Microfluidic 3D Cytotoxic Assay.

Microfluidic-based cytotoxic assays provide high physiological relevance with the potential to replace conventional animal experiments and two-dimensional (2D) assays. Here, a 3D method utilizing a microfluidic platform for analysis of lymphocyte cytotoxicity is introduced in detail, including platform design, cell culture method, real-time cytotoxic assay setup, and image-based analysis. A 2D experimental method is used for comparison, which effectively demonstrates the advantages of 3D microfluidic platforms in closely recapitulating immune responses within the tumor microenvironment. Moreover, a wide range of experimental possibilities and applications using microfluidic 3D cytotoxic assays is introduced in this chapter, along with their capabilities, limitations, and future outlook.

Genome-scale screens identify factors regulating tumor cell responses to natural killer cells.

To systematically define molecular features in human tumor cells that determine their degree of sensitivity to human allogeneic natural killer (NK) cells, we quantified the NK cell responsiveness of hundreds of molecularly annotated 'DNA-barcoded' solid tumor cell lines in multiplexed format and applied genome-scale CRISPR-based gene-editing screens in several solid tumor cell lines, to functionally interrogate which genes in tumor cells regulate the response to NK cells. In these orthogonal studies, NK cell-sensitive tumor cells tend to exhibit 'mesenchymal-like' transcriptional programs; high transcriptional signature for chromatin remodeling complexes; high levels of B7-H6 (NCR3LG1); and low levels of HLA-E/antigen presentation genes. Importantly, transcriptional signatures of NK cell-sensitive tumor cells correlate with immune checkpoint inhibitor (ICI) resistance in clinical samples. This study provides a comprehensive map of mechanisms regulating tumor cell responses to NK cells, with implications for future biomarker-driven applications of NK cell immunotherapies.

Efficacy and safety of ReDuNing injection as a treatment for COVID-19 and its inhibitory effect against SARS-CoV-2.

BACKGROUND: Although the rapid emergence of coronavirus disease 2019 (COVID-19) poses a considerable threat to global public health, no specific treatment is available for COVID-19. ReDuNing injection (RDN) is a traditional Chinese medicine known to exert antibacterial, antiviral, antipyretic, and anti-inflammatory effects. In addition, RDN has been recommended in the diagnosis and treatment of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-associated pneumonia by the National Health Council and the National Administration of Chinese Medicine. However, there is no information regarding its efficacy against COVID-19. AIM OF STUDY: This study was designed to determine the clinical efficacy of RDN in patients with COVID-19 and characterize its antiviral activity against SARS-CoV-2 in vitro. MATERIALS AND METHODS: A total of 50 adults with COVID-19 were included in this study, and the primary endpoint was recovery from clinical symptoms following 14 days of treatment. General improvements were defined as the disappearance of the major symptoms of infection including fever, fatigue, and cough. The secondary endpoints included the proportion of patients who achieved clinical symptom amelioration on days 7 and 10, time to clinical recovery, time to a negative nucleic acid test result, duration of hospitalization, and time to defervescence. Plaque reduction and cytopathic effect assays were also performed in vitro, and reverse-transcription quantitative PCR was performed to evaluate the expression of inflammatory cytokines (TNF-α, IP-10, MCP-1, IL-6, IFN-α, IFN-γ, IL-2 and CCL-5) during SARS-CoV-2 infection. RESULTS: The RDN group exhibited a shorter median time for the resolution of clinical symptoms (120 vs. 220 h, P < 0.0001), less time to a negative PCR test result (215 vs. 310 h, P = 0.0017), shorter hospitalization (14.8 vs. 18.5 days, P = 0.0002), and lower timeframe for defervescence (24.5 vs. 75 h, P = 0.0001) than the control group. In addition, time to improved imaging was also shorter in the RDN group than in the control group (6 vs.8.9 days, P = 0.0273); symptom resolution rates were higher in the RDN group than in the control group at 7 (96.30% vs. 39.13%, P < 0.0001) and 10 days (96.30% vs. 56.52%, P = 0.0008). No allergic reactions or anaphylactic responses were reported in this trial. RDN markedly inhibited SARS-CoV-2 proliferation and viral plaque formation in vitro. In addition, RDN significantly reduced inflammatory cytokine production in infected cells. CONCLUSIONS: RDN relieves clinical symptoms in patients with COVID-19 and reduces SARS-CoV-2 infection by regulating inflammatory cytokine-related disorders, suggestion that this medication might be a safe and effective treatment for COVID-19.

Determination and Quantitation of Cytotoxic T Cell-Mediated Cell Death.

Cytotoxic T cell-induced cell death is well documented. Cytotoxic T cell releases various cytolytic proteins. The cytolytic proteins induce target cell death. T cell-induced cell death can be measured by the lytic assay. One of the well-known lytic assays uses radioactive tracer, Chromium-51 (51Cr), and detects the amount of 51Cr released from target cells. This assay can detect cell death and the efficiency of the T cell-induced cell death by coculture effector cells (T cells) and target cells. This assay can determine the kinetics of the cell lysis. The issue of this approach is the use of radioactive material. This chapter describes measuring T cell-induced cell death by determining the epigenetic remodeling and the release of cytolytic proteins. Determine the efficiency of T cell-induced cell death by using a flow cytometry-based detection method.

Human Leukemia T-Cell Lines as Alternatives to Animal Use for Detecting Biologically Active Staphylococcal Enterotoxin Type B.

Staphylococcal enterotoxin type B (SEB) is associated with food poisoning. Current methods for the detection of biologically active SEB rely upon its ability to cause emesis when administered to live kittens or monkeys. This technique suffers from poor reproducibility and low sensitivity and is ethically disfavored over concerns for the welfare of laboratory animals. The data presented here show the first successful implementation of an alternative method to live animal testing that utilizes SEB super-antigenic activity to induce cytokine production for specific novel cell-based assays for quantifiable detection of active SEB. Rather than using or sacrificing live animals, we found that SEB can bind to the major histocompatibility complex (MHC) class II molecules on Raji B-cells. We presented this SEB-MHC class II complex to specific Vß5.3 regions of the human T-cell line HPB-ALL, which led to a dose-dependent secretion of IL-2 that is capable of being quantified and can further detect 10 pg/mL of SEB. This new assay is 100,000 times more sensitive than the ex vivo murine splenocyte method that achieved a detection limit of 1 µg/mL. The data presented here also demonstrate that SEB induced proliferation in a dose-dependent manner for cells obtained by three different selection methods: by splenocyte cells containing 22% of CD4+ T-cells, by CD4+ T-cells enriched to >90% purity by negative selection methods, and by CD4+ T-cells enriched to >95% purity by positive selection methods. The highly enriched and positively isolated CD4+ T-cells with the lowest concentration of antigen-presenting cells (APC) (below 5%) provided higher cell proliferation than the splenocyte cells containing the highest concentration of APC cells.

Cytotoxicity of ß-Cyclodextrins in Retinal Explants for Intravitreal Drug Formulations.

Cyclodextrins (CDs) have been widely used as pharmaceutical excipients for formulation purposes for different delivery systems. Recent studies have shown that CDs are able to form complexes with a variety of biomolecules, such as cholesterol. This has subsequently paved the way for the possibility of using CDs as drugs in certain retinal diseases, such as Stargardt disease and retinal artery occlusion, where CDs could absorb cholesterol lumps. However, studies on the retinal toxicity of CDs are limited. The purpose of this study was to examine the retinal toxicity of different beta-(ß)CD derivatives and their localization within retinal tissues. To this end, we performed cytotoxicity studies with two different CDs-2-hydroxypropyl-ßCD (HPßCD) and randomly methylated ß-cyclodextrin (RMßCD)-using wild-type mouse retinal explants, the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, and fluorescence microscopy. RMßCD was found to be more toxic to retinal explants when compared to HPßCD, which the retina can safely tolerate at levels as high as 10 mM. Additionally, studies conducted with fluorescent forms of the same CDs showed that both CDs can penetrate deep into the inner nuclear layer of the retina, with some uptake by Müller cells. These results suggest that HPßCD is a safer option than RMßCD for retinal drug delivery and may advance the use of CDs in the development of drugs designed for intravitreal administration.

Determination of Cytotoxic Activities Against Melanoma Cells Using Flow Cytometry.

Within the adaptive and innate immune system, effector lymphocytes known as cytotoxic T cells (CTLs) or natural killer (NK) cells play an essential role in host defense against tumor cells and virally infected cells. Here we describe a flow cytometry-based method to quantify CTLs or NK cell cytotoxic activity against melanoma cells. In this assay, spleen cells, peripheral blood mononuclear cells (PBMCs), or purified NK cell preparations are co-incubated at different ratios with a target tumor cell line. The target cells are pre-labeled with a fluorescent dye to allow their discrimination from the effector cells. After the incubation period, killed target cells are identified by a nucleic acid stain, which specifically permeates dead cells. This method is amenable to both diagnostic and research applications.

Non-invasive image-based cytometry for high throughput NK cell cytolysis analysis.

Natural Killer (NK) cells are lymphocytes that are the first line of defense against malignantly transformed cells, virally infected cells and other stressed cell types. To study the cytolytic function of NK cells in vitro, a cytotoxicity assay is normally conducted against a target cancerous cell line. Current assay methods are typically performed in mixed 2D cocultures with destructive endpoints and low throughput, thereby limiting the scale, time-resolution, and relevance of the assay to in vivo conditions. Here, we evaluated a novel, non-invasive, quantitative image-based cytometry (qIBC) assay for detection of NK-mediated killing of target cells in 2D and 3D environments in vitro and compared its performance to two common flow cytometry- and fluorescence-based cytotoxicity assays. Similar to the other methods evaluated, the qIBC assay allowed for reproducible detection of target cell killing across a range of effector-to-target ratios with reduced variability. The qIBC assay also allowed for detection of NK cytolysis in 3D spheroids, which enabled scalable measurements of cell cytotoxicity in 3D models. Our findings suggest that quantitative image-based cytometry would be suitable for rapid, high-throughput screening of NK cytolysis in vitro, including in quasi-3D structures that model tissue environments in vivo.

Comparative analysis of assays to measure CAR T-cell-mediated cytotoxicity.

The antitumor efficacy of genetically engineered 'living drugs', including chimeric antigen receptor and T-cell receptor T cells, is influenced by their activation, proliferation, inhibition, and exhaustion. A sensitive and reproducible cytotoxicity assay that collectively reflects these functions is an essential requirement for translation of these cellular therapeutic agents. Here, we compare various in vitro cytotoxicity assays (including chromium release, bioluminescence, impedance, and flow cytometry) with respect to their experimental setup, appropriate uses, advantages, and disadvantages, and measures to overcome their limitations. We also highlight the US Food and Drug Administration (FDA) directives for a potency assay for release of clinical cell therapy products. In addition, we discuss advanced assays of repeated antigen exposure and simultaneous testing of combinations of immune effector cells, immunomodulatory antibodies, and targets with variable antigen expression. This review article should help to equip investigators with the necessary knowledge to select appropriate cytotoxicity assays to test the efficacy of immunotherapeutic agents alone or in combination.

Development of an antibody-dependent cellular cytotoxicity reporter assay for measuring anti-Middle East Respiratory Syndrome antibody bioactivity.

Middle East Respiratory Syndrome coronavirus (MERS-CoV) is a highly virulent pathogen that causes Middle East Respiratory Syndrome (MERS). Anti-MERS-CoV antibodies play an integral role in the prevention and treatment against MERS-CoV infections. Bioactivity is a key quality attribute of therapeutic antibodies, and high accuracy and precision are required. The major methods for evaluating the antiviral effect of antiviral antibodies include neutralization assays using live viruses or pseudoviruses are highly variable. Recent studies have demonstrated that the antibody-dependent cellular cytotoxicity (ADCC) activity of antiviral antibodies is more consistent with the virus clearance effect in vivo than neutralization activity. However, no reports evaluating the ADCC activity of anti-MERS antibodies have been published to date. Here, we describe the development of a robust and reliable cell-based reporter gene assay for the determination of ADCC activity of anti-MERS antibodies using 293T/MERS cells stably expressing the spike protein of MERS-CoV (MERS-S) as target cells and the engineered Jurkat/NFAT-luc/FcγRIIIa stably expressing FcγRIIIA and NFAT reporter gene as effector cells. According to the ICH-Q2 analytical method guidelines, we carefully optimized the experimental conditions and assessed the performance of our assay. In addition, we found that the ADCC activity of afucosylated anti-MERS antibodies is higher than their fucosylated counterparts. The establishment of this ADCC determination system provides a novel method for evaluating the bioactivity of anti-MERS antibodies and improving ADCC activity through modification of N-glycosylation of the Fc segment.

Betulinic Acid-Azaprostanoid Hybrids: Synthesis and Pharmacological Evaluation as Anti-inflammatory Agents.

BACKGROUND: Prevention and treatment of chronic inflammatory diseases require effective and low-toxic medicines. Molecular hybridization is an effective strategy to enhance the biological activity of new compounds. Triterpenoid scaffolds are in the focus of attention owing to their anti-inflammatory, antiviral, antiproliferative, and immunomodulatory activities. Heteroprostanoids have different pleiotropic effects in acute and chronic inflammatory processes. OBJECTIVE: The study aimed to develop structurally new and low toxic anti-inflammatory agents via hybridization of betulinic acid with azaprostanoic acids. METHODS: A series of betulinic acid-azaprostanoid hybrids was synthesized. The synthetic pathway included the transformation of betulin via Jones' oxidation into betulonic acid, reductive amination of the latter and coupling obtained by 3ß-amino-3-deoxybetulinic acid with the 7- or 13-azaprostanoic acids and their homo analogues. The hybrids 1-9 were investigated in vivo on histamine-, formalin- and concanavalin A-induced mouse paw edema models and two models of pain - the acetic acid-induced abdominal writhing and the hotplate test. The hybrids were in vitro evaluated for cytotoxic activity on cancer (MCF7, U- 87 MG) and non-cancer humane cell lines. RESULTS: In the immunogenic inflammation model, the substances showed a pronounced anti-inflammatory effect, which was comparable to that of indomethacin. In the models of the exudative inflammation, none of the compounds displayed a statistically significant effect. The hybrids produced weak or moderate analgesic effects. All the agents revealed low cytotoxicity on human immortalized fibroblasts and cancer cell lines compared with 3ß- amino-3-deoxybetulinic acid and doxorubicin. CONCLUSION: The results indicate that the principal anti-inflammatory effect of hybrids is substantially provided with the triterpenoid scaffold and in some cases with the azaprostanoid scaffold, but the latter makes a significant contribution to reducing the toxicity of hybrids. Hybrid 1 is of interest as a potent low toxic agent against immune-mediated inflammation.

A Flow Cytometry-Based Whole Blood Natural Killer Cell Cytotoxicity Assay Using Overnight Cytokine Activation.

Background: Measurement of natural killer (NK) cell function has important clinical utility in several diseases. Although the flow cytometry (FC)-based 4-h NK cytotoxicity assay using peripheral blood mononuclear cells (PBMCs) in the clinical laboratory has been used for this purpose, this assay requires large amounts of blood and a rapid PBMC isolation step. Here, we developed an FC-based overnight NK cytotoxicity assay using whole blood (WB), and applied it to patients with liver diseases. Methods: Peripheral blood of healthy volunteers (n = 28) and patients with liver diseases, including hepatocellular carcinoma (n = 19) and liver cirrhosis (n = 7), was analyzed for complete blood count, absolute NK cell count, and NK cell activity (NKA). NKA was evaluated in three assay types: an FC-based overnight WB NK cytotoxicity assay using carboxyfluorescein diacetate succinimidyl ester-labeled K562 cells in the presence of various cytokine combinations [including interleukin (IL)-2, IL-18, and IL-21], an FC-based 4-h PBMC NK cytotoxicity assay, and an FC-based CD107a degranulation assay using WB and PBMCs. Results: Optimal cytokine combinations for NK cell activation in WB were determined (IL-2/IL-18, IL-2/IL-21, and IL-2/IL-18/IL-21). A good correlation was observed between WB and PBMC NK cytotoxicity assays; absolute NK cell counts were better correlated with the WB NK cytotoxicity assay than with the PBMC NK cytotoxicity assay. This WB NK cytotoxicity assay showed that patients with liver diseases had significantly lower NK cytotoxicity than healthy volunteers, under stimulation with various cytokines (p < 0.001). Conclusion: The proposed FC-based overnight WB NK cytotoxicity assay correlates well with the conventional 4-h PBMC NK cytotoxicity assay, demonstrating future potential as a supportive assay for clinical laboratory research and observational studies.

MRGPRX2 activation as a rapid, high-throughput mechanistic-based approach for detecting peptide-mediated human mast cell degranulation liabilities.

Mast cells play key roles in allergy, anaphylaxis/anaphylactoid reactions, and defense against pathogens/toxins. These cells contain cytoplasmic granules with a wide spectrum of pleotropic mediators that are released upon activation. While mast cell degranulation (MCD) occurs upon clustering of the IgE receptor bound to IgE and antigen, MCD is also triggered through non-IgE-mediated mechanisms, one of which is via Mas-related G protein-coupled receptor X2 (MRGPRX2). MRGPRX2 can be activated by many basic biogenic amines and peptides. Consequently, MRGPRX2-mediated MCD is an important potential safety liability for peptide therapeutics. To facilitate peptide screening for this liability in early preclinical drug development, a rapid, high-throughput engineered CHO-K1 cell-based MRGPRX2 activation assay was evaluated and compared to histamine release in CD34+ stem cell-derived mature human mast cells as a reference assay, using 30 positive control and 29 negative control peptides for MCD. Both G protein-dependent (Ca2+ endpoint) and -independent (ß-arrestin endpoint) pathways were assessed in the MRGPRX2 activation assay. The MRGPRX2 activation assay had a sensitivity of 100% for both Ca2+ and ß-arrestin endpoints and a specificity of 93% (ß-arrestin endpoint) and 83% (Ca2+ endpoint) compared to histamine release in CD34+ stem cell-derived mature human mast cells. These findings suggest that assessing MRGPRX2 activation in an engineered cell model can provide value as a rapid, high-throughput, economical mechanism-based screening tool for early MCD hazard identification during preclinical safety evaluation of peptide-based therapeutics.

Research into biocompatibility and cytotoxicity of daptomycin, gentamicin, vancomycin and teicoplanin antibiotics at common doses added to bone cement.

OBJECTIVES: This study aims to investigate the biocompatibility and cytotoxicity of daptomycin, gentamicin, vancomycin and teicoplanin at commonly-used dose intervals added to polymethylmethacrylate (PMMA) in vitro. MATERIALS AND METHODS: This prospective study was conducted between February 2016 and June 2016. Antibiotics were added to PMMA at doses frequently used in clinical practice. The antibiotic doses added were teicoplanin (2 g, 3 g, 4 g), gentamicin (0.5 g, 0.75 g, 1 g), daptomycin (0.5 g.) and vancomycin (2 g, 3 g, 4 g). Standard cement balls (10 mm) were created. Activated L929 mouse fibroblast cell culture was used for incubation. Agar diffusion, Cell Proliferation Kit II (XTT) test and electron microscope investigations were performed to examine biocompatibility and cytotoxicity. RESULTS: In the cytotoxicity test, teicoplanin at 4 g and daptomycin at 0.5 g doses were observed to cause reductions in viability percentages. The same doses caused 20% and 20-40% cell lysis indices during the agar diffusion test. On electron microscope images, cytotoxic effects in fibroblast cells and involvement with the surface of cement balls were observed. CONCLUSION: Gentamicin, vancomycin and teicoplanin were observed to be non-toxic and biocompatible at commonly-used dose intervals. Teicoplanin at 4 g and daptomycin at 0.5 g doses were identified to be cytotoxic and not biocompatible. When selecting antibiotics to be added to bone cement, care should be taken that the antibiotic is non-toxic and biocompatible.

In vivo assessment of respiratory burst inhibition by xenobiotic exposure using larval zebrafish.

Currently, assessment of the potential immunotoxicity of a given agent involves a tiered approach for hazard identification and mechanistic studies, including observational studies, evaluation of immune function, and measurement of susceptibility to infectious and neoplastic diseases. These studies generally use costly low-throughput mammalian models. Zebrafish, however, offer an excellent alternative due to their rapid development, ease of maintenance, and homology to mammalian immune system function and development. Larval zebrafish also are a convenient model to study the innate immune system with no interference from the adaptive immune system. In this study, a respiratory burst assay (RBA) was utilized to measure reactive oxygen species (ROS) production after developmental xenobiotic exposure. Embryos were exposed to non-teratogenic doses of chemicals and at 96 h post-fertilization, the ability to produce ROS was measured. Using the RBA, 12 compounds with varying immune-suppressive properties were screened. Seven compounds neither suppressed nor enhanced the respiratory burst; five reproducibly suppressed global ROS production, but with varying potencies: benzo[a]pyrene, 17ß-estradiol, lead acetate, methoxychlor, and phenanthrene. These five compounds have all previously been reported as immunosuppressive in mammalian innate immunity assays. To evaluate whether the suppression of ROS by these compounds was a result of decreased immune cell numbers, flow cytometry with transgenic zebrafish larvae was used to count the numbers of neutrophils and macrophages after chemical exposure. With this assay, benzo[a]pyrene was found to be the only chemical that induced a change in the number of immune cells by increasing macrophage but not neutrophil numbers. Taken together, this work demonstrates the utility of zebrafish larvae as a vertebrate model for identifying compounds that impact innate immune function at non-teratogenic levels and validates measuring ROS production and phagocyte numbers as metrics for monitoring how xenobiotic exposure alters the innate immune system.

Measurement of Natural Killer Cell-Mediated Cytotoxicity and Migration in the Context of Hepatic Tumor Cells.

Natural killer (NK) cells are a subset of the cytotoxic lymphocyte population of the innate immune system and participate as a first line of defense by clearing pathogen-infected, malignant, and stressed cells. The ability of NK cells to eradicate cancer cells makes them an important tool in the fight against cancer. Several new immune-based therapies are under investigation for cancer treatment which rely either on enhancing NK cell activity or increasing the sensitivity of cancer cells to NK cell-mediated eradication. However, to effectively develop these therapeutic approaches, cost-effective in vitro assays to monitor NK cell-mediated cytotoxicity and migration are also needed. Here, we present two in vitro protocols that can reliably and reproducibly monitor the effect of NK-cell cytotoxicity on cancer cells (or other target cells). These protocols are non-radioactivity-based, simple to set up, and can be scaled up for high-throughput screening. We also present a flow cytometry-based protocol to quantitatively monitor NK cell migration, which can also be scaled up for high-throughput screening. Collectively, these three protocols can be used to monitor key aspects of NK cell activity that are necessary for the cells' ability to eradicate dysfunctional target cells.

A reliable assay for ensuring the biological activity of anti T lymphocyte immunoglobulin as an alternate to compendial flow cytometry method.

The assay of Anti T lymphocyte immunoglobulin for final drug product testing is carried out using flow cytometry on Peripheral Blood Mononuclear Cells (PBMCs) as specified in European and British Pharmacopeia. An alternate assay was developed wherein the potency based quality control evaluation of Anti T lymphocyte immunoglobulin is carried out by measuring complement dependent cytotoxicity (CDC) using fluorescent resazurin dye. The reported bioassay was specific, linear (R2 = 0.98), precise (%GCV for repeatability was 3.54% and intermediate precision was 4.27%) and accurate with relative bias of -5.54%. On the basis of results obtained from the repeated performances on single available product, system suitability criteria and sample acceptance criteria were proposed wherein Slope from 4 PL curve fit results for Reference Standard (RS) should be > 0.9, EC50 for RS should lie between 0.264 and 1.131 µg/ml and fold response should be > 2. Confidence interval range and estimated relative potency range obtained from the method validation were narrower than those mentioned for compendial method.

Cross-company evaluation of the human lymphocyte activation assay.

Nonclinical immunotoxicity evaluation is an important component of safety assessment for pharmaceuticals. One in vitro assay that can be applied in a weight of evidence assessment is the human lymphocyte activation (HuLA) assay, an antigen recall assay, similar in many respects to the in vivo T-cell-dependent antibody response (TDAR) in that cooperation of multiple immune cell types are needed to produce responses. This assay uses human cells and is more amenable than the TDAR to compound ranking and mechanistic studies. The HuLA assay requires less time and drug than TDAR assays, uses a relevant antigen (influenza), reflects a human immune response, and applies principles of the 3Rs to non-clinical safety assessment. Peripheral blood mononuclear cells (PBMC) from flu-immunized donors are re-stimulated with flu-vaccine in the presence of test articles, and proliferation is measured. Published data demonstrate the applicability of the HuLA assay, but it has not been evaluated for reproducibility across testing sites. To evaluate assay reproducibility, scientists from a consortium of institutions conducted the assay in parallel, using a common pool of donor PBMC, influenza vaccine, and known immunosuppressant compounds (cyclosporine A and mycophenolic acid). The HuLA assay was highly reproducible in identification of inhibition of antigen-specific responses, and there was significant agreement across testing sites in the half maximal inhibitory concentration (IC50) values. Intra-site variability was the largest contributor to the variability observed within the assay. The HuLA assay was demonstrated to be ideally suited to comparing multiple compounds (i.e. compound ranking or benchmarking) within the same assay. Overall, the data reported herein support the HuLA assay as a useful tool in mechanistic evaluations of antigen-specific immune responses.

Interleukin-35 Suppresses CD8+ T Cell Activity in Patients with Viral Hepatitis-Induced Acute-on-Chronic Liver Failure.

BACKGROUND: Interleukin (IL)-35 is a newly indentified cytokine and induces immunotolerance via suppression of CD8+ T cell activity in chronic viral hepatitis. AIMS: To investigate the modulatory function of IL-35 to CD8+ T cells in viral hepatitis-induced acute-on-chronic liver failure (ACLF). METHODS: Fifty-five ACLF patients and 21 healthy controls were enrolled. Serum IL-35 concentration was measured by ELISA. Absolute accounts for T cells, immune checkpoint molecules, and cytotoxic molecules in CD8+ T cells were measured by flow cytometry and real-time PCR, respectively. Direct and indirect contact co-culture systems between CD8+ T cells and HepG2 cells were set up. The regulatory function of IL-35 to CD8+ T cells was assessed by measuring lactate dehydrogenase expression and cytokine production. RESULTS: Serum IL-35 concentration was elevated in ACLF patients and positively correlated with total bilirubin, but negatively correlated with prothrombin time activity. Peripheral CD8+ T cells showed exhausted phenotype in ACLF patients, which manifested as up-regulation of programmed death-1 (PD-1), cytotoxic T-lymphocyte-associated protein-4 (CTLA-4), and lymphocyte activation gene-3 (LAG-3) but down-regulation of perforin, granzyme B, and FasL. Recombinant IL-35 stimulation dampened cytotoxicity and interferon-γ production in both direct and indirect contact co-culture systems. This process was accompanied by elevation of PD-1, CTLA-4, and LAG3, as well as reduction of perforin, granzyme B, and FasL in CD8+ T cells. CONCLUSION: Elevated IL-35 suppressed both cytolytic and non-cytolytic activity of CD8+ T cells in ACLF patients.

Generating stem-like memory T cells with antioxidants for adoptive cell transfer immunotherapy of cancer.

Among the multiple factors that are responsible for the success of adoptive cell transfer (ACT) immunotherapy for cancer, the differentiation status of the in vitro expanded T cell product at the time of transfer seems to play a major role. In particular, less differentiated memory CD8+ T cells endowed with self-renewing capacity and multipotency exert the most potent antitumor activity. To this aim, expansion protocols that generate sufficient numbers of tumor-specific CD8+ T cells with superior capacity to persist in vivo following ACT are needed. We describe a procedure for the differentiation of TCF-1+ stem-like CD8+ memory T cells from peripheral blood naïve precursors that takes advantage of the use of antioxidants, in particular N-acetylcysteine (NAC), in combination with T cell receptor stimulation and proinflammatory cytokines. We additionally describe how to conduct in vitro assays to test the stem-like features of the generated cells at the phenotypic, functional and metabolic level. Balancing the oxidative metabolism by the addition of antioxidants during in vitro manipulation of CD8+ T cells results in the generation of cell products with potent antitumor characteristics following ACT.