Ex vivo expansion of functional T lymphocytes from HIV-infected individuals

Influence of Culture Conditions on Ex Vivo Expansion of T Lymphocytes and Their Function for Therapy: Current Insights and Open Questions

Ex vivo expansion of T lymphocytes is a central process in the generation of cellular therapies targeted at tumors and other disease-relevant structures, which currently cannot be reached by established pharmaceuticals. The influence of culture conditions on T cell functions is, however, incompletely understood. In clinical applications of ex vivo expanded T cells, so far, a relatively classical standard cell culture methodology has been established. The expanded cells have been characterized in both preclinical models and clinical studies mainly using a therapeutic endpoint, for example antitumor response and cytotoxic function against cellular targets, whereas the influence of manipulations of T cells ex vivo including transduction and culture expansion has been studied to a much lesser detail, or in many contexts remains unknown. This includes the circulation behavior of expanded T cells after intravenous application, their intracellular metabolism and signal transduction, and their cytoskeletal (re)organization or their adhesion, migration, and subsequent intra-tissue differentiation. This review aims to provide an overview of established T cell expansion methodologies and address unanswered questions relating in vivo interaction of ex vivo expanded T cells for cellular therapy.

Optimizing interleukin-2 concentration, seeding density and bead-to-cell ratio of T-cell expansion for adoptive immunotherapy

Background

The successful ex vivo expansion of T-cells in great numbers is the cornerstone of adoptive cell therapy. We aimed to achieve the most optimal T-cell expansion condition by comparing the expansion of T-cells at various seeding densities, IL-2 concentrations, and bead-to-cell ratios. we first expanded the peripheral blood mononuclear cells (PBMCs) of a healthy donor at a range of 20 to 500 IU/mL IL-2 concentrations, 125 × 10³ to 1.5 × 10⁶ cell/mL, and 1:10 to 10:1 B:C (Bead-to-cell) ratios and compared the results. We then expanded the PBMC of three healthy donors using the optimized conditions and examined the growth kinetics. On day 28, CD3, CD4, and CD8 expression of the cell populations were analyzed by flow cytometry.

Results

T-cells of the first donor showed greater expansion results in IL-2 concentrations higher than 50 IU/mL compared to 20 IU/mL (P = 0.02). A seeding density of 250 × 10³ cell/mL was superior to higher or lower densities in expanding T-cells (P = 0.025). Also, we witnessed a direct correlation between the B:C ratio and T-cell expansion, in which, in 5:1 and 10:1 B:C ratios T-cell significantly expanded more than lower B:C ratios. The results of PBMC expansions of three healthy donors were similar in growth kinetics. In the optimized condition, 96–98% of the lymphocyte population expressed CD3. While the majority of these cells expressed CD8, the mean expression of CD4 in the donors was 19.3, 16.5, and 20.4%.

Conclusions

Our methodology demonstrates an optimized culture condition for the production of large quantities of polyclonal T-cells, which could be useful for future clinical and research studies.

Lymphocyte expansion in bioreactors: upgrading adoptive cell therapy

Bioreactors are essential tools for the development of efficient and high-quality cell therapy products. However, their application is far from full potential, holding several challenges when reconciling the complex biology of the cells to be expanded with the need for a manufacturing process that is able to control cell growth and functionality towards therapy affordability and opportunity. In this review, we discuss and compare current bioreactor technologies by performing a systematic analysis of the published data on automated lymphocyte expansion for adoptive cell therapy. We propose a set of requirements for bioreactor design and identify trends on the applicability of these technologies, highlighting the specific challenges and major advancements for each one of the current approaches of expansion along with the opportunities that lie in process intensification. We conclude on the necessity to develop targeted solutions specially tailored for the specific stimulation, supplementation and micro-environmental needs of lymphocytes’ cultures, and the benefit of applying knowledge-based tools for process control and predictability.

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.

Epigenetic Modulation of CD8⁺ T Cell Function in Lentivirus Infections: A Review

CD8⁺ T cells are critical for controlling viremia during human immunodeficiency virus (HIV) infection. These cells produce cytolytic factors and antiviral cytokines that eliminate virally- infected cells. During the chronic phase of HIV infection, CD8⁺ T cells progressively lose their proliferative capacity and antiviral functions. These dysfunctional cells are unable to clear the productively infected and reactivated cells, representing a roadblock in HIV cure. Therefore, mechanisms to understand CD8⁺ T cell dysfunction and strategies to boost CD8⁺ T cell function need to be investigated. Using the feline immunodeficiency virus (FIV) model for lentiviral persistence, we have demonstrated that CD8⁺ T cells exhibit epigenetic changes such as DNA demethylation during the course of infection as compared to uninfected cats. We have also demonstrated that lentivirus-activated CD4⁺CD25⁺ T regulatory cells induce forkhead box P3 (Foxp3) expression in virus-specific CD8⁺ T cell targets, which binds the interleukin (IL)-2, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ promoters in these CD8⁺ T cells. Finally, we have reported that epigenetic modulation reduces Foxp3 binding to these promoter regions. This review compares and contrasts our current understanding of CD8⁺ T cell epigenetics and mechanisms of lymphocyte suppression during the course of lentiviral infection for two animal models, FIV and simian immunodeficiency virus (SIV).

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.

HIV-specific T-cell responses detected in the genital tract of chronically HIV-infected women are largely monofunctional

HIV-specific T cells that produce interferon-γ (IFN-γ) are present in the genital tract of HIV-infected women although these do not provide protection against genital HIV shedding. Because polyfunctional HIV-specific T cells have been implicated in better HIV control than those with a single function, this study aimed to investigate whether polyfunctional T cells were present at the female genital mucosa. Cervical cytobrush-derived T cells were obtained from chronically HIV-infected women and compared with blood. CD3(+) T cells from both compartments were expanded with Dynal anti-CD3/CD28 expander beads for 14 days and flow cytometry was used to evaluate four T-cell functions (CD107a, IFN-γ, tumour necrosis factor-α and macrophage inflammatory protein-1β) from 16 women. The majority of Gag-specific T-cell responses in the female genital tract were monofunctional, although low frequencies of HIV Gag-specific polyfunctional CD8(+) T cells were detected at the cervix in 81·3% (13/16) of women. The ability of CD8(+) T cells at both the cervix and in blood to express CD107a and to exhibit polyfunctional responses (two or more functions) following Gag stimulation was inversely associated with plasma viral load and positively associated with blood CD4 counts, suggesting that clinical status impacted on the functionality of HIV-specific T cells at the mucosa, in a similar way to blood. HIV Gag-specific cervical T cells were largely monofunctional. Polyfunctional T cells were detected at the cervix in women with high blood CD4 count and low plasma viral load but these did not protect from HIV genital shedding.

Accelerated production of antigen-specific T cells for preclinical and clinical applications using gas-permeable rapid expansion cultureware (G-Rex)

The clinical manufacture of antigen-specific cytotoxic T lymphocytes (CTLs) for adoptive immunotherapy is limited by the complexity and time required to produce large numbers with the desired function and specificity. The culture conditions required are rigorous, and in some cases only achieved in 2-cm wells in which cell growth is limited by gas exchange, nutrients, and waste accumulation. Bioreactors developed to overcome these issues tend to be complex, expensive, and not always conducive to CTL growth. We observed that antigen-specific CTLs undergo 7 to 10 divisions poststimulation. However, the expected CTL numbers were achieved only in the first week of culture. By recreating the culture conditions present during this first week-low frequency of antigen-specific T cells and high frequency of feeder cells-we were able to increase CTL expansion to expected levels that could be sustained for several weeks without affecting phenotype or function. However, the number of 24-well plates needed was excessive and cultures required frequent media changes, increasing complexity and manufacturing costs. Therefore, we evaluated novel gas-permeable culture devices (G-Rex) with a silicone membrane at the base allowing gas exchange to occur uninhibited by the depth of the medium above. This system effectively supports the expansion of CTL and actually increases output by up to 20-fold while decreasing the required technician time. Importantly, this amplified cell expansion is not because of more cell divisions but because of reduced cell death. This bioprocess optimization increased T-cell output while decreasing the complexity and cost of CTL manufacture, making cell therapy more accessible.

Comparison of polyclonal expansion methods to improve the recovery of cervical cytobrush-derived T cells from the female genital tract of HIV-infected women

Cervical cytobrushing is a useful and non-invasive method for obtaining mucosal mononuclear cells from the female genital tract, but yields few cells. The aim of this study was to compare in vitro expansion protocols (anti-CD3, anti-CD3/CD28 or Dynal anti-CD3/CD28 beads) and cytokine combinations (IL-2, IL-7 and IL-15) to improve cervical T cell yields and viability. Eighteen HIV-infected women were included in this study to compare methods for polyclonal expansion of T cells from the female genital tract and blood. Comparison of T cell yields, viability and maturational status (by differential staining with CD45RO, CCR7 and CD27) was determined following 7 days of in vitro expansion. Anti-CD3 and IL-2 resulted in a 4.5-fold (range 3.7–5.3) expansion of cervical CD3+ T cells in 7 days compared to day 0. Inclusion of anti-CD28 or addition of IL-7 and IL-15 to this combination did not improve expansion. Culturing cells with Dynal beads (1:1) and IL-2, IL-7 and IL-15 gave rise to the highest yields after 7 days in both blood (7.1-fold) and cervix (5.6-fold). While expansion with anti-CD3 led to the accumulation of effector memory T cells (CD45RO+CCR7−CD27−), expansion with Dynabeads selected for accumulation of central memory T cells (CD45RO+CCR7+CD27+). We conclude that in vitro expansion with Dynabeads (1:1) in the presence of IL-2, IL-7 and IL-15 resulted in the greatest increase in viable T cells from both blood and cytobrush. Irrespective of the expansion method used, the T cell memory profile was altered following expansion.

Preparing clinical grade Ag-specific T cells for adoptive immunotherapy trials

The production of clinical-grade T cells for adoptive immunotherapy has evolved from the ex vivo numerical expansion of tumor-infiltrating lymphocytes to sophisticated bioengineering processes often requiring cell selection, genetic modification and other extensive tissue culture manipulations, to produce desired cells with improved therapeutic potential. Advancements in understanding the biology of lymphocyte signaling, activation, homing and sustained in vivo proliferative potential have redefined the strategies used to produce T cells suitable for clinical investigation. When combined with new technical methods in cell processing and culturing, the therapeutic potential of T cells manufactured in academic centers has improved dramatically. Paralleling these technical achievements in cell manufacturing is the development of broadly applied regulatory standards that define the requirements for the clinical implementation of cell products with ever-increasing complexity. In concert with academic facilities operating in compliance with current good manufacturing practice, the prescribing physician can now infuse T cells with a highly selected or endowed phenotype that has been uniformly manufactured according to standard operating procedures and that meets federal guidelines for quality of investigational cell products. In this review we address salient issues related to the technical, immunologic, practical and regulatory aspects of manufacturing these advanced T-cell products for clinical use.

Human lymphocyte PEEK-WC hollow fiber membrane bioreactor

In this study we developed a PEEK-WC hollow fiber (HF) membrane bioreactor for the maintenance of human peripheral lymphocytes as model system for the in vitro investigation of disease pathogenesis, chemical effects and individual drug sensitivity. Peripheral lymphocytes isolated from donor's human buffy coat were cultured in the shell compartment of the PEEK-WC-HF bioreactor and stimulated with PHA 5microg/mL for the first 48h of culture to enhance cytokine production and cell proliferation. Thereafter, cells were cultured in the presence of Hypericum perforatum (St. John's wort) in order to induce cytochrome P450s enzymes, CYP2E, involved in the biotransformation of endogenous molecules and exogenous compounds. The metabolic activity of cells with respect to glucose consumption and oxygen uptake was maintained for all the culture time without the addition of mitogen. Two cytokines IL-2 and IL-10, which are specific pattern of lymphocytes T helper 1 and T helper 2, respectively, were produced in the bioreactor up to 14 days of culture. Lymphocytes were also able to biotransform acetaminophen through the formation of the main metabolite paracetamidofenil-beta-glucuronide, which is the product of glucuronidation reaction, as a result of the Hypericum perforatum administration that induced the catalytic activity of the CYP2E1. These results demonstrated the usefulness of the bioreactor as the support system that reproduces physiological parameters such as a constant perfusion of medium, nutrients and oxygen maintaining the in vitro integrity of lymphocyte viability and functions.

Biomaterial-based notch signaling for the differentiation of hematopoietic stem cells into T cells

Thymocyte development takes place in a complex milieu of supportive cells and ECM that are responsible for the proliferation, adhesion, migration, and selection processes these cells undergo before reaching maturity. In recent years, the role of notch signaling in lymphocyte development, specifically T-cell development, has been extensively characterized. Although notch ligand mediated signals have been shown to be a necessary component of T-cell generation from stem cells, high-throughput, synthetic biomaterial-based systems for notch-directed stem-cell differentiation into lymphocytes are yet to be reported. Here, we present a microbead-based, artificial notch signaling system to study stem-cell differentiation into the T-cell lineage. Magnetic microbeads were functionalized with the notch ligand DLL4 using streptavidin-biotin binding and antibody-antigen coupling. Immunohistochemistry and flow cytometry analysis indicated approximately 65% conjugation efficiency. Efficient notch signaling through these functionalized microbeads was demonstrated through a myotube inhibition assay in C2C12 myoblasts. Thy1.2(+) early T cells were successfully generated from mouse bone marrow hematopoietic stem cells (BMHSCs) using DLL4 functionalized beads using both insert-based and mixed stromal cell (OP9) coculture conditions, indicating that stem cell-stromal cell physical contact is not necessary for DLL4 directed T-cell differentiation. Coculture studies with bead-to-cell ratios of 1:1 generated higher T-cell differentiation efficiencies, compared to bead-to-cell ratios of 5:1. These data demonstrate the promising potential of this biomaterial-based notch signaling system to generate T cells from stem cells and to elucidate the molecular interactions in T-cell development.

Molecular insights into the pleiotropic effects of plasma on ex vivo-expanded T cells using DNA-microarray analysis

OBJECTIVE

Immunotherapy with ex vivo-expanded T cells depends on a large supply of biologically active cells. Understanding the effects of culture parameters is essential for improving cell expansion and efficacy. We used DNA-microarray and flow-cytometric analysis coupled with functional assays to investigate mechanistic aspects of plasma supplementation in ex vivo T-cell expansion.

METHODS

The effect of plasma supplementation on 18 primary T-cell cultures over a 15-day expansion was investigated. Transcriptional analysis of 5 samples was done with time points every 2 to 3 days throughout the 15-day expansion. Quantitative RT-PCR analysis was used to confirm selected microarray data. The expression of granzyme A and vimentin were analyzed using intracellular flow cytometry. T-cell functionality was assessed using a mixed leukocyte reaction (MLR).

RESULTS

We show that the increased expansion of plasma-supplemented cultures of primary human T cells is mostly due to increased cell survival. T cells from plasma-supplemented cultures show higher expression of immunoglobulin genes, integrins, and genes of cytotoxic granules, suggesting a possible enhanced immune function. This was confirmed using a mixed leukocyte reaction and intracellular granzyme-A measurements. A distinct gene expression pattern was correlated to viability differences between plasma-supplemented and serum-free cultures. Ontological analysis of genes in this pattern suggests that the decreased viability of serum-free cultures correlates with higher expression of actin-cytoskeleton and lipid-metabolism genes. Vimentin was found to be expressed higher in serum-free cultures.

CONCLUSIONS

These results indicate that the observed decreased cytotoxicity of T cells cultured in serum-free media may be due to increased oxidative stress and cytoskeleton degradation.

A robust human T-cell culture method suitable for monitoring CD8+ and CD4+ T-cell responses from cancer clinical trial samples

Many tumor antigenic determinants have been identified and included in cancer clinical trials. Due to low T-cell frequencies even after vaccination, few T-cell responses can be revealed ex vivo without in vitro stimulation. Various expansion protocols have been employed for this purpose and the outcomes tend to be quite variable, partly due to the high complexity involved in the protocols. Here we systematically studied various common culture conditions including sera, cytokines and feeders and describe a reliable "bulk" culture method that is robust, simpler and more economical. We demonstrated that fetal calf serum (FCS) supported T-cell proliferation better than multiple commercially available pooled human AB sera. IL-2 is critical in our cultures, but IL-7, IL-15 and anti-CTLA-4 in combination with IL-2 did not further enhance T-cell expansion. We typically achieve more than a 40-fold expansion within a 10-day culture period for antigen-specific T cells measured by HLA-peptide tetramer before and after culture. This method was not only validated by multiple operators as a standard operating procedure for monitoring T-cell responses but was also successfully used for discovering novel CD8+ and CD4+ T cells specific to previously unknown epitopes from the NY-ESO-1 tumor antigen.

T cell stimulation and expansion using anti-CD3/CD28 beads

Following appropriate stimulation, T lymphocytes will proliferate extensively in vitro. Traditionally, mitogenic lectins such as phytohemagglutinin (PHA) and concanavalin A (Con A) have been used for polyclonal T cell stimulation. A more physiologically relevant approach uses beads coated with anti-CD3 and anti-CD28 to stimulate T cells in a manner that partially mimics stimulation by antigen-presenting cells. This protocol describes the steps involved in T cell stimulation and their subsequent in vitro expansion using anti-CD3/CD28 beads.