Methods for Analysis of Nanoparticle Immunosuppressive Properties.

Adverse drug effects on immune system function represent a significant concern in the pharmaceutical industry, because 10-20% of drug withdrawal from the market is attributed to immunotoxicity. Immunosuppression is one such adverse effect. The traditional immune function test used to estimate materials' immunosuppression is T cell dependent antibody response (TDAR). This method involves a 28-day in vivo study evaluating the animal's antibody titer to a known antigen (Keyhole Limpet Hemocyanin; KLH) with and without challenge. Due to the limited quantities of novel drug candidates, an in vitro method called human lymphocyte activation (HuLA) assay has been developed to substitute the traditional TDAR assay during early preclinical development. In this test, leukocytes isolated from healthy donors vaccinated with the current year's flu vaccine are incubated with Fluzone in the presence or absence of nanoparticles. The antigen-specific lymphocyte proliferation is then measured by ELISA analyzing incorporation of BrdU into DNA of the proliferating cells. Here we describe the experimental procedures for investigating immunosuppressive properties of nanoparticles by both TDAR and HuLA assays, discuss the in vitro-in vivo correlation of these methods, and show a case study using the iron oxide nanoparticle formulation, Feraheme.

Understanding the Role of Scavenger Receptor A1 in Nanoparticle Uptake by Murine Macrophages.

Nanoparticles can be cleared from the circulation and taken up by tissue-resident macrophages. This property can be beneficial when drug or antigen delivery to macrophages is desired; however, rapid clearance of nanoparticles not intended for delivery to immune cells may reduce nanoparticle circulation time and affect the efficacy of nanoparticle-formulated drug products. Therefore, understanding nanoparticles' uptake by macrophages is an essential step in the preclinical development of nanotechnology-based drug products. Understanding the route of nanoparticle uptake by macrophages may also provide mechanistic insights into the immunotoxicity of nanomaterials. The protocol described herein can be used to assess the nanoparticles' uptake by macrophages and understand the involvement of scavenger receptor A1 to inform mechanistic studies.

Analysis of Nanoparticle Adjuvant Properties.

Nanoparticles can be engineered for targeted antigen delivery to immune cells and for stimulating an immune response to improve the antigen immunogenicity. This approach is commonly used to develop nanotechnology-based vaccines. In addition, some nanotechnology platforms may be initially designed for drug delivery, but in the course of subsequent characterization, additional immunomodulatory functions may be discovered that can potentially benefit vaccine efficacy. In both of these scenarios, an in vivo proof of concept study to verify the utility of the nanocarrier for improving vaccine efficacy is needed. Here we describe an experimental approach and considerations for designing an animal study to test adjuvant properties of engineered nanomaterials in vivo.

Immunostimulation of Fibrous Nucleic Acid Nanoparticles Can be Modulated through Aptamer-Based Functional Moieties: Unveiling the Structure-Activity Relationship and Mechanistic Insights.

Fibrous nanomaterials containing silica, titanium oxide, and carbon nanotubes are notoriously known for their undesirable inflammatory responses and associated toxicities that have been extensively studied in the environmental and occupational toxicology fields. Biopersistance and inflammation of "hard" nanofibers prevent their broader biomedical applications. To utilize the structural benefits of fibrous nanomaterials for functionalization with moieties of therapeutic significance while preventing undesirable immune responses, researchers employ natural biopolymers─RNA and DNA─to design "soft" and biodegradable nanomaterials with controlled immunorecognition. Nucleic acid nanofibers have been shown to be safe and efficacious in applications that do not require their delivery into the cells such as the regulation of blood coagulation. Previous studies demonstrated that unlike traditional therapeutic nucleic acids (e.g., CpG DNA oligonucleotides) nucleic acid nanoparticles (NANPs), when used without a carrier, are not internalized by the immune cells and, as such, do not induce undesirable cytokine responses. In contrast, intracellular delivery of NANPs results in cytokine responses that are dependent on the physicochemical properties of these nanomaterials. However, the structure-activity relationship of innate immune responses to intracellularly delivered fibrous NANPs is poorly understood. Herein, we employ the intracellular delivery of model RNA/DNA nanofibers functionalized with G-quadruplex-based DNA aptamers to investigate how their structural properties influence cytokine responses. We demonstrate that nanofibers' scaffolds delivered to the immune cells using lipofectamine induce interferon response via the cGAS-STING signaling pathway activation and that DNA aptamers incorporation shields the fibers from recognition by cGAS and results in a lower interferon response. This structure-activity relationship study expands the current knowledge base to inform future practical applications of intracellularly delivered NANPs as vaccine adjuvants and immunotherapies.

Detection of Nanoparticles' Ability to Stimulate Toll-Like Receptors Using HEK-Blue Reporter Cell Lines.

Nanoparticles can be used to formulate Toll-like receptor (TLR) agonists as vaccine and immunotherapy adjuvants or contain undesirable contaminants (e.g., endotoxin, CpG DNA, flagellin) with TLR-agonist activity. In both scenarios, the activation of the innate immune pattern recognition receptor leads to the inflammatory response that can be beneficial as in the case with vaccines and immunotherapies or adverse as in the case with contaminants. The protocol described herein utilizes commercially available reporter cell lines expressing individual TLRs, which, upon activation with their cognate agonists, stimulate the cells to produce secreted alkaline phosphatase detectable using a plate reader.

Multicolor flow cytometry-based immunophenotyping for preclinical characterization of nanotechnology-based formulations: an insight into structure activity relationship and nanoparticle biocompatibility profiles.

Introduction: Immunophenotyping, which is the identification of immune cell subsets based on antigen expression, is an integral technique used to determine changes of cell composition and activation in various disease states or as a response to different stimuli. As nanoparticles are increasingly utilized for diagnostic and therapeutic applications, it is important to develop methodology that allows for the evaluation of their immunological impact. Therefore, the development of techniques such as immunophenotyping are desirable. Currently, the most common technique used to perform immunophenotyping is multicolor flow cytometry. Methods: We developed two distinct multicolor flow cytometry immunophenotyping panels which allow for the evaluation of the effects of nanoparticles on the composition and activation status of treated human peripheral blood mononuclear cells. These two panels assess the presence of various lymphoid and myeloid-derived cell populations as well as aspects of their activation statuses-including proliferation, adhesion, co-stimulation/presentation, and early activation-after treatment with controls or nanoparticles. To conduct assay performance qualification and determine the applicability of this method to preclinical characterization of nanoparticles, we used clinical-grade nanoformulations (AmBisome, Doxil and Feraheme) and research-grade PAMAM dendrimers of different sizes (G3, G4 and G5) and surface functionalities (amine-, carboxy- and hydroxy-). Results and Discussion: We found that formulations possessing intrinsic fluorescent properties (e.g., Doxil and AmBisome) interfere with accurate immunophenotyping; such interference may be partially overcome by dilution. In the absence of interference (e.g., in the case of dendrimers), nanoparticle size and surface functionalities determine their effects on the cells with large amine-terminated dendrimers being the most reactive.

Nanocomplexes of doxorubicin and DNA fragments for efficient and safe cancer chemotherapy.

Cancer-targeted therapy by a chemotherapeutic agent formulated in a nanoscale platform has been challenged by complex and inefficient manufacturing, low drug loading, difficult characterization, and marginally improved therapeutic efficacy. This study investigated facile-to-produce nanocomplexes of doxorubicin (DOX), a widely used cancer drug, and clinically approved DNA fragments that are extracted from a natural source. DOX was found to self-assemble DNA fragments into relatively monodispersed nanocomplexes with a diameter of ∼70 nm at 14.3% (w/w) drug loading by simple and scalable mixing. The resulting DOX/DNA nanocomplexes showed sustained DOX release, unlike overly stable Doxil®, cellular uptake via multiple endocytosis pathways, and high hematological and immunological compatibility. DOX/DNA nanocomplexes eradicated EL4 T lymphoma cells in a time-dependent manner, eventually surpassing free DOX. Extended circulation of DOX/DNA nanocomplexes, while avoiding off-target accumulation in the lung and being cleared from the liver, resulted in rapid accumulation in tumor and lowered cardio toxicity. Finally, tumor growth of EL4-challenged C57BL/6 mice (syngeneic model) and OPM2-challenged NSG mice (human xenograft model) were efficiently inhibited by DOX/DNA nanocomplexes with enhanced overall survival, in comparison with free DOX and Doxil®, especially upon repeated administrations. DOX/DNA nanocomplexes are a promising chemotherapeutics delivery platform for their ease of manufacturing, high biocompatibility, desired drug release and accumulation, efficient tumor eradication with improved safety, and further engineering versatility for extended therapeutic applications.

Innate Immune Stimulation Using 3D Wireframe DNA Origami.

Three-dimensional wireframe DNA origami have programmable structural and sequence features that render them potentially suitable for prophylactic and therapeutic applications. However, their innate immunological properties, which stem from parameters including geometric shape and cytosine-phosphate-guanine dinucleotide (CpG) content, remain largely unknown. Here, we investigate the immunostimulatory properties of 3D wireframe DNA origami on the TLR9 pathway using both reporter cell lines and primary immune cells. Our results suggest that bare 3D polyhedral wireframe DNA origami induce minimal TLR9 activation despite the presence of numerous internal CpG dinucleotides. However, when displaying multivalent CpG-containing ssDNA oligos, wireframe DNA origami induce robust TLR9 pathway activation, along with enhancement of downstream immune response as evidenced by increases in Type I and Type III interferon (IFN) production in peripheral blood mononuclear cells. Further, we find that CpG copy number and spatial organization each contribute to the magnitude of TLR9 signaling and that NANP-attached CpGs do not require phosphorothioate stabilization to elicit signaling. These results suggest key design parameters for wireframe DNA origami that can be programmed to modulate immune pathway activation controllably for prophylactic and therapeutic applications.

Locking and Unlocking Thrombin Function Using Immunoquiescent Nucleic Acid Nanoparticles with Regulated Retention In Vivo.

The unbalanced coagulation of blood is a life-threatening event that requires accurate and timely treatment. We introduce a user-friendly biomolecular platform based on modular RNA-DNA anticoagulant fibers programmed for reversible extracellular communication with thrombin and subsequent control of anticoagulation via a "kill-switch" mechanism that restores hemostasis. To demonstrate the potential of this reconfigurable technology, we designed and tested a set of anticoagulant fibers that carry different thrombin-binding aptamers. All fibers are immunoquiescent, as confirmed in freshly collected human peripheral blood mononuclear cells. To assess interindividual variability, the anticoagulation is confirmed in the blood of human donors from the U.S. and Brazil. The anticoagulant fibers reveal superior anticoagulant activity and prolonged renal clearance in vivo in comparison to free aptamers. Finally, we confirm the efficacy of the "kill-switch" mechanism in vivo in murine and porcine models.

Anhydrous Nucleic Acid Nanoparticles for Storage and Handling at Broad Range of Temperatures.

Recent advances in nanotechnology now allow for the methodical implementation of therapeutic nucleic acids (TNAs) into modular nucleic acid nanoparticles (NANPs) with tunable physicochemical properties which can match the desired biological effects, provide uniformity, and regulate the delivery of multiple TNAs for combinatorial therapy. Despite the potential of novel NANPs, the maintenance of their structural integrity during storage and shipping remains a vital issue that impedes their broader applications. Cold chain storage is required to maintain the potency of NANPs in the liquid phase, which greatly increases transportation costs. To promote long-term storage and retention of biological activities at higher temperatures (e.g., +50 °C), a panel of representative NANPs is first exposed to three different drying mechanisms-vacuum concentration (SpeedVac), lyophilization (Lyo), and light-assisted drying (LAD)-and then rehydrated and analyzed. While SpeedVac primarily operates using heat, Lyo avoids temperature increases by taking advantage of pressure reduction and LAD involves a near-infrared laser for uniform drying in the presence of trehalose. This work compares and defines refinements crucial in formulating an optimal strategy for producing stable, fully functional NANPs and presents a forward advancement in their development for clinical applications.

Expanding Structural Space for Immunomodulatory Nucleic Acid Nanoparticles (Nanps) via Spatial Arrangement of Their Therapeutic Moieties.

Different therapeutic nucleic acids (TNAs) can be unified in a single structure by their elongation with short oligonucleotides designed to self-assemble into nucleic acid nanoparticles (NANPs). With this approach, therapeutic cocktails with precisely controlled composition and stoichiometry of active ingredients can be delivered to the same diseased cells for enhancing pharmaceutical action. In this work, an additional nanotechnology-based therapeutic option that enlists a biocompatible NANP-encoded platform for their controlled patient-specific immunorecognition is explored. For this, a set of representative functional NANPs is extensively characterized in vitro, ex vivo, and in vivo and then further analyzed for immunostimulation of human peripheral blood mononuclear cells freshly collected from healthy donor volunteers. The results of the study present the advancement of the current TNA approach toward personalized medicine and offer a new strategy to potentially address top public health challenges related to drug overdose and safety through the biodegradable nature of the functional platform with immunostimulatory regulation.

An In Vitro Assessment of Immunostimulatory Responses to Ten Model Innate Immune Response Modulating Impurities (IIRMIs) and Peptide Drug Product, Teriparatide.

Understanding, predicting, and minimizing the immunogenicity of peptide-based therapeutics are of paramount importance for ensuring the safety and efficacy of these products. The so-called anti-drug antibodies (ADA) may have various clinical consequences, including but not limited to the alteration in the product's distribution, biological activity, and clearance profiles. The immunogenicity of biotherapeutics can be influenced by immunostimulation triggered by the presence of innate immune response modulating impurities (IIRMIs) inadvertently introduced during the manufacturing process. Herein, we evaluate the applicability of several in vitro assays (i.e., complement activation, leukocyte proliferation, and cytokine secretion) for the screening of innate immune responses induced by ten common IIRMIs (Bacillus subtilis flagellin, FSL-1, zymosan, ODN2006, poly(I:C) HMW, poly(I:C) LMW, CLO75, MDP, ODN2216, and Escherichia coli O111:B4 LPS), and a model biotherapeutic Forteo™ (teriparatide). Our study identifies cytokine secretion from healthy human donor peripheral blood mononuclear cells (PBMC) as a sensitive method for the in vitro monitoring of innate immune responses to individual IIRMIs and teriparatide (TP). We identify signature cytokines, evaluate both broad and narrow multiplex cytokine panels, and discuss how the assay logistics influence the performance of this in vitro assay.

Mini-Factor H Modulates Complement-Dependent IL-6 and IL-10 Release in an Immune Cell Culture (PBMC) Model: Potential Benefits Against Cytokine Storm.

Cytokine storm (CS), an excessive release of proinflammatory cytokines upon overactivation of the innate immune system, came recently to the focus of interest because of its role in the life-threatening consequences of certain immune therapies and viral diseases, including CAR-T cell therapy and Covid-19. Because complement activation with subsequent anaphylatoxin release is in the core of innate immune stimulation, studying the relationship between complement activation and cytokine release in an in vitro CS model holds promise to better understand CS and identify new therapies against it. We used peripheral blood mononuclear cells (PBMCs) cultured in the presence of autologous serum to test the impact of complement activation and inhibition on cytokine release, testing the effects of liposomal amphotericin B (AmBisome), zymosan and bacterial lipopolysaccharide (LPS) as immune activators and heat inactivation of serum, EDTA and mini-factor H (mfH) as complement inhibitors. These activators induced significant rises of complement activation markers C3a, C4a, C5a, Ba, Bb, and sC5b-9 at 45 min of incubation, with or without ~5- to ~2,000-fold rises of IL-1α, IL-1ß, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12, IL-13 and TNFα at 6 and 18 h later. Inhibition of complement activation by the mentioned three methods had differential inhibition, or even stimulation of certain cytokines, among which effects a limited suppressive effect of mfH on IL-6 secretion and significant stimulation of IL-10 implies anti-CS and anti-inflammatory impacts. These findings suggest the utility of the model for in vitro studies on CS, and the potential clinical use of mfH against CS.

Induction of Cytokines by Nucleic Acid Nanoparticles (NANPs) Depends on the Type of Delivery Carrier.

Recent insights into the immunostimulatory properties of nucleic acid nanoparticles (NANPs) have demonstrated that variations in the shape, size, and composition lead to distinct patterns in their immunostimulatory properties. While most of these studies have used a single lipid-based carrier to allow for NANPs' intracellular delivery, it is now apparent that the platform for delivery, which has historically been a hurdle for therapeutic nucleic acids, is an additional means to tailoring NANP immunorecognition. Here, the use of dendrimers for the delivery of NANPs is compared to the lipid-based platform and the differences in resulting cytokine induction are presented.

Application of a Scavenger Receptor A1-Targeted Polymeric Prodrug Platform for Lymphatic Drug Delivery in HIV.

We have developed a macromolecular prodrug platform based on poly(l-lysine succinylated) (PLS) that targets scavenger receptor A1 (SR-A1), a receptor expressed by myeloid and endothelial cells. We demonstrate the selective uptake of PLS by murine macrophage, RAW 264.7 cells, which was eliminated upon cotreatment with the SR-A inhibitor polyinosinic acid (poly I). Further, we observed no uptake of PLS in an SR-A1-deficient RAW 264.7 cell line, even after 24 h incubation. In mice, PLS distributed to lymphatic organs following i.v. injection, as observed by ex vivo fluorescent imaging, and accumulated in lymph nodes following both i.v. and i.d. administrations, based on immunohistochemical analysis with high-resolution microscopy. As a proof-of-concept, the HIV antiviral emtricitabine (FTC) was conjugated to the polymer's succinyl groups via ester bonds, with a drug loading of 14.2% (wt/wt). The prodrug (PLS-FTC) demonstrated controlled release properties in vitro with a release half-life of 15 h in human plasma and 29 h in esterase-inhibited plasma, indicating that drug release occurs through both enzymatic and nonenzymatic mechanisms. Upon incubation of PLS-FTC with human peripheral blood mononuclear cells (PBMCs), the released drug was converted to the active metabolite FTC triphosphate. In a pharmacokinetic study in rats, the prodrug achieved ∼7-19-fold higher concentrations in lymphatic tissues compared to those in FTC control, supporting lymphatic-targeted drug delivery. We believe that the SR-A1-targeted macromolecular PLS prodrug platform has extraordinary potential for the treatment of infectious diseases.

Detection of Beta-Glucan Contamination in Nanotechnology-Based Formulations.

Understanding the potential contamination of pharmaceutical products with innate immunity modulating impurities (IIMIs) is essential for establishing their safety profiles. IIMIs are a large family of molecules with diverse compositions and structures that contribute to the immune-mediated adverse effects (IMAE) of drug products. Pyrogenicity (the ability to induce fever) and activation of innate immune responses underlying both acute toxicities (e.g., anaphylactoid reactions or pseudoallergy, cytokine storm) and long-term effects (e.g., immunogenicity) are among the IMAE commonly related to IIMI contamination. Endotoxins of gram-negative bacteria are the best-studied IIMIs in that both methodologies for and pitfalls in their detection and quantification are well established. Additionally, regulatory guidance documents and research papers from laboratories worldwide are available on endotoxins. However, less information is currently known about other IIMIs. Herein, we focus on one such IIMI, namely, beta-glucans, and review literature and discuss the experience of the Nanotechnology Characterization Lab (NCL) with the detection of beta-glucans in nanotechnology-based drug products.

Erratum: Hong, E., et al. Toll-Like Receptor-Mediated Recognition of Nucleic Acid Nanoparticles (NANPs) in Human Primary Blood Cells. Molecules 2019, 24, 1094.

The Molecules Editorial Office wishes to make the following erratum to this paper [...].

Toll-Like Receptor-Mediated Recognition of Nucleic Acid Nanoparticles (NANPs) in Human Primary Blood Cells.

Infusion reactions (IRs) create a translational hurdle for many novel therapeutics, including those utilizing nanotechnology. Nucleic acid nanoparticles (NANPs) are a novel class of therapeutics prepared by rational design of relatively short oligonucleotides to self-assemble into various programmable geometric shapes. While cytokine storm, a common type of IR, has halted clinical development of several therapeutic oligonucleotides, NANP technologies hold tremendous potential to bring these reactions under control by tuning the particle's physicochemical properties to the desired type and magnitude of the immune response. Recently, we reported the very first comprehensive study of the structure⁻activity relationship between NANPs' shape, size, composition, and their immunorecognition in human cells, and identified the phagolysosomal pathway as the major route for the NANPs' uptake and subsequent immunostimulation. Here, we explore the molecular mechanism of NANPs' recognition by primary immune cells, and particularly the contributing role of the Toll-like receptors. Our current study expands the understanding of the immune recognition of engineered nucleic acid-based therapeutics and contributes to the improvement of the nanomedicine safety profile.

Chemical Modification of CRISPR gRNAs Eliminate type I Interferon Responses in Human Peripheral Blood Mononuclear Cells.

OBJECTIVES: CRISPR/Cas9 is currently the primary tool used for genome editing in mammalian cells. To cleave and alter genomic DNA, both the Cas9 nuclease and a guide RNA (gRNA) must be present in the nucleus. One preferred method of introducing these reagents is direct transfection of a recombinant Cas9 protein complexed with a synthetic gRNA as a ribonucleoprotein (RNP) complex. It is well established from prior work in RNA interference that synthetic RNAs can induce a type I interferon (IFN) response that can limit the application of such methods both in vitro and in vivo. While the immunological properties of short siRNAs are well understood, little is known about the immune recognition of longer CRISPR gRNAs. The objective of our in vitro study was to investigate how the composition of the gRNA influences its recognition by human immune cells. METHODS: The study was performed in vitro in human peripheral blood mononuclear cells (PBMCs). The PBMCs from healthy donor volunteers were treated with gRNA for 24 h, and the levels of type I IFNs in culture supernatants were measured by a multiplex enzyme-linked immunosorbent chemiluminescent assay. Prior to the analysis in PBMCs, the physicochemical parameters and functionality of all nucleic acid constructs were confirmed by electrospray-ionization mass spectrometry and CRISPR/Cas9 gene editing assessment in HEK293-Cas9 cells, respectively. RESULTS: We found that unmodified synthetic CRISPR gRNAs triggered a strong IFN response in PBMC cultures in vitro that could be prevented with chemical modification. Likewise, in vitro-transcribed single-guide RNAs (sgRNAs) also triggered a strong IFN response that could only be partially suppressed by phosphatase removal of the 5'-triphosphate group. However, the process by which the gRNA is prepared (i.e., chemically synthesized as a two-part crRNA:tracrRNA complex or in vitro-transcribed as an sgRNA) does not directly influence the immune response to an unmodified gRNA. When experiments were performed in the HEK293 cells, only in vitro-transcribed sgRNA containing 5'-triphosphate induced IFN secretion. CONCLUSION: The results of our structure-activity relationship study, therefore, suggest that chemical modifications commonly used to reduce the immunostimulation of traditional RNA therapeutics can also be used as effective tools to eliminate undesirable IFN responses to gRNAs.

In Vitro Analysis of Nanoparticle Effects on the Zymosan Uptake by Phagocytic Cells.

This chapter provides a protocol for analysis of nanoparticle effects on the function of phagocytic cells. The protocol relies on luminol chemiluminescence to detect zymosan uptake. Zymosan is an yeast particle which is typically eliminated by phagocytic cells via the complement receptor pathway. The luminol, co-internalized with zymosan, is processed inside the phagosome to generate a chemiluminescent signal. If a test nanoparticle affects the phagocytic function of the cell, the amount of phagocytosed zymosan and, proportionally, the level of generated chemiluminescent signal change. Comparing the zymosan uptake of untreated cells with that of cells exposed to a nanoparticle provides information about the nanoparticle's effects on the normal phagocytic function. This method has been described previously and is presented herein with several changes. The revised method includes details about nanoparticle concentration selection, updated experimental procedure, and examples of the method performance.