Delivery of immunostimulatory monoclonal antibodies by encapsulated hybridoma cells

Cell microencapsulation techniques for cancer modelling and drug discovery

Cell encapsulation into spherical microparticles is a promising bioengineering tool in many fields, including 3D cancer modelling and pre-clinical drug discovery. Cancer microencapsulation models can more accurately reflect the complex solid tumour microenvironment than 2D cell culture and therefore would improve drug discovery efforts. However, these microcapsules, typically in the range of 1 - 5000 µm in diameter, must be carefully designed and amenable to high-throughput production. This review therefore aims to outline important considerations in the design of cancer cell microencapsulation models for drug discovery applications and examine current techniques to produce these. Extrusion (dripping) droplet generation and emulsion-based techniques are highlighted and their suitability to high-throughput drug screening in terms of tumour physiology and ease of scale up is evaluated.

Cell delivery devices for cancer immunotherapy

Adoptive cell therapy (ACT) that leverages allogeneic or autologous immune cells holds vast promise in targeted cancer therapy. Despite the tremendous success of ACT in treating hematopoietic malignancies, its efficacy is limited in eradicating solid tumors via intravenous infusion of immune cells. With the extending technology of cancer immunotherapy, novel delivery strategies have been explored to improve the therapeutic potency of adoptively transferred cells for solid tumor treatment by innovating the administration route, maintaining the cell viability, and normalizing the tumor microenvironment. In this review, a variety of devices for cell delivery are summarized. Perspectives and challenges of cell delivery devices for cancer immunotherapy are also discussed.

Image-guided intratumoral immunotherapy: Developing a clinically practical technology

Immunotherapy has revolutionized the contemporary oncology landscape, with durable responses possible across a range of cancer types. However, the majority of cancer patients do not respond to immunotherapy due to numerous immunosuppressive barriers. Efforts to overcome these barriers and increase systemic immunotherapy efficacy have sparked interest in the local intratumoral delivery of immune stimulants to activate the local immune response and subsequently drive systemic tumor immunity. While clinical evaluation of many therapeutic candidates is ongoing, development is hindered by a lack of imaging confirmation of local delivery, insufficient intratumoral drug distribution, and a need for repeated injections. The use of polymeric drug delivery systems, which have been widely used as platforms for both image guidance and controlled drug release, holds promise for delivery of intratumoral immunoadjuvants and the development of an in situ cancer vaccine for patients with metastatic cancer. In this review, we explore the current state of the field for intratumoral delivery and methods for optimizing controlled drug release, as well as practical considerations for drug delivery design to be optimized for clinical image guided delivery particularly by CT and ultrasound.

Sustained Delivery of a Monoclonal Antibody against SARS-CoV-2 by Microencapsulated Cells: A Proof-of-Concept Study

BACKGROUND

Monoclonal antibody (mAb) therapy is a promising antiviral intervention for Coronovirus disease (COVID-19) with a potential for both treatment and prophylaxis. However, a major barrier to implementing mAb therapies in clinical practice is the intricate nature of mAb preparation and delivery. Therefore, here, in a pre-clinical model, we explored the possibility of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mAb delivery using a mAb-expressing encapsulated cell system.

METHODS

Murine G-8 myoblasts were transfected with plasmids coding for the heavy and light chains of CR3022, a well-characterized SARS-CoV-2 mAb that targets the Spike receptor binding domain (RBD), and then encapsulated into alginate microcapsules. The microcapsules were then intraperitoneally implanted into immunocompetent (C57/BL6J) mice and changes in circulating CR3022 titres were assessed. The in vitro and ex vivo characterization of the mAb was performed using western blotting, RBD ELISA, and microscopy.

RESULTS

Transfected G-8 myoblasts expressed intact CR3022 IgG at levels comparable to transfected HEK-293 cells. Cell encapsulation yielded microcapsules harbouring approximately 1000 cells/capsule and sustainably secreting CR3022 mAb. Subsequent peritoneal G-8 microcapsule implantation into mice resulted in a gradual increase of CR3022 concentration in blood, which by day 7 peaked at 1923 [1656-2190] ng/mL and then gradually decreased ~4-fold by day 40 post-implantation. Concurrently, we detected an increase in mouse anti-CR3022 IgG titers, while microcapsules recovered by day 40 post-implantation showed a reduced per-microcapsule mAb production.

SUMMARY

We demonstrate here that cell microencapsulation is a viable approach to systemic delivery of intact SARS-CoV-2 mAb, with potential therapeutic applications that warrant further exploration.

Current advances in cell therapeutics: A biomacromolecules application perspective

INTRODUCTION

Many chronic diseases have evolved and to circumvent the limitations of using conventional drug therapies, smart cell encapsulating delivery systems have been explored to customize the treatment with alignment to disease longevity. Cell therapeutics has advanced in tandem with improvements in biomaterials that can suitably deliver therapeutic cells to achieve targeted therapy. Among the promising biomacromolecules for cell delivery are those that share bio-relevant architecture with the extracellular matrix and display extraordinary compatibility in the presence of therapeutic cells. Interestingly, many biomacromolecules that fulfil these tenets occur naturally and can form hydrogels.

AREAS COVERED

This review provides a concise incursion into the paradigm shift to cell therapeutics using biomacromolecules. Advances in the design and use of biomacromolecules to assemble smart therapeutic cell carriers is discussed in light of their pivotal role in enhancing cell encapsulation and delivery. In addition, the principles that govern the application of cell therapeutics in diabetes, neuronal disorders, cancers and cardiovascular disease are outlined.

EXPERT OPINION

Cell therapeutics promises to revolutionize the treatment of various secretory cell dysfunctions. Current and future advances in designing functional biomacromolecules will be critical to ensure that optimal delivery of therapeutic cells is achieved with desired biosafety and potency.

Biomaterials for Personalized Cell Therapy

Cell therapy has already had an important impact on healthcare and provided new treatments for previously intractable diseases. Notable examples include mesenchymal stem cells for tissue regeneration, islet transplantation for diabetes treatment, and T cell delivery for cancer immunotherapy. Biomaterials have the potential to extend the therapeutic impact of cell therapies by serving as carriers that provide 3D organization and support cell viability and function. With the growing emphasis on personalized medicine, cell therapies hold great potential for their ability to sense and respond to the biology of an individual patient. These therapies can be further personalized through the use of patient-specific cells or with precision biomaterials to guide cellular activity in response to the needs of each patient. Here, the role of biomaterials for applications in tissue regeneration, therapeutic protein delivery, and cancer immunotherapy is reviewed, with a focus on progress in engineering material properties and functionalities for personalized cell therapies.

Cell Encapsulation Within Alginate Microcapsules: Immunological Challenges and Outlook

Cell encapsulation is a bioengineering technology that provides live allogeneic or xenogeneic cells packaged in a semipermeable immune-isolating membrane for therapeutic applications. The concept of cell encapsulation was first proposed almost nine decades ago, however, and despite its potential, the technology has yet to deliver its promise. The few clinical trials based on cell encapsulation have not led to any licensed therapies. Progress in the field has been slow, in part due to the complexity of the technology, but also because of the difficulties encountered when trying to prevent the immune responses generated by the various microcapsule components, namely the polymer, the encapsulated cells, the therapeutic transgenes and the DNA vectors used to genetically engineer encapsulated cells. While the immune responses induced by polymers such as alginate can be minimized using highly purified materials, the need to cope with the immunogenicity of encapsulated cells is increasingly seen as key in preventing the immune rejection of microcapsules. The encapsulated cells are recognized by the host immune cells through a bidirectional exchange of immune mediators, which induce both the adaptive and innate immune responses against the engrafted capsules. The potential strategies to cope with the immunogenicity of encapsulated cells include the selective diffusion restriction of immune mediators through capsule pores and more recently inclusion in microcapsules of immune modulators such as CXCL12. Combining these strategies with the use of well-characterized cell lines harboring the immunomodulatory properties of stem cells should encourage the incorporation of cell encapsulation technology in state-of-the-art drug development.

Nano-, micro-, and macroscale drug delivery systems for cancer immunotherapy

Immunotherapy is moving to the frontier of cancer treatment. Drug delivery systems (DDSs) have greatly advanced the development of cancer immunotherapeutic regimen and combination treatment. DDSs can spatiotemporally present tumor antigens, drugs, immunostimulatory molecules, or adjuvants, thus enabling the modulation of immune cells including dendritic cells (DCs) or T-cells directly in vivo and thereby provoking robust antitumor immune responses. Cancer vaccines, immune checkpoint blockade, and adoptive cell transfer have shown promising therapeutic efficiency in clinic, and the incorporation of DDSs may further increase antitumor efficiency while decreasing adverse side effects. This review focuses on the use of nano-, micro-, and macroscale DDSs for co-delivery of different immunostimulatory factors to reprogram the immune system to combat cancer. Regarding to nanoparticle-based DDSs, we emphasize the nanoparticle-based tumor immune environment modulation or as an addition to gene therapy, photodynamic therapy, or photothermal therapy. For microparticle or capsule-based DDSs, an overview of the carrier type, fabrication approach, and co-delivery of tumor vaccines and adjuvants is introduced. Finally, macroscale DDSs including hydrogels and scaffolds are also included and their role in personalized vaccine delivery and adoptive cell transfer therapy are described. Perspective and clinical translation of DDS-based cancer immunotherapy is also discussed. We believe that DDSs hold great potential in advancing the fundamental research and clinical translation of cancer immunotherapy. STATEMENT OF SIGNIFICANCE: Immunotherapy is moving to the frontier of cancer treatment. Drug delivery systems (DDSs) have greatly advanced the development of cancer immunotherapeutic regimen and combination treatment. In this comprehensive review, we focus on the use of nano-, micro-, and macroscale DDSs for the co-delivery of different immunostimulatory factors to reprogram the immune system to combat cancer. We also propose the perspective on the development of next-generation DDS-based cancer immunotherapy. This review indicates that DDSs can augment the antitumor T-cell immunity and hold great potential in advancing the fundamental research and clinical translation of cancer immunotherapy by simultaneously delivering dual or multiple immunostimulatory drugs.

Microencapsulated Cells for Cancer Therapy

The microencapsulation of different types of cells that are able to produce therapeutic factors is being investigated for the treatment of several human diseases. Most efforts are focused on chronic and degenerative diseases as this strategy could become an alternative to some commonly used parenteral treatments that need to be repeatedly administered. But, this approach has also been investigated in the field of oncology with the aim of providing immunomodulatory antibodies that are able to enhance the patient's inherent immune response against the tumor. These kind of treatments would provide the patient with the therapeutic drug produced in situ, de novo, and in a sustained way, making the therapy more comfortable.Although different devices are nowadays available to produce cell-enclosing alginate-microcapsules, here, we describe the most important steps and advices in order to fabricate alginate-poly-L-lysine-alginate microcapsules containing hybridoma cells for cancer management using an electrostatic bead generator, and how to evaluate the viability of those cells over the time.

Applications of Cell Microencapsulation

The goal of this chapter is to provide an overview of the different purposes for which the cell microencapsulation technology can be used. These include immunoisolation of non-autologous cells used for cell therapy; immobilization of cells for localized (targeted) delivery of therapeutic products to ablate, repair, or regenerate tissue; simultaneous delivery of multiple therapeutic agents in cell therapy; spatial compartmentalization of cells in complex tissue engineering; expansion of cells in culture; and production of different probiotics and metabolites for industrial applications. For each of these applications, specific examples are provided to illustrate how the microencapsulation technology can be utilized to achieve the purpose. However, successful use of the cell microencapsulation technology for whatever purpose will ultimately depend upon careful consideration for the choice of the encapsulating polymers, the method of fabrication (cross-linking) of the microbeads, which affects the permselectivity, the biocompatibility and the mechanical strength of the microbeads as well as environmental parameters such as temperature, humidity, osmotic pressure, and storage solutions.The various applications discussed in this chapter are illustrated in the different chapters of this book and where appropriate relevant images of the microencapsulation products are provided. It is hoped that this outline of the different applications of cell microencapsulation would provide a good platform for tissue engineers, scientists, and clinicians to design novel tissue constructs and products for therapeutic and industrial applications.

Advances in islet encapsulation technologies

Type 1 diabetes is an autoimmune disorder in which the immune system attacks and destroys insulin-producing islet cells of the pancreas. Although islet transplantation has proved to be successful for some patients with type 1 diabetes, its widespread use is limited by islet donor shortage and the requirement for lifelong immunosuppression. An encapsulation strategy that can prevent the rejection of xenogeneic islets or of stem cell-derived allogeneic islets can potentially eliminate both of these barriers. Although encapsulation technology has met several challenges, the convergence of expertise in materials, nanotechnology, stem cell biology and immunology is allowing us to get closer to the goal of encapsulated islet cell therapy for humans.

Contribution of polymeric materials to progress in xenotransplantation of microencapsulated cells: a review

Cell microencapsulation and subsequent transplantation of the microencapsulated cells require multidisciplinary approaches. Physical, chemical, biological, engineering, and medical expertise has to be combined. Several natural and synthetic polymeric materials and different technologies have been reported for the preparation of hydrogels, which are suitable to protect cells by microencapsulation. However, owing to the frequent lack of adequate characterization of the hydrogels and their components as well as incomplete description of the technology, many results of in vitro and in vivo studies appear contradictory or cannot reliably be reproduced. This review addresses the state of the art in cell microencapsulation with special focus on microencapsulated cells intended for xenotransplantation cell therapies. The choice of materials, the design and fabrication of the microspheres, as well as the conditions to be met during the cell microencapsulation process, are summarized and discussed prior to presenting research results of in vitro and in vivo studies. Overall, this review will serve to sensitize medically educated specialists for materials and technological aspects of cell microencapsulation.

Encapsulation of anti-carbonic anhydrase IX antibody in hydrogel microspheres for tumor targeting

Encapsulation is a well-established method of biomaterial protection, controlled release, and efficient delivery. Here we evaluated encapsulation of monoclonal antibody M75 directed to tumor biomarker carbonic anhydrase IX (CA IX) into alginate microbeads (SA-beads) or microcapsules made of sodium alginate, cellulose sulfate, and poly(methylene-co-guanidine) (PMCG). M75 antibody release was quantified using ELISA and its binding properties were assessed by immunodetection methods. SA-beads showed rapid M75 antibody release in the first hour, followed by steady release during the whole experiment of 7 days. In contrast, the M75 release from PMCG capsules was gradual, reaching the maximum concentration on the 7th day. The release was more efficient at pH 6.8 compared to pH 7.4. The released antibody could recognize CA IX, and target the CA IX-positive cells in 3D spheroids. In conclusion, SA-beads and PMCG microcapsules can be considered as promising antibody reservoirs for targeting of cancer cells.

Generation and characterization of a novel human IgG1 antibody against vascular endothelial growth factor receptor 2

VEGF and its receptors, especially VEGFR2 (KDR), are known to play a critical role in angiogenesis under both physiological and pathological conditions, including cancer and angiogenic retinopathies. This study was aimed at developing a fully human IgG1 antibody (mAb-04) constructed from a phage-derived scFv, targeting the VEGF/VEGFR2 pathway. Firstly, an innovative transfection system, containing two recombinant expression vectors (pMH3 and pCApuro), were introduced into CHO-s cells and clones with higher yield selected accordingly. After an optimal fermentation condition was determined, fed-batch fermentation was performed in 5-L bioreactor with a final yield up to 60 mg/L. Further, cell proliferation, wound healing, transwell invasion, tube formation and chick embryo chorioallantoic membrane assays showed significant anti-angiogenic activity of mAb-04 in vitro and in vivo. In addition, the results of Western blotting indicated the ability of mAb-04 to inhibit VEGF-induced VEGFR2 signaling pathway. Finally, ADCC assay demonstrated that mAb-04 is capable of mediating tumor cell killing in presence of effector cells. This study has therefore proved that the full-length antibody targeting human VEGFR2 has potential clinical applications in the treatment of cancer and other diseases where pathological angiogenesis is involved.

Therapeutic vaccines for cancer: an overview of clinical trials

The therapeutic potential of host-specific and tumour-specific immune responses is well recognized and, after many years, active immunotherapies directed at inducing or augmenting these responses are entering clinical practice. Antitumour immunization is a complex, multi-component task, and the optimal combinations of antigens, adjuvants, delivery vehicles and routes of administration are not yet identified. Active immunotherapy must also address the immunosuppressive and tolerogenic mechanisms deployed by tumours. This Review provides an overview of new results from clinical studies of therapeutic cancer vaccines directed against tumour-associated antigens and discusses their implications for the use of active immunotherapy.

Microencapsulated cell tracking

Microencapsulation of therapeutic cells has been widely pursued to achieve cellular immunoprotection following transplantation. Initial clinical studies have shown the potential of microencapsulation using semi-permeable alginate layers, but much needs to be learned about the optimal delivery route, in vivo pattern of engraftment, and microcapsule stability over time. In parallel with noninvasive imaging techniques for 'naked' (i.e. unencapsulated) cell tracking, microcapsules have now been endowed with contrast agents that can be visualized by (1) H MRI, (19) F MRI, X-ray/computed tomography and ultrasound imaging. By placing the contrast agent formulation in the extracellular space of the hydrogel, large amounts of contrast agents can be incorporated with negligible toxicity. This has led to a new generation of imaging biomaterials that can render cells visible with multiple imaging modalities.

Therapeutic applications of encapsulated cells

The synergy of some promising advances in the fields of cell therapy and biomaterials together with improvements in the fabrication of more refined and tailored microcapsules for drug delivery have triggered the progress of cell encapsulation technology. Cell microencapsulation involves immobilizing the transplanted cells within a biocompatible scaffold surrounded by a membrane in attempt to isolate the cells from the host immune attack and enhance or prolong their function in vivo. This technology represents one strategy which aims to overcome the present difficulties related to local and systemic controlled release of drugs and growth factors as well as to organ graft rejection and thus the requirements for use of immunomodulatory protocols or immunosuppressive drugs. This chapter gives an overview of the current situation of cell encapsulation technology as a controlled drug delivery system, and the essential requirements of the technology, some of the therapeutic applications, the challenges, and the future directions under investigation are highlighted.

Liver gene transfer of interkeukin-15 constructs that become part of circulating high density lipoproteins for immunotherapy

Apolipoprotein A-I (Apo A-I) is a major component of high density lipoproteins (HDL) that transport cholesterol in circulation. We have constructed an expression plasmid encoding a chimeric molecule encompassing interleukin-15 (IL-15) and Apo A-I (pApo-hIL15) that was tested by hydrodynamic injections into mice and was co-administered with a plasmid encoding the sushi domain of IL-15Rα (pSushi) in order to enhance IL-15 trans-presentation and thereby bioactivity. The pharmacokinetics of the Apo A-I chimeric protein were much longer than non-stabilized IL-15 and its bioactivity was enhanced in combination with IL-15Rα Sushi. Importantly, the APO-IL-15 fusion protein was incorporated in part into circulating HDL. Liver gene transfer of these constructs increased NK and memory-phenotype CD8 lymphocyte numbers in peripheral blood, spleen and liver as a result of proliferation documented by CFSE dilution and BrdU incorporation. Moreover, the gene transfer procedure partly rescued the NK and memory T-cell deficiency observed in IL-15Rα^−/− mice. pApo-hIL15+ pSushi gene transfer to the liver showed a modest therapeutic activity against subcutaneously transplanted MC38 colon carcinoma tumors, that was more evident when tumors were set up as liver metastases. The improved pharmacokinetic profile and the strong biological activity of APO-IL-15 fusion protein holds promise for further development in combination with other immunotherapies.

A preliminary approach to the repair of myocardial infarction using adipose tissue-derived stem cells encapsulated in magnetic resonance-labelled alginate microspheres in a porcine model

Adipose tissue-derived stem cells (ASCs) have properties of self-renewal, pluripotency and high proliferative capability that make them useful for the treatment of cardiac ventricular function following ischaemic injury. However, their therapeutic use is limited due to the low retention of the cells at the targeted site. To address this issue, we developed semipermeable membrane microcapsules labelled with Endorem (magnetocapsules) that provide mechanical and immunological immune protection to the cells while maintaining internal cell microenvironment. In addition, the particles allow tracking the presence and migration of injected cells in vivo by Magnetic Resonance Imaging (MRI). Results indicate that after 21 days in culture, the cells encapsulated in the magnetocapsules showed similar viabilities than cells encapsulated in conventional microcapsules. MRI confirmed a gradual loss of the intensity of the iron oxide label in the non-encapsulated Endorem labelled cells, while magnetocapsules were detected throughout the study period, suggesting that cell retention in the myocardium is improved when cells are enclosed within the magnetocapsules. To further evaluate treatment's effect on global cardiac function, MRI determination of infarct size and left ventricular ejection fraction (LVEF) was performed. In vivo results showed no statistically significant differences in heart rate and cardiac output between treatment groups. In conclusion, cells enclosed within magnetocapsules have shown suitable viability and have been detected in vivo throughout the study period. Further studies will evaluate whether increasing cell loading with the particles may help to improve the therapeutic results.

Reprogrammed cell delivery for personalized medicine

In most approaches, personalized medicine requires time- and cost-intensive characterization of an individual's genetic background in order to achieve the best-adapted therapy. For this purpose, cell-based drug delivery offers a promising alternative. In particular, synthetic biology has introduced the vision of cells being programmable therapeutic production facilities that can be introduced into patients. This review highlights the progress made in synthetic biology-based cell engineering toward advanced drug delivery entities. Starting from basic one-input responsive transcriptional or post-transcriptional gene control systems, the field has reached a level on which cells can be engineered to detect cancer cells, to obtain control over T-cell proliferation, and to restore blood glucose homeostasis upon blue light illumination. Furthermore, a cellular implant was developed that detects blood urate level disorders and acts accordingly to restore homeostasis while another cellular implant was engineered as an artificial insemination device that releases bull sperm into bovine ovarian only during ovulation time by recording endogenous luteinizing hormone levels. Soon, the field will reach a stage at which cells can be reprogrammed to detect multiple metabolic parameters and self-sufficiently treat any disorder connected to them.

Cell-mediated drug delivery

INTRODUCTION

Drug targeting to sites of tissue injury, tumor or infection with limited toxicity is the goal for successful pharmaceutics. Immunocytes (including mononuclear phagocytes (dendritic cells, monocytes and macrophages), neutrophils and lymphocytes) are highly mobile; they can migrate across impermeable barriers and release their drug cargo at sites of infection or tissue injury. Thus, immune cells can be exploited as Trojan horses for drug delivery.

AREAS COVERED

This paper reviews how immunocytes laden with drugs can cross the blood-brain or blood-tumor barriers to facilitate treatments for infectious diseases, injury, cancer, or inflammatory diseases. The promises and perils of cell-mediated drug delivery are reviewed, with examples of how immunocytes can be harnessed to improve therapeutic end points.

EXPERT OPINION

Using cells as delivery vehicles enables targeted drug transport and prolonged circulation times, along with reductions in cell and tissue toxicities. Such systems for drug carriage and targeted release represent a new disease-combating strategy being applied to a spectrum of human disorders. The design of nanocarriers for cell-mediated drug delivery may differ from those used for conventional drug delivery systems; nevertheless, engaging different defense mechanisms in drug delivery may open new perspectives for the active delivery of drugs.