Multiparameter flow cytometry monitoring of T cell responses

Studying antigen-specific T cells through a streamlined, whole blood-based extracellular approach

Techniques currently used for the study of antigen-specific T-cell responses are either poorly informative or require a heavy workload. Consequently, many perspectives associated with the broader study of such approaches remain mostly unexplored in translational research. However, these could benefit many fields including but not limited to infectious diseases, oncology, and vaccination. Herein, the main objective of this work was to develop a standardized flow cytometry-based approach that would combine ease of use together with a relevant study of antigen-specific T-cell responses so that they could be more often included in clinical research. To this extent, a streamlined approach relying on 1/ the use of whole blood instead of peripheral blood mononuclear cells and 2/ solely based on the expression of extracellular activation-induced markers (AIMs), called whole blood AIM (WAIM), was developed and further compared to more conventional techniques such as enzyme-linked immunospot (ELISpot) and flow cytometry-based intracellular cytokine staining (ICS). Based on a cohort of 20 individuals receiving the COVID-19 mRNA vaccine and focusing on SARS-CoV-2 and cytomegalovirus (CMV)-derived antigen T-cell-specific responses, a significant level of correlation between the three techniques was found. Based on the use of whole blood and on the expression of extracellular activation-induced markers (CD154, CD137, and CD107a), the WAIM technique appears to be very simple to implement and yet allows interesting patient stratification capabilities as the chosen combination of extracellular markers exhibited higher orthogonality than cytokines that are commonly considered in ICS (IFN-γ, TNF-α, and IL-2).

The Biodegradability and in Vitro Cytological Study on the Composite of PLGA Combined With Magnesium Metal

The main goal of this study was to develop a novel poly (lactic-co-glycolic acid) (PLGA) composite biodegradable material with magnesium (Mg) metal to overcome the acidic degradation of PLGA and to investigate the cytocompatibility and osteogenesis of the novel material. PLGA composites with 5 and 10 wt% Mg were prepared. The samples were initially cut into 10 mm × 10 mm films, which were used to detect the pH value to evaluate the self-neutralized ability. Murine embryo osteoblast precursor (MC3T3-E1) cells were used for in vitro experiments to evaluate the cytotoxicity, apoptosis, adhesion, and osteogenic differentiation effect of the composite biodegradable material. pH monitoring showed that the average value of PLGA with 10 wt% Mg group was closer to the normal physiological environment than that of other groups. Cell proliferation and adhesion assays indicated no significant difference between the groups, and all the samples showed no toxicity to cells. As for cell apoptosis detection, the rate of early apoptotic cells was proportional to the ratio of Mg. However, the ratios of the experimental groups were lower than those of the control group. Alkaline phosphatase activity staining demonstrated that PLGA with 10 wt% Mg could effectively improve the osteogenic differentiation of MC3T3-E1 cells. In summary, PLGA with 10 wt% Mg possessed effective osteogenic properties and cytocompatibility and therefore could provide a wide range of applications in bone defect repair and scaffold-based tissue engineering in clinical practice.

NK and T Cell Immunological Signatures in Hospitalized Patients with COVID-19

Severe acute respiratory syndrome caused by coronavirus 2 emerged in Wuhan (China) in December 2019 and has severely challenged the human population. NK and T cells are involved in the progression of COVID-19 infection through the ability of NK cells to modulate T-cell responses, and by the stimulation of cytokine release. No detailed investigation of the NK cell landscape in clinical SARS-CoV-2 infection has yet been reported. A total of 35 COVID-19 hospitalised patients were stratified for clinical severity and 17 healthy subjects were enrolled. NK cell subsets and T cell subsets were analysed with flow cytometry. Serum cytokines were detected with a bead-based multiplex assay. Fewer CD56dimCD16brightNKG2A+NK cells and a parallel increase in the CD56+CD69+NK, CD56+PD-1+NK, CD56+NKp44+NK subset were reported in COVID-19 than HC. A significantly higher adaptive/memory-like NK cell frequency in patients with severe disease than in those with mild and moderate phenotypes were reported. Moreover, adaptive/memory-like NK cell frequencies were significantly higher in patients who died than in survivors. Severe COVID-19 patients showed higher serum concentrations of IL-6 than mild and control groups. Direct correlation emerged for IL-6 and adaptive/memory-like NK. All these findings provide new insights into the immune response of patients with COVID-19. In particular, they demonstrate activation of NK through overexpression of CD69 and CD25 and show that PD-1 inhibitory signalling maintains an exhausted phenotype in NK cells. These results suggest that adaptive/memory-like NK cells could be the basis of promising targeted therapy for future viral infections.

Human T-Cell Cloning by Limiting Dilution

Human T cells represent a heterogeneous population, including cells with different phenotypical and function properties. Despite, in the last years, several technologies were developed to investigate phenotypical properties of T cells at single cell level, in vitro T cell clone 's culture remains the only way to perform functional study on T cells at single cell levels. Here, we describe the method to obtain human T cell clones by limiting dilution in the presence of feeder cells and to maintain them in culture for further investigations.

Macrophage and dendritic cell subset composition can distinguish endotypes in adjuvant-induced asthma mouse models

Asthma is a heterogeneous disease with neutrophilic and eosinophilic asthma as the main endotypes that are distinguished according to the cells recruited to the airways and the related pathology. Eosinophilic asthma is the treatment-responsive endotype, which is mainly associated with allergic asthma. Neutrophilic asthma is a treatment-resistant endotype, affecting 5-10% of asthmatics. Although eosinophilic asthma is well-studied, a clear understanding of the endotypes is essential to devise effective diagnosis and treatment approaches for neutrophilic asthma. To this end, we directly compared adjuvant-induced mouse models of neutrophilic (CFA/OVA) and eosinophilic (Alum/OVA) asthma side-by-side. The immune response in the inflamed lung was analyzed by multi-parametric flow cytometry and immunofluorescence. We found that eosinophilic asthma was characterized by a preferential recruitment of interstitial macrophages and myeloid dendritic cells, whereas in neutrophilic asthma plasmacytoid dendritic cells, exudate macrophages, and GL7+ activated B cells predominated. This differential distribution of macrophage and dendritic cell subsets reveals important aspects of the pathophysiology of asthma and holds the promise to be used as biomarkers to diagnose asthma endotypes.

A novel co-culture assay to assess anti-tumor CD8+ T cell cytotoxicity via luminescence and multicolor flow cytometry

T cell immunotherapies have shown great promise in patients with advanced cancer disease, revolutionizing treatment. T cell cytotoxicity is crucial in its efficacy, therefore developing ex vivo methods testing tumor and T cell interactions is pivotal. Increasing efforts have been made in developing co-culture assays with sophisticated materials and platforms aiming to mimic the tumor microenvironment (TME), but its complexity makes it difficult to develop the ideal model. In this study, we developed a simple co-culture assay, reproducible in any lab, but respecting the multicellular nature of the TME. Our goal is to combine in a single assay well-established techniques such as a luciferase assay for target cell viability analysis, a CD107a degranulation assay, and multicolor flow cytometry for the detection of cytokines and cytotoxicity markers. Cell suspensions of whole spleens and tumors containing splenic or tumor-infiltrating effector T cells of mice bearing Lewis lung carcinoma (LLC) or CT26 colon carcinoma tumors treated with radiation alone or in combination with immunotherapies were used for co-culture. LLC and CT26 cell lines transduced with the firefly luciferase gene were used as target cells. We demonstrated that splenocytes and tumor-infiltrating T cells derived from mice treated with combination therapy were able to kill approximately 50% of target cells after 48 h of co-culture. This effect was tumor cell-specific and dependent on CD8+ T cells evidenced by in vitro CD8+ T cell depletion. Flow cytometry demonstrated increased expression of CD107a and production of granzyme B, IFNγ, and TNFα by CD8+ T cells. Our co-culture assay is therefore suitable as proof of principle for in vivo therapeutic studies testing immunotherapies, and specifically to assess the involvement of cytotoxic CD8+ T cells in treatment response in LLC and CT26 tumor models. We also propose this assay as an ex vivo platform for high-throughput screening of immunomodulating agents to be tested in these two murine tumor models. This assay can be adapted to other tumor models after optimizations.

Cytokine profiling of tumor-infiltrating T lymphocytes by flow cytometry

Intracellular cytokine staining (ICS) utilizing fluorescently labeled, cytokine-specific antibodies is a powerful technique utilized to evaluate cytokine expression that provides resolution at the single cell level. Combined with multi-parameter flow cytometry, ICS can provide detailed information on complex cytokine profiles and cellular phenotypes within the tumor microenvironment, particularly for the CD4⁺ T helper and CD8⁺ cytotoxic T cell compartments. This technique provides critical information concerning tumor-infiltrating T cell function that is essential for evaluating existing or therapeutically-induced tumor antigen-specific T cell responses in both preclinical models and cancer patients. In this chapter we will discuss in detail the critical steps necessary for a successful ICS assay and outline common protocols for the evaluation of cytokine production from T cell subsets present within the tumor microenvironment.

The use of cell-mediated immunity for the evaluation of influenza vaccines: an upcoming necessity

Influenza vaccines are a fundamental tool for preventing the disease and reducing its consequences, particularly in specific high-risk groups. In order to be licensed, influenza vaccines have to meet strict criteria established by European Medicines Agency. Although the licensure of influenza vaccines started 65 years ago, Hemagglutination Inhibition and Single Radial Hemolysis are the only serological assays that can ascertain correlates of protection. However, they present evident limitations. The present review focuses on the evaluation of cell-mediated immunity (CMI), which plays an important role in the host immune response in protecting against virus-related illness and in the establishment of long-term immunological memory. Although correlates of protection are not currently available for CMI, it would be advisable to investigate this kind of immunological response for the evaluation of next-generation vaccines.

Multiparameter Intracellular Cytokine Staining

Intracellular cytokine staining is a popular method for visualizing cellular responses, most often T-cell responses to antigenic or mitogenic stimulation. It can be coupled with staining for other functional markers, such as upregulation of CD107 or CD154, as well as phenotypic markers that define specific cellular subsets, e.g., effector and memory T-cell compartments, NK cells, or monocytes. Recent advances in multicolor flow cytometry instrumentation and software have allowed the routine combination of 12 or more markers, creating some technical and analytical challenges along the way, and exposing a need for standardization in the field. Here, we will review best practices for antibody panel design and procedural variables for multicolor intracellular cytokine staining, and present an optimized protocol with variations designed for use with specific markers and sample types.

Improved Detection of Cytokines Produced by Invariant NKT Cells

Invariant Natural killer T (iNKT) cells rapidly produce copious amounts of multiple cytokines after in vivo activation, allowing for the direct detection of a number of cytokines directly ex vivo. However, for some cytokines this approach is suboptimal. Here, we report technical variations that allow the improved detection of IL-4, IL-10, IL-13 and IL-17A ex vivo. Furthermore, we describe an alternative approach for stimulation of iNKT cells in vitro that allows a significantly improved detection of cytokines produced by iNKT cells. Together, these protocols allow the detection of iNKT cell cytokines ex vivo and in vitro with increased sensitivity.

Isolation, Cryopreservation, and Immunophenotyping of Human Peripheral Blood Mononuclear Cells

This unit describes procedures for the isolation, cryopreservation, and thawing of human peripheral blood mononuclear cells (HPBMC) and analysis of cell surface markers (CSM) for immunophenotyping using polychromatic flow cytometry. This methodology can be used to ensure that cell integrity and phenotype stability are not altered through cryopreservation and extended storage. For this analysis, HPBMC were isolated from 7 healthy individuals, and 11-color flow cytometry was performed on freshly isolated samples as well as samples cryopreserved for short- and long-term periods. There is no significant difference in the percentage of cells expressing the CSM CD3, CD4, CD8, CD45RO, CD16, CD19, or CD56 between freshly isolated and cryopreserved HPBMC. Hence, cryopreservation of HPBMC does not influence the phenotype of distinct cellular subsets in isolated mononuclear cells. This protocol for HPBMC isolation, cryopreservation, and thawing of HPBMC is intended for long-term studies of large cohorts requiring sample shipment and subsequent batch analysis. © 2017 by John Wiley & Sons, Inc.

Design and characterization of a novel nickel-free cobalt-base alloy for intravascular stents

Co-Cr-W-Ni alloy (L605) with high tensile strength is used in coronary stents. The thickness of individual strut of the stent is reduced which can decrease the stent restenosis rate. However, about 10% Ni element content in L605 is found to cause allergic reactions and pulmonary embolism, similar to the traditional 316L stainless steel. In this study, a novel nickel-free cobalt-base alloy Co-20Cr-12Fe-18Mn-2Mo-4W-N (wt%) was designed and fabricated in order to efficiently avoid the potential hazards of Ni element. Fe and Mn, essential elements of human body, were added in the alloy to substitute part of Co element. In comparison to L605 alloy, the tensile strength of the new alloy was higher than 1000MPa while elongation was above 55%. The pitting potential of the new alloy was measured close to 1000mV, also higher than that of L605 alloy. CCK-8 test indicated that the cytotoxicity of the new alloy is grade 1, reflecting that Co-20Cr-12Fe-18Mn-2Mo-4W-N alloy has no cytotoxic effects. There was no significant difference in the apoptosis rates between Co-20Cr-12Fe-18Mn-2Mo-4W-N and L605 alloy. The newly developed cobalt-base alloy showed excellent mechanical, corrosion resistance and biological properties, which could make it a desirable material for future clinical investigations.

Biomarkers and Immunotherapeutic Targets in Glioblastoma

Glioblastoma (GBM) is an aggressive central nervous system cancer with poor prognosis despite maximal therapy. The recent advent of immunotherapy holds great promise for improving GBM survival and has already made great strides toward changing management strategies. A diverse set of biomarkers have been implicated as immunotherapeutic targets and prognostic indicators in other cancers. Some of the more extensively studied examples include cytokines (IL-4, IL-13, and TGF-β), checkpoint molecules (PD-1, CTLA-4, TIM-3, LAG-3, CD137, GITR, OX40), and growth/angiogenesis proteins (endoglin and EGFR). Emerging theories involving the tumor mutational landscape and microbiome have also been explored in relation to cancer treatment. Although identification of novel biomarkers may improve and help direct treatment of patients with GBM, the next step is to explore the role of biomarkers in precision medicine and selection of specific immunotherapeutic drugs in an individualized manner.

Direct TLR-2 Costimulation Unmasks the Proinflammatory Potential of Neonatal CD4+ T Cells

Neonatal CD4(+) T cells have traditionally been viewed as deficient in their capacity to produce Th1 cytokines in response to polyclonal or Ag-specific stimuli. Thus, defining unique aspects of CD4(+) T cell activation and development into Th1 effector cells in neonates is essential to the successful development of novel vaccines and immunotherapies to protect infants from intracellular pathogens. Using highly purified naive CD4(+) T cells derived from cord and adult peripheral blood, we compared the impact of anti-CD3 stimulation plus costimulation through TLR-2 performed in the absence of APC on CD4(+) T cell cytokine production, proliferation, and expression of activation markers. In both age groups, TLR-2 costimulation elicited activation of naive CD4(+) T cells, characterized by robust production of IL-2 as well as key Th1-type cytokines IFN-γ and TNF-α. TLR-2 costimulation also dramatically reduced naive T cell production of the immunosuppressive cytokine IL-10. We observed that neonatal naive CD4(+) T cells are uniquely sensitive to TLR-2-mediated costimulation, which enabled them to produce equivalent amounts of IFN-γ and more IL-2 when compared with adult responses. Thus, neonatal CD4(+) T cells have a distinctive propensity to use TLR-2-mediated costimulation for development into proinflammatory Th1 effectors, and interventions that target CD4(+) T cell TLR-2-mediated responses may be exploited to enhance neonatal adaptive immunity.

Immune reconstitution after cord blood transplantation: peculiarities, clinical implications and management strategies

Umbilical cord blood (UCB) is now widely used as an alternative hematopoietic stem cell source for patients lacking closely matched related or unrelated adult donors. UCB transplantation has traditionally been associated with delayed engraftment, poor immune reconstitution and consequent increased risk of infection. More recent clinical studies, however, suggest that conditioning regimens and in particular the omission of in vivo T-cell depletion may play a crucial role in post-transplant T-cell expansion, facilitating a uniquely rapid immune recovery after UCB transplantation. The peculiar characteristics of UCB cells, the importance of thymic function and the role of conditioning regimens and graft-versus-host disease influencing immune reconstitution are described. The last part of the review reports available data on UCB, as well as third-party peripheral blood derived anti-viral cell therapy, which provides a novel approach to rescue UCB recipients with viral complications in the post-transplant period.

New approaches to understanding the immune response to vaccination and infection

The immune system is a network of specialized cell types and tissues that communicates via cytokines and direct contact, to orchestrate specific types of defensive responses. Until recently, we could only study immune responses in a piecemeal, highly focused fashion, on major components like antibodies to the pathogen. But recent advances in technology and in our understanding of the many components of the system, innate and adaptive, have made possible a broader approach, where both the multiple responding cells and cytokines in the blood are measured. This systems immunology approach to a vaccine response or an infection gives us a more holistic picture of the different parts of the immune system that are mobilized and should allow us a much better understanding of the pathways and mechanisms of such responses, as well as to predict vaccine efficacy in different populations well in advance of efficacy studies. Here we summarize the different technologies and methods and discuss how they can inform us about the differences between diseases and vaccines, and how they can greatly accelerate vaccine development.

Intracellular Cytokine Staining on PBMCs Using CyTOF™ Mass Cytometry

In this protocol, we use a CyTOF™ mass cytometry to collect single-cell data on a large number of cytokines/chemokines as well as cell-surface proteins that characterize T cells and other immune cells. The current selected mass window in AW 103-203 includes the lanthanides used for most antibody labeling, along with iridium and rhodium for DNA intercalators. The output data are in the format as .txt and .fcs files, which is compatible with many analysis programs. This protocol could be adapted to include tetramers into the staining panel, but we have not optimized for that purpose. The principal steps of intracellular cytokine staining are as follows: First, cells are activated for a few hours using either a specific peptide or a non-specific activation cocktail. An inhibitor of protein transport (e.g. Brefeldin A) is added to retain the cytokines within the cell. Next, EDTA is added to remove adherent cells from the activation vessel. After washing, antibodies to cell surface markers are added to the cells. The cells are then fixed in paraformaldehyde and permeabilized. We use a gentle detergent, saponin, as the permealization buffer because it is less destructive to surface and intracellular epitopes compared to harsh detergents or methanol. After permeabilization, the metal-conjugated anti-cytokine antibodies are added into the cell suspension. The stained cells are then sequentially introduced into the mass cytometry for signal intensity analysis.

Multiparameter Phenotyping of Human PBMCs Using Mass Cytometry

The standard for single-cell analysis of phenotype and function in recent decades has been fluorescence flow cytometry. Mass cytometry is a newer technology that uses heavy metal ions, rather than fluorochromes, as labels for probes such as antibodies. The binding of these ion-labeled probes to cells is quantitated by mass spectrometry. This greatly increases the number of phenotypic and functional markers that can be probed simultaneously. Here, we review topics that must be considered when adapting existing flow cytometry panels to mass cytometry analysis. We present a protocol and representative panels for surface phenotyping and intracellular cytokine staining (ICS) assays.

Mass cytometry: a highly multiplexed single-cell technology for advancing drug development

Advanced single-cell analysis technologies (e.g., mass cytometry) that help in multiplexing cellular measurements in limited-volume primary samples are critical in bridging discovery efforts to successful drug approval. Mass cytometry is the state-of-the-art technology in multiparametric single-cell analysis. Mass cytometers (also known as cytometry by time-of-flight or CyTOF) combine the cellular analysis principles of traditional fluorescence-based flow cytometry with the selectivity and quantitative power of inductively coupled plasma-mass spectrometry. Standard flow cytometry is limited in the number of parameters that can be measured owing to the overlap in signal when detecting fluorescently labeled antibodies. Mass cytometry uses antibodies tagged to stable isotopes of rare earth metals, which requires minimal signal compensation between the different metal tags. This unique feature enables researchers to seamlessly multiplex up to 40 independent measurements on single cells. In this overview we first present an overview of mass cytometry and compare it with traditional flow cytometry. We then discuss the emerging and potential applications of CyTOF technology in the pharmaceutical industry, including quantitative and qualitative deep profiling of immune cells and their applications in assessing drug immunogenicity, extensive mapping of signaling networks in single cells, cell surface receptor quantification and multiplexed internalization kinetics, multiplexing sample analysis by barcoding, and establishing cell ontologies on the basis of phenotype and/or function. We end with a discussion of the anticipated impact of this technology on drug development lifecycle with special emphasis on the utility of mass cytometry in deciphering a drug's pharmacokinetics and pharmacodynamics relationship.

Monitoring the immune competence of cancer patients to predict outcome

A new era of cancer immunotherapy has brought not only successful cancer vaccines but also immunomodulators, such as those that target checkpoint blockade in order to induce endogenous host immune responses. However, the immune system of cancer patients can be compromised through multiple means, including immune suppression by the tumor and by prior therapies such as chemotherapy and radiation. Therefore, a comprehensive means of assessing patient immunocompetence would seem helpful for determining whether patients are ready to benefit from immunotherapy, and perhaps even which immunotherapy might be most appropriate for them. Unfortunately, there are no standardized tests for immune competence, nor is there agreement on what to measure and what will be predictive of outcome. In this review, we will discuss the technologies and assays that might be most useful for this purpose. We argue for a comprehensive approach that should maximize the chances of developing predictive biomarkers for eventual clinical use.

Biomarkers for immunostimulatory monoclonal antibodies in combination strategies for melanoma and other tumor types

Modulation of the immune system by targeting coinhibitory and costimulatory receptors has become a promising new approach of immunotherapy for cancer. The recent approval of the CTLA-4-blocking antibody ipilimumab for the treatment of melanoma was a watershed event, opening up a new era in the field of immunotherapy. Ipilimumab was the first treatment to ever show enhanced overall survival (OS) for patients with stage IV melanoma. However, measuring response rates using standard Response Evaluation Criteria in Solid Tumors (RECIST) or modified World Health Organization criteria or progression-free survival does not accurately capture the potential for clinical benefit for ipilimumab-treated patients. As immunotherapy approaches are translated into more tumor types, it is important to study biomarkers, which may be more predictive of OS to identify the patients most likely to have clinical benefit. Ipilimumab is the first-in-class of a series of immunomodulating antibodies that are in clinical development. Anti-PD1 (nivolumab and MK-3475), anti-PD-L1 (BMS-936 559, RG7446, and MEDI4736), anti-CD137 (urelumab), anti-OX40, anti-GITR, and anti-CD40 monoclonal antibodies are just some of the agents that are being actively investigated in clinical trials, each having the potential for combination with the ipilimumab to enhance its effectiveness. Development of rational combinations of immunomodulatory antibodies with small-molecule pathway inhibitor therapies such as vemurafenib makes the discovery of predictive biomarkers even more important. Identifying reliable biomarkers is a necessary step in personalizing the treatment of each patient's cancer through a baseline assessment of tumor gene expression and/or immune profile to optimize therapy for the best chance of therapeutic success.

A randomized, controlled dose-finding Phase II study of the M72/AS01 candidate tuberculosis vaccine in healthy PPD-positive adults

Purpose

In this dose-finding Phase II study (NCT00621322), we evaluated the safety and immunogenicity of different formulations of the candidate tuberculosis vaccine containing the M72 antigen (10/20/40 μg doses) and the liposome-based AS01 Adjuvant System. We aimed to select the lowest-dose combination of M72 and AS01 that was clinically well tolerated with immunogenicity comparable to that of the previously tested M72/AS01_B (40 μg) candidate vaccine.

Methods

Healthy PPD-positive (induration 3–10 mm) adults (18–45 years) in The Philippines were randomized (4:4:4:4:1:1) to receive 2 injections, 1 month apart, of M72/AS01_B (40 μg), M72/AS01_E (10 μg), M72/AS01_E (20 μg), M72/AS02_D (10 μg), M72/Saline (40 μg) or AS01_B alone, and were followed up for 6 months. AS01_E and AS02_D contain half the quantities of the immunostimulants present in AS01_B. AS02_D is an oil-in-water emulsion. Vaccine selection was based on the CD4⁺ T-cell responses at 1 month post vaccination.

Results

All formulations had a clinically acceptable safety profile with no vaccine-related serious adverse events reported. Two vaccinations of each adjuvanted M72 vaccine induced M72-specific CD4⁺ T-cell and humoral responses persisting at 6 months post vaccination. No responses were observed with AS01_B alone. One month post second vaccination, CD4⁺ T-cell responses induced by each of the three M72/AS01 vaccine formulations were of comparable magnitudes, and all were significantly higher than those induced by M72/AS02_D (10 μg) and M72/Saline.

Conclusions

The formulation with the lowest antigen and adjuvant dose, M72/AS01_E (10 μg), fulfilled our pre-defined selection criteria and has been selected for further clinical development.

Antigen-reactive T cell enrichment for direct, high-resolution analysis of the human naive and memory Th cell repertoire

Ag-specific CD4(+) T cells orchestrating adaptive immune responses are crucial for the development of protective immunity, but also mediate immunopathologies. To date, technical limitations often prevented their direct analysis. In this study, we report a sensitive flow cytometric assay based on magnetic pre-enrichment of CD154(+) T cells to visualize rare Ag-reactive naive and memory Th cells directly from human peripheral blood. The detection limit of ≈ 1 cell within 10(5)-10(6) permitted the direct enumeration and characterization of auto-, tumor-, or neo-Ag-reactive T cells within the naive and even memory CD4(+) T cell repertoire of healthy donors. Furthermore, the analysis of high target cell numbers after pre-enrichment of rare Ag-specific T cells from large blood samples dramatically improved the identification of small subpopulations. As exemplified in this work, the dissection of the Ag-specific memory responses into small cytokine-producing subsets revealed great heterogeneity between pathogens, but also pathogen-related microsignatures refining Th cell subset classification. The possibility to directly analyze CD4(+) T cells reactive against basically any Ag of interest at high resolution within the naive and memory repertoire will open up new avenues to investigate CD4(+) T cell-mediated immune reactions and their use for clinical diagnostics.

Randomized Phase I: Safety, Immunogenicity and Mucosal Antiviral Activity in Young Healthy Women Vaccinated with HIV-1 Gp41 P1 Peptide on Virosomes

Mucosal antibodies harboring various antiviral activities may best protect mucosal surfaces against early HIV-1 entry at mucosal sites and they should be ideally induced by prophylactic HIV-1 vaccines for optimal prevention of sexually transmitted HIV-1. A phase I, double-blind, randomized, placebo-controlled trial was conducted in twenty-four healthy HIV-uninfected young women. The study objectives were to assess the safety, tolerability and immunogenicity of virosomes harboring surface HIV-1 gp41-derived P1 lipidated peptides (MYM-V101). Participants received placebo or MYM-V101 vaccine at 10 μg/dose or 50 μg/dose intramuscularly at week 0 and 8, and intranasally at week 16 and 24. MYM-V101 was safe and well-tolerated at both doses administered by the intramuscular and intranasal routes, with the majority of subjects remaining free of local and general symptoms. P1-specific serum IgGs and IgAs were induced in all high dose recipients after the first injection. After the last vaccination, vaginal and rectal P1-specific IgGs could be detected in all high dose recipients. Approximately 63% and 43% of the low and high dose recipients were respectively tested positive for vaginal P1-IgAs, while 29% of the subjects from the high dose group tested positive for rectal IgAs. Serum samples had total specific IgG and IgA antibody concentrations ≥ 0.4 μg/mL, while mucosal samples were usually below 0.01 μg/mL. Vaginal secretions from MYM-V101 vaccinated subjects were inhibiting HIV-1 transcytosis but had no detectable neutralizing activity. P1-specific Th1 responses could not be detected on PBMC. This study demonstrates the excellent safety and tolerability of MYM-V101, eliciting systemic and mucosal antibodies in the majority of subjects. Vaccine-induced mucosal anti-gp41 antibodies toward conserved gp41 motifs were harboring HIV-1 transcytosis inhibition activity and may contribute to reduce sexually-transmitted HIV-1.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01084343.

mRNA electroporation as a tool for immunomonitoring

Monitoring the immune response is an essential aspect of numerous clinical vaccination trials in order to evaluate the efficacy. In these clinical vaccination trials, peripheral blood mononuclear cells (PBMC) are isolated at different time points from patient blood samples and subsequently cryopreserved to allow batch analysis at a later time point. Here, we present a newly developed short-time assay which allows direct ex vivo analysis of multi-epitope antigen-specific immune responses using mRNA electroporation of cryopreserved PBMC. This novel method is a rapid and elegant tool and will be convenient for monitoring the cellular immune status of patients in clinical vaccination settings.

Functionality of CD4+ and CD8+ T cells from tonsillar tissue

For many years, tonsillectomy has been used routinely in children to treat chronic or recurrent acute tonsillitis. Palatine tonsils are secondary lymphoid organs and the major barrier protecting the digestive and respiratory tracts from potential invasive microorganisms. They have been used as sources of lymphoid tissue; however, despite the hundreds of papers published on tonsillectomy, no studies addressing the functionality of the CD4(+) and CD8(+) T cells from chronically infected tonsils have yet been published. The aim of this study was to analyse the functionality of the CD4(+) and CD8(+) T cells with respect to tonsillar tissue. We used an affordable approach to measure the frequency of antigen-specific CD4(+) T cells, the direct ex-vivo cytotoxicity of CD8(+) T cells, memory T cell phenotype, cytokine profile and DC phenotype. Our results demonstrate that CD4(+) and CD8(+) T cells from tonsillar tissue are totally functional, as shown by their ability to produce cytokines, to degranulate and to differentiate into effector-memory T cells.

Dynamics of cell-mediated immune responses to cytomegalovirus in pediatric transplantation recipients

CMI responses, combined with quantification of CMV DNA (DNAemia), may identify transplantation recipients at risk for invasive disease. PBMC were collected in pediatric transplantation candidates at one, three, and six months post-transplant in 10 subjects (six renal, three cardiac, one stem cell) and at single time points in eight HC and 14 children greater than one yr post-transplant (LTTx). Cells were stimulated with anti-CD3mAb or CMV pp65 peptide pools and responses assessed by IFNG enzyme-linked immunosorbent spot assay and cytokine secretion. IFNG responses to anti-CD3mAb were significantly lower pretransplant relative to HC and were further decreased at one and three months post-transplant, but recovered to levels comparable to HC by six months. Responses to pp65 among CMV-seropositive recipients followed a similar pattern but recovered by three months. CMV-seropositive LTTx and HC showed a Th1 cytokine response to pp65 stimulation. Three LTTx subjects developed CMV DNAemia; two demonstrated decreased responses to anti-CD3mAB (and pp65 in the CMV seropositive subject) at the onset of DNAemia, which recovered as DNAemia resolved. Monitoring CMI in children is feasible and may provide an adjunct biomarker to predict CMV progression and recovery.

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.

Optimization of a highly standardized carboxyfluorescein succinimidyl ester flow cytometry panel and gating strategy design using discriminative information measure evaluation

The design of a panel to identify target cell subsets in flow cytometry can be difficult when specific markers unique to each cell subset do not exist, and a combination of parameters must be used to identify target cells of interest and exclude irrelevant events. Thus, the ability to objectively measure the contribution of a parameter or group of parameters toward target cell identification independent of any gating strategy could be very helpful for both panel design and gating strategy design. In this article, we propose a discriminative information measure evaluation (DIME) based on statistical mixture modeling; DIME is a numerical measure of the contribution of different parameters towards discriminating a target cell subset from all the others derived from the fitted posterior distribution of a Gaussian mixture model. Informally, DIME measures the "usefulness" of each parameter for identifying a target cell subset. We show how DIME provides an objective basis for inclusion or exclusion of specific parameters in a panel, and how ranked sets of such parameters can be used to optimize gating strategies. An illustrative example of the application of DIME to streamline the gating strategy for a highly standardized carboxyfluorescein succinimidyl ester (CFSE) assay is described.

Immunogenicity and protective efficacy in mice and hamsters of a β-propiolactone inactivated whole virus SARS-CoV vaccine

The immunogenicity and efficacy of β-propiolactone (BPL) inactivated whole virion SARS-CoV (WI-SARS) vaccine was evaluated in BALB/c mice and golden Syrian hamsters. The vaccine preparation was tested with or without adjuvants. Adjuvant Systems AS01(B) and AS03(A) were selected and tested for their capacity to elicit high humoral and cellular immune responses to WI-SARS vaccine. We evaluated the effect of vaccine dose and each adjuvant on immunogenicity and efficacy in mice, and the effect of vaccine dose with or without the AS01(B) adjuvant on the immunogenicity and efficacy in hamsters. Efficacy was evaluated by challenge with wild-type virus at early and late time points (4 and 18 wk post-vaccination). A single dose of vaccine with or without adjuvant was poorly immunogenic in mice; a second dose resulted in a significant boost in antibody levels, even in the absence of adjuvant. The use of adjuvants resulted in higher antibody titers, with the AS01(B)-adjuvanted vaccine being slightly more immunogenic than the AS03(A)-adjuvanted vaccine. Two doses of WI-SARS with and without Adjuvant Systems were highly efficacious in mice. In hamsters, two doses of WI-SARS with and without AS01(B) were immunogenic, and two doses of 2 μg of WI-SARS with and without the adjuvant provided complete protection from early challenge. Although antibody titers had declined in all groups of vaccinated hamsters 18 wk after the second dose, the vaccinated hamsters were still partially protected from wild-type virus challenge. Vaccine with adjuvant provided better protection than non-adjuvanted WI-SARS vaccine at this later time point. Enhanced disease was not observed in the lungs or liver of hamsters following SARS-CoV challenge, regardless of the level of serum neutralizing antibodies.

Multiparameter intracellular cytokine staining

Intracellular cytokine staining (ICS) is a popular method for visualizing cellular responses, most often T-cell responses to antigenic or mitogenic stimulation. It can be coupled with staining for other functional markers, such as upregulation of CD107 or CD154, as well as phenotypic markers that define specific cellular subsets, e.g. effector and memory T-cell compartments. Recent advances in multicolor flow cytometry instrumentation and software have allowed the routine combination of 8-12 (or more) markers in combination, creating technical and analytical challenges along the way, and exposing a need for standardization in the field. Here, we will review best practices for antibody panel design and procedural variables for multicolor ICS, and present an optimized protocol with variations designed for use with specific markers and sample types.

H5N1 influenza vaccine formulated with AS03 A induces strong cross-reactive and polyfunctional CD4 T-cell responses

Objective

Adjuvantation of an H5N1 split-virion influenza vaccine with AS03_A substantially reduces the antigen dose required to produce a putatively protective humoral response and promotes cross-clade neutralizing responses. We determined the effect of adjuvantation on antibody persistence and B- and T-cell-mediated immune responses.

Methods

Two vaccinations with a split-virion A/Vietnam/1194/2004 (H5N1, clade 1) vaccine containing 3.75–30 μg hemagglutinin and formulated with or without adjuvant were administered to groups of 50 volunteers aged 18–60 years.

Results

Adjuvantation of the vaccine led to better persistence of neutralizing and hemagglutination-inhibiting antibodies and higher frequencies of antigen-specific memory B cells. Cross-reactive and polyfunctional H5N1-specific CD4 T cells were detected at baseline and were amplified by vaccination. Expansion of CD4 T cells was enhanced by adjuvantation.

Conclusion

Formulation of the H5N1 vaccine with AS03_A enhances antibody persistence and induces stronger T- and B-cell responses. The cross-clade T-cell immunity indicates that the adjuvanted vaccine primes individuals to respond to either infection and/or subsequent vaccination with strains drifted from the primary vaccine strain.

A model for harmonizing flow cytometry in clinical trials

Complexities in sample handling, instrument setup and data analysis are barriers to the effective use of flow cytometry to monitor immunological parameters in clinical trials. The novel use of a central laboratory may help mitigate these issues.

New flow cytometric assays for monitoring cell-mediated cytotoxicity

The exact immunologic responses after vaccination that result in effective antitumor immunity have not yet been fully elucidated and the data from ex vivo T-cell assays have not yet defined adequate surrogate markers for clinical efficacy. A more detailed knowledge of the specific immune responses that correlate with positive clinical outcomes should help to develop better or novel strategies to effectively activate the immune system against tumors. Furthermore, clinically relevant material is often limited and, thus, precludes the ability to perform multiple assays. The two main assays currently used to monitor lymphocyte-mediated cytoxicity in cancer patients are the (51)Cr-release assay and IFN-gamma ELISpot assay. The former has a number of disadvantages, including low sensitivity, poor labeling and high spontaneous release of isotope from some tumor target cells. Additional problems with the (51)Cr-release assay include difficulty in obtaining autologous tumor targets, and biohazard and disposal problems for the isotope. The ELISpot assays do not directly measure cytotoxic activity and are, therefore, a surrogate marker of cyotoxic capacity of effector T cells. Furthermore, they do not assess cytotoxicity mediated by the production of the TNF family of death ligands by the cytotoxic cells. Therefore, assays that allow for the simultaneous measurement of several parameters may be more advantageous for clinical monitoring. In this respect, multifactor flow cytometry-based assays are a valid addition to the currently available immunologic monitoring assays. Use of these assays will enable detection and enumeration of tumor-specific cytotoxic T lymphocytes and their specific effector functions and any correlations with clinical responses. Comprehensive, multifactor analysis of effector cell responses after vaccination may help to detect factors that determine the success or failure of a vaccine and its immunological potency.