The impact of ex vivo clinical grade activation protocols on human T-cell phenotype and function for the generation of genetically modified cells for adoptive cell transfer therapy. J Immunother. 2010;33:759-768. [PMID: 20842061 DOI: 10.1097/CJI.0b013e3181f1d644]

From ex vivo to in vivo chimeric antigen T cells manufacturing: new horizons for CAR T-cell based therapy

In the past decades, Chimeric Antigen Receptor (CAR)-T cell therapy has achieved remarkable success, leading to the approval of six therapeutic products for haematological malignancies. Recently, the therapeutic potential of this therapy has also been demonstrated in non-tumoral diseases. Currently, the manufacturing process to produce clinical-grade CAR-T cells is complex, time-consuming, and highly expensive. It involves multiple steps, including the collection of T cells from patients or healthy donors, in vitro engineering and expansion, and finally reinfusion into patients. Therefore, despite the impressive clinical outcomes, ex vivo manufacturing process makes CAR-T cells out of reach for many cancer patients. Direct in vivo engineering of T cells could be a more rapid solution able to circumvent both the complexity and the costs associated with ex vivo manufactured CAR-T cells. This novel approach allows to completely eliminate ex vivo cell manipulation and expansion while producing therapeutic cell populations directly in vivo. To date, several studies have demonstrated the feasibility of in vivo T cell reprogramming, by employing injectable viral- or nanocarrier-based delivery platforms in tumour animal models. Additionally, in vivo production of CAR-T cells might reduce the incidence, or at least the severity, of systemic toxicities frequently occurring with ex vivo produced CAR-T cells, such as cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome. In this review, we highlight the challenges associated with the current ex vivo manufacturing protocols and review the latest progresses in the emerging field of in vivo CAR-T therapy, by comparing the various platforms so far investigated. Moreover, we offer an overview of the advantages deriving from in vivo reprogramming of other immune cell types, such as Natural Killer and macrophages, with CAR constructs.

Functionalized nanowires for miRNA-mediated therapeutic programming of naïve T cells

Cellular programming of naïve T cells can improve the efficacy of adoptive T-cell therapy. However, the current ex vivo engineering of T cells requires the pre-activation of T cells, which causes them to lose their naïve state. In this study, cationic-polymer-functionalized nanowires were used to pre-program the fate of primary naïve CD8+ T cells to achieve a therapeutic response in vivo. This was done by delivering single or multiple microRNAs to primary naïve mouse and human CD8+ T cells without pre-activation. The use of nanowires further allowed for the delivery of large, whole lentiviral particles with potential for long-term integration. The combination of deletion and overexpression of miR-29 and miR-130 impacted the ex vivo T-cell differentiation fate from the naïve state. The programming of CD8+ T cells using nanowire-delivered co-delivery of microRNAs resulted in the modulation of T-cell fitness by altering the T-cell proliferation, phenotypic and transcriptional regulation, and secretion of effector molecules. Moreover, the in vivo adoptive transfer of murine CD8+ T cells programmed through the nanowire-mediated dual delivery of microRNAs provided enhanced immune protection against different types of intracellular pathogen (influenza and Listeria monocytogenes). In vivo analyses demonstrated that the simultaneous alteration of miR-29 and miR-130 levels in naïve CD8+ T cells reduces the persistence of canonical memory T cells whereas increases the population of short-lived effector T cells. Nanowires could potentially be used to modulate CD8+ T-cell differentiation and achieve a therapeutic response in vivo without the need for pre-activation.

Increasing Gene Editing Efficiency via CRISPR/Cas9- or Cas12a-Mediated Knock-In in Primary Human T Cells

T lymphocytes represent a promising target for genome editing. They are primarily modified to recognize and kill tumor cells or to withstand HIV infection. In most studies, T cell genome editing is performed using the CRISPR/Cas technology. Although this technology is easily programmable and widely accessible, its efficiency of T cell genome editing was initially low. Several crucial improvements were made in the components of the CRISPR/Cas technology and their delivery methods, as well as in the culturing conditions of T cells, before a reasonable editing level suitable for clinical applications was achieved. In this review, we summarize and describe the aforementioned parameters that affect human T cell editing efficiency using the CRISPR/Cas technology, with a special focus on gene knock-in.

Phenotypic characteristics of peripheral immune cells of Myalgic encephalomyelitis/chronic fatigue syndrome via transmission electron microscopy: A pilot study

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex chronic multi-systemic disease characterized by extreme fatigue that is not improved by rest, and worsens after exertion, whether physical or mental. Previous studies have shown ME/CFS-associated alterations in the immune system and mitochondria. We used transmission electron microscopy (TEM) to investigate the morphology and ultrastructure of unstimulated and stimulated ME/CFS immune cells and their intracellular organelles, including mitochondria. PBMCs from four participants were studied: a pair of identical twins discordant for moderate ME/CFS, as well as two age- and gender- matched unrelated subjects-one with an extremely severe form of ME/CFS and the other healthy. TEM analysis of CD3/CD28-stimulated T cells suggested a significant increase in the levels of apoptotic and necrotic cell death in T cells from ME/CFS patients (over 2-fold). Stimulated Tcells of ME/CFS patients also had higher numbers of swollen mitochondria. We also found a large increase in intracellular giant lipid droplet-like organelles in the stimulated PBMCs from the extremely severe ME/CFS patient potentially indicative of a lipid storage disorder. Lastly, we observed a slight increase in platelet aggregation in stimulated cells, suggestive of a possible role of platelet activity in ME/CFS pathophysiology and disease severity. These results indicate extensive morphological alterations in the cellular and mitochondrial phenotypes of ME/CFS patients' immune cells and suggest new insights into ME/CFS biology.

Induction of γδT cells from HSC-enriched BMCs co-cultured with iPSC-derived thymic epithelial cells

T cells bearing γδ antigen receptors have been investigated as potential treatments for several diseases, including malignant tumours. However, the clinical application of γδT cells has been hampered by their relatively low abundance in vivo and the technical difficulty of inducing their differentiation from hematopoietic stem cells (HSCs) in vitro. Here, we describe a novel method for generating mouse γδT cells by co-culturing HSC-enriched bone marrow cells (HSC-eBMCs) with induced thymic epithelial cells (iTECs) derived from induced pluripotent stem cells (iPSCs). We used BMCs from CD45.1 congenic C57BL/6 mice to distinguish them from iPSCs, which expressed CD45.2. We showed that HSC-eBMCs and iTECs cultured with IL-2 + IL-7 for up to 21 days induced CD45.1⁺ γδT cells that expressed a broad repertoire of Vγ and Vδ T-cell receptors. Notably, the induced lymphocytes contained few or no αβT cells, NK1.1⁺ natural killer cells, or B220⁺ B cells. Adoptive transfer of the induced γδT cells to leukemia-bearing mice significantly reduced tumour growth and prolonged mouse survival with no obvious side effects, such as tumorigenesis and autoimmune diseases. This new method suggests that it could also be used to produce human γδT cells for clinical applications.

Empowering patients from within: Emerging nanomedicines for in vivo immune cell reprogramming

Currently, medicine lacks the ability to reprogram selected immune cells so they possess all the functions which, from a clinical standpoint, physicians might wish them to have. To solve this problem, scientists have been marrying concepts from materials science, immunology, and genetic engineering to develop novel nanotherapeutics that directly genetically reprogram immune cells inside the body. These products could address key limitations of existing ex vivo-engineered cell immunotherapies and substantially enhance patient access and outcomes. This review highlights the latest advances in this rapidly emerging biotech field and discusses challenges in translating these preclinical studies into successful clinical nanomedicines.

In Situ Programming of CAR T Cells

Gene therapy makes it possible to engineer chimeric antigen receptors (CARs) to create T cells that target specific diseases. However, current approaches require elaborate and expensive protocols to manufacture engineered T cells ex vivo, putting this therapy beyond the reach of many patients who might benefit. A solution could be to program T cells in vivo. Here, we evaluate the clinical need for in situ CAR T cell programming, compare competing technologies, review current progress, and provide a perspective on the long-term impact of this emerging and rapidly flourishing biotechnology field.

Nonviral gene delivery to T cells with Lipofectamine LTX

Retroviral gene delivery is widely used in T cell therapies for hematological cancers. However, viral vectors are expensive to manufacture, integrate genes in semirandom patterns, and their transduction efficiency varies between patients. In this study, several nonviral gene delivery vehicles, promoters, and additional variables were compared to optimize nonviral transgene delivery and expression in both Jurkat and primary T cells. Transfection of Jurkat cells was maximized to a high efficiency (63.0% ± 10.9% EGFP⁺  cells) by transfecting cells with Lipofectamine LTX in X-VIVO 15 media. However, the same method yielded a much lower transfection efficiency in primary T cells (8.1% ± 0.8% EGFP⁺ ). Subsequent confocal microscopy revealed that a majority of the lipoplexes did not enter the primary T cells, which might be due to relatively low expression levels of heparan sulfate proteoglycans detected via messenger RNA-sequencing. Pyrin and HIN (PYHIN) DNA sensors (e.g., AIM2 and IFI16) that can induce apoptosis or repress transcription after binding cytoplasmic DNA were also detected at high levels in primary T cells. Therefore, transfection of primary T cells appears to be limited at the level of cellular uptake or DNA sensing in the cytoplasm. Both of these factors should be considered in the development of future viral and nonviral T cell gene delivery methods.

Optimization of electroporation and other non-viral gene delivery strategies for T cells

CAR-T therapy is a particularly effective treatment for some types of cancer that uses retroviruses to deliver the gene for a chimeric antigen receptor (CAR) to a patient's T cells ex vivo. The CAR enables the T cells to bind and eradicate cells with a specific surface marker (e.g., CD19⁺ B cells) after they are transfused back into the patient. This treatment was proven to be particularly effective in treating non-Hodgkin's lymphoma (NHL) and acute lymphoblastic leukemia (ALL), but the current CAR-T cell manufacturing process has a few significant drawbacks. For example, while lentiviral and gammaretroviral transduction are both relatively effective, the process of producing viral vectors is time-consuming and costly. Additionally, patients must undergo follow up appointments for several years to monitor them for any unanticipated side effects associated with the virus. Therefore, several studies have endeavored to find alternative non-viral gene delivery methods that are less expensive, more precise, simple, and safe. This review focuses on the current state of the most promising non-viral gene delivery techniques, including electroporation and transfection with cationic polymers or lipids.

Global alteration of T-lymphocyte metabolism by PD-L1 checkpoint involves a block of de novo nucleoside phosphate synthesis

Metabolic obstacles of the tumor microenvironment remain a challenge to T-cell-mediated cancer immunotherapies. To better understand the interplay of immune checkpoint signaling and immune metabolism, this study developed and used an optimized metabolite extraction protocol for non-adherent primary human T-cells, to broadly profile in vitro metabolic changes effected by PD-1 signaling by mass spectrometry-based metabolomics and isotopomer analysis. Inhibitory signaling reduced aerobic glycolysis and glutaminolysis. A general scarcity across the panel of metabolites measured supported widespread metabolic regulation by PD-1. Glucose carbon fate analysis supported tricarboxylic acid cycle reliance on pyruvate carboxylation, catabolic-state fluxes into acetyl-CoA and succinyl-CoA, and a block in de novo nucleoside phosphate synthesis that was accompanied by reduced mTORC1 signaling. Nonetheless, exogenous administration of nucleosides was not sufficient to ameliorate proliferation of T-cells in the context of multiple metabolic insufficiencies due to PD-L1 treatment. Carbon fate analysis did not support the use of primarily glucose-derived carbons to fuel fatty acid beta oxidation, in contrast to reports on T-memory cells. These findings add to our understanding of metabolic dysregulation by PD-1 signaling and inform the effort to rationally develop metabolic interventions coupled with immune-checkpoint blockade for increased treatment efficacy.

Human Platelet Lysate Media Supplement Supports Lentiviral Transduction and Expansion of Human T Lymphocytes While Maintaining Memory Phenotype

Immune cell therapy has emerged as a promising approach to treat malignancies that were up until recently only treated on a palliative basis. Chimeric antigen receptor- (CAR-) modified T lymphocytes (T cells) in particular have proven to be very effective for certain hematological malignancies. The production of CAR T cells usually involves viral transduction and ex vivo culture of T cells. The aim of this study was to explore the use of human platelet lysate (HPL) compared to two commonly used supplements, human AB serum (ABS) and fetal bovine serum (FBS), for modified T cell production. For studying transduction, activated T cells were transduced with lentivirus to deliver GFP transgenes with three different promoters. Transduction efficiency (percent GFP) was similar among the supplements, and a modest increase in the transgene product (mean fluorescence intensity) was observed when HPL was used as a supplement compared to ABS. To study the effect of supplements on expansion, peripheral blood mononuclear cells (PBMCs) were activated and expanded in the presence of interleukin 2 (IL2) for fourteen days. T cell expansions using HPL and ABS were comparable and slightly less than the expansion obtained with FBS. Interestingly, cells expanded in media supplemented with HPL showed a higher percentage of T cells with a central memory phenotype compared to those expanded in ABS or FBS. Protein profiling revealed that the phenotypic differences may be explained by elevated levels of several cytokines in HPL, including IL7. The results suggest that the use of HPL as a cell culture supplement during the production of modified T cells is a reasonable alternative to ABS. Furthermore, the use of HPL may enhance in vivo performance of the final product by enriching for central memory T cells that are associated with long-term persistence following adoptive transfer.

T Cell Microvilli: Sensors or Senders?

Communication between cells is essential for multicellular life. During cognate immune interactions, T cells communicate with antigen-presenting cells (APC) via direct cell-cell contact or the release of molecules and vesicles containing T cell messages. A wide variety of mechanisms have been reported and among them a process called "trogocytosis" has traditionally been thought to be the fastest way to directly transfer membrane portions containing intact proteins from one cell to another; however, the mechanism is unverified. Trogocytosis has been distinguished from the generation of extracellular vesicles (EVs), a term that encompasses exosomes and microvesicles, as EVs are released via a contact-independent manner and are suggested to potentially send molecular messages over a distance. However, some previous reports regarding EVs in T cells may be misleading in terms of explaining their cellular origins. In addition, there is little evidence on how EVs are generated from T cells in vivo and function to regulate complex immune responses. A recent work demonstrated that T cell microvilli-thin and finger-like membrane protrusions-are highly fragile and easily separated as membrane particles by trogocytosis, forming a new class of EVs. Surprisingly, released T cell microvilli-derived particles act as vectors, transmitting T cell messages to cognate APCs. This review focuses on how T cell microvilli vesicles are connected with immune regulation mechanisms discovered previously.

RNA-Modified T Cells Mediate Effective Delivery of Immunomodulatory Cytokines to Brain Tumors

With the presence of the blood-brain barrier (BBB), successful immunotherapeutic drug delivery to CNS malignancies remains a challenge. Immunomodulatory agents, such as cytokines, can reprogram the intratumoral microenvironment; however, systemic cytokine delivery has limited access to the CNS. To bypass the limitations of systemically administered cytokines, we investigated if RNA-modified T cells could deliver macromolecules directly to brain tumors. The abilities of T cells to cross the BBB and mediate direct cytotoxic killing of intracranial tumors make them an attractive tool as biological carriers. Using T cell mRNA electroporation, we demonstrated that activated T cells can be modified to secrete granulocyte macrophage colony-stimulating factor (GM-CSF) protein while retaining their inherent effector functions in vitro. GM-CSF RNA-modified T cells effectively delivered GM-CSF to intracranial tumors in vivo and significantly extended overall survival in an orthotopic treatment model. Importantly, GM-CSF RNA-modified T cells demonstrated superior anti-tumor efficacy as compared to unmodified T cells alone or in combination with systemic administration of recombinant GM-CSF. Anti-tumor effects were associated with increased IFN-γ secretion locally within the tumor microenvironment and systemic antigen-specific T cell expansion. These findings demonstrate that RNA-modified T cells may serve as a versatile platform for the effective delivery of biological agents to CNS tumors.

Optimized DNA electroporation for primary human T cell engineering

Background

Effective gene-delivery systems for primary human T cell engineering are useful tools for both basic research and clinical immunotherapy applications. Pseudovirus-based systems and electro-transfection are the most popular strategies for genetic material transduction. Compared with viral-particle-mediated approaches, electro-transfection is theoretically safer, because it does not promote transgene integration into the host genome. Additionally, the simplicity and speed of the procedure increases the attractiveness of electroporation. Here, we developed and optimized an electro-transfection method for the production of engineered chimeric antigen receptor (CAR)-T cells.

Results

Stimulation of T cells had the greatest effect on their transfection, with stimulation of cells for up to 3 days substantially improving transfection efficiency. Additionally, the strength of the external electric field, input cell number, and the initial amount of DNA significantly affected transfection performance. The voltage applied during electroporation affected plasmid permeation and was negatively correlated with the number of viable cells after electroporation. Moreover, higher plasmid concentration increased the proportion of positively transfected cells, but decreased cell viability, and for single-activated cells, higher cell density enhanced their viability. We evaluated the effects of two clinically relevant factors, serum supplementation in the culture medium and cryopreservation immediately after the isolation of peripheral blood lymphocytes. Our findings showed that our protocol performed well using xeno-free cultured, fresh T cells, with application resulting in a lower but acceptable transfection efficiency of cells cultured with fetal bovine serum or thawed cells. Furthermore, we described an optimized procedure to generate CAR-T cells within 6 days and that exhibited cytotoxicity toward targeted cells.

Conclusions

Our investigation of DNA electro-transfection for the use in human primary T cell engineering established and validated an optimized method for the construction of functional CAR-T cells.

Electronic supplementary material

The online version of this article (10.1186/s12896-018-0419-0) contains supplementary material, which is available to authorized users.

Methodological approach to the ex vivo expansion and detection of T. cruzi-specific T cells from chronic Chagas disease patients

The discovery of T cell epitopes is essential not only for gaining knowledge about host response to infectious disease but also for the development of immune-intervention strategies. In Chagas disease, given the size and complexity of the Trypanosoma cruzi proteome and its interaction with the host’s immune system, the fine specificity of T cells has not been extensively studied yet, and this is particularly true for the CD4⁺ T cell compartment. The aim of the present work was to optimize a protocol for the generation of parasite-specific memory T cell lines, representative of their in vivo precursor populations and capable of responding to parasite antigens after long-term culture. Accordingly, peripheral blood mononuclear cells (PBMC) from both chronic asymptomatic and cardiac patients, and from non-infected individuals, underwent different in vitro culture and stimulation conditions. Subsequently, cells were tested for their capacity to respond against T. cruzi lysate by measuring [³H]-thymidine incorporation and interferon-γ and GM-CSF secretion. Results allowed us to adjust initial T. cruzi lysate incubation time as well as the number of expansions with phytohemagglutinin (PHA) and irradiated allogeneic PBMC prior to specificity evaluation. Moreover, our data demonstrated that parasite specific T cells displayed a clear and strong activation by using T. cruzi lysate pulsed, Epstein-Barr virus (EBV)-transformed human B lymphocytes (B-LCL), as autologous antigen presenting cells. Under these culture conditions, we generated a clone from an asymptomatic patient’s memory CD4⁺ T cells which responded against epimastigote and trypomastigote protein lysate. Our results describe a culture method for isolating T. cruzi specific T cell clones from patients with Chagas disease, which enable the acquisition of information on functionality and specificity of individual T cells.

Three-dimensional localization of T-cell receptors in relation to microvilli using a combination of superresolution microscopies

Leukocyte microvilli are flexible projections enriched with adhesion molecules. The role of these cellular projections in the ability of T cells to probe antigen-presenting cells has been elusive. In this study, we probe the spatial relation of microvilli and T-cell receptors (TCRs), the major molecules responsible for antigen recognition on the T-cell membrane. To this end, an effective and robust methodology for mapping membrane protein distribution in relation to the 3D surface structure of cells is introduced, based on two complementary superresolution microscopies. Strikingly, TCRs are found to be highly localized on microvilli, in both peripheral blood human T cells and differentiated effector T cells, and are barely found on the cell body. This is a decisive demonstration that different types of T cells universally localize their TCRs to microvilli, immediately pointing to these surface projections as effective sensors for antigenic moieties. This finding also suggests how previously reported membrane clusters might form, with microvilli serving as anchors for specific T-cell surface molecules.

Biopolymer implants enhance the efficacy of adoptive T-cell therapy

Although adoptive T cell therapy holds promise for the treatment of many cancers, its clinical utility has been limited by problems in delivering targeted lymphocytes to tumor sites, and their inefficient expansion in the immunosuppressive tumor microenvironment. Here we describe a bioactive polymer implant capable of delivering, expanding and dispersing tumor-reactive T cells. The approach can be used to treat inoperable or incompletely-removed tumors by situating implants near them, or at resection sites. Using a mouse breast cancer resection model, we show that the implants effectively support tumor-targeting T cells throughout resection beds and associated lymph nodes, and reduce tumor relapse compared to conventional delivery modalities. In a multifocal ovarian cancer model, we demonstrate that polymer-delivered T cells trigger regression whereas injected tumor-reactive lymphocytes have little curative effect. Scaffold-based T cell delivery may provide a viable treatment option for inoperable tumors, and reduce the rate of metastatic relapse after surgery.

Shikonin induces cytotoxicity of co-stimulated human cells to gastric cancer cell lines

AIM: To observe the effect of shikonin on the growth of co-stimulated human cells and the cytotoxicity of co-stimulated cells to gastric cancer cell lines NCI-N87, BGC-823 and HGC-27, and to explore the underlying mechanisms．

METHODS: Peripheral blood mononuclear cells were separated form healthy volunteers and induced with various cytokines (CD3 mAb, IL-2, IFN-γ, IL-1α, CD28 mAb, IL-15 and IL-21) to result in co-stimulated human cells in vitro. After co-stimulated cells were incubated with shikonin of different concentrations for 24, 48 and 72 h and co-cultured with the three gastric cancer cell lines, CCK8 assay was used to assess the proliferation of co-stimulated cells, and MTT assay was used to measure the reduced rate of growth of gastric cancer cells. FCM was used to detect the expression of GraB, PFP, CD107a and IFN-γ on co-stimulated cells before and after shikonin treatment. LDH release assay was used to measure the influence of shikonin on cytotoxic activity of co-stimulated cells to gastric cancer cells. Western blot assay was used to measure β-catenin, P-ERK1/2, Bcl-2 and P-AKT expression in co-stimulated cells before and after shikonin induction.

RESULTS: After incubation with shikonin at concentrations ranging from 0.2 to 50 μg/L for 48 h, the proliferation rate of co-stimulated cells increased significantly (P < 0.05). The expression of GraB, PFP, CD107a, IFN-γ, β-catenin, P-ERK1/2, Bcl-2 and P-AKT on co-stimulated cells treated with shikonin at concentrations from 6 to 25 μg/L were significantly higher than that in the control group (P < 005). In addition, the cytotoxic activity of co-stimulated cells treated with shikonin against the three gastric cancer cell lines were significantly higher than that in the control group (P < 0.05).

CONCLUSION: These results suggest that shikonin can promote the growth of co-stimulated cells and increase the cytotoxic activity of co-stimulated cells against gastric cancer cells via mechanisms possibly associated with enhancing the activity of β-catenin, P-ERK1/2, Bcl-2 and P-AKT expression and increasing the expression of PFP, GraB, CD107a and IFN-γ.

Natural killer T cells in advanced melanoma patients treated with tremelimumab

A significant barrier to effective immune clearance of cancer is loss of antitumor cytotoxic T cell activity. Antibodies to block pro-apoptotic/downmodulatory signals to T cells are currently being tested. Because invariant natural killer T cells (iNKT) can regulate the balance of Th1/Th2 cellular immune responses, we characterized the frequencies of circulating iNKT cell subsets in 21 patients with melanoma who received the anti-CTLA4 monoclonal antibody tremelimumab alone and 8 patients who received the antibody in combination with MART-1_26–35 peptide-pulsed dendritic cells (MART-1/DC). Blood T cell phenotypes and functionality were characterized by flow cytometry before and after treatment. iNKT cells exhibited the central memory phenotype and showed polyfunctional cytokine production. In the combination treatment group, high frequencies of pro-inflammatory Th1 iNKT CD8⁺ cells correlated with positive clinical responses. These results indicate that iNKT cells play a critical role in regulating effective antitumor T cell activity.

PET imaging to non-invasively study immune activation leading to antitumor responses with a 4-1BB agonistic antibody

Background

Molecular imaging with positron emission tomography (PET) may allow the non-invasive study of the pharmacodynamic effects of agonistic monoclonal antibodies (mAb) to 4-1BB (CD137). 4-1BB is a member of the tumor necrosis factor family expressed on activated T cells and other immune cells, and activating 4-1BB antibodies are being tested for the treatment of patients with advanced cancers.

Methods

We studied the antitumor activity of 4-1BB mAb therapy using [¹⁸ F]-labeled fluoro-2-deoxy-2-D-glucose ([¹⁸ F]FDG) microPET scanning in a mouse model of colon cancer. Results of microPET imaging were correlated with morphological changes in tumors, draining lymph nodes as well as cell subset uptake of the metabolic PET tracer in vitro.

Results

The administration of 4-1BB mAb to Balb/c mice induced reproducible CT26 tumor regressions and improved survival; complete tumor shrinkage was achieved in the majority of mice. There was markedly increased [¹⁸ F]FDG signal at the tumor site and draining lymph nodes. In a metabolic probe in vitro uptake assay, there was an 8-fold increase in uptake of [³H]DDG in leukocytes extracted from tumors and draining lymph nodes of mice treated with 4-1BB mAb compared to untreated mice, supporting the in vivo PET data.

Conclusion

Increased uptake of [¹⁸ F]FDG by PET scans visualizes 4-1BB agonistic antibody-induced antitumor immune responses and can be used as a pharmacodynamic readout to guide the development of this class of antibodies in the clinic.

Multifunctional T-cell analyses to study response and progression in adoptive cell transfer immunotherapy

Adoptive cell transfer (ACT) of genetically engineered T cells expressing cancer-specific T-cell receptors (TCR) is a promising cancer treatment. Here, we investigate the in vivo functional activity and dynamics of the transferred cells by analyzing samples from 3 representative patients with melanoma enrolled in a clinical trial of ACT with TCR transgenic T cells targeted against the melanosomal antigen MART-1. The analyses included evaluating 19 secreted proteins from individual cells from phenotypically defined T-cell subpopulations, as well as the enumeration of T cells with TCR antigen specificity for 36 melanoma antigens. These analyses revealed the coordinated functional dynamics of the adoptively transferred, as well as endogenous, T cells, and the importance of highly functional T cells in dominating the antitumor immune response. This study highlights the need to develop approaches to maintaining antitumor T-cell functionality with the aim of increasing the long-term efficacy of TCR-engineered ACT immunotherapy.

SIGNIFICANCE

A longitudinal functional study of adoptively transferred TCR–engineered lymphocytes yielded revealing snapshots for understanding the changes of antitumor responses over time in ACT immunotherapy of patients with advanced melanoma.