Optimization of Human T-Cell Expansion Ex Vivo Using Magnetic Beads Conjugated with Anti-CD3 and Anti-CD28 Antibodies

T Cell Activators Exhibit Distinct Downstream Effects on Chimeric Antigen Receptor T Cell Phenotype and Function

T cell activation is an essential step in chimeric Ag receptor (CAR) T (CAR T) cell manufacturing and is accomplished by the addition of activator reagents that trigger the TCR and provide costimulation. We explore several T cell activation reagents and examine their effects on key attributes of CAR T cell cultures, such as activation/exhaustion markers, cell expansion, gene expression, and transduction efficiency. Four distinct activators were examined, all using anti-CD3 and anti-CD28, but incorporating different mechanisms of delivery: Dynabeads (magnetic microspheres), TransAct (polymeric nanomatrix), Cloudz (alginate hydrogel), and Microbubbles (lipid membrane containing perfluorocarbon gas). Clinical-grade lentiviral vector was used to transduce cells with a bivalent CD19/CD22 CAR, and cell counts and flow cytometry were used to monitor the cells throughout the culture. We observed differences in CD4/CD8 ratio when stimulating with the Cloudz activator, where there was a significant skewing toward CD8 T cells. The naive T cell subset expressing CD62L+CCR7+CD45RA+ was the highest in all donors when stimulating with Dynabeads, whereas effector/effector memory cells were highest when using the Cloudz. Functional assays demonstrated differences in killing of target cells and proinflammatory cytokine secretion, with the highest killing from the Cloudz-stimulated cells among all donors. This study demonstrates that the means by which these stimulatory Abs are presented to T cells contribute to the activation, resulting in differing effects on CAR T cell function. These studies highlight important differences in the final product that should be considered when manufacturing CAR T cells for patients in the clinic.

Antigen Presenting Cell Mimetic Lipid Nanoparticles for Rapid mRNA CAR T Cell Cancer Immunotherapy

Chimeric antigen receptor (CAR) T cell therapy has achieved remarkable clinical success in the treatment of hematological malignancies. However, producing these bespoke cancer-killing cells is a complicated ex vivo process involving leukapheresis, artificial T cell activation, and CAR construct introduction. The activation step requires the engagement of CD3/TCR and CD28 and is vital for T cell transfection and differentiation. Though antigen-presenting cells (APCs) facilitate activation in vivo, ex vivo activation relies on antibodies against CD3 and CD28 conjugated to magnetic beads. While effective, this artificial activation adds to the complexity of CAR T cell production as the beads must be removed prior to clinical implementation. To overcome this challenge, this work develops activating lipid nanoparticles (aLNPs) that mimic APCs to combine the activation of magnetic beads and the transfection capabilities of LNPs. It is shown that aLNPs enable one-step activation and transfection of primary human T cells with the resulting mRNA CAR T cells reducing tumor burden in a murine xenograft model, validating aLNPs as a promising platform for the rapid production of mRNA CAR T cells.

Particle-Based Artificial Antigen-Presenting Cell Systems for T Cell Activation in Adoptive T Cell Therapy

T cell-based adoptive cell therapy (ACT) has emerged as a promising treatment for various diseases, particularly cancers. Unlike other immunotherapy modalities, ACT involves directly transferring engineered T cells into patients to eradicate diseased cells; hence, it necessitates methods for effectively activating and expanding T cells in vitro. Artificial antigen-presenting cells (aAPCs) have been widely developed based on biomaterials, particularly micro- and nanoparticles, and functionalized with T cell stimulatory antibodies to closely mimic the natural T cell-APC interactions. Due to their vast clinical utility, aAPCs have been employed as an off-the-shelf technology for T cell activation in FDA-approved ACTs, and the development of aAPCs is constantly advancing with the emergence of aAPCs with more sophisticated designs and additional functionalities. Here, we review the recent advancements in particle-based aAPCs for T cell activation in ACTs. Following a brief introduction, we first describe the manufacturing processes of ACT products. Next, the design and synthetic strategies for micro- and nanoparticle-based aAPCs are discussed separately to emphasize their features, advantages, and limitations. Then, the impact of design parameters of aAPCs, such as size, shape, ligand density/mobility, and stiffness, on their functionality and biomedical performance is explored to provide deeper insights into the design concepts and principles for more efficient and safer aAPCs. The review concludes by discussing current challenges and proposing future perspectives for the development of more advanced aAPCs.

Examining the effect of activated cytotoxic (CD8+) T-cell exosomes to the lung cancer

Lung cancer continues to be a major health problem worldwide owing to its incidence, and causes physical, psychological, social, and economic problems. Activated cytotoxic T cells (ACTC) are positively correlated with the tumor microenvironment (TME), improving the prognosis of cancer patients. Recently, ACTC-derived exosomes (ACTC-dExo) were implicated in this effect by inhibiting mesenchymal stem cells, which may promote metastasis in the TME. Exosomes are thought to be advantageous for the specific delivery of drugs to cancer cells because they have the characteristics of natural liposomes, are nanosized, and remain largely stable in the blood due to the protein and lipid content they carry on their membranes. In this study, we aimed to determine the cytotoxic and metastatic inhibitory effects of ACTC-dExo in A549 cells in vitro. Cytotoxic CD8+ T cells were isolated from whole blood obtained from healthy individuals and cultured for 5-7 days after stimulation. The ACTC-dExo serum-free culture medium was collected by ultracentrifugation. Characterization and quantification of the isolated exosomes were performed using flow cytometry, electron microscopy, zeta-sizer measurements, and bicinchoninic acid (BCA) assays. We co-cultured ACTC and ACTC-dExo with A549 cells for 48 h. The viability of A549 cells was evaluated using a WST-1 assay. The metastasis-related genes MMP2, MMP9, TWIST, SNAI1, and CDH1 were detected by qRT-PCR, and MMP2 and MMP9 proteins were evaluated by confocal microscopy. In addition, changes in cell migration were investigated using a scratch assay. ACTC-dExo were found to have anti-proliferative and anti-metastatic effects and reduced cancer cell proliferation and metastatic properties.

Construction of micro-nano robots: living cells and functionalized biological cell membranes

Micro-nano robots have emerged as a promising research field with vast potential applications in biomedicine. The motor is the key component of micro-nano robot research, and the design of the motor is crucial. Among the most commonly used motors are those derived from living cells such as bacteria with flagella, sperm, and algal cells. Additionally, scientists have developed numerous self-adaptive biomimetic motors with biological functions, primarily cell membrane functionalized micromotors. This novel type of motor exhibits remarkable performance in complex media. This paper provides a comprehensive review of the structure and performance of micro-nano robots that utilize living cells and functionalized biological cell membranes. We also discuss potential practical applications of these mirco-nano robots as well as potential challenges that may arise in future development.

Applications of Anti-Cytomegalovirus T Cells for Cancer (Immuno)Therapy

Infection with cytomegalovirus (CMV) is highly prevalent in the general population and largely controlled by CD8pos T cells. Intriguingly, anti-CMV T cells accumulate over time to extraordinarily high numbers, are frequently present as tumor-resident 'bystander' T cells, and remain functional in cancer patients. Consequently, various strategies for redirecting anti-CMV CD8pos T cells to eliminate cancer cells are currently being developed. Here, we provide an overview of these strategies including immunogenic CMV peptide-loading onto endogenous HLA complexes on cancer cells and the use of tumor-directed fusion proteins containing a preassembled CMV peptide/HLA-I complex. Additionally, we discuss conveying the advantageous characteristics of anti-CMV T cells in adoptive cell therapy. Utilization of anti-CMV CD8pos T cells to generate CAR T cells promotes their in vivo persistence and expansion due to appropriate co-stimulation through the endogenous (CMV-)TCR signaling complex. Designing TCR-engineered T cells is more challenging, as the artificial and endogenous TCR compete for expression. Moreover, the use of expanded/reactivated anti-CMV T cells to target CMV peptide-expressing glioblastomas is discussed. This review highlights the most important findings and compares the benefits, disadvantages, and challenges of each strategy. Finally, we discuss how anti-CMV T cell therapies can be further improved to enhance treatment efficacy.

Magnetic-Acoustic Sequentially Actuated CAR T Cell Microrobots for Precision Navigation and In Situ Antitumor Immunoactivation

Despite its clinical success, chimeric antigen receptor T (CAR T)-cell immunotherapy remains limited in solid tumors, owing to the harsh physical barriers and immunosuppressive microenvironment. Here a CAR-T-cell-based live microrobot (M-CAR T) is created by decorating CAR T with immunomagnetic beads using click conjugation. M-CAR Ts are capable of magnetic-acoustic actuation for precision targeting and in situ activation of antitumor immune responses. Sequential actuation endows M-CAR Ts with magnetically actuated anti-flow and obstacle avoidance as well as tissue penetration driven by acoustic propulsion, enabling efficient migration and accumulation in artificial tumor models. In vivo, sequentially actuated M-CAR Ts achieves long-distance targeting and accumulate at the peritumoural area under programmable magnetic guidance, and subsequently acoustic tweezers actuate M-CAR Ts to migrate into deep tumor tissues, resulting in a 6.6-fold increase in accumulated exogenous CD8⁺ CAR T cells compared with that without actuation. Anti-CD3/CD28 immunomagnetic beads stimulate infiltrated CAR T proliferation and activation in situ, significantly enhancing their antitumor efficacy. Thus, this sequential-actuation-guided cell microrobot combines the merits of autonomous targeting and penetration of intelligent robots with in situ T-cell immunoactivation, and holds considerable promise for precision navigation and cancer immunotherapies.

Therapeutic Potential of Ex Vivo Expanded γδ T Cells against Osteosarcoma Cells

Immunotherapy is an attractive therapeutic strategy for the treatment of osteosarcoma (OS). The unique features of γδ T cells have made them popular for cancer immunotherapy. Here, we expanded γδ T cells using human peripheral blood mononuclear cells (PBMCs) and investigated their therapeutic potential against OS cells. PBMCs from healthy donors were cultured for 10 days with CON medium (unstimulated control); EX media, CON with recombinant human interleukin-2 (rhIL-2) and zoledronate; and EX28 media, CON with rhIL-2, zoledronate, and CD3/CD28 activator. The expanded γδ T cells were isolated by magnetic cell separation or fluorescence-activated cell sorting, cultured with two OS cell lines (KHOS/NP and MG-63) at various cell ratios with or without doxorubicin or ifosfamide, and analyzed for cytotoxicity and cytokine secretion. The number of CD3+γδTCR+Vγ9+ triple-positive γδ T cells and concentrations of IFN-γ and TNF-α were highest in the rhIL-2 (100 IU) and zoledronate (1 μM) supplemented culture conditions. The CD3/CD28 agonist did not show any additional effects on γδ T cell expansion. The expanded γδ T cells exhibited potent in vitro cytotoxicity against OS in a ratio- and time-dependent manner. The γδ T cells may enhance the effect of chemotherapeutic agents against OS and may be a new treatment strategy, including chemo-immunotherapy, for OS.

Modified Manufacturing Process Modulates CD19CAR T-cell Engraftment Fitness and Leukemia-Free Survival in Pediatric and Young Adult Subjects

T cells modified to express a chimeric antigen receptor (CAR) targeting CD19 can induce potent and sustained responses in children with relapsed/refractory acute lymphoblastic leukemia (ALL). The durability of remission is related to the length of time the CAR T cells persist. Efforts to understand differences in persistence have focused on the CAR construct, in particular the costimulatory signaling module of the chimeric receptor. We previously reported a robust intent-to-treat product manufacturing success rate and remission induction rate in children and young adults with recurrent/refractory B-ALL using the SCRI-CAR19v1 product, a second-generation CD19-specific CAR with 4-1BB costimulation coexpressed with the EGFRt cell-surface tag (NCT02028455). Following completion of the phase I study, two changes to CAR T-cell manufacturing were introduced: switching the T-cell activation reagent and omitting midculture EGFRt immunomagnetic selection. We tested the modified manufacturing process and resulting product, designated SCRI-CAR19v2, in a cohort of 21 subjects on the phase II arm of the trial. Here, we describe the unanticipated enhancement in product performance resulting in prolonged persistence and B-cell aplasia and improved leukemia-free survival with SCRI-CAR19v2 as compared with SCRI-CAR19v1.

Leveraging biomaterials for enhancing T cell immunotherapy

The dynamic roles of T cells in the immune system to recognize and destroy the infected or mutated cells render T cell therapy a prospective treatment for a variety of diseases including cancer, autoimmune diseases, and allograft rejection. However, the clinical applications of T cell therapy remain unsatisfactory due to the tedious manufacturing process, off-target cytotoxicity, poor cell persistence, and associated adverse effects. To this end, various biomaterials have been introduced to enhance T cell therapy by facilitating proliferation, enhancing local enrichment, prolonging retention, and alleviating side effects. This review highlights the design strategies of biomaterials developed for T cell expansion, enrichment, and delivery as well as their corresponding therapeutic effects. The prospects of biomaterials for enhancing T cell immunotherapy are also discussed in this review.

Chimeric antigen receptor engineered T cells and their application in the immunotherapy of solid tumours

In this article, we reviewed the current literature studies and our understanding of the parameters that affect the chimeric antigen receptor T cells (CAR-T's) activation, effector function, in vivo persistence, and antitumour effects. These factors include T cell subsets and their differentiation stages, the components of chimeric antigen receptors (CAR) design, the expression promoters and delivery vectors, and the CAR-T production process. The CAR signalling and CAR-T activation were also studied in comparison to TCR. The last section of the review gave special consideration of CAR design for solid tumours, focusing on strategies to improve CAR-T tumour infiltration and survival in the hostile tumour microenvironment. With several hundred clinical trials undergoing worldwide, the pace of CAR-T immunotherapy moves from bench to bedside is unprecedented. We hope that the article will provide readers a clear and comprehensive view of this rapidly evolving field and will help scientists and physician to design effective CAR-Ts immunotherapy for solid tumours.

Large-scale manufacturing and characterization of CMV-CD19CAR T cells

BACKGROUND

Adoptive transfer of CD19-specific chimeric antigen receptor (CD19CAR) T cells can induce dramatic disease regression in patients with B cell malignancies. CD19CAR T cell therapy may be limited by insufficient engraftment and persistence, resulting in tumor relapse. We previously demonstrated a proof of principle that cytomegalovirus (CMV)-specific T cells can be isolated and enriched prior to CD19CAR transduction to produce CMV-CD19CAR T cells, and that these CMV-CD19CAR T cells can be expanded in vivo through CMV vaccination, resulting in better tumor control in a murine model. Here we developed a clinical platform for generating CMV-CD19CAR T cells.

METHODS

Peripheral blood mononuclear cells (PBMCs) collected from CMV-seropositive healthy donors were stimulated with a good manufacturing practices-grade PepTivator overlapping CMVpp65 peptide pool and enriched for CMV-responsive interferon γ (IFNγ)+T cells using IFNγ Catchmatrix, within the CliniMACS Prodigy Cytokine Capture System (Miltenyi Biotec). Resulting CMV-specific T cells were transduced with a lentiviral vector encoding a second generation CD19R:CD28:ζ/EGFRt CAR and expanded with interleukin 2 (IL-2) and IL-15 for 15 days before characterization.

RESULTS

CMV-specific T cells were enriched from 0.8%±0.5 of input PBMC to 76.3%±11.6 in nine full-scale qualification runs (absolute yield of 4.2±3.3×10⁶ IFNγ+T cells from an input of 1×10⁹ PBMCs). Average CD19CAR transduction efficiency of CMV-specific T cells was 27.0%±14.2 in the final products, which underwent rapid expansion, resulting in a total cell dose of 6.2±0.9 × 10⁶ CD19CAR-tranduced T cells with CMV specificity (ie, functionally bispecific). CMV-CD19CAR T cells were polyclonal, expressed memory markers but had low expression of exhaustion markers, responded to both CD19 and CMVpp65 stimulation with rapid proliferation and exhibited antigen-specific effector functions against both CD19-expressing tumors and CMVpp65 antigen. The final products passed release criteria for clinical use.

CONCLUSIONS

We demonstrated the feasibility of our large-scale platform for generating CMV-CD19CAR T cells for clinical application. We plan to initiate a clinical trial at City of Hope using CMV-CD19CAR T cells for patients with intermediate/high-grade B cell non-Hodgkin's lymphoma immediately after autologous hematopoietic cell transplantation followed by vaccination with a novel CMV vaccine based on Modified Vaccinia Ankara (Triplex) 28 days and 56 days post-T cell infusion.

Tuning Antibody Presentation to Enhance T-Cell Activation for Downstream Cytotoxicity

Cytotoxic effector cells are an integral component of the immune response against pathogens and diseases such as cancer and thus of great interest to researchers who wish to enhance the native immune response. Although researchers routinely use particles to stimulate cytotoxic T cells, few studies have comprehensively investigated: (1) beyond initial activation responses (i.e., proliferation and CD25/CD69 expression) to downstream cancer-killing effects and (2) how to drive cytotoxic T-cell responses by adjusting biomolecular and physical properties of particles. In this study, we designed particles displaying an anti-CD3 antibody to activate cytotoxic T cells and study their downstream cytotoxic effects. We evaluated the effect of antibody immobilization, particle size, molecular surface density of an anti-CD3 antibody, and the inclusion of an anti-CD28 antibody on cytolytic granule release by T cells. We found that immobilizing the anti-CD3 antibody onto smaller nanoparticles elicited increased T-cell activation products for an equivalent delivery of the anti-CD3 antibody. We further established that the mechanism behind increased cancer cell death was associated with the proximity of T cells to cancer cells. Functionalizing particles additionally with the anti-CD28 antibody at an optimized antibody density caused increased T-cell proliferation and T-cell binding but we observed no effective increase in cytotoxicity. Meaningfully, our results are discussed within the context of commercially available and widely used anti-CD3/28 Dynabeads. These results showed that T-cell activation and cytotoxicity can be optimized with a molecular presentation on smaller particles and thus, offer exciting new possibilities to engineer T-cell activation responses for effective outcomes.

Semiflexible Immunobrushes Induce Enhanced T Cell Activation and Expansion

A variety of bioactive materials developed to expand T cells for adoptive transfer into cancer patients are currently evaluated in the clinic. In most cases, T cell activating biomolecules are attached to rigid surfaces or matrices and form a static interface between materials and the signaling receptors on the T cells. We hypothesized that a T cell activating polymer brush interface might better mimic the cell surface of a natural antigen-presenting cell, facilitating receptor movement and concomitant advantageous mechanical forces to provide enhanced T cell activating capacities. Here, as a proof of concept, we synthesized semiflexible polyisocyanopeptide (PIC) polymer-based immunobrushes equipped with T cell activating agonistic anti-CD3 (αCD3) and αCD28 antibodies placed on magnetic microbeads. We demonstrated enhanced efficiency of ex vivo expansion of activated primary human T cells even at very low numbers of stimulating antibodies compared to rigid beads. Importantly, the immunobrush architecture appeared crucial for this improved T cell activating capacity. Immunobrushes outperform current benchmarks by producing higher numbers of T cells exhibiting a combination of beneficial phenotypic characteristics, such as reduced exhaustion marker expression, high cytokine production, and robust expression of cytotoxic hallmarks. This study indicates that semiflexible immunobrushes have great potential in making T cell-based immunotherapies more effective.

Modeling human tumor-immune environments in vivo for the preclinical assessment of immunotherapies

Despite the significant contributions of immunocompetent mouse models to the development and assessment of cancer immunotherapies, they inadequately represent the genetic and biological complexity of corresponding human cancers. Immunocompromised mice reconstituted with a human immune system (HIS) and engrafted with patient-derived tumor xenografts are a promising novel preclinical model for the study of human tumor-immune interactions. Whilst overcoming limitations of immunocompetent models, HIS-tumor models often rely on reconstitution with allogeneic immune cells, making it difficult to distinguish between anti-tumor and alloantigen responses. Models that comprise of autologous human tumor and human immune cells provide a platform that is more representative of the patient immune-tumor interaction. However, limited access to autologous tissues, short experimental windows, and poor retention of tumor microenvironment and tumor infiltrating lymphocyte components are major challenges affecting the establishment and application of autologous models. This review outlines existing preclinical murine models for the study of immuno-oncology, and highlights innovations that can be applied to improve the feasibility and efficacy of autologous models.

Antigen-Presenting Hybrid Colloidal Crystal Clusters for Promoting T cells Expansion

T cell based-immunotherapy has been a powerful strategy to eradicate tumor cells in clinical trials. Effectively expanding the therapeutic T cells for clinical demand is still a challenge. Here, artificial antigen-presenting scaffolds are created for T cell ex vivo expansion. The antigen-presenting hybrid colloidal crystal clusters (HCCCs) with multiple stimuli are generated by internal encapsulation with prosurvival cytokines and surface decoration with activating antibodies to CD3ε and CD28, respectively. With the large loading capacity endowed by their abundant nanoporous structures, the antigen-presenting HCCCs can constantly release prosurvival cytokine IL-2. It is found that following the direct and multiple stimulations, the antigen-presenting HCCCs can effectively promote the expansion of T cells, which exhibits robust antitumor activity in vitro. Thus, the antigen-presenting HCCCs provide a novel expansion platform for clinical manufacturing of T cells.

Objectives, benefits and challenges of bioreactor systems for the clinical-scale expansion of T lymphocyte cells

Cell therapies based on T cell have gathered interest over the last decades for treatment of cancers, becoming recently the most investigated lineage for clinical trials. Although results of adoptive cell therapies are very promising, obtaining large batches of T cell at clinical scale is still challenging nowadays. We propose here a review study focusing on how bioreactor systems could increase expansion rates of T cell culture specifically towards efficient, reliable and reproducible cell therapies. After describing the specificities of T cell culture, in particular activation, phenotypical characterization and cell density considerations, we detail the main objectives of bioreactors in this context, namely scale-up, GMP-compliance and reduced time and costs. Then, we report recent advances on the different classes of bioreactor systems commonly investigated for non-adherent cell expansion, in comparison with the current "gold standard" of T cell culture (flasks and culture bag). Results obtained with hollow fibres, G-Rex® flasks, Wave bioreactor, multiple-step bioreactors, spinner flasks as well as original homemade designs are discussed to highlight advantages and drawbacks in regards to T cells' specificities. Although there is currently no consensus on an optimal bioreactor, overall, most systems reviewed here can improve T cell culture towards faster, easier and/or cheaper protocols. They also offer strong outlooks towards automation, process control and complete closed systems, which could be mandatory developments for a massive clinical breakthrough. However, proper controls are sometimes lacking to conclude clearly on the features leading to the progresses regarding cell expansion, and the field could benefit from process engineering methods, such as quality by design, to perform multi parameters studies and face these challenges.

Enriching leukapheresis improves T cell activation and transduction efficiency during CAR T processing

The majority of CD19-directed CAR T cell products are manufactured using an autologous process. Although using a patient's leukapheresis reduces the risks of rejection, it introduces variability in starting material composition and the presence of cell populations that might negatively affect production of chimeric antigen receptor (CAR) T cells, such as myeloid cells. In this work, the effect of monocytes (CD14) on the level of activation, growth, and transduction efficiency was monitored across well plate and culture bag platforms using healthy donor leukapheresis. Removal of monocytes from leukapheresis improved the level of activation 2-fold, achieving the same level of activation as when initiating the process with a purified T cell starting material. Two activation reagents were tested in well plate cultures, revealing differing sensitivities to starting material composition. Monocyte depletion in culture bag systems had a significant effect on transduction efficiency, improving consistency and increasing the level of CAR expression by up to 64% compared to unsorted leukapheresis. Cytotoxicity assays revealed that CAR T cell products produced from donor material depleted of monocytes and isolated T cells consistently outperformed those made from unsorted leukapheresis. Analysis of memory phenotypes and gene expression indicated that CAR T cells produced using depleted starting material displayed a more rested and naive state.

Effective Activation and Expansion of Canine Lymphocytes Using a Novel Nano-Sized Magnetic Beads Approach

Expansion protocols for human T lymphocytes using magnetic beads, which serve as artificial antigen presenting cells (aAPCs), is well-studied. Yet, the efficacy of magnetic beads for propagation and functionality of peripheral blood lymphocytes (PBLs) isolated from companion dogs still remains limited. Domestic dog models are important in immuno-oncology field. Thus, we built the platform for induction of canine PBLs function, proliferation and biological activity using nano-sized magnetic beads (termed as MicroBeads) coated with anti-canine CD3 and CD28 antibodies. Herein we reveal that activation of canine PBLs via MicroBeads induces a range of genes involved in immediate-early response to T cell activation in dogs. Furthermore, canine T lymphocytes are effectively activated by MicroBeads, as measured by cluster formation and induction of activation marker CD25 on canine T cells as quickly as 24 h post stimulation. Similar to human T cells, canine PBLs require lower activation signal strength for efficient proliferation and expansion, as revealed by titration studies using a range of MicroBeads in the culture. Additionally, the impact of temperature was assessed in multiple stimulation settings, showing that both 37°C and 38.5°C are optimal for the expansion of canine T cells. In contrast to stimulation using plant mitogen Concanavalin A (ConA), MicroBead-based activation did not increase activation-induced cell death. In turn, MicroBeads supported the propagation of T cells with an effector memory phenotype that secreted substantial IL-2 and IFN-γ. Thus, MicroBeads represent an accessible and affordable tool for conducting immunological studies on domestic dog models. Similarities in inducing intracellular signaling pathways further underscore the importance of this model in comparative medicine. Presented herein MicroBead-based expansion platforms for canine PBLs may benefit adoptive immunotherapy in dogs and facilitate the design of next-generation clinical trials in humans.

The Immunobiogram, a Novel In Vitro Assay to Evaluate Treatment Resistance in Patients Receiving Immunosuppressive Therapy

Immunosuppressive drugs are widely used to treat several autoimmune disorders and prevent rejection after organ transplantation. However, intra-individual variations in the pharmacological response to immunosuppressive therapy critically influence its efficacy, often resulting in poor treatment responses and serious side effects. Effective diagnostic tools that help clinicians to tailor immunosuppressive therapy to the needs and immunological profile of the individual patient thus constitute a major unmet clinical need. In vitro assays that measure immune cell responses to immunosuppressive drugs constitute a promising approach to individualized immunosuppressive therapy. Here, we present the Immunobiogram, a functional pharmacodynamic immune cell-based assay for simultaneous quantitative measurement of a patient's immune response to a battery of immunosuppressive drugs. Peripheral blood mononuclear cells collected from patients are immunologically stimulated to induce activation and proliferation and embedded in a hydrogel mixture in which they are exposed to a concentration gradient of the immunosuppressants of interest. Analysis of samples from kidney transplant patients using this procedure revealed an association between the sensitivity of individual patients to the immunosuppressive regimen and their immunological risk of transplant rejection. Incorporation of the Immunobiogram assay into clinical settings could greatly facilitate personalized optimization and monitoring of immunosuppressive therapy, and study of the mechanisms underlying resistance to immunosuppressants.

Particulate impurities in cell-based medicinal products traced by flow imaging microscopy combined with deep learning for image analysis

Cell-based medicinal products (CBMPs) are rapidly gaining importance in the treatment of life-threatening diseases. However, the analytical toolbox for characterization of CBMPs is limited. The aim of our study was to develop a method based on flow imaging microscopy (FIM) for the detection, quantification and characterization of subvisible particulate impurities in CBMPs. Image analysis was performed by using an image classification approach based on a convolutional neural network (CNN). Jurkat cells and Dynabeads were used in our study as a representation of cellular material and non-cellular particulate impurities, respectively. We demonstrate that FIM assisted with CNN is a powerful method for the detection and quantification of Dynabeads and cells with other process related impurities, such as cell agglomerates, cell-bead adducts and debris. By using CNN, we achieved a more than 50-fold lower misclassification rate compared with the use of output parameters from the FIM software. The limit of detection was ~15 000 beads/mL in the presence of ~500 000 cells/mL, making this approach suitable for the detection of these particulate impurities in CBMPs. In conclusion, CNN-assisted FIM is a powerful method for the detection and quantification of cells, Dynabeads and other subvisible process impurities potentially present in CBMPs.

Approaches of T Cell Activation and Differentiation for CAR-T Cell Therapies

Chimeric antigen receptor (CAR) T cell therapies are ex vivo manufactured cellular products that have been useful in the treatment of blood cancers and solid tumors. The quality of the final cellular product is influenced by several amenable factors during the manufacturing process. This review discusses several of the influences on cell product phenotype, including the raw starting material, methods of activation and transduction, and culture supplementation.

At the Intersection of Biomaterials and Gene Therapy: Progress in Non-viral Delivery of Nucleic Acids

Biomaterials play a critical role in technologies intended to deliver therapeutic agents in clinical settings. Recent explosion of our understanding of how cells utilize nucleic acids has garnered excitement to develop a range of older (e.g., antisense oligonucleotides, plasmid DNA and transposons) and emerging (e.g., short interfering RNA, messenger RNA and non-coding RNAs) nucleic acid agents for therapy of a wide range of diseases. This review will summarize biomaterials-centered advances to undertake effective utilization of nucleic acids for therapeutic purposes. We first review various types of nucleic acids and their unique abilities to deliver a range of clinical outcomes. Using recent advances in T-cell based therapy as a case in point, we summarize various possibilities for utilizing biomaterials to make an impact in this exciting therapeutic intervention technology, with the belief that this modality will serve as a therapeutic paradigm for other types of cellular therapies in the near future. We subsequently focus on contributions of biomaterials in emerging nucleic acid technologies, specifically focusing on the design of intelligent nanoparticles, deployment of mRNA as an alternative to plasmid DNA, long-acting (integrating) expression systems, and in vitro/in vivo expansion of engineered T-cells. We articulate the role of biomaterials in these emerging nucleic acid technologies in order to enhance the clinical impact of nucleic acids in the near future.

Phenotypic Screening Using Patient-Derived Induced Pluripotent Stem Cells Identified Pyr3 as a Candidate Compound for the Treatment of Infantile Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a genetic disorder that is characterized by hypertrophy of the myocardium. Some of the patients are diagnosed for HCM during infancy, and the prognosis of infantile HCM is worse than general HCM. Nevertheless, pathophysiology of infantile HCM is less investigated and remains largely unknown. In the present study, we generated induced pluripotent stem cells (iPSCs) from two patients with infantile HCM: one with Noonan syndrome and the other with idiopathic HCM. We found that iPSC-derived cardiomyocytes (iPSC-CMs) from idiopathic HCM patient were significantly larger and showed higher diastolic intracellular calcium concentration compared with the iPSC-CMs from healthy subject. Unlike iPSC-CMs from the adult/adolescent HCM patient, arrhythmia was not observed as a disease-related phenotype in iPSC-CMs from idiopathic infantile HCM patient. Phenotypic screening revealed that Pyr3, a transient receptor potential channel 3 channel inhibitor, decreased both the cell size and diastolic intracellular calcium concentration in iPSC-CMs from both Noonan syndrome and idiopathic infantile HCM patients, suggesting that the target of Pyr3 may play a role in the pathogenesis of infantile HCM, regardless of the etiology. Further research may unveil the possibility of Pyr3 or its derivatives in the treatment of infantile HCM.

Cationic polymers for non-viral gene delivery to human T cells

The clinical success of chimeric antigen receptor (CAR) T cell immunotherapy in treating multiple blood cancers has created a need for efficient methods of ex vivo gene delivery to primary human T cells for cell engineering. Here, we synthesize and evaluate a panel of cationic polymers for gene delivery to both cultured and primary human T cells. We show that a subset of comb- and sunflower-shaped pHEMA-g-pDMAEMA polymers can mediate transfection with efficiencies up to 50% in the Jurkat human T cell line with minimal concomitant toxicity (>90% viability). We then optimize primary human T cell transfection conditions including activation time, cell density, DNA dose, culture media, and cytokine treatment. We demonstrate transfection of both CD4+ and CD8+ primary human T cells with messenger RNA and plasmid DNA at efficiencies up to 25 and 18%, respectively, with similarly high viability.

Extensive Proliferation of Cd4+ Lymphocyte by Both Phytohaemagglutinin A and Anti-Cd2/Cd3/ Cd28 Macsibeads

Background: Lymphocytes proliferate considerably following appropriate stimulation in vitro. Autologous T cells are obtained from whole blood or tissue sites in relatively limited amounts. We need a method to expand these cells efficiently, study their functions and manipulate them to create appropriate cells for transferring to the patient with infection and cancer. Objectives: The aim of this study is to determine proliferation ability of two different stimulators on CD4+ lymphocytes. Methods: Lymphocytes were isolated from blood samples of healthy donors after removing adherent cells (monocytes).The efficacy of MACSiBead™ coated with anti-CD2, anti-CD3, anti-CD28 (anti-CD2/CD3/CD28) was compared with Phytohaemagglutinin A (PHA) on CD4+ lymphocytes proliferation using carboxyfluorescein diacetate succinimidyl ester (CFSE) in cell culture media. The percentage of proliferating cells was analyzed using flow cytometry. Results: Both stimulators induced extensive proliferation of CD4+ lymphocytes but proliferation ability of PHA was higher compared to stimulation by anti-CD2/CD3/CD28 MACSiBead™. The proliferation rate of cells stimulated by PHA was 93.8% ± 3.37% whereas it was 85.2% ± 4.7% in cells stimulated by anti-CD2/CD3/CD28 MACSiBead™. Conclusions: Our results show that MACSiBead™ along with PHA can be used to obtain a large number of expanded CD4+ lymphocytes.

Efficacy of Adoptive T-cell Therapy Is Improved by Treatment with the Antioxidant N-Acetyl Cysteine, Which Limits Activation-Induced T-cell Death

Although adoptive transfer of autologous tumor antigen-specific T-cell immunotherapy can produce remarkable clinical efficacy, most patients do not achieve durable complete responses. We hypothesized that reducing susceptibility of T cells to activation-induced cell death (AICD), which increases during the rapid in vitro expansion of therapeutic T cells before their infusion, might improve the persistence of adoptively transferred cells. Our investigations revealed that repetitive stimulation of the T-cell receptor (TCR) induced AICD, as a result of activating the DNA damage response pathway through ATM-mediated Ser15 phosphorylation of p53. Activation of this DNA damage response pathway also occurred upon antigen-specific restimulation in TCR-transduced TIL1383I T cells prepared for adoptive transfer to patients as part of a clinical trial. Notably, treatment with the antioxidant N-acetyl cysteine (NAC) significantly reduced upregulation of the DNA damage marker γH2AX, subsequent ATM activation, and cell death. In the Pmel mouse model of melanoma, the presence of NAC during ex vivo T-cell expansion improved the persistence of adoptively transferred cells, reduced tumor growth, and increased survival. Taken together, our results offer a preclinical proof of concept for the addition of NAC to current therapeutic T-cell expansion protocols, offering immediate potential to improve the quality and therapeutic efficacy of adoptive T-cell therapeutics infused into patients. Cancer Res; 76(20); 6006-16. ©2016 AACR.

Intact CD100-CD72 Interaction Necessary for TCR-Induced T Cell Proliferation

Targeting CD100 by antibody blockade is a potential therapeutic strategy for cancers, but the functional effects on T cells following blockade of this immune activating molecule are rarely considered. Indeed, CD100 is highly expressed in T cells and anti-CD100 antibodies play a role during T cell proliferation; however, the outcome varies from different studies and the underlying mechanism is still unclear. To address this, monoclonal antibody clones directed against CD100 were evaluated. In their soluble form, four of these antibodies significantly reduced the expansion of T cells in the presence of bead-bound anti-CD3/CD28, either in total peripheral blood mononuclear cell or purified T cell culture systems. Similar inhibition was seen when blocking CD100–CD72 interaction by soluble anti-CD72 instead of anti-CD100 antibodies. Conversely, restoring the interaction by CD72-Fc eliminated the soluble anti-CD100-induced inhibitory effect. Taken together, these results reveal that T cell proliferation is regulated by CD100 via interaction with CD72. They further establish an in vitro system to evaluate the inhibitory effect of anti-CD100 antibodies on T cells, to which attention should be paid in clinical trials in order to avoid potential side effects.

Inclusion of Strep-tag II in design of antigen receptors for T-cell immunotherapy

The tactical introduction of Strep-tag II into synthetic antigen receptors provides engineered T cells with a marker for identification and rapid purification, and a functional element for selective antibody coated microbead-driven large-scale expansion. Such receptor designs can be applied to chimeric antigen receptors of different ligand specificities and costimulatory domains, and to T cell receptors to facilitate cGMP manufacturing of adoptive T cell therapies to treat cancer and other diseases.

Costimulation with anti-cluster of differentiation 3 and anti-cluster of differentiation 28 reduces the activity of mucin 1-stimulated human mononuclear cells

Cytotoxic T-lymphocyte activation and extension of the cell life span is necessary in order to enable immunotherapy to perform effectively against cancer. In the present study, mucin 1 (MUC1)-stimulated human mononuclear cells (M1SHMCs) were costimulated with bead-attached monoclonal antibodies specific for cluster of differentiation (CD)3 and CD28 receptors. The study was undertaken to determine whether costimulation was capable of enhancing the killing of cancer cells in vitro and of protecting non-obese diabetic severe combined immunodeficient mice from tumor development. Lysis of MCF-7 tumor cells by M1SHMCs was reduced following costimulation with anti-CD3 and anti-CD28. Furthermore, costimulation with anti-CD3 and anti-CD28 eliminated the protective effects of M1SHMCs on MCF-7 breast cancer cell growth in the non-obese diabetic severe combined immunodeficient mice. The present study suggested that costimulation with anti-CD3 and anti-CD28 is not advisable following antigen activation of lymphocytes under the conditions used here. Using a lower anti-CD3/CD28 bead to T-cell ratio may prevent immune suppression, however, further studies are required to support this hypothesis.

CMVpp65 Vaccine Enhances the Antitumor Efficacy of Adoptively Transferred CD19-Redirected CMV-Specific T Cells

PURPOSE

T cells engineered with chimeric antigen receptors (CAR) recognizing CD19 can induce complete remission of B-cell malignancies in clinical trials; however, in some disease settings, CAR therapy confers only modest clinical benefit due to attenuated persistence of CAR T cells. The purpose of this study was to enhance persistence and augment the antitumor activity of adoptively transferred CD19CAR T cells by restimulating CAR(+) T cells through an endogenous cytomegalovirus (CMV)-specific T-cell receptor.

EXPERIMENTAL DESIGN

CMV-specific T cells from CMV seropositive healthy donors were selected after stimulation with pp65 protein and transduced with clinical-grade lentivirus expressing the CD19R:CD28:ζ/EGFRt CAR. The resultant bispecific T cells, targeting CMV and CD19, were expanded via CD19 CAR-mediated signals using CD19-expressing cells.

RESULTS

The bispecific T cells proliferated vigorously after engagement with either endogenous CMVpp65 T-cell receptors or engineered CD19 CARs, exhibiting specific cytolytic activity and IFNγ secretion. Upon adoptive transfer into immunodeficient mice bearing human lymphomas, the bispecific T cells exhibited proliferative response and enhanced antitumor activity following CMVpp65 peptide vaccine administration.

CONCLUSIONS

We have redirected CMV-specific T cells to recognize and lyse tumor cells via CD19CARs, while maintaining their ability to proliferate in response to CMV antigen stimulation. These results illustrate the clinical applications of CMV vaccine to augment the antitumor activity of adoptively transferred CD19CAR T cells in patients with B-cell malignancies.

Shifting paradigms in the treatment of chronic lymphocytic leukemia

The treatment of chronic lymphocytic leukemia (CLL) is evolving rapidly. Insight into the genetics and biology of the disease, including the importance of intracellular signaling pathways and interactions with the microenvironment has led to the development of rational targeted therapies which are having a major impact on the survival of patients with relapsed and high-risk disease. In addition, an exciting array of cellular therapies and immunotherapy options are in various stages of development. We review the current understanding of CLL genetics and biology, current treatment strategies in specific patient groups and opportunities for future treatment combinations which will bring the goal of cure or long-term disease control with minimal toxicity within reach for the majority of patients.

A reproducible method for the expansion of mouse CD8+ T lymphocytes

Murine adoptive CD8 + T-cell immunotherapy studies require the generation of large numbers of high viability CD8 + cells. Here we report a tissue culture protocol for the reliable expansion of CD8 + T-cells derived from murine spleen to give a 20-fold expansion after 4 days in culture. The cells were transfected with an mRNA GFP construct and transferred into NOD mice. GFP positive cells could be detected 7 days after transfer thus confirming that the cells survive and are functional for up to 1 week.

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A technique for reliable expansion of murine CD8 + T cells

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Excellent cell viability

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Allows for electroporation of cells with mRNA constructs and detection of expression up to 7 days in vivo

Intramuscular therapeutic vaccination targeting HPV16 induces T cell responses that localize in mucosal lesions

About 25% of high-grade cervical intraepithelial neoplasias (CIN2/3) caused by human papillomavirus serotype 16 (HPV16) undergo complete spontaneous regression. However, to date, therapeutic vaccination strategies for HPV disease have yielded limited success when measured by their ability to induce robust peripheral blood T cell responses to vaccine antigen. We report marked immunologic changes in the target lesion microenvironment after intramuscular therapeutic vaccination targeting HPV16 E6/E7 antigens, in subjects with CIN2/3 who had modest detectable responses in circulating T lymphocytes. Histologic and molecular changes, including markedly (average threefold) increased intensity of CD8(+) T cell infiltrates in both the stromal and epithelial compartments, suggest an effector response to vaccination. Postvaccination cervical tissue immune infiltrates included organized tertiary lymphoid-like structures in the stroma subjacent to residual intraepithelial lesions and, unlike infiltrates in unvaccinated lesions, showed evidence of proliferation induced by recognition of cognate antigen. At a molecular level, these histologic changes in the stroma were characterized by increased expression of genes associated with immune activation (CXCR3) and effector function (Tbet and IFNβ), and were also associated with an immunologic signature in the overlying dysplastic epithelium. High-throughput T cell receptor sequencing of unmanipulated specimens identified clonal expansions in the tissue that were not readily detectable in peripheral blood. Together, these findings indicate that peripheral therapeutic vaccination to HPV antigens can induce a robust tissue-localized effector immune response, and that analyses of immune responses at sites of antigen are likely to be much more informative than analyses of cells that remain in the circulation.

Fine tuning and efficient T cell activation with stimulatory aCD3 nanoarrays

Anti-CD3 (aCD3) nanoarrays fabricated by self-assembled nanopatterning combined with site-directed protein immobilization techniques represent a novel T cell stimulatory platform that allows tight control over ligand orientation and surface density. Here, we show that activation of primary human CD4+ T cells, defined by CD69 upregulation, IL-2 production and cell proliferation, correlates with aCD3 density on nanoarrays. Immobilization of aCD3 through nanopatterning had two effects: cell activation was significantly higher on these surfaces than on aCD3-coated plastics and allowed unprecedented fine-tuning of T cell response.

T cell-based gene therapy of cancer

Adoptive immunotherapy using gene engineered T cells is a promising and rapidly evolving field, and the ability to engineer T cells to manifest desired phenotypes and functions has become a practical reality. In this review, we describe and summarize current thought about gene engineering of T cells. We focus on the identified requirements for the successful application of T cell based immunotherapy and discuss gene-therapy based strategies that address these requirements and have the potential to enhance the successful implementation of this promising approach to treat cancer.

Bidirectional coupling between ryanodine receptors and Ca2+ release-activated Ca2+ (CRAC) channel machinery sustains store-operated Ca2+ entry in human T lymphocytes

The expression and functional significance of ryanodine receptors (RyR) were investigated in resting and activated primary human T cells. RyR1, RyR2, and RyR3 transcripts were detected in human T cells. RyR1/2 transcript levels increased, whereas those of RyR3 decreased after T cell activation. RyR1/2 protein immunoreactivity was detected in activated but not in resting T cells. The RyR agonist caffeine evoked Ca(2+) release from the intracellular store in activated T cells but not in resting T cells, indicating that RyR are functionally up-regulated in activated T cells compared with resting T cells. In the presence of store-operated Ca(2+) entry (SOCE) via plasmalemmal Ca(2+) release-activated Ca(2+) (CRAC) channels, RyR blockers reduced the Ca(2+) leak from the endoplasmic reticulum (ER) and the magnitude of SOCE, suggesting that a positive feedback relationship exists between RyR and CRAC channels. Overexpression of fluorescently tagged RyR2 and stromal interaction molecule 1 (STIM1), an ER Ca(2+) sensor gating CRAC channels, in HEK293 cells revealed that RyR are co-localized with STIM1 in the puncta formed after store depletion. These data indicate that in primary human T cells, the RyR are coupled to CRAC channel machinery such that SOCE activates RyR via a Ca(2+)-induced Ca(2+) release mechanism, which in turn reduces the Ca(2+) concentration within the ER lumen in the vicinity of STIM1, thus facilitating SOCE by reducing store-dependent CRAC channel inactivation. Treatment with RyR blockers suppressed activated T cell expansion, demonstrating the functional importance of RyR in T cells.

Generation of autologous tumor-specific T cells for adoptive transfer based on vaccination, in vitro restimulation and CD3/CD28 dynabead-induced T cell expansion

Adoptive cell transfer (ACT) of in vitro expanded autologous tumor-infiltrating lymphocytes (TIL) has been shown to exert therapeutic efficacy in melanoma patients. We aimed to develop an ACT protocol based on tumor-specific T cells isolated from peripheral blood and in vitro expanded by Dynabeads® ClinExVivo™CD3/CD28. We show here that the addition of an in vitro restimulation step with relevant peptides prior to bead expansion dramatically increased the proportion of tumor-specific T cells in PBMC-cultures. Importantly, peptide-pulsed dendritic cells (DCs) as well as allogeneic tumor lysate-pulsed DCs from the DC vaccine preparation could be used with comparable efficiency to peptides for in vitro restimulation, to increase the tumor-specific T-cell response. Furthermore, we tested the use of different ratios and different types of Dynabeads® CD3/CD28 and CD3/CD28/CD137 T-cell expander, for optimized expansion of tumor-specific T cells. A ratio of 1:3 of Dynabeads® CD3/CD28 T-cell expander to T cells resulted in the maximum number of tumor-specific T cells. The addition of CD137 did not improve functionality or fold expansion. Both T-cell expansion systems could generate tumor-specific T cells that were both cytotoxic and effective cytokine producers upon antigen recognition. Dynabeads®-expanded T-cell cultures shows phenotypical characteristics of memory T cells with potential to migrate and expand in vivo. In addition, they possess longer telomeres compared to TIL cultures. Taken together, we demonstrate that in vitro restimulation of tumor-specific T cells prior to bead expansion is necessary to achieve high numbers of tumor-specific T cells. This is effective and easily applicable in combination with DC vaccination, by use of vaccine-generated DCs, either pulsed with peptide or tumor-lysate.

CAR-T cells and solid tumors: tuning T cells to challenge an inveterate foe

Recent reports on the impressive efficacy of adoptively transferred T cells to challenge cancer in early phase clinical trials have significantly raised the profile of T cell therapy. Concomitantly, general expectations are also raised by these reports, with the natural aspiration to deliver this therapy over a wide range of tumor indications. Chimeric antigen receptors (CARs) endow T cell populations with defined antigen specificities that function independently of the natural T cell receptor and permit targeting of T cells towards virtually any tumor. Here, we review the current clinical application of CAR-T cells and relate clinical efficacy and safety of CAR-T cell trials to parameters considered critical for CAR engineering, classified as the three T's of CAR-T cell manipulation.

In vitro stimulation and expansion of human tumour-reactive CD8+ cytotoxic T lymphocytes by anti-CD3/CD28/CD137 magnetic beads

Adoptive immunotherapy with tumour-reactive CD8(+) cytotoxic T lymphocytes (CTLs) requires efficient in vitro approaches allowing the expansion of CTLs to large numbers prior infusion. Here, we investigated the antigen-independent activation and the expansion of human T cells in peripheral blood mononuclear cells (PBMCs) and in tumour-reactive CTLs using Dynabeads coated with monoclonal antibodies to CD3 and to the costimulatory molecules CD28 and CD137 (4-1BB). T cells in PBMCs showed an increased expansion rate of 15- to 17-fold during a 2-week culture period using antibody-conjugated beads with interleukin-2 (IL-2) added versus IL-2 alone. No significant difference between CD3/CD28 beads and CD3/CD28/CD137 beads was observed (P = 0.4). In contrast, expansion of tumour-reactive CD8(+) CTLs over 2 weeks was more efficient using CD3/CD28/CD137 beads (14.4-fold ± 1.2) compared with CD3/CD28 beads (10.6-fold ± 0.7) (P = 0.03) and matched well to the control arm using weekly stimulation with tumour cells. Although all modes of in vitro stimulation decreased the expression of central memory markers CD62L and CCR7 on CTLs, bead-activated cultures expressed consistently higher levels than tumour-stimulated cultures. CTLs analysed after bead-induced expansion versus weekly tumour stimulation showed equal IFN-γ production in ELISPOT assay. Furthermore, cytotoxicity assays demonstrated an either unchanged or slightly reduced capability of tumour cell lysis for antigen-independent stimulated CTLs versus those that maintained on weekly tumour stimulation, regardless of which type of beads was used. Our data suggest that the conjugation of anti-CD137 antibodies to conventional CD3/CD28 beads results in a minor but significant increase in the expansion capacity for tumour-reactive CD8(+) CTLs.

Biomarkers in T cell therapy clinical trials

T cell therapy represents an emerging and promising modality for the treatment of both infectious disease and cancer. Data from recent clinical trials have highlighted the potential for this therapeutic modality to effect potent anti-tumor activity. Biomarkers, operationally defined as biological parameters measured from patients that provide information about treatment impact, play a central role in the development of novel therapeutic agents. In the absence of information about primary clinical endpoints, biomarkers can provide critical insights that allow investigators to guide the clinical development of the candidate product. In the context of cell therapy trials, the definition of biomarkers can be extended to include a description of parameters of the cell product that are important for product bioactivity.

This review will focus on biomarker studies as they relate to T cell therapy trials, and more specifically: i. An overview and description of categories and classes of biomarkers that are specifically relevant to T cell therapy trials, and ii. Insights into future directions and challenges for the appropriate development of biomarkers to evaluate both product bioactivity and treatment efficacy of T cell therapy trials.

Retroviral insertional mutagenesis can contribute to immortalization of mature T lymphocytes

Several cases of T-cell leukemia caused by gammaretroviral insertional mutagenesis in children treated for x-linked severe combined immunodeficiency (SCID) by transplantation of autologous gene-modified stem cells were reported. In a comparative analysis, we recently showed that mature T cells, on the contrary, are highly resistant to transformation by gammaretroviral gene transfer. In the present study, we observed immortalization of a single T-cell clone in vitro after gammaretroviral transduction of the T-cell protooncogene LMO2. This clone was CD4/CD8 double-negative, but expressed a single rearranged T-cell receptor. The clone was able to overgrow nonmanipulated competitor T-cell populations in vitro, but no tumor formation was observed after transplantation into Rag-1 deficient recipients. The retroviral integration site (RIS) was found to be near the IL2RA and IL15RA genes. As a consequence, both receptors were constitutively upregulated on the RNA and protein level and the immortalized cell clone was highly IL-2 dependent. Ectopic expression of both, the IL2RA chain and LMO2, induced long-term growth in cultured primary T cells. This study demonstrates that insertional mutagenesis can contribute to immortalization of mature T cells, although this is a rare event. Furthermore, the results show that signaling of the IL-2 receptor and the protooncogene LMO2 can act synergistically in maligniant transformation of mature T lymphocytes.

Development of genetically engineered CD4+ and CD8+ T cells expressing TCRs specific for a M. tuberculosis 38-kDa antigen

Cell-mediated immunity is critical to the clearance of Mycobacterium tuberculosis due to the primarily intracellular niche of this pathogen. Adoptive transfer of M. tuberculosis-specific effector T cells has been shown to confer immunity to M. tuberculosis-infected recipients resulting in M. tuberculosis clearance. However, it is difficult to generate sufficient numbers of M. tuberculosis antigen-specific T cells in a short time. Recent studies have developed T cell receptor (TCR) gene-modified T cells that allow for the rapid generation of large numbers of antigen-specific T cells. Many TCRs that target various tumor and viral antigens have now been isolated and shown to have functional activity. Nevertheless, TCRs specific for intracellular bacterial antigens (including M. tuberculosis antigens) have yet to be isolated and their functionality confirmed. We isolated M. tuberculosis 38-kDa antigen-specific HLA class I and class II-restricted TCRs and modified the TCR gene C regions by substituting nine amino acids with their murine TCR homologs (minimal murinization). Results showed that both wild-type and minimal murinized TCR genes were successfully cloned into retroviral vectors and transduced into primary CD4(+) and CD8(+) T cells and displayed anti-M. tuberculosis activity. As expected, minimal murinized TCRs displayed higher cell surface expression levels and stronger anti-M. tuberculosis activity than wild-type TCRs. To the best of our knowledge, this is the first report describing TCRs targeting M. tuberculosis antigens and this investigation provides the basis for future TCR gene-based immunotherapies that can be designed for the treatment of immunocompromised M. tuberculosis-infected patients.

Surfactant-free poly(styrene-co-glycidyl methacrylate) particles with surface-bound antibodies for activation and proliferation of human T cells

In this article, we present our results on the design of new polymeric carriers for antibodies. Polymer colloids based on poly(styrene-co-glycidyl methacrylate) were synthesized by surfactant-free emulsion polymerization. Obtained polymer particles stabilized by grafted poly(ethylene glycol) (PEG) chains and carrying active epoxy groups were used for the covalent immobilization of activating antibodies against the human surface proteins CD (cluster of differentiation) 3 and CD28. The particle-antibody conjugates were employed for the stimulation of human CD4 memory T cells. This was analyzed by the up-regulation of the activation markers CD69 and CD25 on T cells and T cell proliferation as assessed by the dilution of a fluorescent dye on dividing daughter T cells. The particle-antibody conjugates were able to stimulate T cells at least as efficiently as conventional methods, e.g., surface-immobilized antibodies. Furthermore, an increase of the PEG chain length of the particles decreased the efficiency of the particle-antibody conjugates to activate T cells.

Monoclonal antibody-induced cytokine-release syndrome

Monoclonal antibodies (mAbs) are widely used in anti-inflammatory and tumor therapy. Although effective, mAbs can cause a variety of adverse effects. An important toxicity seen with a few mAbs is cytokine-release syndrome (CRS). These mAbs include: alemtuzumab, muromonab-CD3, rituximab, tosituzumab, CP-870,893, LO-CD2a/BTI-322 and TGN1412. By contrast, over 30 mAbs used clinically are not associated with CRS. In this review, the clinical aspects of CRS, the mAbs associated with CRS, the cytokines involved and putative mechanisms mediating cytokine release will be discussed. This will be followed by a discussion of the poor predictive value of studies in animals and the prospects for creating in vitro screens. Finally, approaches to decreasing the probability of CRS, decreasing the severity or treating CRS, should it occur, will be described.