with liposome. In preparation of EPS liposome (EPSL) test, an orthogonal L(9) (3(4)) test design was used to optimize the preparation condition of EPSL. In adjuvant activity test, 350 14-day-old chickens were randomly assigned to 7 groups and vaccinated with Newcastle disease (ND) vaccine. Simultaneously, the chickens in experimental groups were injected with EPSL at three doses, EPS and blank liposome, respectively. The activity of lymphocytes proliferation, titer of serum antibody and concentrations of cytokines were determined. Results showed that the optimal preparation condition of EPSL was that ratio of drug to lipid, ratio of soybean phospholipid to cholesterol, ultrasonic time, and water bath temperature were 1:30, 4:1, 10 min and 40°C, respectively. EPSL could significantly enhance the immune response of ND vaccine and promote cytokines secretion, and its high dose possessed the best efficacy. These findings indicated that liposome encapsulation could significantly improve the adjuvant activity of EPS.

Triggering liposomal drug release with a lysosomotropic agent

Drug release from liposomes in the endosome-lysosomal organelles into cytoplasm is critical to cytotoxicity and anticancer effects. Chloroquine is a lysosomotropic agent that has been reported to enhance in vitro cytotoxicity of basic anticancer drugs. To investigate the mechanism of chloroquine triggering basic anticancer drugs release from liposomes and the potential to treat solid tumors in clinic, daunorubicin was loaded into folate-targeted liposomes by ammonium sulfate remote loading method. In vitro triggered release profiles showed that chloroquine can instantly expel about 11% daunorubicin out of liposomes. In vitro cytotoxicity of folate-targeted liposomal daunorubicin on L1210JF(FR+) was enhanced by chloroquine, which was further confirmed by confocal micrographs. Intraliposomal pH was increased by adding chloroquine into 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) liposomes with ammonium sulfate gradient, but was not higher than 5.5. Ion exchange and pH rising are the most plausible mechanisms of chloroquine triggering daunorubicin release from liposomes. In vivo anticancer effects on a murine solid tumor model with L1210JF indicated that chloroquine induced daunorubicin release from liposomes as well. Overall, these results support the potential application of chloroquine to trigger the release of liposomal drugs and ultimately to improve the therapeutic efficacy.

Folate-PEG coated cationic modified chitosan--cholesterol liposomes for tumor-targeted drug delivery

In this paper, a folate-PEG coated polymeric liposome (FPL) formed from octadecyl-quaternized lysine modified chitosan (OQLCS) and cholesterol has been prepared successfully. The OQLCS and its derivatives were characterized using (1)H NMR and infrared spectrum analysis. The FPLs properties were extensively studied by dynamic light scattering (DLS), fluorescence spectroscopy, and transmission electron microscopy (TEM). Due to the amphiphilic property and positive zeta potential of OQLCS, the OQLCS and cholesterol can form stable core-shell FPLs with small size (effective diameter: 163.5 nm) and narrow distribution (polydispersity: 0.108) in aqueous solutions. The PLs could form multi-lamellar structure similar to that of traditional liposomes prepared from phosphatidylcholine/cholesterol (PC/Chol). Compared with traditional liposome, calcein-loaded Polymeric Liposome exhibited high encapsulation efficiency in aqueous solution and slow, controlled release under different pH conditions. Most important, in cellular uptake experiment, folate coated FPLs showed significant higher uptake by MCF-7 cells as compared to FPLs without folate and traditional liposomes, because of the folate-receptor mediated endocytosis. The data suggest that the folate-PEG coated polymeric liposomes (FPLs) may be a useful drug delivery system.