Engineered red blood cells as an off-the-shelf allogeneic anti-tumor therapeutic

Tailoring cell-inspired biomaterials to fuel cancer therapy

Cancer stands as a predominant cause of mortality across the globe. Traditional cancer treatments, including surgery, radiotherapy, and chemotherapy, are effective yet face challenges like normal tissue damage, complications, and drug resistance. Biomaterials, with their advantages of high efficacy, targeting, and spatiotemporal controllability, have been widely used in cancer treatment. However, the biocompatibility limitations of traditional synthetic materials have restricted their clinical translation and application. Natural cell-inspired biomaterials inherently possess the targeting abilities of cells, biocompatibility, and immune evasion capabilities. Therefore, cell-inspired biomaterials can be used alone or in combination with other drugs or treatment strategies for cancer therapy. In this review, we first introduce the timeline of key milestones in cell-inspired biomaterials for cancer therapy. Then, we describe the abnormalities in cancer including biophysics, cellular biology, and molecular biology aspects. Afterwards, we summarize the design strategies of cell-inspired antitumor biomaterials. Subsequently, we elaborate on the application of antitumor biomaterials inspired by various cell types. Finally, we explore the current challenges and prospects of cell-inspired antitumor materials. This review aims to provide new opportunities and references for the development of antitumor cell-inspired biomaterials.

In situ self-reassembling nanosystem enhances PD-L1 blockade for cancer immunotherapy

Although immune checkpoint inhibitors (ICIs) have made great progress in cancer treatment, their off-tumor distribution, low affinity of traditional ICIs and insufficient T cells infiltration at tumor site limit immunotherapeutic efficacy. Herein, we engineer a highly specific and effective PD-L1 inhibitor (PEC) that modulates the level of binding sites with PD-L1. Specifically, PEC is a hybrid system composed of E. coli membrane expressing PD-L1 binding protein and cancer cell membrane. Notably, PEC can target the tumor site, produce oxygen in response to H2O2, rupture into membrane fragments, and reassemble to form vesicles retaining the PD-L1 binding protein. Through in situ fracture and reassembly, PEC transforms from a hybrid membrane to a single E. coli membrane, leading to the increased density of PD-L1 binding protein. Consequently, the reassembled vesicles can bind to more PD-L1 on tumor cells and induce its degradation in lysosomes. Furthermore, the cGAS-STING signaling activators HZD is encapsulated into PEC to promote T cells infiltration. We demonstrate that PEC@HZD achieves sequential T cells recruitment and functional enhancement, thus stimulating a powerful antitumor immune response. This work provides a new perspective on tailoring ICIs to improve cancer immunotherapy.

Interleukin in Immune-Mediated Diseases: An Updated Review

The immune system comprises various regulators and effectors that elicit immune responses against various attacks on the body. The pathogenesis of autoimmune diseases is derived from the deregulated expression of cytokines, the major regulators of the immune system. Among cytokines, interleukins have a major influence on immune-mediated diseases. These interleukins initiate the immune response against healthy and normal cells of the body, resulting in immune-mediated disease. The major interleukins in this respect are IL-1, IL-3, IL-4, IL-6, IL-10 and IL-12 which cause immune responses such as excessive inflammation, loss of immune tolerance, altered T-cell differentiation, immune suppression dysfunction, and inflammatory cell recruitment. Systemic Lupus Erythematosus (SLE) is an autoimmune illness characterized by dysregulation of interleukins. These immune responses are the signs of diseases such as rheumatoid arthritis, inflammatory bowel disease, psoriasis, type I diabetes, and multiple sclerosis.

Recent advances with erythrocytes as therapeutics carriers

Erythrocytes have gained popularity as a natural option for in vivo drug delivery due to their advantages, which include lengthy circulation times, biocompatibility, and biodegradability. Consequently, the drug's pharmacokinetics and pharmacodynamics in red blood cells can be considerably up the dosage. Here, we provide an overview of the erythrocyte membrane's structure and discuss the characteristics of erythrocytes that influence their suitability as carrier systems. We also cover current developments in the erythrocyte-based nanocarrier, which could be used for both active and passive targeting of disease tissues, particularly those of the reticuloendothelial system (RES) and cancer tissues. We also go over the most recent discoveries about the in vivo and in vitro uses of erythrocytes for medicinal and diagnostic purposes. Moreover, the clinical relevance of erythrocytes is discussed in order to improve comprehension and enable the potential use of erythrocyte carriers in the management of various disorders.

Cell-mediated nanoparticle delivery systems: towards precision nanomedicine

Cell-mediated nanoparticle delivery systems (CMNDDs) utilize cells as carriers to deliver the drug-loaded nanoparticles. Unlike the traditional nanoparticle drug delivery approaches, CMNDDs take the advantages of cell characteristics, such as the homing capabilities of stem cells, inflammatory chemotaxis of neutrophils, prolonged blood circulation of red blood cells, and internalization of macrophages. Subsequently, CMNDDs can easily prolong the blood circulation, cross biological barriers, such as the blood-brain barrier and the bone marrow-blood barrier, and rapidly arrive at the diseased areas. Such advantageous properties make CMNDDs promising delivery candidates for precision targeting. In this review, we summarize the recent advances in CMNDDs fabrication and biomedical applications. Specifically, ligand-receptor interactions, non-covalent interactions, covalent interactions, and internalization are commonly applied in constructing CMNDDs in vitro. By hitchhiking cells, such as macrophages, red blood cells, monocytes, neutrophils, and platelets, nanoparticles can be internalized or attached to cells to construct CMNDDs in vivo. Then we highlight the recent application of CMNDDs in treating different diseases, such as cancer, central nervous system disorders, lung diseases, and cardiovascular diseases, with a brief discussion about challenges and future perspectives in the end.

Engineered Nanoparticles for Enhanced Antitumoral Synergy Between Macrophages and T Cells in the Tumor Microenvironment

T cells and macrophages have the potential to collaborate to eliminate tumor cells efficiently. Macrophages can eliminate tumor cells through phagocytosis and subsequently activate T cells by presenting tumor antigens. The activated T cells, in turn, can kill tumor cells and redirect tumor-associated macrophages toward an antitumoral M1 phenotype. However, checkpoint molecules expressed on tumor cells impede the collaborative action of these immune cells. Meanwhile, monotherapy with a single immune checkpoint inhibitor (ICI) for either macrophages or T cells yields suboptimal efficacy in cancer patients. To address this challenge, here a nanoparticle capable of efficiently delivering dual ICIs to tumors for both macrophages and T cells is developed. These programmed cell death protein 1 (PD-1)-transfected macrophage membrane-derived nanoparticles (PMMNPs) can target tumors and provide signal-regulatory protein alpha and PD-1 to block CD47 and programmed cell death-ligand 1 (PD-L1), respectively, on tumor cells. PMMNPs enhance macrophage-mediated cancer cell phagocytosis and antigen presentation, promote T cell activation, and induce the reprogramming of macrophages toward an antitumoral phenotype. In syngeneic tumor-bearing mice, PMMNPs demonstrate superior therapeutic efficacy compared to nanoparticles delivering single ICIs and non-targeted delivery of anti-CD47 and anti-PD-L1 antibodies. PMMNPs capable of augmenting the antitumoral interplay between macrophages and T cells may offer a promising avenue for cancer immunotherapy.

Harnessing the potential of red blood cells in immunotherapy

Red blood cell (RBC) transfusion represents one of the earliest and most widespread forms of cellular therapy. While the primary purpose of RBC transfusions is to enhance the oxygen-carrying capacity of the recipient, RBCs also possess unique properties that make them attractive vehicles for inducing antigen-specific immune tolerance. Preclinical studies have demonstrated that RBC transfusion alone, in the absence of inflammatory stimuli, often fails to elicit detectable alloantibody formation against model RBC antigens. Several studies also suggest that RBC transfusion without inflammation may not only fail to generate a detectable alloantibody response but can also induce a state of antigen-specific non-responsiveness, a phenomenon potentially influenced by the density of the corresponding RBC alloantigen. The unique properties of RBCs, including their inability to divide and their stable surface antigen expression, make them attractive platforms for displaying exogenous antigens with the goal of leveraging their ability to induce antigen-specific non-responsiveness. This could facilitate antigen presentation to the host's immune system without triggering innate immune activation, potentially enabling the induction of antigen-specific tolerance for therapeutic applications in autoimmune disorders, preventing immune responses against protein therapeutics, or reducing alloreactivity in the setting of transfusion and transplantation.

Developing an erythrocyte‒MHC-I conjugate for cancer treatment

Mature erythrocytes are known to lack major histocompatibility complex (MHC) proteins. However, the presence of MHC molecules on erythrocytes has been occasionally reported, though without a defined function. In this study, we designed erythrocyte conjugated solely with a fusion protein consisting of an antigenic peptide linked to MHC class I (MHC-I) protein, termed MHC-I‒Ery. The modified erythrocyte, decorated with the peptide derived from human papillomavirus (HPV) 16 oncoprotein E6/E7, effectively activated antigen-specific CD8+ T cells in peripheral blood mononuclear cells (PBMCs) from HPV16+ cervical cancer patients. Additionally, MHC-I‒Ery monotherapy was shown to inhibit antigen-positive tumor growth in mice. This treatment immediately activated CD8+ T cells and reduced suppressive myeloid cells in the spleen, leading to systemic anti-tumor activity. Safety and tolerability evaluations of MHC-I‒Ery in non-human primates further supported its clinical potential. Our results first demonstrated that erythrocytes equipped solely with antigen peptide‒MHC-I complexes can robustly stimulate the immune system, suggesting a novel and promising approach for advancing cancer immunotherapy.

A general pHLA-CD80 scaffold fusion protein to promote efficient antigen-specific T cell-based immunotherapy

Inadequate antigen-specific T cells activation hampers immunotherapy due to complex antigen presentation. In addition, therapeutic in vivo T cell expansion is constrained by slow expansion rates and limited functionality. Herein, we introduce a model fusion protein termed antigen-presenting cell-mimic fusion protein (APC-mimic), designed to greatly mimicking the natural antigen presentation pattern of antigen-presenting cells and directly expand T cells both in vitro and in vivo. The APC-mimic comprises the cognate peptide-human leukocyte antigen (pHLA) complex and the co-stimulatory marker CD80, which are natural ligands on APCs. Following a single stimulation, APC-mimic leads to an approximately 400-fold increase in the polyclonal expansion of antigen-specific T cells compared with the untreated group in vitro without the requirement for specialized antigen-presenting cells. Through the combination of single-cell TCR sequencing (scTCR-seq) and single-cell RNA sequencing (scRNA-seq), we identify an approximately 600-fold monoclonal expansion clonotype among these polyclonal clonotypes. It also exhibits suitability for in vivo applications confirmed in the OT-1 mouse model. Furthermore, T cells expanded by APC-mimic effectively inhibits tumor growth in adoptive cell transfer (ACT) murine models. These findings pave the way for the versatile APC-mimic platform for personalized therapeutics, enabling direct expansion of polyfunctional antigen-specific T cell subsets in vitro and in vivo.

Theoretical basis, state and challenges of living cell-based drug delivery systems

The therapeutic efficacy of drugs is determined, to a certain extent, by the efficiency of drug delivery. The low efficiency of drug delivery systems (DDSs) is frequently associated with serious toxic side effects and can even prove fatal in certain cases. With the rapid development of technology, drug delivery has evolved from using traditional frameworks to using nano DDSs (NDDSs), endogenous biomaterials DDSs (EBDDSs), and living cell DDSs (LCDDSs). LCDDSs are receiving widespread attention from researchers at present owing to the unique advantages of living cells in targeted drug delivery, including their excellent biocompatibility properties, low immunogenicity, unique biological properties and functions, and role in the treatment of diseases. However, the theoretical basis and techniques involved in the application of LCDDSs have not been extensively summarized to date. Therefore, this review comprehensively summarizes the properties and applications of living cells, elaborates the various drug loading approaches and controlled drug release, and discusses the results of clinical trials. The review also discusses the current shortcomings and prospects for the future development of LCDDSs, which will serve as highly valuable insights for the development and clinical transformation of LCDDSs in the future.

Advances in manufacturing chimeric antigen receptor immune cell therapies

Biomedical research has witnessed significant strides in manufacturing chimeric antigen receptor T cell (CAR-T) therapies, marking a transformative era in cellular immunotherapy. Nevertheless, existing manufacturing methods for autologous cell therapies still pose several challenges related to cost, immune cell source, safety risks, and scalability. These challenges have motivated recent efforts to optimize process development and manufacturing for cell therapies using automated closed-system bioreactors and models created using artificial intelligence. Simultaneously, non-viral gene transfer methods like mRNA, CRISPR genome editing, and transposons are being applied to engineer T cells and other immune cells like macrophages and natural killer cells. Alternative sources of primary immune cells and stem cells are being developed to generate universal, allogeneic therapies, signaling a shift away from the current autologous paradigm. These multifaceted innovations in manufacturing underscore a collective effort to propel this therapeutic approach toward broader clinical adoption and improved patient outcomes in the evolving landscape of cancer treatment. Here, we review current CAR immune cell manufacturing strategies and highlight recent advancements in cell therapy scale-up, automation, process development, and engineering.

Cell-membrane engineering strategies for clinic-guided design of nanomedicine

Cells are the fundamental units of life. The cell membrane primarily composed of two layers of phospholipids (a bilayer) structurally defines the boundary of a cell, which can protect its interior from external disturbances and also selectively exchange substances and conduct signals from the extracellular environment. The complexity and particularity of transmembrane proteins provide the foundation for versatile cellular functions. Nanomedicine as an emerging therapeutic strategy holds tremendous potential in the healthcare field. However, it is susceptible to recognition and clearance by the immune system. To overcome this bottleneck, the technology of cell membrane coating has been extensively used in nanomedicines for their enhanced therapeutic efficacy, attributed to the favorable fluidity and biocompatibility of cell membranes with various membrane-anchored proteins. Meanwhile, some engineering strategies of cell membranes through various chemical, physical and biological ways have been progressively developed to enable their versatile therapeutic functions against complex diseases. In this review, we summarized the potential clinical applications of four typical cell membranes, elucidated their underlying therapeutic mechanisms, and outlined their current engineering approaches. In addition, we further discussed the limitation of this technology of cell membrane coating in clinical applications, and possible solutions to address these challenges.

Building Synthetic Biosensors Using Red Blood Cell Proteins

As the use of engineered cell therapies expands from pioneering efforts in cancer immunotherapy to other applications, an attractive but less explored approach is the use of engineered red blood cells (RBCs). Compared to other cells, RBCs have a very long circulation time and reside in the blood compartment, so they could be ideally suited for applications as sentinel cells that enable in situ sensing and diagnostics. However, we largely lack tools for converting RBCs into biosensors. A unique challenge is that RBCs remodel their membranes during maturation, shedding many membrane components, suggesting that an RBC-specific approach may be needed. Toward addressing this need, here we develop a biosensing architecture built on RBC membrane proteins that are retained through erythropoiesis. This biosensor employs a mechanism in which extracellular ligand binding is transduced into intracellular reconstitution of a split output protein (including either a fluorophore or an enzyme). By comparatively evaluating a range of biosensor architectures, linker types, scaffold choices, and output signals, we identify biosensor designs and design features that confer substantial ligand-induced signal in vitro. Finally, we demonstrate that erythroid precursor cells engineered with our RBC-protein biosensors function in vivo. This study establishes a foundation for developing RBC-based biosensors that could ultimately address unmet needs including noninvasive monitoring of physiological signals for a range of diagnostic applications.

Complement C3 and marginal zone B cells promote IgG-mediated enhancement of RBC alloimmunization in mice

Administration of anti-RhD immunoglobulin (Ig) to decrease maternal alloimmunization (antibody-mediated immune suppression [AMIS]) was a landmark clinical development. However, IgG has potent immune-stimulatory effects in other settings (antibody-mediated immune enhancement [AMIE]). The dominant thinking has been that IgG causes AMIS for antigens on RBCs but AMIE for soluble antigens. However, we have recently reported that IgG against RBC antigens can cause either AMIS or AMIE as a function of an IgG subclass. Recent advances in mechanistic understanding have demonstrated that RBC alloimmunization requires the IFN-α/-β receptor (IFNAR) and is inhibited by the complement C3 protein. Here, we demonstrate the opposite for AMIE of an RBC alloantigen (IFNAR is not required and C3 enhances). RBC clearance, C3 deposition, and antigen modulation all preceded AMIE, and both CD4+ T cells and marginal zone B cells were required. We detected no significant increase in antigen-specific germinal center B cells, consistent with other studies of RBC alloimmunization that show extrafollicular-like responses. To the best of our knowledge, these findings provide the first evidence of an RBC alloimmunization pathway which is IFNAR independent and C3 dependent, thus further advancing our understanding of RBCs as an immunogen and AMIE as a phenomenon.

A natural IgM hitchhiking strategy for delivery of cancer nanovaccines to splenic marginal zone B cells

B cell-targeted cancer vaccines are receiving increasing attention in immunotherapy due to the combined antibody-secreting and antigen-presenting functions. In this study, we propose a natural IgM-hitchhiking delivery strategy to co-deliver tumor antigens and adjuvants to splenic marginal zone B (MZB) cells. We constructed nanovaccines (FA-sLip/OVA/MPLA) consisting of classical folic acid (FA)-conjugated liposomes co-loaded with ovalbumin (OVA) and toll-like receptor 4 agonists, MPLA. We found that natural IgM absorption could be manipulated at the bio-nano interface on FA-sLip/OVA/MPLA, enabling targeted delivery to splenic MZB cells. Systemic administration of FA-sLip/OVA/MPLA effectively activated splenic MZB cells via IgM-mediated multiplex pathways, eliciting antigen-specific humoral and cytotoxic T lymphocyte responses, and ultimately retarding E.G7-OVA tumor growth. In addition, combining FA-sLip/OVA/MPLA immunization with anti-PD-1 treatments showed improved antitumor efficiency. Overall, this natural IgM-hitchhiking delivery strategy holds great promise for efficient, splenic MZB cell-targeted delivery of cancer vaccines in future applications.

Artificial cells for in vivo biomedical applications through red blood cell biomimicry

Recent research in artificial cell production holds promise for the development of delivery agents with therapeutic effects akin to real cells. To succeed in these applications, these systems need to survive the circulatory conditions. In this review we present strategies that, inspired by the endurance of red blood cells, have enhanced the viability of large, cell-like vehicles for in vivo therapeutic use, particularly focusing on giant unilamellar vesicles. Insights from red blood cells can guide modifications that could transform these platforms into advanced drug delivery vehicles, showcasing biomimicry's potential in shaping the future of therapeutic applications.

Therapeutic approaches of cell therapy based on stem cells and terminally differentiated cells: Potential and effectiveness

Cell-based therapy, as a promising regenerative medicine approach, has been a promising and effective strategy to treat or even cure various kinds of diseases and conditions. Generally, two types of cells are used in cell therapy, the first is the stem cell, and the other is a fully differentiated cell. Initially, all cells in the body are derived from stem cells. Based on the capacity, potency and differentiation potential of stem cells, there are four types: totipotent (produces all somatic cells plus perinatal tissues), pluripotent (produces all somatic cells), multipotent (produces many types of cells), and unipotent (produces a particular type of cells). All non-totipotent stem cells can be used for cell therapy, depending on their potency and/or disease state/conditions. Adult fully differentiated cell is another cell type for cell therapy that is isolated from adult tissues or obtained following the differentiation of stem cells. The cells can then be transplanted back into the patient to replace damaged or malfunctioning cells, promote tissue repair, or enhance the targeted organ's overall function. With increasing science and knowledge in biology and medicine, different types of techniques have been developed to obtain efficient cells to use for therapeutic approaches. In this study, the potential and opportunity of use of all cell types, both stem cells and fully differentiated cells, are reviewed.

Advances in Targeting Drug Biological Carriers for Enhancing Tumor Therapy Efficacy

Chemotherapy drugs continue to be the main component of oncology treatment research and have been proven to be the main treatment modality in tumor therapy. However, the poor delivery efficiency of cancer therapeutic drugs and their potential off-target toxicity significantly limit their effectiveness and extensive application. The recent integration of biological carriers and functional agents is expected to camouflage synthetic biomimetic nanoparticles for targeted delivery. The promising candidates, including but not limited to red blood cells and their membranes, platelets, tumor cell membrane, bacteria, immune cell membrane, and hybrid membrane are typical representatives of biological carriers because of their excellent biocompatibility and biodegradability. Biological carriers are widely used to deliver chemotherapy drugs to improve the effectiveness of drug delivery and therapeutic efficacy in vivo, and tremendous progress is made in this field. This review summarizes recent developments in biological vectors as targeted drug delivery systems based on microenvironmental stimuli-responsive release, thus highlighting the potential applications of target drug biological carriers. The review also discusses the possibility of clinical translation, as well as the exploitation trend of these target drug biological carriers.

Red blood cells: a potential delivery system

Red blood cells (RBCs) are the most abundant cells in the body, possessing unique biological and physical properties. RBCs have demonstrated outstanding potential as delivery vehicles due to their low immunogenicity, long-circulating cycle, and immune characteristics, exhibiting delivery abilities. There have been several developments in understanding the delivery system of RBCs and their derivatives, and they have been applied in various aspects of biomedicine. This article compared the various physiological and physical characteristics of RBCs, analyzed their potential advantages in delivery systems, and summarized their existing practices in biomedicine.

Current Status of Human Papillomavirus-Targeted Therapies Development in Head and Neck Cancer

PURPOSE

While the incidence of smoking-related head and neck squamous cell carcinoma (HNSCC) has been declining, that of human papillomavirus (HPV)-mediated HNSCC has rapidly increased in the past decades worldwide. Despite rapid advances in therapeutics for solid tumors with novel immunotherapy and targeted therapeutic agents, no breakthroughs have yet been made in the treatment of advanced HPV+ HNSCCs. This review aims to summarize the concepts and designs, early trial results, and future directions of various HPV-targeted experimental therapeutics for HPV+ HNSCC.

MATERIALS AND METHODS

Guided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement, a systemic literature search of PubMed was conducted for HPV-targeted therapeutics using the following search terms: HPV, head and neck squamous cell carcinoma, and therapy. For clinical trial data, publications, major oncology conference abstracts, and the National Institutes of Health Clinical Trials Registry (ClinicalTrials.gov) information were reviewed. This review focused on the ones that are in the clinical stage and currently in active ongoing evaluation. The therapeutics not actively evaluated in HNSCC, in the preclinical stage, or terminated for further development were excluded.

RESULTS

Diverse approaches are being actively explored to target HPV+ HNSCC, including therapeutic vaccines of various modalities, HPV-specific immune cell-activating agents, and adaptive cellular therapeutics. All these novel agents use immune-based mechanisms and target constitutively expressed oncogenic HPV E6 and/or E7 viral proteins. Most therapeutics demonstrated excellent safety but single-agent activities are only modest. Many are being tested in combination with immune checkpoint inhibitors.

CONCLUSION

Our review summarized various novel HPV-targeted therapeutics that are in the clinical phase for HPV+ HNSCC. Early-phase trial data suggest the feasibility and promising efficacy. Further strategies, including selecting the optimal combination and understanding and overcoming resistant mechanisms, are warranted for successful development.

Erythrocytes: Member of the Immune System that Should Not Be Ignored

Erythrocytes are the most abundant type of cells in the blood and have a relatively simple structure when mature; they have a long life-span in the circulatory system. The primary function of erythrocytes is as oxygen carriers; however, they also play an important role in the immune system. Erythrocytes recognize and adhere to antigens and promote phagocytosis. The abnormal morphology and function of erythrocytes are also involved in the pathological processes of some diseases. Owing to the large number and immune properties of erythrocytes, their immune functions should not be ignored. Currently, research on immunity is focused on immune cells other than erythrocytes. However, research on the immune function of erythrocytes and the development of erythrocyte-mediated applications is of great significance. Therefore, we aimed to review the relevant literature and summarize the immune functions of erythrocytes.

Nanovaccine Displaying Immunodominant T Cell Epitopes of Fibroblast Activation Protein Is Effective Against Desmoplastic Tumors

Cancer-associated fibroblasts (CAFs), which are dominant cell types in the tumor microenvironment (TME), support tumor growth by secreting cytokines and forming an extracellular matrix (ECM) that hampers the penetration of chemical and biological therapeutics within the tumor and thereby limits their therapeutic efficacy. Here, we report a cancer nanovaccine targeting fibroblast activation protein α (FAP)-expressing CAFs as a potential pan-tumor vaccine. We predicted immunodominant FAP-specific epitope peptides in silico and selected two candidate peptides after in vitro and in vivo screening for immunogenicity and antitumor efficacy. Next, we developed a nanoparticle-based vaccine that displays the two selected epitope peptides on the surface of lipid nanoparticles encapsulating CpG adjuvant (FAP_PEP-SLNPs). Immunization with one of two FAP_PEP-SLNP nanovaccines led to considerable growth inhibition of various tumors, including desmoplastic tumors, by depleting FAP⁺ CAFs and thereby reducing ECM production in the TME while causing little appreciable adverse effects. Furthermore, when combined with a chemotherapeutic drug, the FAP_PEP-SLNP nanovaccine increased drug accumulation and resulted in a synergistic antitumor efficacy far better than that of each corresponding monotherapy. These findings suggest that our FAP_PEP-SLNP nanovaccine has potential for use as an "off-the-shelf" pan-tumor vaccine applicable to a variety of tumors and may be a suitable platform for use in various combination therapies.

Advances in Drug Delivery Systems Based on Red Blood Cells and Their Membrane-Derived Nanoparticles

Red blood cells (RBCs) and RBC membrane-derived nanoparticles have been historically developed as bioinspired drug delivery systems to combat the issues of premature clearance, toxicity, and immunogenicity of synthetic nanocarriers. RBC-based delivery systems possess characteristics including biocompatibility, biodegradability, and long circulation time, which make them suited for systemic administration. Therefore, they have been employed in designing optimal drug formulations in various preclinical models and clinical trials to treat a wide range of diseases. In this review, we provide an overview of the biology, synthesis, and characterization of drug delivery systems based on RBCs and their membrane including whole RBCs, RBC membrane-camouflaged nanoparticles, RBC-derived extracellular vesicles, and RBC hitchhiking. We also highlight conventional and latest engineering strategies, along with various therapeutic modalities, for enhanced precision and effectiveness of drug delivery. Additionally, we focus on the current state of RBC-based therapeutic applications and their clinical translation as drug carriers, as well as discussing opportunities and challenges associated with these systems.

Alloantigen Copy Number as a Critical Factor in RBC Alloimmunization

RBC alloimmunization remains a significant barrier to ongoing transfusion therapy leading to morbidity, and in extreme cases mortality, due to delayed or insufficient units of compatible RBCs. In addition, the monitoring and characterization of alloantibodies, often with multiple specificities in a single patient, consumes substantial health care resources. Extended phenotypic matching has mitigated, but not eliminated, RBC alloimmunization and is only logistically available for specialized populations. Thus, RBC alloimmunization remains a substantial problem. In recent decades it has become clear that mechanisms of RBC alloimmunization are distinct from other antigens and lack of mechanistic understanding likely contributes to the fact that there are no approved interventions to prevent RBC alloimmunization from transfusion. The combination of human studies and murine modeling have identified several key factors in RBC alloimmunization. In both humans and mice, immunogenicity is a function of alloantigen copy number on RBCs. Murine studies have further shown that copy number not only changes rates of immunization but the mechanisms of antibody formation. This review summarizes the current understanding of quantitative and qualitative effects of alloantigen copy number on RBC alloimmunization.

Recent applications of immunomodulatory biomaterials for disease immunotherapy

Immunotherapy is used to regulate systemic hyperactivation or hypoactivation to treat various diseases. Biomaterial-based immunotherapy systems can improve therapeutic effects through targeted drug delivery, immunoengineering, etc. However, the immunomodulatory effects of biomaterials themselves cannot be neglected. In this review, we outline biomaterials with immunomodulatory functions discovered in recent years and their applications in disease treatment. These biomaterials can treat inflammation, tumors, or autoimmune diseases by regulating immune cell function, exerting enzyme-like activity, neutralizing cytokines, etc. The prospects and challenges of biomaterial-based modulation of immunotherapy are also discussed.

Expansion and differentiation of ex vivo cultured erythroblasts in scalable stirred bioreactors

Transfusion of donor-derived red blood cells (RBCs) is the most common form of cell therapy. Production of transfusion-ready cultured RBCs (cRBCs) is a promising replacement for the current, fully donor-dependent therapy. A single transfusion unit, however, contains 2 × 10¹² RBC, which requires large scale production. Here, we report on the scale-up of cRBC production from static cultures of erythroblasts to 3 L stirred tank bioreactors, and identify the effect of operating conditions on the efficiency of the process. Oxygen requirement of proliferating erythroblasts (0.55-2.01 pg/cell/h) required sparging of air to maintain the dissolved oxygen concentration at the tested setpoint (2.88 mg O₂ /L). Erythroblasts could be cultured at dissolved oxygen concentrations as low as 0.7 O₂ mg/ml without negative impact on proliferation, viability or differentiation dynamics. Stirring speeds of up to 600 rpm supported erythroblast proliferation, while 1800 rpm led to a transient halt in growth and accelerated differentiation followed by a recovery after 5 days of culture. Erythroblasts differentiated in bioreactors, with final enucleation levels and hemoglobin content similar to parallel cultures under static conditions.

Engineered red blood cells (activating antigen carriers) drive potent T cell responses and tumor regression in mice

Activation of T cell responses is essential for effective tumor clearance; however, inducing targeted, potent antigen presentation to stimulate T cell responses remains challenging. We generated Activating Antigen Carriers (AACs) by engineering red blood cells (RBCs) to encapsulate relevant tumor antigens and the adjuvant polyinosinic-polycytidylic acid (poly I:C), for use as a tumor-specific cancer vaccine. The processing method and conditions used to create the AACs promote phosphatidylserine exposure on RBCs and thus harness the natural process of aged RBC clearance to enable targeting of the AACs to endogenous professional antigen presenting cells (APCs) without the use of chemicals or viral vectors. AAC uptake, antigen processing, and presentation by APCs drive antigen-specific activation of T cells, both in mouse in vivo and human in vitro systems, promoting polyfunctionality of CD8+ T cells and, in a tumor model, driving high levels of antigen-specific CD8+ T cell infiltration and tumor killing. The efficacy of AAC therapy was further enhanced by combination with the chemotherapeutic agent Cisplatin. In summary, these findings support AACs as a potential vector-free immunotherapy strategy to enable potent antigen presentation and T cell stimulation by endogenous APCs with broad therapeutic potential.

Targeted In Vivo Loading of Red Blood Cells Markedly Prolongs Nanocarrier Circulation

Engineering drug delivery systems for prolonged pharmacokinetics (PK) has been an ongoing pursuit for nearly 50 years. The gold standard for PK enhancement is the coating of nanoparticles with polymers, namely polyethylene glycol (PEGylation), which has been applied in several clinically used products. In the present work, we utilize the longest circulating and most abundant component of blood─the erythrocyte─to improve the PK behavior of liposomes. Antibody-mediated coupling of liposomes to erythrocytes was tested in vitro to identify a loading dose that did not adversely impact the carrier cells. Injection of erythrocyte targeting liposomes into mice resulted in a ∼2-fold improvement in the area under the blood concentration versus time profile versus PEGylated liposomes and a redistribution from the plasma into the cellular fraction of blood. These results suggest that in vivo targeting of erythrocytes is a viable strategy to improve liposome PK relative to current, clinically viable strategies.

Red Blood Cell Inspired Strategies for Drug Delivery: Emerging Concepts and New Advances

In the past five decades, red blood cells (RBCs) have been extensively explored as drug delivery systems due to their distinguishing potential in modulating the pharmacokinetic, pharmacodynamics, and biological activity of carried payloads. The extensive interests in RBC-mediated drug delivery technologies are in part derived from RBCs' unique biological features such as long circulation time, wide access to many tissues in the body, and low immunogenicity. Owing to these outstanding properties, a large body of efforts have led to the development of various RBC-inspired strategies to enable precise drug delivery with enhanced therapeutic efficacy and reduced off-target toxicity. In this review, we discuss emerging concepts and new advances in such RBC-inspired strategies, including native RBCs, ghost RBCs, RBC-mimetic nanoparticles, and RBC-derived extracellular vesicles, for drug delivery.

Chemical Conjugation in Drug Delivery Systems

Cancer is one of the diseases with the highest mortality rate. Treatments to mitigate cancer are usually so intense and invasive that they weaken the patient to cure as dangerous as the own disease. From some time ago until today, to reduce resistance generated by the constant administration of the drug and improve its pharmacokinetics, scientists have been developing drug delivery system (DDS) technology. DDS platforms aim to maximize the drugs’ effectiveness by directing them to reach the affected area by the disease and, therefore, reduce the potential side effects. Erythrocytes, antibodies, and nanoparticles have been used as carriers. Eleven antibody–drug conjugates (ADCs) involving covalent linkage has been commercialized as a promising cancer treatment in the last years. This review describes the general features and applications of DDS focused on the covalent conjugation system that binds the antibody carrier to the cytotoxic drug.

In vivo mRNA delivery to virus-specific T cells by light-induced ligand exchange of MHC class I antigen-presenting nanoparticles

Simultaneous delivery of mRNA to multiple populations of antigen (Ag)-specific CD8+ T cells is challenging given the diversity of peptide epitopes and polymorphism of class I major histocompatibility complexes (MHCI). We developed Ag-presenting nanoparticles (APNs) for mRNA delivery using pMHCI molecules that were refolded with photocleavable peptides to allow rapid ligand exchange by UV light and site-specifically conjugated with a lipid tail for postinsertion into preformed mRNA lipid nanoparticles. Across different TCR transgenic mouse models (P14, OT-1, and Pmel), UV-exchanged APNs bound and transfected their cognate Ag-specific CD8+ T cells equivalent to APNs produced using conventionally refolded pMHCI molecules. In mice infected with PR8 influenza, multiplexed delivery of UV-exchanged APNs against three immunodominant epitopes led to ~50% transfection of a VHH mRNA reporter in cognate Ag-specific CD8+ T cells. Our data show that UV-mediated peptide exchange can be used to rapidly produce APNs for mRNA delivery to multiple populations of Ag-specific T cells in vivo.

Lighting the way to personalized mRNA immune cell therapies

Nanoparticles, mRNA, and ultraviolet light combine to reprogram specific immune cells directly in the body.

A Multifunctional Magnetic Red Blood Cell-Mimetic Micromotor for Drug Delivery and Image-Guided Therapy

Inspired by nature, innovative devices have been made to imitate the morphology and functions of natural red blood cells (RBCs). Here, we report a red blood cell-mimetic micromotor (RBCM), which was fabricated based on a layer-by-layer assembly method and precisely controlled by an external rotating uniform magnetic field. The main framework of the RBCM was constructed by the natural protein zein and finally camouflaged with the RBC membrane. Functional cargos such as Fe₃O₄ nanoparticles and the chemotherapeutic agent doxorubicin were loaded within the wall part of the RBCM for tumor therapy. Due to the massive loading of Fe₃O₄ nanoparticles, the RBCM can be precisely navigated by an external rotating uniform magnetic field and be used as a magnetic resonance imaging contrast agent for tumor imaging. The RBCM has been proven to be biocompatible, biodegradable, magnetically manipulated, and imageable, which are key requisites to take micromotors from the chalkboard to clinics. We expect the RBC-inspired biohybrid device to achieve wide potential applications.

Vaccine-Based Immunotherapy for Head and Neck Cancers

Simple Summary

Therapeutic vaccines are given to patients with cancer, as opposed to prophylactic vaccines given to a healthy population. The challenge for therapeutic oncological vaccines is to stimulate an immune T cell response against endogenous (or derived) antigens that is sufficiently potent to induce cytotoxic activity and broad enough to take tumor heterogeneity into account. The purpose of this article is to provide an updated review of the prophylactic and therapeutic vaccines that target viral or non-viral antigens, particularly in head and neck cancers.

Abstract

In 2019, the FDA approved pembrolizumab, a monoclonal antibody targeting PD-1, for the first-line treatment of recurrent or metastatic head and neck cancers, despite only a limited number of patients benefiting from the treatment. Promising effects of therapeutic vaccination led the FDA to approve the use of the first therapeutic vaccine in prostate cancer in 2010. Research in the field of therapeutic vaccination, including possible synergistic effects with anti-PD(L)1 treatments, is evolving each year, and many vaccines are in pre-clinical and clinical studies. The aim of this review article is to discuss vaccines as a new therapeutic strategy, particularly in the field of head and neck cancers. Different vaccination technologies are discussed, as well as the results of the first clinical trials in HPV-positive, HPV-negative, and EBV-induced head and neck cancers.

Erythrocyte-enabled immunomodulation for vaccine delivery

Erythrocytes capture pathogens in circulation and present them to antigen-presenting cells (APCs) in the spleen. Senescent or apoptotic erythrocytes are physiologically eliminated by splenic APCs in a non-inflammatory manner as to not induce an immune reaction, while damaged erythrocytes tend to induce immune activation. The distinct characteristics of erythrocytes in their lifespan or different states inspire the design of targeting splenic APCs for vaccine delivery. Specifically, normal or damaged erythrocyte-driven immune targeting can induce antigen-specific immune activation, whereas senescent or apoptotic erythrocytes can be tailored to achieve antigen-specific immune tolerance. Recent studies have revealed the potential of erythrocyte-based vaccine delivery; however, there is still no in-depth review to describe the latest progress. This review summarizes the characteristics, different immune functions, and diverse vaccine delivery behaviors and biomedical applications of erythrocytes in different states. This review aims to contribute to the rational design and development of erythrocyte-based vaccine delivery systems for treating various infections, tumors, inflammatory diseases, and autoimmune diseases.

Red blood cells: The metamorphosis of a neglected carrier into the natural mothership for artificial nanocarriers

Drug delivery research pursues many types of carriers including proteins and other macromolecules, natural and synthetic polymeric structures, nanocarriers of diverse compositions and cells. In particular, liposomes and lipid nanoparticles represent arguably the most advanced and popular human-made nanocarriers, already in multiple clinical applications. On the other hand, red blood cells (RBCs) represent attractive natural carriers for the vascular route, featuring at least two distinct compartments for loading pharmacological cargoes, namely inner space enclosed by the plasma membrane and the outer surface of this membrane. Historically, studies of liposomal drug delivery systems (DDS) astronomically outnumbered and surpassed the RBC-based DDS. Nevertheless, these two types of carriers have different profile of advantages and disadvantages. Recent studies showed that RBC-based drug carriers indeed may feature unique pharmacokinetic and biodistribution characteristics favorably changing benefit/risk ratio of some cargo agents. Furthermore, RBC carriage cardinally alters behavior and effect of nanocarriers in the bloodstream, so called RBC hitchhiking (RBC-HH). This article represents an attempt for the comparative analysis of liposomal vs RBC drug delivery, culminating with design of hybrid DDSs enabling mutual collaborative advantages such as RBC-HH and camouflaging nanoparticles by RBC membrane. Finally, we discuss the key current challenges faced by these and other RBC-based DDSs including the issue of potential unintended and adverse effect and contingency measures to ameliorate this and other concerns.

Novel concepts in red blood cell clearance

PURPOSE OF REVIEW

Red blood cell (RBC) clearance has been studied for decades in many different pathologies, which has revealed different routes of RBC degradation, depending on the situation. This review summarizes the latest mechanistic insights on RBC clearance in different contexts; during homeostatic removal, immune-mediated destruction, and systemic inflammation.

RECENT FINDINGS

Besides the recognition of a variety of potential 'eat me' signals on RBCs, recent evidence suggests that normal RBC degradation is driven by the increase of the adhesive properties of RBCs, mediating the retention in the spleen and leading to RBC hemolysis. Furthermore, immune-mediated degradation of RBCs seems to be fine-tuned by the balance between the density of the antigens expressed on RBCs and the presence of 'don't eat me' signals. Moreover, besides RBC clearance by macrophages, neutrophils seem to play a much more prominent role in immune-mediated RBC removal than anticipated. Lastly, RBC clearance during systemic inflammation appears to be driven by a combination of extreme macrophage activity in response to proinflammatory cytokines as well as direct damage of RBC by the inflammation or inflammatory agent.

SUMMARY

Recent studies on RBC clearance have expanded our knowledge on their destruction in different contexts.