Delivery of lipids and liposomal proteins to the cytoplasm and Golgi of antigen-presenting cells. mangala.rao@na.amedd.army.mil

A Reliable Quantification of Cholesterol and 25-Hydroxycholesterol in Liposomal Adjuvant Formulation by Liquid Chromatography High-Resolution Tandem Mass Spectrometry

Cholesterol, as one of the major components of liposomes, plays a critical role in modulating membrane bilayer permeability, fluidity, and structural stability. Controlling these quality attributes is essential to maintaining the efficacy and fitness of the liposomes in various applications. However, during the manufacture and storage of liposomes, cholesterol has a propensity to undergo oxidative degradation. Hence, an analytical tool that is capable of determining not only the identity and quantity of cholesterol but also its associated degradants is a prerequisite to effective process control and product quality and safety assessments. In this view, a new liquid chromatography electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) method with parallel reaction monitoring (PRM) was developed and qualified to accurately quantify cholesterol and monitor the formation of 25-hydroxycholesterol degradant in liposomal drug formulations without the use of an isotopic internal standard (IS). The method was qualified according to the FDA Quality Guidance for Industry: Q2(R1). Study results showed that the method presents good specificity for cholesterol and 25-hydroxycholesterol detection in the liposomal matrix, good sensitivity characterized by LOD/LOQ in the nanomolar range, and accuracy within the range of 80 to 120%. The described method enables accurate evaluation of in-process and product release samples of Army Liposome Formulation with QS21 (ALFQ).

Synthesis and Evaluation of a Self-Adjuvanting Pseudomonal Vaccine Based on Major Outer Membrane Porin OprF Epitopes Formulated with Low-Toxicity QS-21-Containing Liposomes

Pseudomonas aeruginosa (PA) is a Gram-negative pathogen that the World Health Organization has ranked as a priority 1 (critical) threat. One potential prophylactic approach to preventing or reducing the incidence of PA would be development of a long sought-after vaccine. Both antibody and CD4+ T-cell responses have been noted as playing key roles in protection against infection. In these studies, we have designed a prototype vaccine consisting of several known linear B-cell epitopes derived from an outer membrane porin F (OprF). The resulting thiol-containing protein was conjugated to a version of the lipopeptide-based Toll-like receptor agonist Pam3CysSK4Mal (10) containing a maleimide moiety and formulated into dipalmitoylphosphatidylcholine (DPPC)/cholesterol (Chol) liposomes. Mice immunized with the resulting vaccine generated antibodies that bound PA14 (serotype O10) in vitro and induced opsonization in the presence of rabbit complement and murine macrophage RAW264.7 cells. The liposome was optimized to contain 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-dimyristoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DMPG), Chol, Pam3CysSK4-OprF (12) and the Quillaja saponaria-derived saponin adjuvant QS-21. The resulting vaccine formulation produced significantly higher antibody titers, increased the IgG2a antibody isotype, and increased the number of IgG-producing B-cells as well as splenic primed T-cells. In summary, the liposomal vaccine platform was found highly useful for the generation of a robust and balanced TH1/TH2 response.

Magnetic Resonance Imaging-Guided Multi-Stimulus-Responsive Drug Delivery Strategy for Personalized and Precise Cancer Treatment

The emergence of nano-targeted controlled release liposomal drug carriers has provided a breakthrough in cancer therapy. However, their clinical efficacy is unsatisfactory, which is related to individualized differences in targeted drugs and poor in vivo release efficiency. In this paper, we prepared a class of personalized targeted and precisely controlled-release therapeutic drug carriers (GF liposomes) by co-assembling targeting and traceable o-nitrobenzyl ester lipids to propose a magnetic resonance imaging (MRI)-guided personalized in vivo targeted drug screening strategy and a multi-stimulus superimposed controlled-release strategy. Furthermore, by following the drug release process of drug-loaded liposomes (GF-D), it was found that these liposomes could rely on energy superposition to achieve more sensitive and efficient controlled drug release. In addition, the indispensable adjustment of liposome formulation for personalized MRI-based targeted therapy was verified by differential cellular uptake and in vivo magnetic resonance imaging. In the end, the 10.22-fold tumor suppression effect in the stimulus superposition group (GF-D-UV) indicates that the multi-stimulus cumulative response strategy and MRI-guided in vivo screening strategy can more effectively treat cancer. This contribution provides a concise and clever design idea for the future development of personalized precise and efficient clinical cancer therapies.

Liposome Formulations as Adjuvants for Vaccines

Development of liposome-based formulations as vaccine adjuvants has been intimately associated with, and dependent on, and informed by, a fundamental understanding of biochemical and biophysical properties of liposomes themselves. The Walter Reed Army Institute of Research (WRAIR) has a fifty-year history of experience of basic research on liposomes; and development of liposomes as drug carriers; and development of liposomes as adjuvant formulations for vaccines. Uptake of liposomes by phagocytic cells in vitro has served as an excellent model for studying the intracellular trafficking patterns of liposomal antigen. Differential fluorescent labeling of proteins and liposomal lipids, together with the use of inhibitors, has enabled the visualization of physical locations of antigens, peptides, and lipids to elucidate mechanisms underlying the MHC class I and class II pathways in phagocytic APCs. Army Liposome Formulation (ALF) family of vaccine adjuvants, which have been developed and improved since 1986, and which range from nanosize to microsize, are currently being employed in phase 1 studies with different types of candidate vaccines.

Extracellular Vesicles isolated from Mesenchymal Stromal Cells Modulate CD4+ T Lymphocytes Toward a Regulatory Profile

Mesenchymal stromal cells (MSCs) can generate immunological tolerance due to their regulatory activity in many immune cells. Extracellular vesicles (EVs) release is a pivotal mechanism by which MSCs exert their actions. In this study, we evaluate whether mesenchymal stromal cell extracellular vesicles (MSC-EVs) can modulate T cell response. MSCs were expanded and EVs were obtained by differential ultracentrifugation of the supernatant. The incorporation of MSC-EVs by T cells was detected by confocal microscopy. Expression of surface markers was detected by flow cytometry or CytoFLEX and cytokines were detected by RT-PCR, FACS and confocal microscopy and a miRNA PCR array was performed. We demonstrated that MSC-EVs were incorporated by lymphocytes in vitro and decreased T cell proliferation and Th1 differentiation. Interestingly, in Th1 polarization, MSC-EVs increased Foxp3 expression and generated a subpopulation of IFN-γ⁺/Foxp3⁺T cells with suppressive capacity. A differential expression profile of miRNAs in MSC-EVs-treated Th1 cells was seen, and also a modulation of one of their target genes, TGFbR2. MSC-EVs altered the metabolism of Th1-differentiated T cells, suggesting the involvement of the TGF-β pathway in this metabolic modulation. The addition of MSC-EVs in vivo, in an OVA immunization model, generated cells Foxp3⁺. Thus, our findings suggest that MSC-EVs are able to specifically modulate activated T cells at an alternative regulatory profile by miRNAs and metabolism shifting.

Army Liposome Formulation (ALF) family of vaccine adjuvants

Introduction: From its earliest days, the US. military has embraced the use of vaccines to fight infectious diseases. The Army Liposome Formulation (ALF) has been a pivotal innovation as a vaccine adjuvant that provides excellent safety and potency and could lead to dual-use military and civilian benefits. For protection of personnel against difficult disease threats found in many areas of the world, Army vaccine scientists have created novel liposome-based vaccine adjuvants.Areas covered: ALF consists of liposomes containing saturated phospholipids, cholesterol, and monophosphoryl lipid A (MPLA) as an immunostimulant. ALF exhibited safety and strong potency in many vaccine clinical trials. Improvements based on ALF include: ALF adsorbed to aluminum hydroxide (ALFA); ALF containing QS21 saponin (ALFQ); and ALFQ adsorbed to aluminum hydroxide (ALFQA). Preclinical safety and efficacy studies with ALF, LFA, ALFQ, and ALFQA are discussed in preparation for upcoming vaccine trials targeting malaria, HIV-1, bacterial diarrhea, and opioid addiction.Expert opinion: The introduction of ALF in the 1980s stimulated commercial interest in vaccines to infectious diseases, and therapeutic vaccines to cancer, and Alzheimer's disease. It is likely that ALF, ALFA, and ALFQ, will provide momentum for new types of modern vaccines with improved efficacy and safety.

Development of nano-carriers for Leishmania vaccine delivery

Introduction: Leishmaniasis is a neglected tropical infection caused by several species of intracellular protozoan parasites of the genus Leishmania. It is strongly believed that the development of vaccines is the most appropriate approach to control leishmaniasis. However, there is no vaccine available yet and the lack of an appropriate adjuvant delivery system is the main reason.Areas covered: Adjuvants are the utmost important part of a vaccine, to induce the immune response in the right direction. Limitations and drawbacks of conventional adjuvants have been necessitated the development of novel particulate delivery systems as adjuvants to obtain desirable protection against infectious diseases such as leishmaniasis. This review focused on particulate adjuvants especially nanoparticles that are in use to develop vaccines against leishmaniasis. The list of adjuvants includes generally lipids-, polymers-, or mineral-based delivery systems that target antigens specifically to the site of action within the host's body and enhance immune responses.Expert opinion: Over the past few years, there has been an increasing interest in developing particulate adjuvants as alternatives to immunostimulatory types. The composition of nano-carriers and particularly the physicochemical properties of nanoparticles have great potential to overcome challenges posed to leishmaniasis vaccine developments.

Recombinant PBP2a of methicillin-resistant S. aureus formulation in Alum and Montanide ISA266 adjuvants induced cellular and humoral immune responses with protection in Balb/C mice

Staphylococcus aureus is an important cause of both hospital and community acquired infections worldwide. S.aureus can develop multidrug resistance; thus, immunotherapy can be a rational alternative. High level β-lactam resistance of S. aureus has been attributed to the penicillin binding protein 2a (PBP2a). In this study, we assessed the immunogenicity and protectivity of PBP2a formulated in Montanide ISA266 and Alum adjuvants. Recombinant PBP2a with a molecular weight of approximately 13 kDa was expressed and purified by nickel-nitrilotriacetic acid (NI-NTA) affinity chromatography and characterized by SDS-PAGE and Western blot. To investigate the immunogenicity and protective effects of recombinant protein, 20 μg of r-PBP2a in various formulations were subcutaneously injected in different groups. Two booster vaccinations were carried out in two-week intervals and blood samples were collected two weeks after each injection. To determine the type of induced immune response, sera and splenocytes were analyzed by ELISA for total IgG and isotypes (IgG1 and IgG2a) and cytokine secretion (IFN-γ, IL-4, IL-17 and TNF-α), respectively. Three weeks following the last immunization, experimental mice were challenged with 5 × 10⁸ CFU of bacteria intraperitoneally and mortality rate and bacterial load were assessed. Interestingly, analysis of humoral immune responses revealed that administration of r-PBP2a with Montanide ISA266 significantly increased specific IgG responses and also IgG1 isotype compared to alum-adjuvanted vaccine group. Also, r-PBP2a formulation with alum and MontanideISA266 adjuvants raised IFN-γ, IL-4, IL-17 cytokines secretion, and protectivity following experimental challenge. The results of the present study provide evidences for immunogenicity and protectivity of PBP2a protein as a vaccine candidate.

Determination of Cholesterol and its Derivatives in Nanoliposomes as Drug Delivery Conveyances by HPLC-UV: A Simple, Accurate and Cost-Effective Method Development and Validation Approach

Nanoliposomes are extensively used as ideal vehicles in drug delivery systems due to their unique biocompatibility and biodegradability properties. They can be used as sustained release and target selective conveyances to deliver the encapsulated drugs at specific cells or tissues by improving their efficacy along with reducing the side effects. As an analytical perspective, the determination of various lipid components in the final formulation is one of the practical issues while the agents are applied in an industrial-scale. Herein, the maximum ultra violet (UV) absorbances for the most of the lipids are within 200-210 nm that cause significant cut-off conflicts with the general solvents or additives of high-performance liquid chromatography (HPLC) during its method development procedure. In this study, a simple, accurate and cost-effective isocratic HPLC-UV method has been successfully developed for the simultaneous determination of α-(3-O-cholesteryloxy)-δ-(N-ethylmorpholine)-succineamide (MoChol), cholesteryl-hemisuccinate (Chems) and Cholesterol in nanoliposomes drug carriers containing an active pharmaceutical ingredient (anti-BCL-2 DNA oligonucleotide). The isocratic mobile phase consisted of ethanol/acetonitrile/water including trifluoroacetic acid (60/30/10 with 0.1% v/v, respectively) at a flow rate of 1.0 mL min-1 was run through a commercial reverse-phase C18 analytical column while UV detector was set at 202 nm. To confirm the applicability, a full validation of the proposed method was performed according to the International Council for Harmonization (ICH) guidelines.

Improvements in chemical carriers of proteins and peptides

The successful intracellular delivery of biologically active proteins and peptides plays an important role for therapeutic applications. Indeed, protein/peptide delivery could overcome some problems of gene therapy, for example, controlling the expression levels and the integration of transgene into the host cell genome. Thus, protein/peptide drug delivery showed a promising and safe approach for treatment of cancer and infectious diseases. Due to the unique physical and chemical properties of proteins, their production (e.g., isolation, purification & formulation) and delivery represented significant challenges in pharmaceutical studies. Modification in the structural moieties of these protein/peptide drugs could improve their solubility, stability, crystallinity, lipophilicity, enzymatic susceptibility and targetability, and subsequently, therapies and cures against various diseases. Using the structural modification of protein/peptide, their delivery provided overall higher success rates including high specificity, high activity, bioreactivity and safety. Recently, biotechnological and pharmaceutical companies have tried to find novel techniques for the modifications and improve delivery systems/carriers. However, each carrier has its own benefits and drawbacks, and an appropriate carrier is often established by the physicochemical properties of protein or peptide, the ideal route of injection, and clinical characteristics of therapy. In this review, an attempt was made to give an overview on the chemical carriers for proteins and peptides as well as the recent advances in this field.

Nanomaterial Preparation by Extrusion through Nanoporous Membranes

Template synthesis represents an important class of nanofabrication methods. Herein, recent advances in nanomaterial preparation by extrusion through nanoporous membranes that preserve the template membrane without sacrificing it, which is termed as "non-sacrificing template synthesis," are reviewed. First, the types of nanoporous membranes used in nanoporous membrane extrusion applications are introduced. Next, four common nanoporous membrane extrusion strategies: vesicle extrusion, membrane emulsification, precipitation extrusion, and biological membrane extrusion, are examined. These methods have been utilized to prepare a wide range of nanomaterials, including liposomes, emulsions, nanoparticles, nanofibers, and nanotubes. The principle and historical context of each specific technology are discussed, presenting prominent examples and evaluating their positive and negative features. Finally, the current challenges and future opportunities of nanoporous membrane extrusion methods are discussed.

Liposomal adjuvant development for leishmaniasis vaccines

Leishmaniasis is a parasitic disease that ranges in severity from skin lesions to fatality. Since long-lasting protection is induced upon recovery from cutaneous leishmaniasis, development of an effective vaccine is promising. However, there is no vaccine for use in humans yet. It seems limited efficacy in leishmaniasis vaccines is due to lack of an appropriate adjuvant or delivery system. Hence, the use of particulate adjuvants such as liposomes for effective delivery to the antigen presenting cells (APCs) is a valuable strategy to enhance leishmaniasis vaccine efficacy. The extraordinary versatility of liposomes because of their unique amphiphilic and biphasic nature allows for using antigens or immunostimulators within the core, on the surface or within the bilayer, and modulates both the magnitude and the T-helper bias of the immune response. In this review article, we attempt to summarize the role of liposomal adjuvants in the development of Leishmania vaccines and describe the main physicochemical properties of liposomes like phospholipid composition, surface charge, and particle size during formulation design. We also suggest potentially useful formulation strategies in order for future experiments to have a chance to succeed as liposomal vaccines against leishmaniasis.

Noninvasive imaging of sialyltransferase activity in living cells by chemoselective recognition

To elucidate the biological and pathological functions of sialyltransferases (STs), intracellular ST activity evaluation is necessary. Focusing on the lack of noninvasive methods for obtaining the dynamic activity information, this work designs a sensing platform for in situ FRET imaging of intracellular ST activity and tracing of sialylation process. The system uses tetramethylrhodamine isothiocyanate labeled asialofetuin (TRITC-AF) as a ST substrate and fluorescein isothiocyanate labeled 3-aminophenylboronic acid (FITC-APBA) as the chemoselective recognition probe of sialylation product, both of which are encapsulated in a liposome vesicle for cellular delivery. The recognition of FITC-APBA to sialylated TRITC-AF leads to the FRET signal that is analyzed by FRET efficiency images. This strategy has been used to evaluate the correlation of ST activity with malignancy and cell surface sialylation, and the sialylation inhibition activity of inhibitors. This work provides a powerful noninvasive tool for glycan biosynthesis mechanism research, cancer diagnostics and drug development.

Evaluation of the immunoprophylactic potential of a killed vaccine candidate in combination with different adjuvants against murine visceral leishmaniasis

Despite a large number of field trials, till date no prophylactic antileishmanial vaccine exists for human use. Killed antigen formulations offer the advantage of being safe but they have limited immunogenicity. Recent research has documented that efforts to develop effective Leishmania vaccine have been limited due to the lack of an appropriate adjuvant. Addition of adjuvants to vaccines boosts and directs the immunogenicity of antigens. So, the present study was done to evaluate the effectiveness of four adjuvants i.e. alum, saponin, cationic liposomes and monophosphoryl lipid-A in combination with Autoclaved Leishmania donovani (ALD) antigen against murine visceral leishmaniasis (VL). BALB/c mice were immunized thrice with respective vaccine formulation. Two weeks after last booster, challenge infection was given. Mice were sacrificed 15 days after last immunization and on 30, 60 and 90 post infection/challenge days. A considerable protective efficacy was shown by all vaccine formulations. It was evident from significant reduction in parasite load, profound delayed type hypersensitivity responses (DTH), increased IgG2a titres and high levels of Th1 cytokines (IFN-γ, IL-12) as compared to the infected controls. However, level of protection varied with the type of adjuvant used. Maximum protection was achieved with the use of liposome encapsulated ALD antigen and it was closely followed by group immunized with ALD+MPL-A. Significant results were also obtained with ALD+saponin, ALD+alum and ALD antigen (alone) but the protective efficacy was reduced as compared to other immunized groups. The present study reveals greater efficacy of two vaccine formulations i.e. ALD+liposome and ALD+MPL-A against murine VL.

Nanobiotechnologic approach to a promising vaccine prototype for immunisation against leishmaniasis: a fast and effective method to incorporate GPI-anchored proteins of Leishmania amazonensis into liposomes

Liposomes are known to be a potent adjuvant for a wide range of antigens, as well as appropriate antigen carriers for antibody generation response in vivo. In addition, liposomes are effective vehicles for peptides and proteins, thus enhancing their immunogenicity. Considering these properties of liposomes and the antigenicity of the Leishmania membrane proteins, we evaluated if liposomes carrying glycosylphosphatidylinositol (GPI)-anchored proteins of Leishmania amazonensis promastigotes could induce protective immunity in BALB/c mice. To assay protective immunity, BALB/c mice were intraperitoneally injected with liposomes, GPI-protein extract (EPSGPI) as well as with the proteoliposomes carrying GPI-proteins. Mice inoculated with EPSGPI and total protein present in constitutive proteoliposomes displayed a post-infection protection of about 70% and 90%, respectively. The liposomes are able to work as adjuvant in the EPSGPI protection. These systems seem to be a promising vaccine prototype for immunisation against leishmaniasis.

Preliminary evaluation of the immunoenhancement potential of Newcastle disease vaccine formulated as a cationic liposome

This study evaluates the enhancement of immune response of birds to Newcastle disease (ND) vaccine encapsulated in 1,2-dioleoyl-3-trimethylammonium propane (DOTAP)-based liposomes. The vesicles of the liposomal ND vaccine were physically characterized for shape, particle size and zeta potential. The results of the analyses showed that vesicles of the liposomal ND vaccine were spherical and tightly packed. The mean size distribution was below 100 nm. The mean zeta potential was 24 mV. Sixty experimental birds were then divided into an unvaccinated group, a liposomal ND vaccine group and a live La Sota(®) vaccine group. Both the liposomal ND vaccine and live La Sota(®) vaccine groups were vaccinated orally at 3 and 6 weeks of age. The mean antibody titres, total and differential white blood cell count, and blood chemistry, respectively, were assessed. Ten birds from each group were challenged by oral administration of 0.2 ml virulent Herts 33 strain at 9 weeks of age. The log(2) mean antibody titre induced by the liposomal ND vaccine after secondary immunization of the birds was 9.60±0.95 while that of the live La Sota( (®) ) vaccine was 6.00±0.63. Nine of the 10 challenged birds in the unvaccinated group died while none died from the liposomal ND vaccine group or the live La Sota(®) vaccine group. After the boost vaccination, the chickens vaccinated with the liposomal ND vaccine had a higher mean antibody titre, indicating that encapsulating ND vaccine in DOTAP-based liposome induced significantly higher immunity than the live La Sota(®) vaccine.

Toxicity Study of Streptococcus pneumoniae Vaccine Administrated Subcutaneously in Rats

This study was performed to evaluate the toxicity of polysaccharide-based Streptococcus pneumoniae vaccine in Specific Pathogen Free (SPF), Sprague-Dawley (SD) rats. S. pneumoniae vaccine was administrated subcutaneously each dose level of high (560 μg/rat), medium (280 μg/rat) and low (140 μg/rat) on days 0, 14, 28. The rats were observed for 2 weeks or 4 weeks after the final injection. During this test, there were no significant dose-dependent changes in body weight, water and food consumption. In urinalysis and serum chemistry, dose-related changes were not detected. In hematology, the percent of neutrophils and lymphocytes in white blood cells were changed significantly. According to the measurement of organ weight, only spleen weight was significantly increased in all groups of administration compared to the control group. In the histopathological examination, an antigen-deposit, vacuolated macrophages, infiltrated inflammatory cells and a formation of granulation tissue were observed at the site of an administration. These results are considered as an outcome by immune responses through a vaccination. Consequently, the results of this study demonstrated that S. pneumoniae vaccine has no toxicity when it was administrated subcutaneously three times in 2-week interval at a high dose of 560 μg/rat.

Liposomes containing lipid A: an effective, safe, generic adjuvant system for synthetic vaccines

Liposomes containing monophosphoryl lipid A (MPLA) have previously exhibited considerable potency and safety in human trials with a variety of candidate vaccines, including vaccines to malaria, HIV-1 and several different types of cancer. The long history of research and development of MPLA and liposomal MPLA as vaccine adjuvants reveals that there are numerous opportunities for creation and development of generic (nonproprietary) adjuvant system formulations with these materials that are not only highly potent and safe, but also readily available as native materials or as synthetic compounds. They are easily manufactured as potentially inexpensive and easy to use adjuvant systems and might be effective even with synthetic peptides as antigens.

Design considerations for liposomal vaccines: influence of formulation parameters on antibody and cell-mediated immune responses to liposome associated antigens

Liposomes (phospholipid bilayer vesicles) are versatile and robust delivery systems for induction of antibody and T lymphocyte responses to associated subunit antigens. In the last 15 years, liposome vaccine technology has matured and now several vaccines containing liposome-based adjuvants have been approved for human use or have reached late stages of clinical evaluation. Given the intensifying interest in liposome-based vaccines, it is important to understand precisely how liposomes interact with the immune system and stimulate immunity. It has become clear that the physicochemical properties of liposomal vaccines - method of antigen attachment, lipid composition, bilayer fluidity, particle charge, and other properties - exert dramatic effects on the resulting immune response. Here, we present a comprehensive review of the physicochemical properties of liposomal vaccines and how they influence immune responses. A discussion of novel and emerging immunomodulators that are suitable for inclusion in liposomal vaccines is also presented. Through a comprehensive analysis of the body of liposomal vaccine literature, we enumerate a series of principles that can guide the rational design of liposomal vaccines to elicit immune responses of a desired magnitude and quality. We also identify major unanswered questions in the field, pointing the direction for future study.

Cationic liposomes containing soluble Leishmania antigens (SLA) plus CpG ODNs induce protection against murine model of leishmaniasis

Development of an effective vaccine against leishmaniasis is possible due to the fact that individuals cured from cutaneous leishmaniasis (CL) are protected from further infection. First generation Leishmania vaccines consisting of whole killed parasites reached to phase 3 clinical trials but failed to show enough efficacies mainly due to the lack of an appropriate adjuvant. In this study, an efficient liposomal protein-based vaccine against Leishmania major infection was developed using soluble Leishmania antigens (SLA) as a first generation vaccine and cytidine phosphate guanosine oligodeoxynucleotides (CpG ODNs) as an immunostimulatory adjuvant. 1, 2-Dioleoyl-3-trimethylammonium-propane was used as a cationic lipid to prepare the liposomes due to its intrinsic adjuvanticity. BALB/c mice were immunized subcutaneously (SC), three times in 2-week intervals, with Lip-SLA-CpG, Lip-SLA, SLA + CpG, SLA, or HEPES buffer. As criteria for protection, footpad swelling at the site of challenge and spleen parasite loads were assessed, and the immune responses were evaluated by determination of IFN-γ and IL-4 levels of cultured splenocytes, and IgG subtypes. The group of mice that received Lip-SLA-CpG showed a significantly smaller footpad swelling, lower spleen parasite burden, higher IgG2a antibody, and lower IL-4 level compared to the control groups. It is concluded that cationic liposomes containing SLA and CpG ODNs are appropriate to induce Th1 type of immune response and protection against leishmaniasis.

Delivery of nanomedicines to extracellular and intracellular compartments of a solid tumor

Advances in molecular medicines have led to identification of promising targets on cellular and molecular levels. These targets are located in extracellular and intracellular compartments. The latter include cytosol, nucleus, mitochondrion, Golgi apparatus and endoplasmic reticulum. This report gives an overview on the barriers to delivering nanomedicines to various target sites within a solid tumor, the experimental approaches to overcome such barriers, and the potential utility of nanotechnology.

Comparison of BCG, MPL and cationic liposome adjuvant systems in leishmanial antigen vaccine formulations against murine visceral leishmaniasis

Background

The development of an effective vaccine against visceral leishmaniasis (VL) caused by Leishmania donovani is an essential aim for controlling the disease. Use of the right adjuvant is of fundamental importance in vaccine formulations for generation of effective cell-mediated immune response. Earlier we reported the protective efficacy of cationic liposome-associated L. donovani promastigote antigens (LAg) against experimental VL. The aim of the present study was to compare the effectiveness of two very promising adjuvants, Bacille Calmette-Guerin (BCG) and Monophosphoryl lipid A (MPL) plus trehalose dicorynomycolate (TDM) with cationic liposomes, in combination with LAg, to confer protection against murine VL.

Results

All the three formulations afforded significant protection against L. donovani in both the visceral organs, liver and spleen. Although comparable level of protection was observed in BCG+LAg and MPL-TDM+LAg immunized mice, highest level of protection was exhibited by the liposomal LAg immunized group. Significant increase in anti-LAg IgG levels were detected in both MPL-TDM+LAg and liposomal LAg immunized animals with higher levels of IgG2a than IgG1. But BCG+LAg failed to induce any antibody response. As an index of cell-mediated immunity DTH responses were measured and significant response was observed in mice vaccinated with all the three different formulations. However, highest responses were observed with liposomal vaccine immunization. Comparative evaluation of IFN-γ and IL-4 responses in immunized mice revealed that MPL-TDM+LAg group produced the highest level of IFN-γ but lowest IL-4 level, while BCG+LAg demonstrated generation of suboptimum levels of both IFN-γ and IL-4 response. Elicitation of moderate levels of prechallenge IFN-γ along with optimum IL-4 corresponds with successful vaccination with liposomal LAg.

Conclusion

This comparative study reveals greater effectiveness of the liposomal vaccine for protection against progressive VL in BALB/c. Again, evaluation of the immune responses by vaccination emphasizes the need of stimulation of potent cellular immunity based on both Th1 and Th2 cell responses to confer protection against VL.

Mucosal adjuvanticity of a Shigella invasin complex with dna-based vaccines

Protection against many infectious diseases may require the induction of cell-mediated and mucosal immunity. Immunization with plasmid DNA-based vaccines has successfully induced cell-mediated immune responses in small animals but is less potent in humans. Therefore, several methods are under investigation to augment DNA vaccine immunogenicity. In the current study, a mucosal adjuvant consisting of an invasin protein-lipopolysaccharide complex (Invaplex) isolated from Shigella spp. was evaluated as an adjuvant for DNA-based vaccines. Coadministration of plasmid DNA encoding the Orientia tsutsugamushi r56Karp protein with Invaplex resulted in enhanced cellular and humoral responses in intranasally immunized mice compared to immunization with DNA without adjuvant. Mucosal immunoglobulin A, directed to plasmid-encoded antigen, was detected in lung and intestinal compartments after Invaplex-DNA immunization followed by a protein booster. Moreover, immunization with Invaplex elicited Shigella-specific immune responses, highlighting its potential use in a combination vaccine strategy. The capacity of Invaplex to enhance the immunogenicity of plasmid-encoded genes suggested that Invaplex promoted the uptake and expression of the delivered genes. To better understand the native biological activities of Invaplex related to its adjuvanticity, interactions between Invaplex and mammalian cells were characterized. Invaplex rapidly bound to and was internalized by nonphagocytic, eukaryotic cells in an endocytic process dependent on actin polymerization and independent of microtubule formation. Invaplex also mediated transfection with several plasmid DNA constructs, which could be inhibited with monoclonal antibodies specific for IpaB and IpaC or Invaplex-specific polyclonal sera. The cellular binding and transport capabilities of Invaplex likely contribute to the adjuvanticity and immunogenicity of Invaplex.

Recent developments in leishmaniasis vaccine delivery systems

BACKGROUND

The observation that recovery from infection with Leishmania confers immunity to reinfection suggests that control of leishmaniasis by vaccination may be possible. New generation vaccines, particularly those based on recombinant proteins and DNA, are found to be less immunogenic.

OBJECTIVE

There is an urgent need for the development of new and improved vaccine adjuvants.

METHODS

Based on their principal mechanisms of action, adjuvants can be broadly separated into two classes: immunostimulatory adjuvants and vaccine delivery systems. Vaccine delivery systems can carry both antigen and adjuvant for effective delivery to the antigen-presenting cells (APCs). In this article, we review the adjuvants, the delivery systems and their combinations used in the search of an effective vaccine against leishmaniasis.

CONCLUSION

Based on current knowledge, cationic liposomes appear to have better prospects as effective delivery systems for developing a vaccine for leishmaniasis.

Amplification of Antibody Responses to Antigen Using Small Multilamellar Vesicles for Delivery System

New vaccines based on subunits, synthetic peptides, or DNA need innovative adjuvants or antigen delivery systems: Spherulites are multilamellar vesicles made of incompatible lipid bilayers without any aqueous core. In this study, we evaluated their ability to induce immune responses against human serum albumin (HSA). Mice were immunized by the intraperitoneal/intravenous route or subcutaneously with HSA without any adjuvant or in its encapsulated form. We showed that Spherulites strongly enhanced the seric antibody responses and led to a mixed isotypic distribution characterized by an IgG(2a) potentiation. This demonstrated that Spherulites can improve the presentation of weak antigens to the immune system.

Humoral immune response against epidermal growth factor encapsulated in dehydration rehydration vesicles of different phospholipid composition

We investigated the influence of dehydration-rehydration vesicles (DRV) phospholipid composition and the addition of other components on human recombinant epidermal growth factor (hrEGF) encapsulation efficiency and its release from liposomes. Encapsulation of EGF into DRV composed of phosphatidylcholine with different unsaturation levels was around 20-35%. The best result was obtained with dipalmitoyl phosphatidylcholine: cholesterol (DPPC:Ch) liposomes (35%) corresponding to the lowest hrEGF release during one month of storage. Even with this phospholipid composition, modification of the DRV procedure by including an extrusion step did not improve hrEGF encapsulation efficiency, rendering less stable particles. The inclusion of recombinant P64k from Neisseria meningitidis (rP64k), as such or conjugated to hrEGF, decreased the encapsulation efficiency of the latter protein into DRV or freeze and thaw multilamellar vesicles (FATMLV). The hrEGF release from liposomes could be related to the interaction between this polypeptide and the bilayer, as evidenced by increased carboxyfluorescein release from hrEGF-DRV; less susceptibility to fluorescence quenching by acrylamide in the presence of liposomes; and a measurable decrease of phospholipid phase transition Delta enthalpy (DeltaH). DRV comprising saturated phospholipids (DPPC:Ch or distearoyl phosphatidylcholine [DSPC]:Ch) and containing the conjugate EGF-P64k induced a more efficient immune response against hrEGF than unsaturated phospholipid and alum in terms of total IgG, IgG(2a), and IgG(2b) subclasses and the ability of antibody to inhibit the interaction of the EGF receptor with hrEGF.

Developing idiotype vaccines for lymphoma: from preclinical studies to phase III clinical trials

Therapeutic vaccines for B-cell non-Hodgkin lymphoma (NHL) using the clonal tumour immunoglobulin idiotype (Id) have been under development for more than three decades. A major obstacle for rapid progress in the field has been that the Id vaccine is patient-specific and required the generation of a custom-made product. The manufacturing issues were recently overcome by advances in hybridoma and recombinant DNA technology which facilitated the completion of several phase I and II clinical trials. The strong immunogenicity and apparent clinical benefit observed on the early phase studies led to the initiation of three randomized phase III clinical trials that are also nearing completion. This review will focus on the development of Id vaccines before and after the introduction of rituximab for the treatment of B-cell NHL and also discuss potential strategies to enhance the efficacy of active immunotherapy in the future.

gp63 in stable cationic liposomes confers sustained vaccine immunity to susceptible BALB/c mice infected with Leishmania donovani

Visceral leishmaniasis is deadly if not treated, and development of a vaccine with long-term immunity remains a challenge. In this study, we showed that cationic distearoyl phosphatidylcholine (DSPC) liposomes, when used as vaccine adjuvant with the immunodominant 63-kDa glycoprotein (gp63) of Leishmania donovani promastigotes, induced significant protection against progressive visceral leishmaniasis in susceptible BALB/c mice. gp63 used without adjuvant elicited partial protection but in association with liposomes exhibited marked resistance in both the livers and spleens of the mice challenged 10 days after the last vaccination. The protective efficacy of liposomal gp63 vaccination was dose dependent, with 2.5 mug of protein showing optimal protection. The immunity conferred by this vaccine formulation was durable, as mice challenged 12 weeks after immunization were still protected, and the infection was controlled for at least 3 months postchallenge. Production of gamma interferon (IFN-gamma) and interleukin-4 (IL-4) by splenic T cells, and of serum immunoglobulin G1 (IgG1) and IgG2a following immunization, suggested that a mixed Th1/Th2 response had been induced following immunization. However, control of disease progression and parasitic burden in mice vaccinated with gp63 in cationic DSPC liposomes was associated with enhancement of antigen-specific IFN-gamma and downregulation of IL-4, demonstrating a Th1 bias. Long-term immunity elicited by this vaccine corresponded to, in addition to the presence of antigen-specific Th1, CD8+ T-cell responses. Our results demonstrated that stable cationic liposomes containing gp63 acted as a potent adjuvant for protein antigen to induce long-term protection against L. donovani that represents an alternative to DNA vaccination.

Depletion of cellular cholesterol interferes with intracellular trafficking of liposome-encapsulated ovalbumin

Cholesterol is a major constituent of plasma cell membranes and influences the functions of proteins residing in the membrane. To assess the role of cholesterol in phagocytosis and intracellular trafficking of liposomal antigen, macrophages were treated with inhibitors of cholesterol biosynthesis for various time periods and levels of cholesterol depletion were assessed by thin layer chromatography. In control macrophages, cholesterol was present in the plasma membrane and in intracellular stores, as visualised by staining with the cholesterol-binding compound filipin, whereas macrophages treated with cholesterol inhibitors failed to stain with filipin. However, these macrophages were still capable of phagocytosis as evidenced by their internalisation of fluorescent-labelled bacteria and liposome-encapsulated Texas red labelled-ovalbumin, L(TR-OVA). While fluorescent ovalbumin (OVA) was consistently transported to the Golgi in macrophages incubated with L(TR-OVA), in cells treated with cholesterol inhibitors, OVA remained spread diffusely throughout the cytoplasm. Even though the mean fluorescence intensity of MHC class I molecules on cholesterol inhibitor-treated macrophages was equivalent to that of the control macrophages, the amount of MHC class I-liposomal OVA-peptide complex detected on the cell surface of cholesterol inhibitor-treated macrophages, was only 45.6 +/- 7.4% (n = 4, mean +/- SEM) of control levels after intracellular processing of L(OVA). We conclude that cholesterol depletion does not eliminate phagocytosis or MHC class I surface expression, but does affect the trafficking and consequently the MHC class I antigen-processing pathway.

Leishmanial antigens in liposomes promote protective immunity and provide immunotherapy against visceral leishmaniasis via polarized Th1 response

Leishmaniasis affects 12 million people, and it is generally agreed that vaccination provides the best long-term strategy for its control. An ideal vaccine should be effective in both preventing and treating leishmaniasis. However, immunological correlates to predict vaccine efficacy and success of treatment in visceral leishmaniasis (VL) remain ill defined. Here, we correlated the vaccine efficacy of soluble leishmanial antigens (SLA) from Leishmania donovani promastigote membrane, entrapped in negative, neutral and positively charged liposomes with the elicited immune responses to predict vaccine success in experimental VL. Production of both IFN-gamma and IL-4 with a dominance of Th1 response following immunization was required for optimum success against L. donovani infection in BALB/c mice. The best vaccine formulation, SLA in positively charged liposomes, was then used for immunotherapy. This vaccine induced more than 90% elimination of parasites from both liver and spleen. The success of immunotherapy exhibited an immune modulation with surge in Th1 cytokines, IFN-gamma and IL-12 with extreme down regulation of disease promoting IL-4 and IL-10. These findings suggest that an immune modulation towards Th1 is effective for both successful vaccination and immunotherapy.

Encapsulation in liposomal nanoparticles enhances the immunostimulatory, adjuvant and anti-tumor activity of subcutaneously administered CpG ODN

Immunostimulatory oligodeoxynucleotides (ODN) containing cytosine-guanine (CpG) motifs are powerful stimulators of innate as well as adaptive immune responses, exerting their activity through triggering of the Toll-like receptor 9. We have previously shown that encapsulation in liposomal nanoparticles (LN) enhances the immunostimulatory activity of CpG ODN (LN-CpG ODN) (Mui et al. in J Pharmacol Exp Ther 298:1185, 2001). In this work we investigate the effect of encapsulation on the immunopotency of subcutaneously (s.c.) administered CpG ODN with regard to activation of innate immune cells as well as its ability to act as a vaccine adjuvant with tumor-associated antigens (TAAs) to induce antigen (Ag)-specific, adaptive responses and anti-tumor activity in murine models. It is shown that encapsulation specifically targets CpG ODN for uptake by immune cells. This may provide the basis, at least in part, for the significantly enhanced immunostimulatory activity of LN-CpG ODN, inducing potent innate (as judged by immune cell activation and plasma cytokine/chemokine levels) and adaptive, Ag-specific (as judged by MHC tetramer positive T lymphocytes, IFN-gamma secretion and cytotoxicity) immune responses. Finally, in efficacy studies, it is shown that liposomal encapsulation enhances the ability of CpG ODN to adjuvanate adaptive immune responses against co-administered TAAs after s.c. immunization, inducing effective anti-tumor activity against both model and syngeneic tumor Ags in murine tumor models of thymoma and melanoma.

A novel proteoliposomal vaccine induces antitumor immunity against follicular lymphoma

Clinical studies suggest that treatment with vaccines comprised of idiotype protein may be associated with improved clinical outcome in follicular lymphoma patients. The time-consuming process required to generate patient-specific vaccines is a major limitation, however. Here we report results of a pilot clinical trial with a novel autologous, tumor-derived proteoliposome vaccine formulation that could be rapidly produced within a single day. Vaccination was safe, induced autologous tumor-specific type 1 cytokine responses in 5 out of 10 follicular lymphoma patients, and was associated with induction of a sustained complete response in one patient. Other patients had large tumor burdens and progressed after a median duration of 8 months. These results suggest that further testing of this vaccine formulation, particularly in the setting of minimal disease, is warranted. Furthermore, the proteoliposome formulation may provide a model for vaccine development for other human cancers, for which tumor-associated antigens need not be defined.

Pretreatment with empty liposomes attenuates the immunopathology of invasive pulmonary aspergillosis in corticosteroid-immunosuppressed mice

In a nonneutropenic murine model of invasive pulmonary aspergillosis, pretreatment with empty liposomes (E-lipo) was nearly as effective as 10 mg/kg of body weight liposomal amphotericin B and superior to 1 mg/kg amphotericin B deoxycholate. The beneficial immunomodulatory properties of E-lipo appear to compensate for their lack of direct antifungal activity.

Engineered nanoparticles as precise drug delivery systems

With the remarkable development of nanotechnology in recent years, new drug delivery approaches based on the state-of-the-art nanotechnology have been receiving significant attention. Nanoparticles, an evolvement of nanotechnology, are increasingly considered as a potential candidate to carry therapeutic agents safely into a targeted compartment in an organ, particular tissue or cell. These particles are colloidal structures with a diameter smaller than 1,000 nm, and therefore can penetrate through diminutive capillaries into the cell's internal machinery. This innovative delivery technique might be a promising technology to meet the current challenges in drug delivery. When loaded with a gene or drug agent, nanoparticles can become nanopills, which can effectively treat problematical diseases such as cancer. This article summarizes different types of nanoparticles drug delivery systems under investigation and their prospective therapeutic applications. Also, this article presents a closer look at the advances, current challenges, and future direction of nanoparticles drug delivery systems.

Eradication of established HPV 16-expressing tumors by a single administration of a vaccine composed of a liposome-encapsulated CTL-T helper fusion peptide in a water-in-oil emulsion

Human papillomavirus (HPV)-induced cervical cancer is the second most common cancer among women worldwide with half a million new cases per year. Despite the encouraging development of a preventive vaccine for HPV, a therapeutic vaccine for cervical cancer or pre-cancerous lesions remains a high priority. The preclinical study reported here used VacciMax((R)) (VM) to deliver a peptide-based vaccine composed of an HPV 16 E7-derived cytotoxic T lymphocyte (CTL) epitope fused to the T helper epitope PADRE (FP) and combined with CpG or lipopeptide adjuvant. In the study, C57BL/6 mice received 0.5million HPV 16-expressing C3 tumor cells. Mice were inoculated post-tumor challenge with a single s.c. injection of FP-CpG-VM on either day 4, 5, 6, 9, or 14. All mice that received the FP-CpG-VM vaccine were tumor-free to day 130 when the experiment was terminated. In contrast, only a minority of mice that received a control vaccine were tumor-free on day 60. Cytotoxicity assays, ELISPOT and intracellular staining for interferon (IFN)-gamma showed the immune response was specific for the selected CTL epitope. All mice that received the FP-CpG-VM vaccine remained tumor-free when re-challenged with 6million C3 cells. Cytotoxicity assays 4 months post-challenge showed that only splenocytes from mice inoculated with the FP-CpG-VM vaccine had high lysis activity. These results indicate that VacciMax((R)) causes a rapid, robust, durable and therapeutic CTL response to HPV 16 E7 protein expressing tumors.

Human autologous tumor-specific T-cell responses induced by liposomal delivery of a lymphoma antigen

PURPOSE

The idiotype (Id) of the immunoglobulin on a given B-cell malignancy is a clonal marker that can serve as a tumor-specific antigen. We developed a novel vaccine formulation by incorporating Id protein with liposomal lymphokine that was more potent than a prototype, carrier-conjugated Id protein vaccine in preclinical studies. In the present study, we evaluated the safety and immunogenicity of this vaccine in follicular lymphoma patients.

EXPERIMENTAL DESIGN

Ten patients with advanced-stage follicular lymphoma were treated with five doses of this second generation vaccine after chemotherapy-induced clinical remission. All patients were evaluated for cellular and humoral immune responses.

RESULTS

Autologous tumor and Id-specific type I cytokine responses were induced by vaccination in 10 and 9 patients, respectively. Antitumor immune responses were mediated by both CD4+ and CD8+ T cells, were human lymphocyte antigen class I and II associated, and persisted 18 months beyond the completion of vaccination. Specific anti-Id antibody responses were detected in four patients. After a median follow-up of 50 months, 6 of the 10 patients remain in continuous first complete remission.

CONCLUSIONS

This first clinical report of a liposomal cancer vaccine demonstrates that liposomal delivery is safe, induces sustained tumor-specific CD4+ and CD8+ T-cell responses in lymphoma patients, and may serve as a model for vaccine development against other human cancers and infectious pathogens.

Immunostimulatory CpG motifs induce CTL responses to HIV type I oligomeric gp140 envelope protein

In the present study we investigated the immunomodulatory effects of two adjuvants, liposomal lipid A [L(LA)] and CpG-containing oligodeoxynucleotides (CpG ODN), to the HIV-1 ogp140 envelope protein. Administration of each of these adjuvants separately with unencapsulated ogp140 resulted in low antibody titres. Encapsulation of ogp140 in liposomes containing lipid A resulted in a sixfold increase in anti-ogp140 antibodies. The antibody titres were further enhanced threefold by the addition of CpG ODN. Priming and boosting BALB/c mice with unencapsulated ogp140 with L(LA) or encapsulation in liposomes containing lipid A induced a mixed Th1/Th2 type of immune response. In contrast, immunization with L(ogp140 + LA) plus CpG ODN switched the immune response to a Th-1 response with elevated anti-ogp140 IgG2a antibodies and IFN-gamma levels. Both adjuvants induced excellent ogp140-specific proliferative and CTL responses. Therefore, for the induction of high titre antibodies, but not for cellular responses, the antigen and lipid A have to be present in the same liposomes. These results can have significant implications in directing the Th1 or Th2 differentiation of antigen-specific immune responses in the context of vaccine development.

Liposome-stabilized oil-in-water emulsions as adjuvants: increased emulsion stability promotes induction of cytotoxic T lymphocytes against an HIV envelope antigen

Protective or therapeutic immunity against HIV infection is currently believed to require both antibody and CTL responses against the envelope protein. In the present study, the adjuvant activity of a unique oil-in-water emulsion, in which liposomes containing lipid A (LA) and encapsulated antigen served as the emulsifying agent, was examined in mice using oligomeric gp140 (ogp140) derived from the HIV-1 envelope as the antigen. Emulsions rendered either highly stable or unstable by altering the ratio of liposomes to oil were used to examine the effect of stability of the emulsion on adjuvant activity. Stable and unstable emulsions had similar potencies for inducing both IgG antibodies to ogp140 and antigen-specific T-lymphocyte proliferation. Stable emulsions, but not unstable emulsions, induced antigen-specific CTL responses, possibly because of the depot effect of the stable emulsions. Furthermore, stable emulsions induced lower IgG2a/IgG1 ratios than the unstable emulsions. We conclude that stable liposomal oil-in-water emulsions provide an effective means of obtaining both antibody and CTL responses against an HIV envelope antigen.