Efficient ex vivo induction of T cells with potent anti-tumor activity by protein antigen encapsulated in nanoparticles

Nanomaterials-Based Novel Immune Strategies in Clinical Translation for Cancer Therapy

Immunotherapy shows a lot of promise for addressing the problems with traditional cancer treatments. Researchers and clinicians are working to create innovative immunological techniques for cancer detection and treatment that are more selective and have lower toxicity. An emerging field in cancer therapy, immunomodulation offers patients an alternate approach to treating cancer. These therapies use the host's natural defensive systems to identify and remove malignant cells in a targeted manner. Cancer treatment is now undergoing somewhat of a revolution due to recent developments in nanotechnology. Diverse nanomaterials (NMs) have been employed to overcome the limits of conventional anti-cancer treatments such as cytotoxic, surgery, radiation, and chemotherapy. Aside from that, NMs could interact with live cells and influence immune responses. In contrast, unexpected adverse effects such as necrosis, hypersensitivity, and inflammation might result from the immune system (IS)'s interaction with NMs. Therefore, to ensure the efficacy of immunomodulatory nanomaterials, it is essential to have a comprehensive understanding of the intricate interplay that exists between the IS and NMs. This review intends to present an overview of the current achievements, challenges, and improvements in using immunomodulatory nanomaterials (iNMs) for cancer therapy, with an emphasis on elucidating the mechanisms involved in the interaction between NMs and the immune system of the host.

Cancer Resistance to Immunotherapy: Molecular Mechanisms and Tackling Strategies

Cancer immunotherapy has fundamentally altered cancer treatment; however, its efficacy is limited to a subset of patients in most clinical settings. The immune system plays a key role in cancer progression from tumor initiation to the metastatic state. Throughout the treatment course, communications between the immune cells in the tumor microenvironment and the immune macroenvironment, as well as interactions between the immune system and cancer cells, are dynamic and constantly evolving. To improve the clinical benefit for patients who do not respond completely to immunotherapy, the molecular mechanisms of resistance to immunotherapy must be elucidated in order to develop effective strategies to overcome resistance. In an attempt to improve and update the current understanding of the molecular mechanisms that hinder immunotherapy, we discuss the molecular mechanisms of cancer resistance to immunotherapy and the available treatment strategies.

Nanoparticle mediated cancer immunotherapy

The versatility and nanoscale size have helped nanoparticles (NPs) improve the efficacy of conventional cancer immunotherapy and opened up exciting approaches to combat cancer. This review first outlines the tumor immune evasion and the defensive tumor microenvironment (TME) that hinders the activity of host immune system against tumor. Then, a detailed description on how the NP based strategies have helped improve the efficacy of conventional cancer vaccines and overcome the obstacles led by TME. Sustained and controlled drug delivery, enhanced cross presentation by immune cells, co-encapsulation of adjuvants, inhibition of immune checkpoints and intrinsic adjuvant like properties have aided NPs to improve the therapeutic efficacy of cancer vaccines. Also, NPs have been efficient modulators of TME. In this context, NPs facilitate better penetration of the chemotherapeutic drug by dissolution of the inhibitory meshwork formed by tumor associated cells, blood vessels, soluble mediators and extra cellular matrix in TME. NPs achieve this by suppression, modulation, or reprogramming of the immune cells and other mediators localised in TME. This review further summarizes the applications of NPs used to enhance the efficacy of cancer vaccines and modulate the TME to improve cancer immunotherapy. Finally, the hurdles faced in commercialization and translation to clinic have been discussed and intriguingly, NPs owe great potential to emerge as clinical formulations for cancer immunotherapy in near future.

Recent development in biodegradable nanovehicle delivery system-assisted immunotherapy

A schematic illustration of BNDS biodegradation and release antigen delivery for assisting immunotherapy.

Integration of nano drug-delivery system with cancer immunotherapy

Immune checkpoint therapy represents a new, revolutionary type of cancer therapy, but emerging evidence indicates that only a minority of patients will benefit from it. The issue of how to improve and widen the clinical response is a pivotal issue, and combining other types of therapy with immune checkpoint inhibitors is currently under development. A nanotechnology-based drug-delivery system (nano DDS) could be an important contribution to the development of an effective combination therapy. In this document, we review recent findings in the field of tumor immunology, which provide a strategy for an efficient combination therapy, and discuss nano DDS that are associated with cancer immunotherapy and nano DDS strategies based on the immune status in tumor microenvironments.

Recruitment of bone marrow CD11b+Gr-1+ cells by polymeric nanoparticles for antigen cross-presentation

The objective of this study was to investigate the function of poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) on the activation of antigen-specific CD8⁺ T cell responses via the CD11b⁺Gr^-1⁺ myeloid subpopulations in murine bone marrow (BM). PLGA NPs containing ovalbumin (OVA) were fabricated by the double-emulsion method. The CD11b⁺Gr-1^lowLy-6C^high and CD11b⁺Gr-1^highLy-6C^low subsets from mice bone marrow were sorted and treated with the PLGA/OVA NPs, followed by co-culture with the carboxyfluorescein succinimidyl ester (CFSE)-labelled OT-I CD8⁺ cells. Co-culture of OT-I CD8⁺ T cells with PLGA/OVA NPs-primed CD11b⁺Gr-1⁺ subsets upregulated the expression of IL-2, TNF-α, INF-γ, granzyme B, and perforin, resulting in proliferation of CD8⁺ T cells and differentiation into effector cytotoxic T lymphocytes (CTLs). In vivo proliferation of CFSE-labelled OT-I CD8⁺ cells in response to OVA was also obtained in the animals immunized with PLGA/OVA NPs. The results presented in this study demonstrate the ability of polymeric NPs to recruit two CD11b⁺Gr^-1⁺ myeloid subsets for effective presentation of exogenous antigen to OT-I CD8⁺ T cells in the context of major histocompatibility complex (MHC) class I, leading to an induction of antigen-specific cell proliferation and differentiation into effector cells.

Bioengineering a bacterial pathogen to assemble its own particulate vaccine capable of inducing cellular immunity

Many bacterial pathogens naturally form cellular inclusions. Here the immunogenicity of polyhydroxyalkanoate (PHA) inclusions and their use as particulate vaccines delivering a range of host derived antigens was assessed. Our study showed that PHA inclusions of pathogenic Pseudomonas aeruginosa are immunogenic mediating a specific cell-mediated immune response. Protein engineering of the PHA inclusion forming enzyme by translational fusion of epitopes from vaccine candidates outer membrane proteins OprI, OprF, and AlgE mediated self-assembly of PHA inclusions coated by these selected antigens. Mice vaccinated with isolated PHA inclusions produced a Th1 type immune response characterized by antigen-specific production of IFN-γ and IgG2c isotype antibodies. This cell-mediated immune response was found to be associated with the production of functional antibodies reacting with cells of various P. aeruginosa strains as well as facilitating opsonophagocytic killing. This study showed that cellular inclusions of pathogenic bacteria are immunogenic and can be engineered to display selected antigens suitable to serve as particulate subunit vaccines against infectious diseases.

In vivo stepwise immunomodulation using chitosan nanoparticles as a platform nanotechnology for cancer immunotherapy

Dentritic cell (DC)-based cancer immunotherapy faces challenges in both efficacy and practicality. However, DC-based vaccination requires multiple injections and elaborates ex vivo manipulation, which substantially limits their use. Therefore, we sought to develop a chitosan nanoparticle (CH-NP)-based platform for the next generation of vaccines to bypass the ex vivo manipulation and induce immune responses via active delivery of polyinosinic-polycytidylic acid sodium salt (poly I:C) to target Toll-like receptor 3 (TLR3) in endosomes. We developed CH-NPs encapsulating ovalbumin (OVA) as a model antigen and poly I:C as the adjuvant in an ionic complex. These CH-NPs showed increased in vivo intracellular delivery to the DCs in comparison with controls after injection into tumor-bearing mice, and promoted DC maturation, leading to emergence of antigen-specific cytotoxic CD8+ T cells. Finally, the CH-NPs showed significantly greater antitumor efficacy in EG.7 and TC-1 tumor-bearing mice compared to the control (p < 0.01). Taken together, these data show that the CH-NP platform can be used as an immune response modulatory vaccine for active cancer immunotherapy without ex vivo manipulation, thus resulting in increased anticancer efficacy.

Toll-like receptor 3-induced immune response by poly(d,l-lactide-co-glycolide) nanoparticles for dendritic cell-based cancer immunotherapy

Dendritic cells (DCs) are potent professional antigen-presenting cells that are capable of initiating a primary immune response and activating T cells, and they play a pivotal role in the immune responses of the host to cancer. Prior to antigen presentation, efficient antigen and adjuvant uptake by DCs is necessary to induce their maturation and cytokine generation. Nanoparticles (NPs) are capable of intracellular delivery of both antigen and adjuvant to DCs. Here, we developed an advanced poly(d,l-lactide-co-glycolide) (PLGA)-NP encapsulating both ovalbumin (OVA) as a model antigen and polyinosinic-polycytidylic acid sodium salt (Toll-like receptor 3 ligand) as an adjuvant to increase intracellular delivery and promote DC maturation. The PLGA-NPs were taken up by DCs, and their uptake greatly facilitated major histocompatibility class I antigen presentation in vitro. Moreover, vaccination with PLGA-NP-treated DCs led to the generation of ovalbumin-specific CD8⁺ T cells, and the resulting antitumor efficacy was significantly increased in EG.7 and TC-1 tumor-bearing mice compared to control mice (P<0.01). Taken together, these findings demonstrated that the PLGA-NP platform may be an effective method for delivering tumor-specific antigens or adjuvants to DCs.

Nanomaterials for enhanced immunity as an innovative paradigm in nanomedicine

Since the advent of nanoparticle technology, novel and versatile properties of nanomaterials have been introduced, which has constantly expanded their applications in therapeutics. Introduction of nanomaterials for immunomodulation has opened up new avenues with tremendous potential. Interesting properties of nanoparticles, such as adjuvanticity, capability to enhance cross-presentation, polyvalent presentation, siRNA delivery for silencing of immunesuppressive gene, targeting and imaging of immune cells have been known to have immense utility in vaccination and immunotherapy. A thorough understanding of the merits associated with nanomaterials is crucial for designing of modular and versatile nanovaccines, for improved immune response. With the emerging prerequisites of vaccination, nanomaterial-based immune stimulation, seems to be capable of taking the field of immunization to a next higher level.

Tumor progression and the different faces of the PERK kinase

The serine/threonine endoplasmic reticulum (ER) kinase, protein kinase R (PKR)-like ER kinase (PERK), is a pro-adaptive protein kinase whose activity is regulated indirectly by protein misfolding within the ER. As the oxidative folding environment in the ER is sensitive to a variety of cellular stresses, many of which occur during neoplastic transformation and in the tumor microenvironment, there has been considerable interest in defining whether PERK positively contributes to tumor progression and whether it represents a significant therapeutic target. Herein, we review the current knowledge of PERK-dependent signaling pathways, the contribution of downstream substrates including recently characterized new PERK substrates transcription factors Forkhead box O protein and diacyglycerol a lipid signaling second messenger, and efforts to develop small molecule PERK inhibitors.

Spatial separation of the processing and MHC class I loading compartments for cross-presentation of the tumor-associated antigen HER2/neu by human dendritic cells

Cross-presentation is the process by which professional antigen presenting cells (APCs) (B cells, dendritic cells (DCs) and macrophages) present endocytosed antigens (Ags) via MHC-I to CD8⁺ T cells. This process is crucial for induction of adaptive immune responses against tumors and infected cells. The pathways and cellular compartments involved in cross-presentation are unresolved and controversial. Among the cells with cross-presenting capacity, DCs are the most efficient, which was proposed to depend on prevention of endosomal acidification to block degradation of the epitopes. Contrary to this view, we show in this report that some cargoes induce strong endosomal acidification following uptake by human DCs, while others not. Moreover, processing of the tumor-associated antigen HER2/neu delivered in nanoparticles (NP) for cross-presentation of the epitope HER2/neu_369-377 on HLA-A2 depended on endosomal acidification and cathepsin activity as well as proteasomes, and newly synthesized HLA class I. However, the HLA-A*0201/HER2/neu_369-377 complexes were not found in the endoplasmic reticulum (ER) nor in endolysosomes but in hitherto not described vesicles. The data thus indicate spatial separation of antigen processing and loading of MHC-I for cross-presentation: antigen processing occurs in the uptake compartment and the cytosol whereas MHC-I loading with peptide takes place in a distinct subcellular compartment. The findings further elucidate the cellular pathways involved in the cross-presentation of a full-length, clinically relevant tumor-associated antigen by human DCs, and the impact of the vaccine formulation on antigen processing and CD8⁺ T cell induction.

Near-infrared labeled, ovalbumin loaded polymeric nanoparticles based on a hydrophilic polyester as model vaccine: In vivo tracking and evaluation of antigen-specific CD8(+) T cell immune response

Particulate antigen delivery systems aimed at the induction of antigen-specific T cells form a promising approach in immunotherapy to replace pharmacokinetically unfavorable soluble antigen formulations. In this study, we developed a delivery system using the model protein antigen ovalbumin (OVA) encapsulated in nanoparticles based on the hydrophilic polyester poly(lactide-co-hydroxymethylglycolic acid) (pLHMGA). Spherical nanoparticles with size 300-400 nm were prepared and characterized and showed a strong ability to deliver antigen to dendritic cells for cross-presentation to antigen-specific T cells in vitro. Using near-infrared (NIR) fluorescent dyes covalently linked to both the nanoparticle and the encapsulated OVA antigen, we tracked the fate of this formulation in mice. We observed that the antigen and the nanoparticles are efficiently co-transported from the injection site to the draining lymph nodes, in a more gradual and durable manner than soluble OVA protein. OVA-loaded pLHMGA nanoparticles efficiently induced antigen cross-presentation to OVA-specific CD8+ T cells in the lymph nodes, superior to soluble OVA vaccination. Together, these data show the potential of pLHMGA nanoparticles as attractive antigen delivery vehicles.

Use of enhanced interleukin-2 formulations for improved immunotherapy against cancer

The use of interleukin-2 (IL-2) for the stimulation of an effector immune response against metastatic cancer dates back to the early 1980s. Administration of unmodified IL-2, either alone or together with antigen-specific approaches, has resulted in remarkably long-term survival of some patients suffering from metastatic melanoma. However, such treatment is usually hampered by the appearance of toxic adverse effects, which has motivated the engineering of modified IL-2 formulations showing reduced toxicity while being more potent at stimulating anti-tumor effector immune cells. In this review we summarize and discuss the features and biological relevance of several enhanced IL-2 formulations, compare these to IL-15-based therapeutics, and try to foreshadow their potential in immunological research and immunotherapy.