Discovery of inulin acetate as a novel immune-active polymer and vaccine adjuvant: synthesis, material characterization, and biological evaluation as a toll-like receptor-4 agonist

Application prospect of polysaccharide in the development of vaccine adjuvants

Vaccination is an effective strategy for preventing infectious diseases. Subunit vaccines offer more precise targeting and safer protection compared with traditional inactivated virus vaccines. However, due to their poor immunogenicity, subunit vaccines necessitate the use of adjuvants to stimulate the immune system. Adjuvants have long been incorporated into vaccines to enhance the body's immune response, allowing for reduced dosage and lower production costs. Despite the development of numerous vaccine adjuvants, few exhibit the necessary potency and low toxicity for clinical use, often due to limited efficacy or adverse side effects. This underscores the urgent need for novel human vaccine adjuvants that are safe, effective, and cost-efficient. Recent studies have identified certain natural polysaccharides as promising human vaccine adjuvants due to their immunostimulatory properties, low toxicity, and high safety profiles, which enhance both humoral and cellular immunity. These natural polysaccharides are primarily derived from traditional Chinese medicine (TCM) plants, bacteria, and yeast. This review comprehensively analyzes several promising polysaccharide adjuvants, discussing their clinical applications, market potential, and immunoregulatory activities. In summary, the future prospects of polysaccharides provide valuable insights for the application and development of vaccine adjuvants.

Effect of microencapsulated Fiber2-displaying probiotics loaded with inulin nanoparticles on immunity against fowl adenovirus serotype 4 in chickens

In this study, phthalate inulin nanoparticles (PINs) were chemically modified and characterized. The internalization of PINs into the probiotic E. faecalis, which delivering Fiber2 protein of fowl adenovirus serotype 4 (FAdV-4), was investigated. The expression of the Fiber2 protein in E. faecalis was detected using western blot analysis. To protect recombinant E. faecalis from degradation of in the gastric acid environment, sodium alginate was used to encapsulate the bacteria. The survival ratio and release of E. faecalis in simulated gastrointestinal fluid was assessed. Oral administration of microencapsulated E. faecalis loaded with PINs (Micro-E/Fiber2-PINs) or inulin (Micro-E/Fiber2-inulin) was conducted, followed by an experimental challenge with FAdV-4 in chickens to evaluate immune responses and protection. The results showed the internalization of PINs into the bacteria promoted bacteria growth, and significantly improved the expression level of Fiber2. After incubation in simulated gastric fluid, the number of viable bacteria from the Micro-E/Fiber2-PINs group was significantly higher than that from the E. faecalis/Fiber2 group. The release of bacteria from the microcapsules was completed within 30 min. Animal experiments demonstrated that oral immunization with Micro-E/Fiber2-PINs significantly enhanced humoral and cellular immune responses, relieved inflammatory injury in FAdV-targeted organs, and improved survival rate of challenged chickens. This study presents promising potential for developing oral vaccines against pathogen infection.

In Silico-Guided Discovery of Polysaccharide Derivatives as Adjuvants in Nanoparticle Vaccines for Cancer Immunotherapy

Cancer vaccines utilizing nanoparticle (NP) structures that integrate antigens and adjuvants to enhance delivery and stimulate immune responses are emerging as a promising avenue in cancer immunotherapy. However, the development of cancer vaccines has been significantly hindered by the low immunogenicity of tumor antigens. To address this challenge, substantial efforts have been made in developing innovative adjuvants to elicit effective immune responses. In this study, we develop a NP cancer vaccine assisted by a polysaccharide derivative adjuvant, designed through a computational strategy, to evoke effective antigen-specific antitumor immunity. Using TLR4 as the putative receptor, we conducted a comprehensive evaluation of a prescreening library consisting of 34 inulin derivatives through docking and molecular dynamics simulation. Consequently, a new derivative, benzoylated inulin (InBz), is selected as the most promising TLR4 agonist. The adjuvant effect of InBz is evaluated by fabricating InBz NPs encapsulating the model antigen ovalbumin (OVA). In vitro, InBz-OVA NPs effectively activate the TLR4 signaling pathways and facilitate dendritic cell maturation, thereby enhancing the antigen delivery and presentation. In vivo, InBz-OVA NPs outperform a commercial aluminum-based adjuvant, elicit robust antibody titers, induce antigen-specific cytotoxic T lymphocytes, and achieve significant tumor suppression in murine models. Besides, the adjuvant effects of other representative derivatives, namely, acetylated and chloroacetylated inulin, with moderate and low potential from the library, are also chemically synthesized and experimentally evaluated and found to be in agreement with computational predictions, confirming the credibility of the strategy. This study provides an effective platform for the pursuit of efficient polysaccharide-based vaccine adjuvants.

A Polysaccharide-Based Oral-Vaccine Delivery System and Adjuvant for the Influenza Virus Vaccine

Influenza virus enters the host body through the mucosal surface of the respiratory tract. An efficient immune response at the mucosal site can interfere with virus entry and prevent infection. However, formulating oral vaccines and eliciting an effective mucosal immune response including at respiratory mucosa presents numerous challenges including the potential degradation of antigens by acidic gastric fluids and the risk of antigen dilution and dispersion over a large surface area of the gut, resulting in minimal antigen uptake by the immune cells. Additionally, oral mucosal vaccines have to overcome immune tolerance in the gut. To address the above challenges, in the current study, we evaluated inulin acetate (InAc) nanoparticles (NPs) as a vaccine adjuvant and antigen delivery system for oral influenza vaccines. InAc was developed as the first polysaccharide polymer-based TLR4 agonist; when tailored as a nanoparticulate vaccine delivery system, it enhanced antigen delivery to dendritic cells and induced a strong cellular and humoral immune response. This study compared the efficacy of InAc-NPs as a delivery system for oral vaccines with Poly (lactic-co-glycolic acid) (PLGA) NPs, utilizing influenza A nucleoprotein (Inf-A) as an antigen. InAc-NPs effectively protected the encapsulated antigen in both simulated gastric (pH 1.1) and intestinal fluids (pH 6.8). Moreover, InAc-NPs facilitated enhanced antigen delivery to macrophages, compared to PLGA-NPs. Oral vaccination studies in Balb/c mice revealed that InAc-Inf-A NPs significantly boosted the levels of Influenza virus-specific IgG and IgA in serum, as well as total and virus-specific IgA in the intestines and lungs. Furthermore, mice vaccinated with InAc-Inf-A-NPs exhibited notably higher hemagglutination inhibition (HI) titers at mucosal sites compared to those receiving the antigen alone. Overall, our study underscores the efficacy of InAc-NPs in safeguarding vaccine antigens post-oral administration, enhancing antigen delivery to antigen-presenting cells, and eliciting higher virus-neutralizing antibodies at mucosal sites following vaccination.

Exploring structural engineering approach to formulate and characterize next-generation adjuvants

It is critical to emphasize the importance of vaccination as it protects us against harmful pathogens. Despite significant progress in vaccine development, there is an ongoing need to develop vaccines that are not only safe but also highly effective in protecting against severe infections. Subunit vaccines are generally safe, but they frequently fail to elicit strong immune responses. As a result, there is a need to improve vaccine effectiveness by combining them with adjuvants, which have the potential to boost the immune system many folds. The process of developing these adjuvants requires searching for molecules capable of activating the immune system, combining these promising compounds with an antigen, and then testing this combination using animal models before approving it for clinical use. Liposomal adjuvants work as delivery adjuvants and its activity depends on certain parameters such as surface charge, vesicle size, surface modification and route of administration. Self-assembly property of peptide adjuvants and discovery of hybrid peptides have widened the scope of peptides in vaccine formulations. Since most pathogenic molecules are not peptide based, phage display technique allows for screening peptide mimics for such pathogens that have potential as adjuvants. This chapter discusses about peptide and liposome-based adjuvants focusing on their properties imparting adjuvanticity along with the methods of formulating them. Methods of adjuvant characterization important for an adjuvant to be approved for clinical trials are also discussed. These include assays for cytotoxicity, T-lymphocyte proliferation, dendritic cell maturation, cytokine and antibody production, toll-like receptor dependent signaling and adjuvant half-life.

Inulin: Unveiling its potential as a multifaceted biopolymer in prebiotics, drug delivery, and therapeutics

In recent years, inulin has gained much attention as a promising multifunctional natural biopolymer with numerous applications in drug delivery, prebiotics, and therapeutics. It reveals a multifaceted biopolymer with transformative implications by elucidating the intricate interplay between inulin and the host, microbiome, and therapeutic agents. Their flexible structure, exceptional targetability, biocompatibility, inherent ability to control release behavior, tunable degradation kinetics, and protective ability make them outstanding carriers in healthcare and biomedicine. USFDA has approved Inulin as a nutritional dietary supplement for infants. The possible applications of inulin in biomedicine research inspired by nature are presented. The therapeutic potential of inulin goes beyond its role in prebiotics and drug delivery. Recently, significant research efforts have been made towards inulin's anti-inflammatory, antioxidant, and immunomodulatory properties for their potential applications in treating various chronic diseases. Moreover, its ability to reduce inflammation and modulate immune responses opens new avenues for treating conditions such as autoimmune disorders and gastrointestinal ailments. This review will attempt to illustrate the inulin's numerous and interconnected roles, shedding light on its critical contributions to the advancement of healthcare and biomedicine and its recent advancement in therapeutics, and conclude by taking valuable insights into the prospects and opportunities of inulin.

Stimuli-Responsive Polymeric Nanovaccines Toward Next-Generation Immunotherapy

The development of nanovaccines that employ polymeric delivery carriers has garnered substantial interest in therapeutic treatment of cancer and a variety of infectious diseases due to their superior biocompatibility, lower toxicity and reduced immunogenicity. Particularly, stimuli-responsive polymeric nanocarriers show great promise for delivering antigens and adjuvants to targeted immune cells, preventing antigen degradation and clearance, and increasing the uptake of specific antigen-presenting cells, thereby sustaining adaptive immune responses and improving immunotherapy for certain diseases. In this review, the most recent advances in the utilization of stimulus-responsive polymer-based nanovaccines for immunotherapeutic applications are presented. These sophisticated polymeric nanovaccines with diverse functions, aimed at therapeutic administration for disease prevention and immunotherapy, are further classified into several active domains, including pH, temperature, redox, light and ultrasound-sensitive intelligent nanodelivery systems. Finally, the potential strategies for the future design of multifunctional next-generation polymeric nanovaccines by integrating materials science with biological interface are proposed.

Toll-like receptor (TLRs) agonists and antagonists for COVID-19 treatments

Severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) rapidly infects humans and animals which make coronavirus disease 2019 (COVID-19) a grievous epidemic worldwide which broke out in 2020. According to data analysis of the other coronavirus family, for instance severe acute respiratory syndrome SARS coronavirus (SARS-CoV), can provide experience for the mutation of SARS-CoV-2 and the prevention and treatment of COVID-19. Toll-like receptors (TLRs) as a pattern recognition receptor (PRRs), have an indispensable function in identifying the invader even activate the innate immune system. It is possible for organism to activate different TLR pathways which leads to secretion of proinflammatory cytokines such as Interleukin 1 (IL-1), Interleukin 6 (IL-6), Tumor necrosis factor α (TNFα) and type Ⅰ interferon. As a component of non-specific immunity, TLRs pathway may participate in the SARS-CoV-2 pathogenic processes, due to previous works have proved that TLRs are involved in the invasion and infection of SARS-CoV and MERS to varying degrees. Different TLR, such as TLR2, TLR4, TLR7, TLR8 and TLR9 probably have a double-sided in COVID-19 infection. Therefore, it is of great significance for a correctly acknowledging how TLR take part in the SARS-CoV-2 pathogenic processes, which will be the development of treatment and prevention strategies.

An Overview of Recent Insights into the Response of TLR to SARS-CoV-2 Infection and the Potential of TLR Agonists as SARS-CoV-2 Vaccine Adjuvants

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to coronavirus disease (COVID-19), a global health pandemic causing millions of deaths worldwide. However, the immunopathogenesis of COVID-19, particularly the interaction between SARS-CoV-2 and host innate immunity, remains unclear. The innate immune system acts as the first line of host defense, which is critical for the initial detection of invading pathogens and the activation and shaping of adaptive immunity. Toll-like receptors (TLRs) are key sensors of innate immunity that recognize pathogen-associated molecular patterns and activate downstream signaling for pro-inflammatory cytokine and chemokine production. However, TLRs may also act as a double-edged sword, and dysregulated TLR responses may enhance immune-mediated pathology, instead of providing protection. Therefore, a proper understanding of the interaction between TLRs and SARS-CoV-2 is of great importance for devising therapeutic and preventive strategies. The use of TLR agonists as vaccine adjuvants for human disease is a promising approach that could be applied in the investigation of COVID-19 vaccines. In this review, we discuss the recent progress in our understanding of host innate immune responses in SARS-CoV-2 infection, with particular focus on TLR response. In addition, we discuss the use of TLR agonists as vaccine adjuvants in enhancing the efficacy of COVID-19 vaccine.

Inulin and Its Application in Drug Delivery

Inulin’s unique and flexible structure, stabilization/protective effects, and organ targeting ability make it an excellent drug delivery carrier compared to other biodegradable polysaccharides. The three hydroxyl groups attached to each fructose unit serve as an anchor for chemical modification. This, in turn, helps in increasing bioavailability, improving cellular uptake, and achieving targeted, sustained, and controlled release of drugs and biomolecules. This review focuses on the various types of inulin drug delivery systems such as hydrogel, conjugates, nanoparticles, microparticles, micelles, liposomes, complexes, prodrugs, and solid dispersion. The preparation and applications of the different inulin drug delivery systems are further discussed. This work highlights the fact that modification of inulin allows the use of this polymer as multifunctional scaffolds for different drug delivery systems.

Eosinophils and COVID-19: diagnosis, prognosis, and vaccination strategies

The unprecedented impact of the coronavirus disease 2019 (COVID-19) pandemic has resulted in global challenges to our health-care systems and our economic security. As such, there has been significant research into all aspects of the disease, including diagnostic biomarkers, associated risk factors, and strategies that might be used for its treatment and prevention. Toward this end, eosinopenia has been identified as one of many factors that might facilitate the diagnosis and prognosis of severe COVID-19. However, this finding is neither definitive nor pathognomonic for COVID-19. While eosinophil-associated conditions have been misdiagnosed as COVID-19 and others are among its reported complications, patients with pre-existing eosinophil-associated disorders (e.g., asthma, eosinophilic gastrointestinal disorders) do not appear to be at increased risk for severe disease; interestingly, several recent studies suggest that a diagnosis of asthma may be associated with some degree of protection. Finally, although vaccine-associated aberrant inflammatory responses, including eosinophil accumulation in the respiratory tract, were observed in preclinical immunization studies targeting the related SARS-CoV and MERS-CoV pathogens, no similar complications have been reported clinically in response to the widespread dissemination of either of the two encapsulated mRNA-based vaccines for COVID-19.

Toll-like Receptor-4 (TLR4) Agonist-Based Intranasal Nanovaccine Delivery System for Inducing Systemic and Mucosal Immunity

Eliciting a robust immune response at mucosal sites is critical in preventing the entry of mucosal pathogens such as influenza and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This task is challenging to achieve without the inclusion of a strong and safe mucosal adjuvant. Previously, inulin acetate (InAc), a plant-based polymer, is shown to activate toll-like receptor-4 (TLR4) and elicit a robust systemic immune response as a vaccine adjuvant. This study investigates the potential of nanoparticles prepared with InAc (InAc-NPs) as an intranasal vaccine delivery system to generate both mucosal and systemic immune responses. InAc-NPs (∼250 nm in diameter) activated wild-type (WT) macrophages but failed to activate macrophages from TLR4 knockout mice or WT macrophages when pretreated with a TLR4 antagonist (lipopolysaccharide-RS (LPS-RS)), which indicates the selective nature of a InAc-based nanodelivery system as a TLR4 agonist. Intranasal immunization using antigen-loaded InAc-NPs generated ∼65-fold and 19-fold higher serum IgG1 and IgG2a titers against the antigen, respectively, as compared to PLGA-NPs as a delivery system. InAc-NPs have also stimulated the secretion of sIgA at various mucosal sites, including nasal-associated lymphoid tissues (NALTs), lungs, and intestine, and produced a strong memory response indicative of both humoral and cellular immune activation. Overall, by stimulating both systemic and mucosal immunity, InAc-NPs laid a basis for a potential intranasal delivery system for mucosal vaccination.

Ionotropic Gelation of Chitosan Flat Structures and Potential Applications

The capability of some polymers, such as chitosan, to form low cost gels under mild conditions is of great application interest. Ionotropic gelation of chitosan has been used predominantly for the preparation of gel beads for biomedical application. Only in the last few years has the use of this method been extended to the fabrication of chitosan-based flat structures. Herein, after an initial analysis of the major applications of chitosan flat membranes and films and their usual methods of synthesis, the process of ionotropic gelation of chitosan and some recently proposed novel procedures for the synthesis of flat structures are presented.

Polymeric Nanoparticle-Based Vaccine Adjuvants and Delivery Vehicles

As vaccine formulations have progressed from including live or attenuated strains of pathogenic components for enhanced safety, developing new adjuvants to more effectively generate adaptive immune responses has become necessary. In this context, polymeric nanoparticles have emerged as a promising platform with multiple advantages, including the dual capability of adjuvant and delivery vehicle, administration via multiple routes, induction of rapid and long-lived immunity, greater shelf-life at elevated temperatures, and enhanced patient compliance. This comprehensive review describes advances in nanoparticle-based vaccines (i.e., nanovaccines) with a particular focus on polymeric particles as adjuvants and delivery vehicles. Examples of the nanovaccine approach in respiratory infections, biodefense, and cancer are discussed.

Combination of inulin and β-cyclodextrin properties for colon delivery of hydrophobic drugs

Colon drug delivery is aimed at the administration of selected drugs to act locally or even systematically. Corticosteroid drugs are often used exerting even pronounced side effects due to systemic absorption. Here a new drug delivery system (DDS) based on the chemical conjugation of β-cyclodextrin to inulin to form the INUCD bioconjugate is described. It was designed with the aim to provide this DDS with colon degradable portions (inulin) which degradation products have direct beneficial effects on the well-being of the colon and with a carrier that can solubilize hydrophobic drugs (β-cyclodextrin). This system was specifically designed to promote a local/topical activity with a significant reduction of the drug systemic absorption. The INUCD bioconjugate was obtained by a simple chemistry binding β-cyclodextrin to an inulin succinate previously synthesized. The bioconjugate was then characterized in terms of physicochemical properties by ATR-FTIR, ¹H NMR, DSC and TGA, DLS and SEM. Furthermore phase-solubility test by using curcumin as a model drug were performed as well as biologic evaluations for cytocompatibility and drug transport across in vitro simulated physiological barriers. Moreover enzymatic degradation studies by inulinase were performed. From the gained results a predictable local drug release of the payload could be attained so allowing a local delivery of e.g. corticosteroids thus avoiding a systemic absorption especially in prolonged therapies.

A Hybrid Glioma Tumor Cell Lysate Immunotherapy Vaccine Demonstrates Good Clinical Efficacy in the Rat Model

Background

Conventional immunotherapy for glioma is not only expensive but also demonstrates less-than-desired clinical efficacy. In this study, we evaluated the immunotherapeutic efficacy of a tumor cell lysate-based hybrid glioma vaccine developed using a molecular-based approach.

Methods

First, the ability of the autologous (9L-cell lysate) and allogeneic (C6-cell lysate) vaccines against glioma, individually and in combination, to activate Fischer344 rat dendritic cells (DCs) was determined. Next, the activated DCs were co-cultured with T lymphocytes and screened for the optimal DC-to-T-cell ratio. The in vitro efficacy of the DC/T-cell vaccine formulations subjected to different immunogen treatments and co-cultured with glioma cells was evaluated based on glioma cell viability and monocyte chemoattractant protein (MCP)-2 and interferon (IFN)-γ secretion. Subsequently, the efficacy of the 9L + C6 hybrid vaccine was evaluated in 32 glioma rat models, randomly allocated to the following five treatment groups: blank control, tumor, vaccine treatment, thymosin treatment, and vaccine + thymosin treatment (combined treatment). Changes in survival duration, intracranial tumor volume, peripheral blood immune-cell (CD4+ T, CD8+ T, and natural killer [NK] cell) count, and serum cytokine (interleukin [IL]-2, IL-10) levels were assessed in these groups.

Results

The hybrid vaccine demonstrated the highest glioma cell apoptosis and the lowest cell viability and promoted MCP-2 and IFN-γ secretion in vitro. The vaccine treatment and combined treatment groups demonstrated longer survival duration, lower intracranial tumor volume, and higher immune cell glioma tissue infiltration and IL-2 secretion than the untreated tumor group, indicating the vaccine's good in vivo efficacy. Thymosin treatment had minimal effect in enhancing anti-glioma immunity.

Conclusion

We demonstrated the feasibility of combining autologous and allogeneic tumor cell lysates to stimulate specific host cell immune response against glioma cells. The good clinical efficacy of our developed glioma hybrid vaccine in rat models suggests its potential clinical application.

Enhanced Efficacy of Immunization with a Foot-and-Mouth Disease Multi-Epitope Subunit Vaccine Using Mannan-Decorated Inulin Microparticles

BACKGROUND

Despite the many advantages of recombinant subunit vaccines, they have critical weaknesses that include a low efficacy for promoting cellular and humoral immune responses against antigens because of their poor immunogenicity, and a rapidly cleared properties as a result of proteolytic enzymes in the body. To circumvent these problems, we developed mannan-decorated inulin acetate microparticles (M-IA MPs) that functioned as carriers and adjuvants for immunization with the recombinant foot-and-mouth disease multi-epitope subunit vaccine (M5BT).

METHODS

The M5BT-loaded M-IA MPs were obtained by a double-emulsion solvent-evaporation method. Their properties including morphology, size and release ability were determined by field emission scanning electron microscope, dynamic light-scattering spectrophotometer and spectrophotometer. To assess the immunization efficacy of the MPs, mice were immunized with MPs and their sera were analyzed by ELISA.

RESULTS

The M-IA MPs obtained by a double-emulsion solvent-evaporation method were spherical and approximately 2-3 µm, and M5BT was encapsulated in the M-IA MPs. The M5BT-loaded M-IA MPs showed higher antigen-specific IgG, IgG1, IgG2a and anti-FMDV antibodies than the M5BT-loaded IA MPs and the Freund's adjuvant as a control.

CONCLUSION

The M-IA MPs showed a powerful and multifunctional polymeric system that combined two toll-like receptor agonists compared to the conventional adjuvant.

Chitosan Derivatives and Their Application in Biomedicine

Chitosan is a product of the deacetylation of chitin, which is widely found in nature. Chitosan is insoluble in water and most organic solvents, which seriously limits both its application scope and applicable fields. However, chitosan contains active functional groups that are liable to chemical reactions; thus, chitosan derivatives can be obtained through the chemical modification of chitosan. The modification of chitosan has been an important aspect of chitosan research, showing a better solubility, pH-sensitive targeting, an increased number of delivery systems, etc. This review summarizes the modification of chitosan by acylation, carboxylation, alkylation, and quaternization in order to improve the water solubility, pH sensitivity, and the targeting of chitosan derivatives. The applications of chitosan derivatives in the antibacterial, sustained slowly release, targeting, and delivery system fields are also described. Chitosan derivatives will have a large impact and show potential in biomedicine for the development of drugs in future.

Adjuvants: What a Difference 15 Years Makes!

Vaccination is a critical tool in modern animal production and key to maintaining animal health. Adjuvants affect the immune response by increasing the rate, quantity, or quality of the protective response generated by the target antigens. Although adjuvant technology dates back to the nineteenth century, there was relatively little improvement in adjuvant technology before the late twentieth century. With the discovery of molecular pathways that regulate the timing, quantity, and quality of the immune response, new technologies are focused on bringing safer, more effective, and inexpensive adjuvants to commercial use.

Confinement of Suspension-Cultured Cells in Polyethylene Glycol/Polyethylene Oxide-Albumin Aqueous Two-Phase Systems

Aqueous two-phase systems (ATPSs) have numerous applications in separation science, and more recently, in bioassays enabled by the solution micropatterning of cells. The most frequently used ATPS in these applications is the polyethylene glycol (PEG)-dextran (Dex) system, as the polymers that form this ATPS have been extensively characterized in terms of their physicochemical properties. However, in addition to this well-known system, there exist many other ATPSs with properties that may be exploited to improve upon the PEG-dextran system for specific applications. One of these underexplored systems is the ATPS formed from PEG/polyethylene oxide (PEO) and albumin. In this article, we characterize the phase separation of PEG (35 kDa) and polyethylene oxide (PEO) (200, 900, and 4,000 kDa) with bovine serum albumin (BSA). We describe the microscopic emulsion behavior of these systems in the presence of NaCl and compounds (NaHCO3, NaH2PO4, and HEPES) commonly used in buffer solutions and cell culture media. We further demonstrate that PEG- and PEO-albumin systems can be used in place of the PEG-dextran system for confinement of suspension-cultured cells (Jurkat T cells and RPMI-8226 B cells). Cell viability and morphology are examined for various polymer formulations relative to the commonly used PEG 35 kDa-Dex 500 kDa system and polymer-free cell culture medium. In addition, we examine cell activation for various phase-separating medium components by measuring IL-2 and IL-6 secretion. We demonstrate that we can confine immune cells and cytokines in the PEG-BSA system, and that this system can be employed to screen immune responses by enzyme-linked immunospot (ELISpot) assay. This new system represents a promising ATPS formulation for applications where low levels of baseline cell activation are required, for instance, when culturing immune cells.

Dendritic Cell-Targeted Nanovaccine Delivery System Prepared with an Immune-Active Polymer

Targeting dendritic cells (DCs), either ex vivo (Ex. Sipuleucel-T) or in vivo, for stimulating cellular immunity has been a leading approach for cancer vaccines. We have rationally engineered a nanoparticle (NP)-based delivery system for vaccines (InAc-NPs) using inulin acetate (InAc) as the polymer to target DCs. The material and the antigen-encapsulated InAc-NPs (∼190 nm in diameter) were characterized for their physicochemical properties. As a potent vaccine adjuvant, InAc-NPs activated TLR4 on multiple immune cells, including DCs and primary swine and human cells, to secrete various cytokines as detected by enzyme-linked immunosorbent assay and quantitative polymerase chain reaction. In addition, InAc-NPs promoted the maturation of DCs as observed by a decreased phagocytic ability and enhanced capability to activate various maturation markers (MHC-I, MHC-II, CD40, and CD80) quantified using flow cytometry. In mice, the InAc-NPs produced strong serum antibody titers (total IgG, IgG1, and IgG2a) against the encapsulated antigen (ovalbumin) similar to complete Freund's adjuvant. Additionally, as a dose-sparing delivery system, antigen delivered through InAc-NPs generated higher antibody titers (IgG1, 1.57 times; IgG-total, 1.66 times; and IgG2a, 29.8 times) even at 100 times less antigen dose. High amounts of cytokines representing both humoral (IL4 and IL10) and cell-mediated (IL2 and IFN-γ) immunities were secreted from splenocytes of mice immunized with InAc-NPs. Importantly, InAc-NPs provided complete protection in 100% of the vaccinated mice from metastasis of intravenously injected melanoma cells (B₁₆-F₁₀) to lungs. In addition, the InAc-NPs were cleared from the injection site within 30 h of injection (in vivo imaging) and displayed no toxicity at the injection site (histology). The current study demonstrates that the multifunctional InAc-based nanovaccine delivery system has potential applications in cancer immunotherapy and delivering vaccines against various infectious diseases.

A new way of producing pediocin in Pediococcus acidilactici through intracellular stimulation by internalized inulin nanoparticles

One of the most challenging aspects of probiotics as a replacement for antibiotics is to enhance their antimicrobial activity against pathogens. Given that prebiotics stimulate the growth and/or activity of probiotics, we developed phthalyl inulin nanoparticles (PINs) as prebiotics and observed their effects on the cellular and antimicrobial activities of Pediococcus acidilactici (PA). First, we assessed the internalization of PINs into PA. The internalization of PINs was largely regulated by glucose transporters in PA, and the process was energy-dependent. Once internalized, PINs induced PA to produce substantial amounts of antimicrobial peptide (pediocin), which is effective against both Gram-positive (Salmonella Gallinarum) and Gram-negative (Listeria monocytogenes) pathogens. When treated with small-sized PINs, PA witnessed a nine-fold increase in antimicrobial activity. The rise in pediocin activity in PA treated with PINs was accompanied by enhanced expression of stress response genes (groEL, groES, dnaK) and pediocin biosynthesis genes (pedA, pedD). Although the mechanism is not clear, it appears that the internalization of PINs by PA causes mild stress to activate the PA defense system, leading to increased production of pediocin. Overall, we identified a prebiotic in nanoparticle form for intracellular stimulation of probiotics, demonstrating a new avenue for the biological production of antimicrobial peptides.

Pathogen-mimicking vaccine delivery system designed with a bioactive polymer (inulin acetate) for robust humoral and cellular immune responses

New and improved vaccines are needed against challenging diseases such as malaria, tuberculosis, Ebola, influenza, AIDS, and cancer. The majority of existing vaccine adjuvants lack the ability to significantly stimulate the cellular immune response, which is required to prevent the aforementioned diseases. This study designed a novel particulate based pathogen-mimicking vaccine delivery system (PMVDS) to target antigen-presenting-cells (APCs) such as dendritic cells. The uniqueness of PMVDS is that the polymer used to prepare the delivery system, Inulin Acetate (InAc), activates the innate immune system. InAc was synthesized from the plant polysaccharide, inulin. PMVDS provided improved and persistent antigen delivery to APCs as an efficient vaccine delivery system, and simultaneously, activated Toll-Like Receptor-4 (TLR-4) on APCs to release chemokine's/cytokines as an immune-adjuvant. Through this dual mechanism, PMVDS robustly stimulated both the humoral (>32 times of IgG1 levels vs alum) and the cell-mediated immune responses against the encapsulated antigen (ovalbumin) in mice. More importantly, PMVDS stimulated both cytotoxic T cells and natural killer cells of cell-mediated immunity to provide tumor (B16-ova-Melanoma) protection in around 40% of vaccinated mice and significantly delayed tumor progression in rest of the mice. PMVDS is a unique bio-active vaccine delivery technology with broader applications for vaccines against cancer and several intracellular pathogens, where both humoral and cellular immune responses are desired.