Induction of tumor antigen-specific cytotoxic T cell responses in naïve mice by latex microspheres-based artificial antigen-presenting cell constructs

Peptide–MHC complexes: dressing up to manipulate T cells against autoimmunity and cancer

Antigen-specificity of T cells provides important clues to the pathogenesis of T cell-mediated autoimmune diseases and immune-evasion strategies of tumors. Identification of T cell clones involved in autoimmunity or cancer is achieved with soluble peptide–MHC (pMHC) complex multimers. Importantly, these complexes can also be used to manipulate disease-relevant T cells to restore homeostasis of T cell-mediated immune response. While auto-antigen-specific T cells can be deleted or anergized by T cell receptor engagement with cognate pMHC complexes in the absence of costimulation, integration of these complexes in artificial antigen-presenting systems can activate tumor antigen-specific T cells. Here the authors discuss the advancements in pMHC-complex-mediated immunotherapeutic strategies in autoimmunity and cancer and identify the lacunae in these strategies that need to be addressed to facilitate clinical implementation.

Materials for Immunotherapy

Breakthroughs in materials engineering have accelerated the progress of immunotherapy in preclinical studies. The interplay of chemistry and materials has resulted in improved loading, targeting, and release of immunomodulatory agents. An overview of the materials that are used to enable or improve the success of immunotherapies in preclinical studies is presented, from immunosuppressive to proinflammatory strategies, with particular emphasis on technologies poised for clinical translation. The materials are organized based on their characteristic length scale, whereby the enabling feature of each technology is organized by the structure of that material. For example, the mechanisms by which i) nanoscale materials can improve targeting and infiltration of immunomodulatory payloads into tissues and cells, ii) microscale materials can facilitate cell-mediated transport and serve as artificial antigen-presenting cells, and iii) macroscale materials can form the basis of artificial microenvironments to promote cell infiltration and reprogramming are discussed. As a step toward establishing a set of design rules for future immunotherapies, materials that intrinsically activate or suppress the immune system are reviewed. Finally, a brief outlook on the trajectory of these systems and how they may be improved to address unsolved challenges in cancer, infectious diseases, and autoimmunity is presented.

Biomaterial-assisted targeted modulation of immune cells in cancer treatment

The past decade has witnessed the accelerating development of immunotherapies for cancer treatment. Immune checkpoint blockade therapies and chimeric antigen receptor (CAR)-T cell therapies have demonstrated clinical efficacy against a variety of cancers. However, issues including life-threatening off-target side effects, long processing times, limited patient responses and high cost still limit the clinical utility of cancer immunotherapies. Biomaterial carriers of these therapies, though, enable one to troubleshoot the delivery issues, amplify immunomodulatory effects, integrate the synergistic effect of different molecules and, more importantly, home and manipulate immune cells in vivo. In this Review, we will analyse thus-far developed immunomaterials for targeted modulation of dendritic cells, T cells, tumour-associated macrophages, myeloid-derived suppressor cells, B cells and natural killer cells, and summarize the promises and challenges of cell-targeted immunomodulation for cancer treatment.

Modulating T-cell-based cancer immunotherapy via particulate systems

Immunotherapy holds tremendous promise for improving cancer treatment in which an appropriate stimulator may naturally trigger the immune system to control cancer. Up-to-date, adoptive T-cell therapy has received two new FDA approvals that provide great hope for some cancer patient groups. Nevertheless, expense and safety-related issues require further study to obtain insight into targets for efficient immunotherapy. The development of material science was largely responsible for providing a promising horizon to strengthen immunoengineering. In this review, we focus on T-cell characteristics in the context of the immune system against cancer and discuss several approaches of exploiting engineered particles to manipulate the responses of T cells and the tumour microenvironment.

Bioengineering of Artificial Antigen Presenting Cells and Lymphoid Organs

The immune system protects the body against a wide range of infectious diseases and cancer by leveraging the efficiency of immune cells and lymphoid organs. Over the past decade, immune cell/organ therapies based on the manipulation, infusion, and implantation of autologous or allogeneic immune cells/organs into patients have been widely tested and have made great progress in clinical applications. Despite these advances, therapy with natural immune cells or lymphoid organs is relatively expensive and time-consuming. Alternatively, biomimetic materials and strategies have been applied to develop artificial immune cells and lymphoid organs, which have attracted considerable attentions. In this review, we survey the latest studies on engineering biomimetic materials for immunotherapy, focusing on the perspectives of bioengineering artificial antigen presenting cells and lymphoid organs. The opportunities and challenges of this field are also discussed.

Towards efficient cancer immunotherapy: advances in developing artificial antigen-presenting cells

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Active immunotherapy is promising for the development of potent cancer therapeutics.

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Various types of artificial antigen-presenting cells (aAPCs) may be used as ‘off-the-shelf’ products to induce antigen-specific T cell activation both ex vivo and in vivo.

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Size, shape, cytokine delivery mechanism, ligand composition, ligand mobility, and ligand positioning on aAPCs all have significant effects on T cell activation, and therefore should be taken into account when designing novel constructs.

Active anti-cancer immune responses depend on efficient presentation of tumor antigens and co-stimulatory signals by antigen-presenting cells (APCs). Therapy with autologous natural APCs is costly and time-consuming and results in variable outcomes in clinical trials. Therefore, development of artificial APCs (aAPCs) has attracted significant interest as an alternative. We discuss the characteristics of various types of acellular aAPCs, and their clinical potential in cancer immunotherapy. The size, shape, and ligand mobility of aAPCs and their presentation of different immunological signals can all have significant effects on cytotoxic T cell activation. Novel optimized aAPCs, combining carefully tuned properties, may lead to efficient immunomodulation and improved clinical responses in cancer immunotherapy.

Latex bead-based artificial antigen-presenting cells induce tumor-specific CTL responses in the native T-cell repertoires and inhibit tumor growth

Cell-free artificial antigen-presenting cells (aAPCs) were generated by coupling H-2K(b)/TRP2 tetramers together with anti-CD28 and anti-4-1BB antibodies onto cell-sized latex beads and injected intravenously and subcutaneously into naïve mice and antigen-primed mice (B6, H-2K(b)). Vigorous tumor antigen-specific CTL responses in the native T-cell repertoire in each mouse model were elicited as evaluated by measuring surface CD69 and CD25, intracellular IFN-γ, tetramer staining and cytolysis of melanoma cells. Furthermore, the aAPCs efficiently inhibited subcutaneous tumor growth and markedly delayed tumor progression in tumor-bearing mice. These data suggest that bead-based aAPCs represent a potential strategy for the active immunotherapy of cancers or persistent infections.

Killer artificial antigen-presenting cells deplete alloantigen-specific T cells in a murine model of alloskin transplantation

FasL-expressing killer antigen-presenting cells (KAPCs) have the ability to delete antigen-specific T cells and, therefore, could potentially be used for the treatment of allograft rejection and autoimmunity; however, their cellular nature markedly limits their clinical use. Novel bead-based killer artificial antigen-presenting cells (KaAPCs), which are generated by coupling major histocompatibility complex (MHC) class I antigens together with the apoptosis-inducing anti-Fas monoclonal antibody (mAb) onto magnetic beads, have recently attracted more attention. KaAPCs have a number of advantages over KAPCs and are able to deplete specific T cells in cocultures. However, it remains unknown whether bead-based KaAPCs can also induce apoptosis of alloreactive or autoreactive T cells and, consequently, generate hyporesponsiveness in vivo. In this study, H-2K(b)/peptide monomers and anti-Fas mAb have been covalently coupled to latex beads and administered intravenously into BALB/c mice (H-2K(d)) that had previously been grafted with skin squares from C57BL/6 mice (H-2K(b)). Alloskin graft survival was prolonged for 6 days. A 60% decrease of H-2K(b) antigen-alloreactive T cells was demonstrated by several measures 2 days after each injection of KaAPCs, but intact immune function, including antitumor activity, was maintained. These data provide the first in vivo evidence that bead-based KaAPCs can selectively deplete antigen-specific T cells without the loss of overall immune responsiveness and, therefore, highlight the therapeutic potential of this novel strategy for the treatment of allograft rejection and autoimmune disorders.

Artificial antigen-presenting cells for use in adoptive immunotherapy

The observation that T cells can recognize and specifically eliminate cancer cells has spurred interest in the development of efficient methods to generate large numbers of T cells with specificity for tumor antigens that can be harnessed for use in cancer therapy. Recent studies have demonstrated that during encounter with tumor antigen, the signals delivered to T cells by professional antigen-presenting cells can affect T-cell programming and their subsequent therapeutic efficacy. This has stimulated efforts to develop artificial antigen-presenting cells that allow optimal control over the signals provided to T cells. In this review, we will discuss the advantages and disadvantages of cellular and acellular artificial antigen-presenting cell systems and their use in T-cell adoptive immunotherapy for cancer.