Influence of particle size, an elongated particle geometry, and adjuvants on dendritic cell activation

Impact of Protein Nanoparticle Shape on the Immunogenicity of Antimicrobial Glycoconjugate Vaccines

Protein self-assembling nanoparticles (NPs) can be used as carriers for antigen delivery to increase vaccine immunogenicity. NPs mimic the majority of invading pathogens, inducing a robust adaptive immune response and long-lasting protective immunity. In this context, we investigated the potential of NPs of different sizes and shapes-ring-, rod-like, and spherical particles-as carriers for bacterial oligosaccharides by evaluating in murine models the role of these parameters on the immune response. Oligosaccharides from Neisseria meningitidis type W capsular polysaccharide were conjugated to ring-shape or nanotubes of engineered Pseudomonas aeruginosa Hemolysin-corregulated protein 1 (Hcp1cc) and to spherical Helicobacter pylori ferritin. Glycoconjugated NPs were characterized using advanced technologies such as High-Performance Liquid Chromatography (HPLC), Asymmetric Flow-Field Flow fractionation (AF4), and Transmission electron microscopy (TEM) to verify their correct assembly, dimensions, and glycosylation degrees. Our results showed that spherical ferritin was able to induce the highest immune response in mice against the saccharide antigen compared to the other glycoconjugate NPs, with increased bactericidal activity compared to benchmark MenW-CRM197. We conclude that shape is a key attribute over size to be considered for glycoconjugate vaccine development.

Multivariate Analysis of Cellular Uptake Characteristics for a (Co)polymer Particle Library

Controlling cellular responses to nanoparticles so far is predominantly empirical, typically requiring multiple rounds of optimization of particulate carriers. In this study, a systematic model-assisted approach should lead to the identification of key parameters that account for particle properties and their cellular recognition. A copolymer particle library was synthesized by a combinatorial approach in soap free emulsion copolymerization of styrene and methyl methacrylate, leading to a broad compositional as well as constitutional spectrum. The proposed structure-property relationships could be elucidated by multivariate analysis of the obtained experimental data, including physicochemical characteristics such as molar composition, molecular weight, particle diameter, and particle charge as well as the cellular uptake pattern of nanoparticles. It was found that the main contributors for particle size were the polymers' molecular weight and the zeta potential, while particle uptake is mainly directed by the particles' composition. This knowledge and the reported model-assisted procedure to identify relevant parameters affecting particle engulfment of particulate carriers by nonphagocytic and phagocytic cells can be of high relevance for the rational design of pharmaceutical nanocarriers and assessment of biodistribution and nanotoxicity, respectively.

Harnessing biomaterial architecture to drive anticancer innate immunity

Immunomodulation is a powerful therapeutic approach that harnesses the body's own immune system and reprograms it to treat diseases, such as cancer. Innate immunity is key in mobilizing the rest of the immune system to respond to disease and is thus an attractive target for immunomodulation. Biomaterials have widely been employed as vehicles to deliver immunomodulatory therapeutic cargo to immune cells and raise robust antitumor immunity. However, it is key to consider the design of biomaterial chemical and physical structure, as it has direct impacts on innate immune activation and antigen presentation to stimulate downstream adaptive immunity. Herein, we highlight the widespread importance of structure-driven biomaterial design for the delivery of immunomodulatory cargo to innate immune cells. The incorporation of precise structural elements can be harnessed to improve delivery kinetics, uptake, and the targeting of biomaterials into innate immune cells, and enhance immune activation against cancer through temporal and spatial processing of cargo to overcome the immunosuppressive tumor microenvironment. Structural design of immunomodulatory biomaterials will profoundly improve the efficacy of current cancer immunotherapies by maximizing the impact of the innate immune system and thus has far-reaching translational potential against other diseases.

Environmentally weathered polystyrene particles induce phenotypical and functional maturation of human monocyte-derived dendritic cells

Micro- and nanoplastics (MNP) are ubiquitously present in the environment due to their high persistence and bioaccumulative properties. Humans get exposed to MNP via various routes and consequently, they will encounter dendritic cells (DC) which are antigen-presenting cells involved in regulating immune responses. The consequences of DC exposure to MNP are an important, yet understudied, cause of concern. Therefore, this study aimed to assess the uptake and effect of MNP in vitro by exposing human monocyte-derived dendritic cells (MoDC) to virgin and environmentally weathered polystyrene (PS) particles of different sizes (0.2, 1, and 10 µm), at different concentrations ranging from 1 to 100 µg/ml. The effects of these particles were examined by measuring co-stimulatory surface marker (i.e. CD83 and CD86) expression. In addition, T-cell proliferation was measured via a mixed-leukocyte reaction (MLR) assay. The results showed that MoDC were capable of absorbing PS particles, and this was facilitated by pre-incubation in heat-inactivated (HI) plasma. Furthermore, depending on their size, weathered PS particles in particular caused increased expression of CD83 and CD86 on MoDC. Lastly, weathered 0.2 µm PS particles were able to functionally activate MoDC, leading to an increase in T-cell activation. These in vitro data suggest that, depending on their size, weathered PS particles might act as an immunostimulating adjuvant, possibly leading to T-cell sensitization.

Development of multistage recombinant protein vaccine formulations against toxoplasmosis using a new chitosan and porin based adjuvant system

Toxoplasmosis is a global health problem affecting both human and animal populations. The lack of effective treatment makes the development of a vaccine against toxoplasmosis one of the main goals in the management of this disease. In our study, vaccine formulations containing the multistage recombinant antigens, rBAG1 + rGRA1 were developed with a combined adjuvant system consisting of chitosan and Salmonella Typhi porins in micro (MicroAS) and nanoparticulate (NanoAS) forms. BALB/c mice were immunized intraperitoneally with vaccine formulations two times at three-week intervals. Three weeks after the second vaccination, mice were challenged with 7-8 live tissue cysts of the virulent T. gondii PRU strain by oral gavage. Higher cellular uptake by macrophages and enhanced cellular (IFN-γ and I-4 in stimulated spleen cells) and humoral (IgG, IgG1, IgG2a) responses were obtained with the adjuvanted formulation, higher with microsystem when compared to that of nanosystem. Microsystem was found to stimulate Th1-polarized immune responses, whereasnon-adjuvanted antigens stimulated Th2-polarized immune response. The highest survival rate and reduction in cysts numbers and T. gondii DNA were obtained with the adjuvanted antigens.Our study showed that adjuvanted multistage recombinant vaccine systems increase theimmune response with strong protection againstT. gondii, more profoundly in microparticulate form.

Advances in design and applications of polymer brush modified anisotropic particles

Current advancements in the creation of anisotropy in particles and their surface modification with polymer brushes have established a new class of hybrid materials termed polymer brush modified anisotropic particles (PBMAP). PBMAPs display unique property combinations, e.g., multi-functionality in multiple directions along with smart behavior, which is not easily achievable in traditional hybrid materials. Typically, anisotropic particles can be categorized based on three different factors, such as shape anisotropy (geometry driven), compositional anisotropy (functionality driven), and surface anisotropy (spatio-selective surface modification driven). In this review, we have particularly focused on the synthetic strategies to construct the various type of PBMAPs based on inorganic or organic core which may or may not be isotropic in nature, and their applications in various fields ranging from drug delivery to catalysis. In addition, superior performances and fascinating properties of PBMAPs over their isotropic analogues are also highlighted. A brief overview of their future developments and associated challenges have been discussed at the end.

Polymeric particle-based therapies for acute inflammatory diseases

Acute inflammation is essential for initiating and coordinating the body's response to injuries and infections. However, in acute inflammatory diseases, inflammation is not resolved but propagates further, which can ultimately lead to tissue damage such as in sepsis, acute respiratory distress syndrome and deep vein thrombosis. Currently, clinical protocols are limited to systemic steroidal treatments, fluids and antibiotics that focus on eradicating inflammation rather than modulating it. Strategies based on stem cell therapeutics and selective blocking of inflammatory molecules, despite showing great promise, still lack the scalability and specificity required to treat acute inflammation. By contrast, polymeric particle systems benefit from uniform manufacturing at large scales while preserving biocompatibility and versatility, thus providing an ideal platform for immune modulation. Here, we outline design aspects of polymeric particles including material, size, shape, deformability and surface modifications, providing a strategy for optimizing the targeting of acute inflammation.

Mesoporous Silica Nanoparticles as Carriers for Biomolecules in Cancer Therapy

Mesoporous silica nanoparticles (MSNs) offer many advantageous properties for applications in the field of nanobiotechnology. Loading of small molecules into MSNs is straightforward and widely applied, but with the upswing of both research and commercial interest in biological drugs in recent years, also biomacromolecules have been loaded into MSNs for delivery purposes. MSNs possess many critical properties making them a promising and versatile carrier for biomacromolecular delivery. In this chapter, we review the effects of the various structural parameters of MSNs on the effective loading of biomacromolecular therapeutics, with focus on maintaining stability and drug delivery performance. We also emphasize recent studies involving the use of MSNs in the delivery of biomacromolecular drugs, especially for cancer treatment.

Development and in vitro evaluation of a new adjuvant system containing Salmonella Typhi porins and chitosan

In order to improve the immunogenicity of the highly purified vaccine antigens, addition of an adjuvant to formulation, without affecting the safety of the vaccine, has been the key aim of the vaccine formulators. In recent years, adjuvants which are composed of a delivery system and immunopotentiators have been preferred to induce potent immune responses. In this study, we have combined Salmonella Typhi porins and chitosan to develop a new adjuvant system to enhance the immunogenicity of the highly purified antigens. Cationic gels, microparticle (1.69 ± 0.01 μm) and nanoparticles (337.7 ± 1.7 nm) based on chitosan were prepared with high loading efficiency of porins. Cellular uptake was examined by confocal laser scanning microscopy, and the macrophage activation was investigated by measuring the surface marker as well as the cytokine release in vitro in J774A.1 macrophage murine cells. Porins alone were not taken up by the macrophage cells whereas in combination with chitosan a significant uptake was obtained. Porins-chitosan combination systems were found to induce CD80, CD86 and MHC-II expressions at different levels by different formulations depending on the particle size. Similarly, TNF-α and IL-6 levels were found to increase with porins-chitosan combination. Our results demonstrated that combination of porins with chitosan as a particulate system exerts enhanced adjuvant effect, suggesting a promising adjuvant system for subunit vaccines with combined immunostimulating activity.

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.

Nonspherical Nanoparticle Shape Stability Is Affected by Complex Manufacturing Aspects: Its Implications for Drug Delivery and Targeting

The shape of nanoparticles is known recently as an important design parameter influencing considerably the fate of nanoparticles with and in biological systems. Several manufacturing techniques to generate nonspherical nanoparticles as well as studies on in vitro and in vivo effects thereof have been described. However, nonspherical nanoparticle shape stability in physiological-related conditions and the impact of formulation parameters on nonspherical nanoparticle resistance still need to be investigated. To address these issues, different nanoparticle fabrication methods using biodegradable polymers are explored to produce nonspherical nanoparticles via the prevailing film-stretching method. In addition, systematic comparisons to other nanoparticle systems prepared by different manufacturing techniques and less biodegradable materials (but still commonly utilized for drug delivery and targeting) are conducted. The study evinces that the strong interplay from multiple nanoparticle properties (i.e., internal structure, Young's modulus, surface roughness, liquefaction temperature [glass transition (T_g ) or melting (T_m )], porosity, and surface hydrophobicity) is present. It is not possible to predict the nonsphericity longevity by merely one or two factor(s). The most influential features in preserving the nonsphericity of nanoparticles are existence of internal structure and low surface hydrophobicity (i.e., surface-free energy (SFE) > ≈55 mN m^-1 , material-water interfacial tension <6 mN m^-1 ), especially if the nanoparticles are soft (<1 GPa), rough (R_rms > 10 nm), porous (>1 m² g^-1 ), and in possession of low bulk liquefaction temperature (<100 °C). Interestingly, low surface hydrophobicity of nanoparticles can be obtained indirectly by the significant presence of residual stabilizers. Therefore, it is strongly suggested that nonsphericity of particle systems is highly dependent on surface chemistry but cannot be appraised separately from other factors. These results and reviews allot valuable guidelines for the design and manufacturing of nonspherical nanoparticles having adequate shape stability, thereby appropriate with their usage purposes. Furthermore, they can assist in understanding and explaining the possible mechanisms of nonspherical nanoparticles effectivity loss and distinctive material behavior at the nanoscale.

Phagocytosis of spherical and ellipsoidal micronetwork colloids from crosslinked poly(ε-caprolactone)

The effect of non-spherical particle shapes on cellular uptake has been reported as a general design parameter to control cellular recognition of particulate drug carriers. Beside shape, also size and cell-particle ratio should mutually effect phagocytosis. Here, the capability to control cellular uptake of poly(ɛ-caprolactone) (PCL) based polymer micronetwork colloids (MNC), a carrier system that can be transferred to various shapes, is explored in vitro at test conditions allowing multiple cell-particle contacts. PCL-based MNC were synthesized as spheres with a diameter of ∼6, ∼10, and 13 µm, loaded with a fluorescent dye by a specific technique of swelling, re-dispersion and drying, and transferred into different ellipsoidal shapes by a phantom stretching method. The boundaries of MNC deformability to prolate ellipsoid target shapes were systematically analyzed and found to be at an aspect ratio AR of ∼4 as obtained by a phantom elongation ε_ph of ∼150%. Uptake studies with a murine macrophages cell line showed shape dependency of phagocytosis for selected conditions when varying particle sizes (∼6 and 10 μm),and shapes (ε_ph: 0, 75 or 150%), cell-particle ratios (1:1, 1:2, 1:10, 1:50), and time points (1-24 h). For larger-sized MNC, there was no significant shape effect on phagocytosis as these particles may associate with more than one cell, thus increasing the possibility of phagocytosis by any of these cells. Accordingly, controlling shape effects on phagocytosis for carriers made from degradable polymers relevant for medical applications requires considering further parameters besides shape, such as kinetic aspects of the exposure and uptake by cells.

Aspherical and Spherical InvA497-Functionalized Nanocarriers for Intracellular Delivery of Anti-Infective Agents

Purpose

The objective of this work was to evaluate the potential of polymeric spherical and aspherical invasive nanocarriers, loaded with antibiotic, to access and treat intracellular bacterial infections.

Methods

Aspherical nanocarriers were prepared by stretching of spherical precursors, and both aspherical and spherical nanocarriers were surface-functionalized with the invasive protein InvA497. The relative uptake of nanocarriers into HEp-2 epithelial cells was then assessed. Nanocarriers were subsequently loaded with a preparation of the non-permeable antibiotic gentamicin, and tested for their ability to treat HEp-2 cells infected with the enteroinvasive bacterium Shigella flexneri.

Results

InvA497-functionalized nanocarriers of both spherical and aspherical shape showed a significantly improved rate and extent of uptake into HEp-2 cells in comparison to non-functionalized nanocarriers. Functionalized and antibiotic-loaded nanocarriers demonstrated a dose dependent killing of intracellular S. flexneri. A slight but significant enhancement of intracellular bacterial killing was also observed with aspherical as compared to spherical functionalized nanocarriers at the highest tested concentration.

Conclusions

InvA497-functionalized, polymer-based nanocarriers were able to efficiently deliver a non-permeable antibiotic across host cell membranes to affect killing of intracellular bacteria. Functionalized nanocarriers with an aspherical shape showed an interesting future potential for intracellular infection therapy.

Electronic supplementary material

The online version of this article (10.1007/s11095-018-2521-3) contains supplementary material, which is available to authorized users.

Raw starch microparticles have immunostimulant activity in mice vaccinated with BCG and challenged with Mycobacterium tuberculosis

The main challenge for vaccine development or improvement is the lack of safe adjuvants or immunostimulants that induce protective immune responses and can be used for mucosal immunization, which is a highly desirable strategy for vaccination against infectious diseases acquired by oral or intranasal routes. One promising alternative is the use of biodegradable and biocompatible polymeric microparticles. Recently, we developed an immobilization and delivery system with starch microparticles (SMPs) and a starch-binding domain (SBD_tag) suitable for the mucosal administration of antigens and the induction of antigen-specific immune responses. Here, we explore the immunostimulant and reinforcing potential of the system using BALB/c mice with progressive pulmonary tuberculosis (PPT). The heat shock protein alpha-crystallin from Mycobacterium tuberculosis immobilized on SMPs (µAcr-SBD_tag) or SMPs alone were administered nasally as boosters to BCG-vaccinated mice without any extra adjuvant. The mice were challenged intratracheally with either moderately virulent or highly virulent M. tuberculosis strains. Our results showed that the administration of either the immobilized antigen or SMPs asa booster for the BCG vaccination induced a significant reduction of bacterial loads in the lungs of mice, even more than in mice that received the BCG vaccination alone. Since no difference was observed in pulmonary bacillary burdens between the two reinforced groups, the obtained effect was most likely primarily caused by the starch. As determined by histological study, the administration of boosters did not contribute to the progress of pneumonia, which diminishes the safety concerns related to the administration of SMPs intranasally. Taken together, our findings suggest that this system may be considered asa new carbohydrate-based adjuvant suitable for mucosal vaccines against tuberculosis and other infectious diseases, and more generally, they highlight the potential of particulate α-glucans as immune response modifiers.

Role for Mechanotransduction in Macrophage and Dendritic Cell Immunobiology

Tissue homeostasis is not only controlled by biochemical signals but also through mechanical forces that act on cells. Yet, while it has long been known that biochemical signals have profound effects on cell biology, the importance of mechanical forces has only been recognized much more recently. The types of mechanical stress that cells experience include stretch, compression, and shear stress, which are mainly induced by the extracellular matrix, cell-cell contacts, and fluid flow. Importantly, macroscale tissue deformation through stretch or compression also affects cellular function.Immune cells such as macrophages and dendritic cells are present in almost all peripheral tissues, and monocytes populate the vasculature throughout the body. These cells are unique in the sense that they are subject to a large variety of different mechanical environments, and it is therefore not surprising that key immune effector functions are altered by mechanical stimuli. In this chapter, we describe the different types of mechanical signals that cells encounter within the body and review the current knowledge on the role of mechanical signals in regulating macrophage, monocyte, and dendritic cell function.

Effect of Biophysical Properties of Phosphatidylserine Particle on Immune Tolerance Induction Toward Factor VIII in a Hemophilia A Mouse Model

A major complication in the replacement therapy of Factor VIII (FVIII) for Hemophilia A is the development of unwanted immune responses. Previous studies from our laboratory have shown that pretreatment of FVIII in the presence of phosphatidylserine (PS) resulted in hyporesponsiveness to subsequent administration of FVIII alone, due to the ability of PS to convert an immunogen to a tolerogen. We investigated the importance of biophysical properties of PS liposomes on its ability to convert an immunogen to a tolerogen. PS particles were prepared differing in size, protein-lipid topology, lamellarity, and % association to FVIII keeping the composition of the particle same. PS particles were prepared in 2 different sizes with differing biophysical properties: smaller particles in the nanometer range (200 nm) and larger size particles in the micron range (2 μm). Hemophilia A animals treated with both the nanometer and micron size PS particles showed a significant reduction in anti-FVIII antibody titers when compared to animals receiving free FVIII alone. Upon rechallenge with free FVIII animals that received FVIII along with the nanometer size particle continued to show reduced antibody responses. Animals receiving the micron size particle showed a slight increase in titers although they remained significantly lower than the free FVIII treated group. Upon culture with bone marrow derived dendritic cells, the nanometer size particle showed a reduction in CD40 expression and an increase in transforming growth factor-β cytokine production, which was not observed with the micron size particle. These results show that biophysical properties of PS play an important role in tolerance.

Orchestrating immune responses: How size, shape and rigidity affect the immunogenicity of particulate vaccines

Particulate carrier systems are promising drug delivery vehicles for subunit vaccination as they can enhance and direct the type of T cell response. In order to develop vaccines with optimal immunogenicity, a thorough understanding of parameters that could affect the strength and quality of immune responses is required. Pathogens have different dimensions and stimulate the immune system in a specific way. It is therefore not surprising that physicochemical characteristics of particulate vaccines, such as particle size, shape, and rigidity, affect multiple processes that impact their immunogenicity. Among these processes are the uptake of the particles from the site of administration, passage through lymphoid tissue and the uptake, antigen processing and activation of antigen-presenting cells. Herein, we systematically review the role of the size, shape and rigidity of particulate vaccines in enhancing and skewing T cell response and attempted to provide a "roadmap" for rational vaccine design.