Antigen uptake and immunoadjuvant activity of pathogen-mimetic hollow silica particles conjugated with β-glucan

Glucans and applications in drug delivery

Glucan is a natural polysaccharide widely distributed in cereals and microorganisms that has various biological activities, including immunomodulatory, anti-infective, anti-inflammatory, and antitumor activities. In addition to wide applications in the broad fields of food, healthcare, and biomedicines, glucans hold promising potential as drug delivery carrier materials or ligands. Specifically, glucan microparticles or yeast cell wall particles are naturally enclosed vehicles with an interior cavity that can be exploited to carry and deliver drug payloads. The biological activities and targeting capacities of glucans depend largely on the recognition of glucan moieties by receptors such as dectin-1 and complement receptor 3, which are widely expressed on the cell membranes of mononuclear phagocytes, dendritic cells, neutrophils, and some lymphocytes. This review summarizes the chemical structures, sources, fundamental properties, extraction methods, and applications of these materials, with an emphasis on drug delivery. Glucans are utilized mainly as vaccine adjuvants, targeting ligands and as carrier materials for various drug entities. It is believed that glucans and glucan microparticles may be useful for the delivery of both small-molecule and macromolecular drugs, especially for potential treatment of immune-related diseases.

Risedronate-functionalized manganese-hydroxyapatite amorphous particles: A potent adjuvant for subunit vaccines and cancer immunotherapy

The cGAS-STING pathway and the Mevalonate Pathway are druggable targets for vaccine adjuvant discovery. Manganese (Mn) and bisphosphonates are known to exert adjuvant effects by targeting these two pathways, respectively. This study found the synergistic potential of the two pathways in enhancing immune response. Risedronate (Ris) significantly amplified the Mn adjuvant early antibody response by 166-fold and fortified its cellular immunity. However, direct combination of Mn2+ and Ris resulted in increased adjuvant toxicity (40% mouse mortality). By the combination of doping property of hydroxyapatite (HA) and its high affinity for Ris, we designed Ris-functionalized Mn-HA micro-nanoparticles as an organic-inorganic hybrid adjuvant, named MnHARis. MnHARis alleviated adjuvant toxicity (100% vs. 60% survival rate) and exhibited good long-term stability. When formulated with the varicella-zoster virus glycoprotein E (gE) antigen, MnHARis triggered a 274.3-fold increase in IgG titers and a 61.3-fold surge in neutralization titers while maintaining a better long-term humoral immunity compared to the aluminum adjuvant. Its efficacy spanned other antigens, including ovalbumin, HPV18 VLP, and SARS-CoV-2 spike protein. Notably, the cellular immunity elicited by the group of gE + MnHARis was comparable to the renowned Shingrix®. Moreover, intratumoral co-administration with an anti-trophoblast cell surface antigen 2 nanobody revealed synergistic antitumor capabilities. These findings underscore the potential of MnHARis as a potent adjuvant for augmenting vaccine immune responses and improving cancer immunotherapy outcomes.

Aminated β-Glucan with immunostimulating activities and collagen composite sponge for wound repair

Immunostimulating activities of yeast β(1 → 3)-D-Glucan (β-Glucan) mainly depended on its structures. However, due to the tight triple helix structure of β-Glucan, its immunostimulating activity is greatly weakened. Therefore, in order to partially unwind the tight triple helix structure of β-glucan and improve its solubility in the medium, we modified it by amination in this study (A-Glu). The results showed that A-Glu could stimulate Raw264.7 macrophages and significantly enhance its TNF-α, IL-6, and IL-10 cytokine expression levels in vitro. A-Glu could also induce a shift of M0 Raw264.7 toward M1, and M2 toward M1. To expand the application of A-Glu in wound repair, the composite sponge consisting of A-Glu and type I collagen via the formation of a stable polyion complex (PIC) was developed. Moreover, the composite sponge could accelerate wound repair significantly. These results reveal that soluble A-Glu as an immunostimulating agent has potential applications in biomedicine.

Flower-like mesoporous silica nanoparticles as an antigen delivery platform to promote systemic immune response

Virus-like particles (VLPs), a kind of superior subunit vaccine, are assembled from the viral structural proteins with similar capsids to viruses. However, the efficiency of cell uptake is not satisfactory. We prepared flower-like mesoporous silica nanoparticles (SiNPs) with large pore channels and interior cavities to solve the problem. The highly loaded VLPs-SiNPs composites not only enhanced the stability of VLPs, but also delivered antigen to cells and improved the cellular uptake efficiency. Compared with naked VLPs, mice intramuscularly immunized with the VLPs-SiNPs composite induced higher specific antibodies, greater lymphocyte activation and higher level of cytokine secretion. Moreover, the VLPs-SiNPs composite as vaccine also promoted mucosal immune response through intranasal immune pathway. Therefore, the VLPs-SiNPs enable to induce strong cellular, humoral, and slight mucosal immune response through different immunization routes. These results are potentially useful for vaccine formulations and may provide further reference for vaccine design and delivery systems.

Preparation of a water soluble aminated β-1,3-D-glucan for gene carrier: The in vitro study of the anti-inflammatory activity and transfection efficiency

β-1,3-D-glucan has been reported to have a series of bioactivities including antitumor, antimicrobial, anti-inflammatory and antioxidative effects; however, its insolubility in neutral aqueous solution significantly restricts the potential application in biological and medicine fields. Herein, a water-soluble aminated β-1,3-D-glucan (AG) was synthesized and the anti-inflammatory effect, cytotoxicity and plasmid DNA (pDNA) binding capacity of AG, serum stability, the particle sizes and zeta potentials of AG/pDNA nanocomposites, and the transfection efficiency and mechanism of action were studied. AG shows no obvious cytotoxicity within the range of working concentration (1-64 μg/ml) and it exerts potent anti-inflammatory effect independent on Dectin-1 and TLR2. AG/pDNA nanocomposites prepared by electrostatic interaction possess an appropriate particle size ranged from 192.8 to 118.4 nm and zeta potentials ranged from 20.880 to 27.16 mV with the N/P ratios from 5 to 100. AG/pDNA nanocomposites at the N/P ratios of 10 and 20 were able to show superior transfection efficiencies in RAW 264.7 cells as a result of their suitable particle size, zeta potential, anti-inflammatory effect, and the specific interaction with pattern recognition receptors (Dectin-1 and TLR2). These results indicate that AG is a potential candidate for DNA delivery system due to its potent anti-inflammatory effect and high transfection efficiency.

Recent Advances in Hyperthermia Therapy-Based Synergistic Immunotherapy

The past decades have witnessed hyperthermia therapy (HTT) as an emerging strategy against malignant tumors. Nanomaterial-based photothermal therapy (PTT) and magnetic hyperthermia (MHT), as highly effective and noninvasive treatment models, offer advantages over other strategies in the treatment of different types of tumors. However, both PTT and MHT cannot completely cure cancer due to recurrence and distal metastasis. In recent years, cancer immunotherapy has attracted widespread attention owing to its capability to activate the body's own natural defense to identify, attack, and eradicate cancer cells. Significant efforts have been devoted to studying the activated immune responses caused by hyperthermia-ablated tumors. In this article, the synergistic mechanism of HTT in immunotherapy, including immunogenic cell death and reversal of the immunosuppressive tumor microenvironment is discussed. The reports of the combination of HTT or HTT-based multimodal therapy with immunotherapy, including immunoadjuvant exploitation, immune checkpoint blockade therapy, and adoptive cellular immunotherapy are summarized. As highlighted, these strategies could achieve synergistically enhanced therapeutic outcomes against both primary tumors and metastatic lesions, prevent cancer recurrence, and prolong the survival period. Finally, current challenges and prospective developments in HTT-synergized immunotherapy are also reviewed.

Carbohydrate Immune Adjuvants in Subunit Vaccines

Modern subunit vaccines are composed of antigens and a delivery system and/or adjuvant (immune stimulator) that triggers the desired immune responses. Adjuvants mimic pathogen-associated molecular patterns (PAMPs) that are typically associated with infections. Carbohydrates displayed on the surface of pathogens are often recognized as PAMPs by receptors on antigen-presenting cells (APCs). Consequently, carbohydrates and their analogues have been used as adjuvants and delivery systems to promote antigen transport to APCs. Carbohydrates are biocompatible, usually nontoxic, biodegradable, and some are mucoadhesive. As such, carbohydrates and their derivatives have been intensively explored for the development of new adjuvants. This review assesses the immunological functions of carbohydrate ligands and their ability to enhance systemic and mucosal immune responses against co-administered antigens. The role of carbohydrate-based adjuvants/delivery systems in the development of subunit vaccines is discussed in detail.

Biomimic strategies for modulating the interaction between particle adjuvants and antigen-presenting cells

The design strategies of particle adjuvants by mimicking natural pathogens to strengthen their interaction with antigen-presenting cells.