Methods of effective conjugation of antigens to nanoparticles as non-inflammatory vaccine carriers

Synergistically enhanced cancer immunotherapy by combining protamine-based nanovaccine with PD-L1 gene silence nanoparticle

Tumor vaccine has brought a new dawn for cancer immunotherapy, but disillusionary therapeutic outcomes have been achieved due to the inefficient in vivo vaccine delivery. Moreover, tumor cells customarily resort to various wily tricks to circumvent the recognition and sweeping of the immune system, the immune escape effect has badly aggravated the difficulty of cancer management. With respect to the foregoing, in this study, a promising combinational strategy which cooperated nanovaccine with immune escape inhibition was developed for synergistically enhancing the oncotherapy efficiency. On the one hand, natural polycationic macromolecule protamine (PRT) was utilized as the carrier to construct an antigen and adjuvant co-packaged nanovaccine for facilitating the ingestion in antigen-presenting cells, amplifying antigen cross-presentation and optimizing in vivo delivery. On the other hand, PD-L1 silence gene was selected and hitchhiked in a pH-responsive nanoparticle developed in our previous study. The therapeutic gene could be successfully delivered into the tumors to down-regulate PD-L1 expression and cripple tumor immune escape. The combination of nanovaccine with PD-L1 gene silence nanoparticle could synchronously stimulate antitumor immune responses and reduce immune escape, synergistically enhance the therapeutic efficiency. This study will furnish the prospective tactics for the research of cancer immunotherapy.

Advances in nanotechnology-based platforms for survivin-targeted drug discovery

INTRODUCTION

Due to its unique functional impact on multiple cancer cell circuits including proliferation, apoptosis, tumor dissemination, DNA damage repair and immune response, the inhibitor of apoptosis protein (IAP) survivin has gained high interest as a molecular target and a multitude of therapeutics were developed to interfere with survivin expression and functionality. First clinical evaluations of these therapeutics, however, were disappointing highlighting the need to develop advanced delivery systems of survivin-targeting molecules to increase stability, bioavailability as well as the selective guidance to tumor tissue.

AREAS COVERED

: This review focuses on advancements in nanocarriers to molecularly target survivin in human malignancies. A plethora of nanoparticle platforms, including liposomes, polymeric systems, dendrimers, inorganic nanocarriers, RNA/DNA nanotechnology and exosomes are discussed in the background of survivin-tailored RNA interference, small molecule inhibitors, dominant negative mutants or survivin vaccination or combined modality treatment with chemotherapeutic drugs and photo- dynamic/photothermal strategies.

EXPERT OPINION

Novel therapeutic approaches include the use of biocompatible nanoformulations carrying gene silencing or drug molecules to directly or indirectly target proteins, allow for a more precise and controlled delivery of survivin therapeutics. Moreover, surface modification of these nanocarriers may result in a tumor entity specific delivery. Therefore, nanomedicine exploiting survivin-tailored strategies in a multimodal background is considered the way forwaerd to enhance the development of future personalized medicine.

Nano vaccines for T. gondii Ribosomal P2 Protein With Nanomaterials as a Promising DNA Vaccine Against Toxoplasmosis

Caused by Toxoplasma gondii, toxoplasmosis has aroused great threats to public health around the world. So far, no effective vaccine or drug is commercially available, and the demands for a safe and effective therapeutic strategy have become more and more urgent. In the current study, we constructed a DNA vaccine encoding T. gondii ribosomal P2 protein (TgP2) and denoted as TgP2-pVAX1 plasmid. To improve the immunoprotection, nanomaterial poly-lactic-co-glycolic acid (PLGA) and chitosan were used as the delivery vehicle to construct TgP2-pVAX1/PLGA and TgP2-pVAX1/CS nanospheres. Before vaccinations in BALB/c mice, TgP2-pVAX1 plasmids were transiently transfected into Human Embryonic Kidney (HEK) 293-T cells, and the expression of the eukaryotic plasmids was detected by laser confocal microscopy and Western blotting. Then the immunoprotection of naked DNA plasmids and their two nano-encapsulations were evaluated in the laboratory animal model. According to the investigations of antibody, cytokine, dendritic cell (DC) maturation, molecule expression, splenocyte proliferation, and T lymphocyte proportion, TgP2-pVAX1 plasmid delivered by two types of nanospheres could elicit a mixed Th1/Th2 immune response and Th1 immunity as the dominant. In addition, TgP2-pVAX1/PLGA and TgP2-pVAX1/CS nanospheres have great advantages in enhancing immunity against a lethal dose of T. gondii RH strain challenge. All these results suggested that TgP2-pVAX1 plasmids delivered by PLGA or chitosan nanomaterial could be promising vaccines in resisting toxoplasmosis and deserve further investigations and applications.

Therapeutic Strategies and Nano-Drug Delivery Applications in Management of Aging Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder in which the death of brain cells causes memory loss and cognitive decline. Existing drugs only suppress symptoms or delay further deterioration but do not address the cause of the disease. In spite of screening numerous drug candidates against various molecular targets of AD, only a few candidates, such as acetylcholinesterase inhibitors, are currently utilized as an effective clinical therapy. Currently, nano-based therapies can make a difference, providing new therapeutic options by helping drugs to cross the blood-brain barrier and enter the brain more effectively. The main aim of this review was to highlight advances in research on the development of nano-based therapeutics for improved treatment of AD.

Protein and Peptide Nanocluster Vaccines

Recombinant protein- and peptide-based vaccines can deliver large amounts of specific antigens for tailored immune responses. One class of these are protein and peptide nanoclusters (PNCs), which are made entirely from the crosslinked antigen. PNCs leverage the inherent immunogenicity of nanoparticulate antigens while minimizing the use of excipients normally used to create them. In this chapter, we discuss PNC fabrication methods, immunostimulatory properties of nanoclusters observed in vitro and in vivo, and protective benefits of PNC vaccines against influenza and cancer mouse models. We conclude with an outlook on future studies of PNCs and PNC design strategies, as well as their use in future vaccine formulations.

Pullulan-Coated Iron Oxide Nanoparticles for Blood-Stage Malaria Vaccine Delivery

Vaccines against blood-stage malaria often aim to induce antibodies to neutralize parasite entry into red blood cells, interferon gamma (IFNγ) produced by T helper 1 (Th1) CD4+ T cells or interleukin 4 (IL-4) produced by T helper 2 (Th2) cells to provide B cell help. One vaccine delivery method for suitable putative malaria protein antigens is the use of nanoparticles as vaccine carriers. It has been previously shown that antigen conjugated to inorganic nanoparticles in the viral-particle size range (~40–60 nm) can induce protective antibodies and T cells against malaria antigens in a rodent malaria challenge model. Herein, it is shown that biodegradable pullulan-coated iron oxide nanoparticles (pIONPs) can be synthesized in this same size range. The pIONPs are non-toxic and do not induce conventional pro-inflammatory cytokines in vitro and in vivo. We show that murine blood-stage antigen MSP4/5 from Plasmodium yoelii could be chemically conjugated to pIONPs and the use of these conjugates as immunogens led to the induction of both specific antibodies and IFNγ CD4+ T cells reactive to MSP4/5 in mice, comparable to responses to MSP4/5 mixed with classical adjuvants (e.g., CpG or Alum) that preferentially induce Th1 or Th2 cells individually. These results suggest that biodegradable pIONPs warrant further exploration as carriers for developing blood-stage malaria vaccines.

Enhancement of Tetravalent Immune Responses to Highly Conserved Epitopes of a Dengue Peptide Vaccine Conjugated to Polystyrene Nanoparticles

Vaccination remains the major approach to the prevention of dengue. Since the only licensed live attenuated vaccine (LAV) lacked efficacy against all four serotypes, other vaccine platforms, such as synthetic peptide vaccines, should be explored. In this study, four multi-epitope peptides (P1-P4) were designed by linking a universal T-helper epitope (PADRE or TpD) to the highly conserved CD8 T cell epitope and B cell epitope (B1 or B2) against all four DENV serotypes. The multi-epitope peptides were conjugated to polystyrene nanoparticles (PSNPs) and four nanovaccines (NP1-NP4) were constructed. Mice immunized with NP1-NP4 elicited significantly higher titers of IgG and neutralizing antibodies when compared to immunization with naked P1-P4. The immune responses in mice immunized with peptide vaccines were compared with nanovaccines using ELISA, ELISPOT, and a neutralization test based on FRNT₅₀. Among the four conjugated peptide nanovaccines, NP3 comprising the TpD T-helper epitope linked to the highly conserved B1 epitope derived from the E protein was able to elicit significant levels of IFN-γ and neutralizing antibodies to all four dengue serotypes. NP3 is a promising tetravalent synthetic peptide vaccine, but the selection of a more effective CD8⁺ T cell epitope and adjuvants to further improve the immunogenicity is warranted.

Functional Recognition by CD8+ T Cells of Epitopes with Amino Acid Variations Outside Known MHC Anchor or T Cell Receptor Recognition Residues

Peptide-based vaccines can be safer and more cost effective than whole organism vaccines. Previous studies have shown that inorganic polystyrene nanoparticles (PSNPs) covalently conjugated to the minimal immunodominant peptide epitope from murine liver stage malaria (SYIPSAEKI) induced potent CD8+ T cell responses. Many pathogens, including malaria, have polymorphic T cell epitope regions. Amino acid changes in positions that are contact residues for the T cell receptor (TCR) often alter the specific cross-reactivity induced by the peptide antigen, and it is largely assumed that changes outside of these residues have little impact. Herein, each amino acid residue (except major histocompatibility complex (MHC) anchors) was systematically changed to an alanine. Peptide epitopes with altered amino acids outside T cell contact residues were still recognized by T cells induced by PSNPs-SYIPSAEKI (KI) vaccines, albeit at lower levels, except for the variant SYIPSAAKI (A7). PSNPs-SYIPSAAKI vaccines further elicited high responses to the index KI peptide. None of the epitopes displayed altered peptide ligand (APL) antagonism in vitro, and re-stimulating SYIPSAEKI and SYIPSAAKI together synergistically enhanced IFN-γ production by the T cells. These results show epitope variation in non-TCR recognition residues can have effects on T cell reactivity, suggesting that such natural variation may also be driven by immune pressure. Additionally, when re-modelling peptides to enhance the cross-reactivity of vaccines, both TCR recognition and non-recognition residues should be considered.

Biodegradable PLGA-b-PEG Nanoparticles Induce T Helper 2 (Th2) Immune Responses and Sustained Antibody Titers via TLR9 Stimulation

Sustained immune responses, particularly antibody responses, are key for protection against many endemic infectious diseases. Antibody responses are often accompanied by T helper (Th) cell immunity. Herein we study small biodegradable poly (ethylene glycol)-b-poly (lactic-co-glycolic acid) nanoparticles (PEG-b-PLGA NPs, 25-50 nm) as antigen- or adjuvant-carriers. The antigen carrier function of PEG-b-PLGA NPs was compared against an experimental benchmark polystyrene nanoparticles (PS NPs, 40-50 nm), both conjugated with the model antigen ovalbumin (OVA-PS NPs, and OVA-PEG-b-PLGA NPs). The OVA-PEG-b-PLGA NPs induced sustained antibody responses to Day 120 after two immunizations. The OVA-PEG-b-PLGA NPs as a self-adjuvanting vaccine further induced IL-4 producing T-helper cells (Th2), but not IFN-γ producing T-cells (Th1). The PEG-b-PLGA NPs as a carrier for CpG adjuvant (CpG-PEG-b-PLGA NPs) were also tested as mix-in vaccine adjuvants comparatively for protein antigens, or for protein-conjugated to PS NPs or to PEG-b-PLGA NPs. While the addition of this adjuvant NP did not further increase T-cell responses, it improved the consistency of antibody responses across all immunization groups. Together these data support further development of PEG-b-PLGA NPs as a vaccine carrier, particularly where it is desired to induce Th2 immunity and achieve sustained antibody titers in the absence of affecting Th1 immunity.

HBs antigen and mannose loading on the surface of iron oxide nanoparticles in order to immuno-targeting: fabrication, characterization, cellular and humoral immunoassay

Mannosylation of nanovaccine is an appropriate strategy for targeting the mannose receptors on DCs. Here, HBsAg and mannose loaded on the surface of iron oxide nanoparticles to increases HBsAg vaccine potency. Nanoparticles are made by co-precipitation method and bonded to the HBsAg and mannose by chemical bonding. The physicochemical properties of nano-vaccines, their toxicity and antigenicity were determined. The synthesized nano-vaccine showed spherical shape with a mean particle size of 60 nm, a zeta potential of -44 mV, an antigen-binding efficiency of around 100% and for mannose 78%. In vitro release of nanoparticles exhibited about 30% at the first day and about 60% until the third day. SDSPAGE analysis confirmed structural integrity of HBsAg loaded on nanoparticles. The HBsAg-loaded LCMNP and MLCMNP nanoparticles had no toxic effects on HEK293 cell line. The quantification of the intracellular Fe by ICP-OES as a criterion of nano-vaccine uptake revealed mannose intensify uptake of MLCMNP. In addition, mannose in the structure of MLCMNP improved IL-6, TNF-α and IFN-γ (>16 fold) cytokines genes expression by macrophage/dendritic cells after exposure in 12 h. Immunization of experimental mice (subcutaneously, two times with 2-week intervals) with 5 µg of HBsAg loaded on MLCMNP nanoparticles increased specific total IgG and IgG2a/IgG1 ratio. In addition, TNF-α, IL-12, IL-2 and IL-4 cytokines in mannosylated nano-vaccine increased versus nano-vaccine group while lymphocyte proliferation and IFN-γ responses in the targeted nano-vaccine group show a tiny increase versus the nano-vaccine group. The results show that mannosylated nano-vaccine promotes higher level of cellular and humoural immune responses against HBsAg nano-vaccine.

A Synthetic Nanoparticle Based Vaccine Approach Targeting MSP4/5 Is Immunogenic and Induces Moderate Protection Against Murine Blood-Stage Malaria

Malaria remains a significant health problem in many tropical and sub-tropical regions. The development of vaccines against the clinically active blood-stage of infection needs to consider variability and polymorphism in target antigens, and an adjuvant system able to induce broad spectrum immunity comprising both antibodies and helper T cells. Moreover, recent studies have shown some conventional pro-inflammatory adjuvants can also promote expansion of immunosuppressive regulatory T cells (Treg) and myeloid derived suppressor cells (MDSC), both of which could negatively impact malaria disease progression. Herein, we explore the ability of a model nanoparticle delivery system (polystyrene nanoparticles; PSNPs), previously proven to not induce conventional inflammation, Treg or MDSC, to induce immunity to MSP4/5 from Plasmodium yoelii, a member of the MSP4 and MSP5 family of proteins which are highly conserved across diverse malaria species including P. falciparum. The results show PSNPs-MSP4/5 conjugates are highly immunogenic, inducing immune responses comprising both T helper 1 (Th1) and Th2 cellular immunity, and a spectrum of antibody subclasses including IgG1, IgG2a, and IgG2b. Benchmarked against Alum and Complete Freund's Adjuvant (CFA), the immune responses that were induced were of comparable or higher magnitude, for both T cell frequencies by ELISpot and antibody responses in terms of ELISA end titer. Importantly, immunization with PSNPs-MSP4/5 induced partial protection against malaria blood-stage infection (50–80%) shown to be mechanistically dependent on interferon gamma (IFN-γ) production. These results expand the scope of adjuvants considered for malaria blood-stage vaccine development to those that do not use conventional adjuvant pathways and emphasizes the critical role of cellular immunity and specifically IFN-γ producing cells in providing moderate protection against blood-stage malaria comparable to Freunds adjuvant.

Design of Peptide-Based Nanovaccines Targeting Leading Antigens From Gynecological Cancers to Induce HLA-A2.1 Restricted CD8+ T Cell Responses

Gynecological cancers are a leading cause of mortality in women. CD8⁺ T cell immunity largely correlates with enhanced survival, whereas inflammation is associated with poor prognosis. Previous studies have shown polystyrene nanoparticles (PSNPs) are biocompatible, do not induce inflammation and when used as vaccine carriers for model peptides induce CD8⁺ T cell responses. Herein we test the immunogenicity of 24 different peptides, from three leading vaccine target proteins in gynecological cancers: the E7 protein of human papilloma virus (HPV); Wilms Tumor antigen 1 (WT1) and survivin (SV), in PSNP conjugate vaccines. Of relevance to vaccine development was the finding that a minimal CD8⁺ T cell peptide epitope from HPV was not able to induce HLA-A2.1 specific CD8⁺ T cell responses in transgenic humanized mice using conventional adjuvants such as CpG, but was nevertheless able to generate strong immunity when delivered as part of a specific longer peptide conjugated to PSNPs vaccines. Conversely, in most cases, when the minimal CD8⁺ T cell epitopes were able to induce immune responses (with WT1 or SV super agonists) in CpG, they also induced responses when conjugated to PSNPs. In this case, extending the sequence around the CD8⁺ T cell epitope, using the natural protein context, or engineering linker sequences proposed to enhance antigen processing, had minimal effects in enhancing or changing the cross-reactivity pattern induced by the super agonists. Nanoparticle approaches, such as PSNPs, therefore may offer an alternative vaccination strategy when conventional adjuvants are unable to elicit the desired CD8⁺ T cell specificity. The findings herein also offer sequence specific insights into peptide vaccine design for nanoparticle-based vaccine carriers.

Mitochondrial therapeutic interventions in Alzheimer's disease

Alzheimer's Disease (AD) is one of the most common age-related neurodegenerative diseases in the developed world. Treatment of AD is particularly challenging as the drug must overcome the blood brain barrier (BBB) before it can reach its target. Mitochondria are recognized as one of the most important targets for neurological drugs as the organelle is known to play a critical role in diverse cellular processes such as energy production and apoptosis regulation. Mitochondrial targeting was originally developed to study mitochondrial dysfunction and the organelles interaction with other sub-cellular organelles. The purpose of this review is to provide an overview of mitochondrial dysfunction and its role in late onset AD pathology. We then highlight recent antioxidant and enzymatic treatments used to alleviate mitochondrial dysfunction. Finally, we describe current applications of targeted mitochondrial delivery in the treatment of AD.

Induction of adaptive immune response by self-aggregating peptides

INTRODUCTION

Recently, subunit vaccines are replacing some of the traditional vaccines because they offer a higher margin of safety. However, generally subunit vaccines have low antigenicity. Adjuvants are used in vaccine formulations to increase their immunogenicity, but current research suggests that adjuvants could induce serious side effects in susceptible individuals; therefore, the improvement of antigens and adjuvants is important.

AREAS COVERED

Here we reviewed some self-aggregating peptides (SAPs) used as antigen delivery systems. SAPs are based on a short sequence of amino acids, which have self-aggregating properties, inducing self-interaction among peptide molecules by means of non-covalent interactions to generate nanoparticles (NPs).

EXPERT COMMENTARY

SAPs increase the immunogenicity of fused/conjugated antigens because they can interact with antigen-presenting cells and induce adaptive immunity based on both humoral and cellular responses. As an example, we report an antigen delivery system based on SAPs forming NPs. These NPs are synthesized using a recombinant baculovirus. We fused the green fluorescent protein to the first 110 amino acids of polyhedrin protein from Autographa californica nucleopolyhedrovirus, which has self-aggregating properties. We showed that these NPs prompt high antibody levels without inducing inflammation, similarly to some SAPs reported here.

Synthetic Nanoparticles That Promote Tumor Necrosis Factor Receptor 2 Expressing Regulatory T Cells in the Lung and Resistance to Allergic Airways Inflammation

Synthetic glycine coated 50 nm polystyrene nanoparticles (NP) (PS50G), unlike ambient NP, do not promote pulmonary inflammation, but instead, render lungs resistant to the development of allergic airway inflammation. In this study, we show that PS50G modulate the frequency and phenotype of regulatory T cells (Treg) in the lung, specifically increasing the proportion of tumor necrosis factor 2 (TNFR2) expressing Treg. Mice pre-exposed to PS50G, which were sensitized and then challenged with an allergen a month later, preferentially expanded TNFR2⁺Foxp3⁺ Treg, which further expressed enhanced levels of latency associated peptide and cytotoxic T-lymphocyte associated molecule-4. Moreover, PS50G-induced CD103⁺ dendritic cell activation in the lung was associated with the proliferative expansion of TNFR2⁺Foxp3⁺ Treg. These findings provide the first evidence that engineered NP can promote the selective expansion of maximally suppressing TNFR2⁺Foxp3⁺ Treg and further suggest a novel mechanism by which NP may promote healthy lung homeostasis.

Cytokine-Induced Killer Cells As Pharmacological Tools for Cancer Immunotherapy

Cytokine-induced killer (CIK) cells are a heterogeneous population of effector CD3⁺CD56⁺ natural killer T cells, which can be easily expanded in vitro from peripheral blood mononuclear cells. CIK cells work as pharmacological tools for cancer immunotherapy as they exhibit MHC-unrestricted, safe, and effective antitumor activity. Much effort has been made to improve CIK cells cytotoxicity and treatments of CIK cells combined with other antitumor therapies are applied. This review summarizes some strategies, including the combination of CIK with additional cytokines, dendritic cells, check point inhibitors, antibodies, chemotherapeutic agents, nanomedicines, and engineering CIK cells with a chimeric antigen receptor. Furthermore, we briefly sum up the clinical trials on CIK cells and compare the effect of clinical CIK therapy with other immunotherapies. Finally, further research is needed to clarify the pharmacological mechanism of CIK and provide evidence to formulate uniform culturing criteria for CIK expansion.

Engineered Hydrogen-Bonded Glycopolymer Capsules and Their Interactions with Antigen Presenting Cells

Hollow glycopolymer microcapsules were fabricated by hydrogen-bonded layer-by-layer (LbL) assembly, and their interactions with a set of antigen presenting cells (APCs), including dendritic cells (DCs), macrophages (MACs), and myeloid derived suppressor cells (MDSCs), were investigated. The glycopolymers were obtained by cascade postpolymerization modifications of poly(oligo(2-ethyl-2-oxazoline methacrylate)-stat-glycidyl methacrylate) involving the modification of the glycidyl groups with propargylamine and the subsequent attachment of mannose azide by copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC). Multilayer assembly of the hydrogen-bonding pair (glycopolymer/poly(methacrylic acid) (PMA)) onto planar and particulate supports (SiO₂ particles, d = 1.16 μm) yielded stable glycopolymer films upon cross-linking by CuAAC. The silica (SiO₂) particle templates were removed yielding hollow monodisperse capsules, as demonstrated by fluorescence and scanning electron microscopy. Cellular uptake studies using flow cytometry revealed the preferential uptake of the capsules by DCs when compared to MACs or MDSCs. Mannosylated capsules showed a cytokine independent cis-upregulation of CD80 specifically on DCs and a trans-downregulation of PDL-1 on MDSCs. Thus, the glycopolymer capsules may have potential as vaccine carriers, as they are able to upregulate costimulatory molecules for immune cell stimulation on DCs and at the same time downregulate immune inhibitory receptors on suppressor APC such as MDSCs.

Co-Administration of Lipid Nanoparticles and Sub-Unit Vaccine Antigens Is Required for Increase in Antigen-Specific Immune Responses in Mice

A vast body of evidence suggests that nanoparticles function as potent immune-modulatory agents. We have previously shown that Merck proprietary Lipid NanoParticles (LNPs) markedly boost B-cell and T-cell responses to sub-unit vaccine antigens in mice. To further evaluate the specifics of vaccine delivery and dosing regimens in vivo, we performed immunogenicity studies in BALB/c and C57BL/6 mice using two model antigens, Hepatitis B Surface Antigen (HBsAg) and Ovalbumin (OVA), respectively. To assess the requirement for co-administration of antigen and LNP for the elicitation of immune responses, we evaluated immune responses after administering antigen and LNP to separate limbs, or administering antigen and LNP to the same limb but separated by 24 h. We also evaluated formulations combining antigen, LNP, and aluminum-based adjuvant amorphous aluminum hydroxylphosphate sulfate (MAA) to look for synergistic adjuvant effects. Analyses of antigen-specific B-cell and T-cell responses from immunized mice revealed that the LNPs and antigens must be co-administered—both at the same time and in the same location—in order to boost antigen-specific immune responses. Mixing of antigen with MAA prior to formulation with LNP did not impact the generation of antigen-specific B-cell responses, but drastically reduced the ability of LNPs to boost antigen-specific T-cell responses. Overall, our data demonstrate that the administration of LNPs and vaccine antigen together enables their immune-stimulatory properties.

Induction of a balanced Th1/Th2 immune responses by co-delivery of PLGA/ovalbumin nanospheres and CpG ODNs/PEI-SWCNT nanoparticles as TLR9 agonist in BALB/c mice

To develop effective and safe vaccines with reduced dose of antigen and adjuvant, intelligent delivery systems are required. Many delivery systems have been developed to enhance the biological activity of cytosine-phosphorothioate-guanine oligodeoxynucleotides (CpG ODN) as both immunotherapeutic agents and vaccine adjuvants. In this study we designed a novel CpG ODN delivery system based on single-walled carbon nanotube (SWCNT) functionalized with polyethylenimine (PEI) and alkylcarboxylated PEI (AL-PEI). The physicochemical characteristics, cytotoxicity and cellular uptake studies of these carriers were performed. All carriers were conjugated with CpG ODN followed by co-delivery with ovalbumin (OVA) encapsulated into poly (lactic-co-glycolic acid) nanospheres (PLGA NSs) to enhance the induction of immune responses. The effect of these formulations on antibody (IgG1, IgG2a) and cytokine (IL-1β, IFN-γ, IL-4) production was evaluated in an in vivo experiment. The results showed that all nano-adjuvant formulations had a strong influence in up-regulation of IFN-γ and IL-4 in parallel with high IgG1-IgG2a isotype antibody titers in mice. In particular, SWCNT-AL-PEI nano-adjuvant formulation generated a balanced Th1 and Th2 immune response with more biased toward Th1 response without exhibiting any inflammatory and toxic effects. Therefore this nano-adjuvant formulation could be used as an efficient prophylactic immune responses agent.

Mitochondria and neurodegenerative diseases: the promising role of nanotechnology in targeted drug delivery

INTRODUCTION

Neurodegenerative diseases (NDs) represent a group of different clinical entities that, despite the specific primary etiologies, share a common signature in terms of a general mitochondrial dysfunction with consequent oxidative stress accumulation. As these two events occur early during neurodegenerative process, they could be considered ideal therapeutic targets. Areas covered: This review describes the nanotechnologies explored for the specific targeted delivery of drugs, in order to precisely direct molecules into the intended site, where they can practice their therapeutic effects. Expert opinion: Conventional drug delivery systems cannot provide adequate restoration and connection patterns that are essential for a functional recovery in NDs. Since orally delivered antioxidants are easily destroyed by acids and enzymes, only a small portion of consumed antioxidants gets absorbed, leading to low bioavailability and low concentration at the target site. In this scenario, the identification of new proenergetic drugs, in combination with the development of methods for selectively delivering biologically active molecules into mitochondria, will potentially launch new therapeutic approaches for the treatment of NDs, where energetic imbalance plays a central role.

A Model to Study the Impact of Polymorphism Driven Liver-Stage Immune Evasion by Malaria Parasites, to Help Design Effective Cross-Reactive Vaccines

Malaria parasites engage a multitude of strategies to evade the immune system of the host, including the generation of polymorphic T cell epitope sequences, termed altered peptide ligands (APLs). Herein we use an animal model to study how single amino acid changes in the sequence of the circumsporozoite protein (CSP), a major target antigen of pre-erythrocytic malaria vaccines, can lead to a reduction of cross reactivity by T cells. For the first time in any APL model, we further compare different inflammatory adjuvants (Montanide, Poly I:C), non-inflammatory adjuvants (nanoparticles), and peptide pulsed dendritic cells (DCs) for their potential capacity to induce broadly cross reactive immune responses. Results show that the capacity to induce a cross reactive response is primarily controlled by the T cell epitope sequence and cannot be modified by the use of different adjuvants. Moreover, we identify how specific amino acid changes lead to a one-way cross reactivity: where variant-x induced responses are re-elicited by variant-x and not variant-y, but variant-y induced responses can be re-elicited by variant-y and variant-x. We discuss the consequences of the existence of this one-way cross reactivity phenomenon for parasite immune evasion in the field, as well as the use of variant epitopes as a potential tool for optimized vaccine design.

A novel lipid nanoparticle adjuvant significantly enhances B cell and T cell responses to sub-unit vaccine antigens

Sub-unit vaccines are primarily designed to include antigens required to elicit protective immune responses and to be safer than whole-inactivated or live-attenuated vaccines. But their purity and inability to self-adjuvant often result in weaker immunogenicity. Emerging evidence suggests that bio-engineered nanoparticles can be used as immunomodulatory adjuvants. Therefore, in this study we explored the potential of novel Merck-proprietary lipid nanoparticle (LNP) formulations to enhance immune responses to sub-unit viral antigens. Immunization of BALB/c and C57BL/6 mice revealed that LNPs alone or in combination with a synthetic TLR9 agonist, immune-modulatory oligonucleotides, IMO-2125 (IMO), significantly enhanced immune responses to hepatitis B virus surface antigen (HBsAg) and ovalbumin (OVA). LNPs enhanced total B-cell responses to both antigens tested, to levels comparable to known vaccine adjuvants including aluminum based adjuvant, IMO alone and a TLR4 agonist, 3-O-deactytaled monophosphoryl lipid A (MPL). Investigation of the quality of B-cell responses demonstrated that the combination of LNP with IMO agonist elicited a stronger Th1-type response (based on the IgG2a:IgG1 ratio) than levels achieved with IMO alone. Furthermore, the LNP adjuvant significantly enhanced antigen specific cell-mediated immune responses. In ELISPOT assays, depletion of specific subsets of T cells revealed that the LNPs elicited potent antigen-specific CD4(+) and CD8(+)T cell responses. Intracellular FACS analyses revealed that LNP and LNP+IMO formulated antigens led to higher frequency of antigen-specific IFNγ(+)TNFα(+)IL-2(+), multi-functional CD8(+)T cell responses, than unadjuvanted vaccine or vaccine with IMO only. Overall, our results demonstrate that lipid nanoparticles can serve as future sub-unit vaccine adjuvants to boost both B-cell and T-cell responses in vivo, and that addition of IMO can be used to manipulate the quality of immune responses.

A Nanoparticle Based Sp17 Peptide Vaccine Exposes New Immuno-Dominant and Species Cross-reactive B Cell Epitopes

Sperm protein antigen 17 (Sp17), expressed in primary as well as in metastatic lesions in >83% of patients with ovarian cancer, is a promising ovarian cancer vaccine candidate. Herein we describe the formulation of nanoparticle based vaccines based on human Sp17 (hSp17) sequence derived peptides, and map the immuno-dominant T cell and antibody epitopes induced using such formulations. The primary T and B cell immuno-dominant region within Sp17 was found to be the same when using biocompatible nanoparticle carriers or the conventional “mix-in” pro-inflammatory adjuvant CpG, both mapping to amino acids (aa) 111–142. However, delivery of hSp17_111–142 as a nanoparticle conjugate promoted a number of new properties, changing the dominant antibody isotype induced from IgG2a to IgG1 and the fine specificity of the B cell epitopes within hSp17_111–142, from an immuno-dominant region 134–142 aa for CpG, to region 121–138 aa for nanoparticles. Associated with this change in specificity was a substantial increase in antibody cross-reactivity between mouse and human Sp17. These results indicate conjugation of antigen to nanoparticles can have major effects on fine antigen specificity, which surprisingly could be beneficially used to increase the cross-reactivity of antibody responses.

Nanoparticles modify dendritic cell homeostasis and induce non-specific effects on immunity to malaria

BACKGROUND

Many current vaccines to a specific pathogen influence responses to other pathogens in a process called heterologous immunity. We propose that their particulate nature contributes to non-specific effects. Herein, we demonstrate polystyrene nanoparticles modulate dendritic cell (DC) homeostasis, thereby promoting a persistent enhanced state of immune readiness to a subsequent infectious challenge.

METHODS

Particles (approximately 40 nm and 500 nm carboxylated polystyrene nanoparticles; PSNPs) alone or conjugated to a model antigen were injected in mice, and DCs in draining lymph nodes (dLNs) and bone-marrow (BM) quantified by flow cytometry. BM cells were tested for capacity to generate DCs upon culture with granulocyte and macrophage colony stimulating factor. Mice were challenged with Plasmodium yoelli. Blood parasitaemias were monitored by GIEMSA. Sera was analyzed for antibodies by ELISA.

RESULTS

Intradermal administration of 40 nm PSNPs induced anti-inflammatory cytokines, chemokines and growth factors, increased numbers and proportions of DCs in the dLN, and increased the capacity of BM to generate DCs. Consistent with these unexpected changes, 40 nm PSNPs pre-injected mice had enhanced ability to generate immunity to a subsequent malarial infection.

CONCLUSIONS

Intradermal administration of 40 nm PSNPs modifies DC homeostasis, which may at least in part explain the observed beneficial heterologous effects of current particulate vaccines. Further nanotechnological developments may exploit such strategies to promote beneficial non-specific effects.

Harnessing nanoparticles for immune modulation

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NPs can be generated from numerous biocompatible compounds.

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Specific physiochemical characteristics can be manipulated to modulate the immune response.

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Severe inflammation can be treated using NP-based approaches.

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Antigen delivery via NPs can restore peripheral immune tolerance.

Recent approaches using nanoparticles engineered for immune regulation have yielded promising results in preclinical models of disease. The number of nanoparticle therapies is growing, fueled by innovations in nanotechnology and advances in understanding of the underlying pathogenesis of immune-mediated diseases. In particular, recent mechanistic insight into the ways in which nanoparticles interact with the mononuclear phagocyte system and impact its function during homeostasis and inflammation have highlighted the potential of nanoparticle-based therapies for controlling severe inflammation while concurrently restoring peripheral immune tolerance in autoimmune disease. Here we review recent advances in nanoparticle-based approaches aimed at immune-modulation, and discuss these in the context of concepts in polymeric nanoparticle development, including particle modification, delivery and the factors associated with successful clinical deployment.

Montanide, Poly I:C and nanoparticle based vaccines promote differential suppressor and effector cell expansion: a study of induction of CD8 T cells to a minimal Plasmodium berghei epitope

The development of practical and flexible vaccines to target liver stage malaria parasites would benefit from an ability to induce high levels of CD8 T cells to minimal peptide epitopes. Herein we compare different adjuvant and carrier systems in a murine model for induction of interferon gamma (IFN-γ) producing CD8 T cells to the minimal immuno-dominant peptide epitope from the circumsporozoite protein (CSP) of Plasmodium berghei, pb9 (SYIPSAEKI, referred to as KI). Two pro-inflammatory adjuvants, Montanide and Poly I:C, and a non-classical, non-inflammatory nanoparticle based carrier (polystyrene nanoparticles, PSNPs), were compared side-by-side for their ability to induce potentially protective CD8 T cell responses after two immunizations. KI in Montanide (Montanide + KI) or covalently conjugated to PSNPs (PSNPs-KI) induced such high responses, whereas adjuvanting with Poly I:C or PSNPs without conjugation was ineffective. This result was consistent with an observed induction of an immunosuppressed environment by Poly I:C in the draining lymph node (dLN) 48 h post injection, which was reflected by increased frequencies of myeloid derived suppressor cells (MDSCs) and a proportion of inflammation reactive regulatory T cells (Treg) expressing the tumor necrosis factor receptor 2 (TNFR2), as well as decreased dendritic cell (DC) maturation. The other inflammatory adjuvant, Montanide, also promoted proportional increases in the TNFR2⁺ Treg subpopulation, but not MDSCs, in the dLN. By contrast, injection with non-inflammatory PSNPs did not cause these changes. Induction of high CD8 T cell responses, using minimal peptide epitopes, can be achieved by non-inflammatory carrier nanoparticles, which in contrast to some conventional inflammatory adjuvants, do not expand either MDSCs or inflammation reactive Tregs at the site of priming.

Oral delivery of nanoparticle-based vaccines

Most infectious diseases are caused by pathogenic infiltrations from the mucosal tract. Therefore, vaccines delivered to the mucosal tissues can mimic natural infections and provide protection at the first site of infection. Thus, mucosal, especially, oral delivery is becoming the most preferred mode of vaccination. However, oral vaccines have to overcome several barriers such as the extremely low pH of the stomach, the presence of proteolytic enzymes and bile salts as well as low permeability in the intestine. Several formulations based on nanoparticle strategies are currently being explored to prepare stable oral vaccine formulations. This review briefly discusses several molecular mechanisms involved in intestinal immune cell activation and various aspects of oral nanoparticle-based vaccine design that should be considered for improved mucosal and systemic immune responses.

Nanoparticle-delivered transforming growth factor-β siRNA enhances vaccination against advanced melanoma by modifying tumor microenvironment

Achievement of potent immunoresponses against self/tumor antigens and effective therapeutic outcome against advanced tumors remain major challenges in cancer immunotherapy. The specificity and efficiency of two nanoparticle-based delivery systems, lipid-calcium-phosphate (LCP) nanoparticle (NP) and liposome-protamine-hyaluronic acid (LPH) NP, provide us an opportunity to address both challenges. A mannose-modified LCP NP delivered both tumor antigen (Trp 2 peptide) and adjuvant (CpG oligonucleotide) to the dendritic cells and elicited a potent, systemic immune response regardless of the existence or the stage of tumors in the host. This vaccine was less effective, however, against later stage B16F10 melanoma in a subcutaneous syngeneic model. Mechanistic follow-up studies suggest that elevated levels of immune-suppressive cytokines within the tumor microenvironment, such as TGF-β, might be responsible. We strategically augment the efficacy of LCP vaccine on an advanced tumor by silencing TGF-β in tumor cells. The delivery of siRNA using LPH NP resulted in about 50% knockdown of TGF-β in the late stage tumor microenvironment. TGF-β down-regulation boosted the vaccine efficacy and inhibited tumor growth by 52% compared with vaccine treatment alone, as a result of increased levels of tumor infiltrating CD8+ T cells and decreased level of regulatory T cells. Combination of systemic induction of antigen-specific immune response with LCP vaccine and targeted modification of tumor microenvironment with LPH NP offers a flexible and powerful platform for both mechanism study and immunotherapeutic strategy development.

Adjuvants in the Driver's Seat: How Magnitude, Type, Fine Specificity and Longevity of Immune Responses Are Driven by Distinct Classes of Immune Potentiators

The mechanism by which vaccine adjuvants enhance immune responses has historically been considered to be the creation of an antigen depot. From here, the antigen is slowly released and provided to immune cells over an extended period of time. This "depot" was formed by associating the antigen with substances able to persist at the injection site, such as aluminum salts or emulsions. The identification of Pathogen-Associated Molecular Patterns (PAMPs) has greatly advanced our understanding of how adjuvants work beyond the simple concept of extended antigen release and has accelerated the development of novel adjuvants. This review focuses on the mode of action of different adjuvant classes in regards to the stimulation of specific immune cell subsets, the biasing of immune responses towards cellular or humoral immune response, the ability to mediate epitope spreading and the induction of persistent immunological memory. A better understanding of how particular adjuvants mediate their biological effects will eventually allow them to be selected for specific vaccines in a targeted and rational manner.

Drug targeting using solid lipid nanoparticles

The present review aims to show the features of solid lipid nanoparticles (SLNs) which are at the forefront of the rapidly developing field of nanotechnology with several potential applications in drug delivery and research. Because of some unique features of SLNs such as their unique size dependent properties it offers possibility to develop new therapeutics. A common denominator of all these SLN-based platforms is to deliver drugs into specific tissues or cells in a pathological setting with minimal adverse effects on bystander cells. SLNs are capable to incorporate drugs into nanocarriers which lead to a new prototype in drug delivery which maybe used for drug targeting. Hence solid lipid nanoparticles hold great promise for reaching the goal of controlled and site specific drug delivery and hence attracted wide attention of researchers. This review presents a broad treatment of targeted solid lipid nanoparticles discussing their types such as antibody SLN, magnetic SLN, pH sensitive SLN and cationic SLN.

Recent advances in surface chemistry strategies for the fabrication of functional iron oxide based magnetic nanoparticles

The synthesis of superparamagnetic nanostructures, especially iron-oxide based nanoparticles (IONPs), with appropriate surface functional groups has been intensively researched for many high-technological applications, including high density data storage, biosensing and biomedicine. In medicine, IONPs are nowadays widely used as contrast agents for magnetic resonance imaging (MRI), in hyperthermia therapy, but are also exploited for drug and gene delivery, detoxification of biological fluids or immunoassays, as they are relatively non-toxic. The use of magnetic particles in vivo requires IONPs to have high magnetization values, diameters below 100 nm with overall narrow size distribution and long time stability in biological fluids. Due to the high surface energies of IONPs agglomeration over time is often encountered. It is thus of prime importance to modify their surface to prevent aggregation and to limit non-specific adsorption of biomolecules onto their surface. Such chemical modifications result in IONPs being well-dispersed and biocompatible, and allow for targeted delivery and specific interactions. The chemical nature of IONPs thus determines not only the overall size of the colloid, but also plays a significant role for in vivo and in vitro applications. This review discusses the different concepts currently used for the surface functionalization and coating of iron oxide nanoparticles. The diverse strategies for the covalent linking of drugs, proteins, enzymes, antibodies, and nucleotides will be discussed and the chemically relevant steps will be explained in detail.

Nanoparticle-based vaccine delivery for cancer immunotherapy

Development of nano-sized carriers including nanoparticles, nanoemulsions or liposomes holds great potential for advanced delivery systems for cancer immunotherapy, as such nanostructures can be used to more effectively manipulate or deliver immunologically active components to specific target sites. Successful development of nanotechnology based platform in the field of immunotherapy will allow the application of vaccines, adjuvants and immunomodulatory drugs that improve clinical outcomes for immunological diseases. Here, we review current nanoparticle-based platforms in the efficacious delivery of vaccines in cancer immunotherapy.