Novel high-throughput cell-based hybridoma screening methodology using the Celigo Image Cytometer

Protocol for monitoring phagocytosis of cancer cells by TAM-like macrophages using imaging cytometry

Here, we present a protocol for monitoring phagocytosis by M2-type macrophages using automated counting of phagocytic events with an imaging cytometer. We describe steps for isolating and differentiating peripheral blood mononuclear cell (PBMC)-derived monocytes into M2-like macrophages, preparing cancer cells expressing a green fluorescence marker, labeling with a pH-sensitive dye, and co-culturing with macrophages. We then outline procedures for enumerating phagocytic events using an imaging cytometer. For complete details on the use and execution of this protocol, please refer to Mishra et al.1.

A Functional Hydrogel Bead-Based High-Throughput Screening System for Mammalian Cells with Enhanced Secretion of Therapeutic Antibodies

Droplet-based high-throughput screening systems are an emerging technology that provides a quick test to screen millions of cells with distinctive characteristics. Biopharmaceuticals, specifically therapeutic proteins, are produced by culturing cells that secrete heterologous recombinant proteins with different populations and expression levels; therefore, a technology to discriminate cells that produce more target proteins is needed. Here, we present a droplet-based microfluidic strategy for encapsulating, screening, and selecting target cells with redox-responsive hydrogel beads (HBs). As a proof-of-concept study, we demonstrate the enrichment of hybridoma cells with enhanced capability of antibody secretion using horseradish peroxidase (HRP)-catalyzed hydrogelation of tetra-thiolate poly(ethylene glycol); hybridoma cells were encapsulated in disulfide-bonded HBs. Recombinant protein G or protein M with a C-terminal cysteine residue was installed in the HBs via disulfide bonding to capture antibodies secreted from the cells. HBs were fluorescently stained by adding the protein L-HRP conjugate using a tyramide signal amplification system. HBs were then separated by fluorescence-activated droplet sorting and degraded by reducing the disulfide bonds to recover the target cells. Finally, we succeeded in the selection of hybridoma cells with enhanced antibody secretion, indicating the potential of this system in the therapeutic protein production.

A Dynamic and Pseudo-Homogeneous MBs-icELISA for the Early Detection of Aflatoxin B1 in Food and Feed

Aflatoxin B1 (AFB1) is one of the most toxic and harmful fungal toxins to humans and animals, and the fundamental way to prevent its entry into humans is to detect its presence in advance. In this paper, the monoclonal antibody mAbA2-2 was obtained via three-step sample amplification and multi-concentration standard detection using a subcloning method based on the limited dilution method with AFB1 as the target. A dynamic and pseucdo-homogeneous magnetic beads enzyme-linked immunosorbent assay (MBs-icELISA) was established using the prepared antibody as the recognition element and immunomagnetic beads as the antigen carrier. The MBs-icELISA showed good linear correlation in the concentration range of 0.004-10 ng/mL with R2 = 0.99396. The limit of detection (LOD) of the MBs-icELISA for AFB1 was 0.0013 ng/mL. This new ELISA strategy significantly shortened AFB1 detection time through improved sensitivity compared to the conventional ELISA method.

Flow Cytometry - Sophisticated Tool for Basic Research or/and Routine Diagnosis; Impact of the Complementarity in Both Pre- as Well as Clinical Studies

Flow cytometry is a sophisticated technology used widely in both basic research and as a routine tool in clinical diagnosis. The technology has progressed from single parameter detection in the 1970s and 1980s to high end multicolor analysis, with currently 30 parameters detected simultaneously, allowing the identification and purification of rare subpopulations of cells of interest. Flow cytometry continues to evolve and expand to facilitate the investigation of new diagnostic and therapeutic avenues. The present review gives an overview of basic theory and instrumentation, presents and compares the advantages and disadvantages of conventional, spectral and imaging flow cytometry as well as mass cytometry. Current methodologies and applications in both research, pre- and clinical settings are discussed, as well as potential limitations and future evolution. This finding encourages the reader to promote such relationship between basic science, diagnosis and multidisciplinary approach since the standard methods have limitations (e.g., in differentiating the cells after staining). Moreover, such path inspires future cytometry specialists develop new/alternative frontiers between pre- and clinical diagnosis and be more flexible in designing the study for both human as well as veterinary medicine.

Monoclonal Antibody Discovery Based on Precise Selection of Single Transgenic Hybridomas with an On-Cell-Surface and Antigen-Specific Anchor

Hybridoma technology is widely used for monoclonal antibody (mAb) discovery, whereas the generation and identification of single hybridomas by the limiting dilution method (LDM) are tedious, inefficient, and time- and cost-consuming, especially for hapten molecules. Here, we describe a single transgenic hybridoma selection method (STHSM) that employs a transgenic Sp2/0 with an artificial and stable on-cell-surface anchor. The anchor was designed by combining the truncated variant transmembrane domain of EGFR with a biotin acceptor peptide AVI-tag, which was stably integrated into the genome of Sp2/0 via a piggyBac transposon. To ensure the subsequent precise selection of the hybridoma, the number of on-cell-surface anchors of the transfected Sp2/0 for fusion with immunized splenocytes was further normalized by flow cytometry at the single cell level. Then the single antigen-specific transgenic hybridomas were precisely identified and automatically selected using a CellenONE platform based on the fluorescence assay of the on-cell-surface anchor with the corresponding secreted antigen-specific mAb. The STHSM produced 579 single chloramphenicol (CAP)-specific transgenic hybridomas with a positive rate of 62.7% in 10 plates within 2 h by one-step selection, while only 12 single CAP-specific hybridomas with a positive rate of 6.3% in 40 plates required at least 32 days using the LDM with multiple subcloning steps. The best affinity of mAbs from the STHSM was more than 2-fold higher than that of those from the LDM, and this was mainly due to the preaffinity selection based on the on-cell-surface anchors and more interactions between the mAb and CAP. Then the mAbs from the STHSM and LDM were used to develop an immunoassay for CAP in spiked and natural biological samples. The method displayed satisfactory sensitivity, accuracy, and precision, demonstrating that the STHSM we developed is a versatile, practical, and efficient method for mAb discovery.

Actin-granule formation is an additional step in cardiac myofibroblast differentiation

Background

Atrial fibrillation is the most common and long-lasting cardiac arrhythmia, and profoundly effects the daily lives of patients. The pathogenesis and persistence of atrial fibrillation is closely related to the cardiac fibroblast and its myofibroblast differentiation as increased collagen synthesis and migration capability. Thus better understanding of myofibroblast differentiation is essential for the prevention and treatment of atrial fibrillation.

Methods

Cardiac fibroblasts were isolated from neonatal rats and its actin structure was analyzed by immunofluorescence staining. Myofibroblast differentiation was induced by Angiotensin II (Ang II) and ROCK signaling related proteins were determined by western blot. Fasudil and Ricolinostat were employed to abrogate ROCK signaling and their effects on myofibroblast differentiation were assessed by IF microscopy and Celigo Image Cytometry.

Results

Stress actin fibers similar to actin filaments in myofibroblast differentiation are regulated by ROCK signaling, and our results also suggested Guanine nucleotide exchange factor-H1 (GEF-H1) phosphorylation could be induced by Ang II. In addition, Fasudil could down-regulate RhoA, GEF-H1, and phosphorylated GEF-H1 to inhibit ROCK signaling and further reduce Col I expression and the myofibroblast proportion.

Conclusions

An individual phase characterized by actin-granule formation was identified in cardiac myofibroblast differentiation. In the meanwhile, myofibroblast differentiation and its F-actin assembly could be detained in this phase by Fasudil abrogating the ROCK signaling pathway.

High-Throughput Image Cytometry Detection Method for CAR-T Transduction, Cell Proliferation, and Cytotoxicity Assays

Chimeric antigen receptor (CAR)-T cell therapy has drawn much attention due to its recent clinical success in B-cell malignancies. In general, the CAR-T cell discovery process consists of CAR identification, T-cell activation, transduction, and expansion, as well as assessment of CAR-T cytotoxicity. The current evaluation methods for the CAR-T discovery process can be time-consuming, low-throughput and requires the preparation of multiple sacrificial samples in order to produce kinetic data. In this study, we employed the use of a plate-based image cytometer to monitor anti-CAIX (carbonic anhydrase IX) G36 CAR-T generation and assess its cytotoxic potency of direct and selective killing against CAIX⁺ SKRC-59 human renal cell carcinoma cells. The transduction efficiency and cytotoxicity results were analyzed using image cytometry and compared directly to flow cytometry and Chromium 51 (⁵¹ Cr) release assays, showing that image cytometry was comparable against these conventional methods. Image cytometry method streamlines the assays required during the CAR-T cell discovery process by analyzing a plate of T cells from CAR-T generation to in vitro functional assays with minimum disruption. The proposed method can reduce assay time and uses less cell samples by imaging and analyze the same plate over time without the need to sacrifice any cells. The ability to monitor kinetic data can allow additional insights into the behavior and interaction between CAR-T and target tumor cells. © 2020 International Society for Advancement of Cytometry.

High-throughput viral microneutralization method for feline coronavirus using image cytometry

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There are no approved antiviral drugs or recommended vaccines for feline coronavirus infection.

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Plate-based image cytometry is used for high-throughput viral microneutralization assays.

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Image cytometry is faster and more sensitive than traditional plaque reduction neutralization tests.

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Cell seeding density, plate surface coating, virus concentration and incubation time, fluorescent labeling, and buffers were optimized.

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Cross-neutralization between FCoV type I and II viruses was not observed.

Feline coronaviruses (FCoV) are members of the alphacoronavirus genus that are further characterized by serotype (types I and II) based on the antigenicity of the spike (S) protein and by pathotype based on the associated clinical conditions. Feline enteric coronaviruses (FECV) are associated with the vast majority of infections and are typically asymptomatic. Within individual animals, FECV can mutate and cause a severe and usually fatal disease called feline infectious peritonitis (FIP), the leading infectious cause of death in domestic cat populations. There are no approved antiviral drugs or recommended vaccines to treat or prevent FCoV infection. The plaque reduction neutralization test (PRNT) traditionally employed to assess immune responses and to screen therapeutic and vaccine candidates is time-consuming, low-throughput, and typically requires 2–3 days for the formation and manual counting of cytolytic plaques. Host cells are capable of carrying heavy viral burden in the absence of visible cytolytic effects, thereby reducing the sensitivity of the assay. In addition, operator-to-operator variation can generate uncertainty in the results and digital records are not automatically created. To address these challenges we developed a novel high-throughput viral microneutralization assay, with quantification of virus-infected cells performed in a plate-based image cytometer. Host cell seeding density, microplate surface coating, virus concentration and incubation time, wash buffer and fluorescent labeling were optimized. Subsequently, this FCoV viral neutralization assay was used to explore immune correlates of protection using plasma from naturally FECV-infected cats. We demonstrate that the high-throughput viral neutralization assay using the Celigo Image Cytometer provides a robust and efficient method for the rapid screening of therapeutic antibodies, antiviral compounds, and vaccines. This method can be applied to various viral infectious diseases to accelerate vaccine and antiviral drug discovery and development.

Quantifying drug tissue biodistribution by integrating high content screening with deep-learning analysis

Quantitatively determining in vivo achievable drug concentrations in targeted organs of animal models and subsequent target engagement confirmation is a challenge to drug discovery and translation due to lack of bioassay technologies that can discriminate drug binding with different mechanisms. We have developed a multiplexed and high-throughput method to quantify drug distribution in tissues by integrating high content screening (HCS) with U-Net based deep learning (DL) image analysis models. This technology combination allowed direct visualization and quantification of biologics drug binding in targeted tissues with cellular resolution, thus enabling biologists to objectively determine drug binding kinetics.

A high-throughput chemotaxis detection method for CCR4+ T cell migration inhibition using image cytometry

Chemotaxis is an important aspect of immune cell behavior within the tumor microenvironment (TME). One prominent example of chemotaxis within the TME is the migration of regulatory T cells (Tregs) in response to the chemokine ligands CCL17 and CCL22. Tregs within the TME cause the suppression of anti-tumor immunity and inhibition of the effect of immunotherapeutic treatments. Therefore, the ability to screen for therapeutic antibodies that can inhibit or stimulate the chemotaxis of various immune cell types is crucial. Traditionally, chemotaxis is studied by determining the number of cells in the bottom reservoir of a Transwell microplate using flow cytometry; however, this method is time-consuming and thus not appropriate for high-throughput screening purposes. The Celigo Image Cytometer has been employed to perform high-throughput cell-based assays and was used to develop a new detection method for chemotaxis measurement. The image-based detection method was developed using chemokine ligands CCL17 and CCL22 to induce the migration of CCR4⁺ T cells and directly count them on the bottom of the Transwell plates. Finally, the method was applied to measure the inhibitory effects of commercially available anti-CCL17 and anti-CCL22 antibodies, which caused a dose-dependent decrease in the number of migrated T cells. The proposed image cytometry method allowed screening of multiple antibodies at various concentrations, simultaneously, which can improve the efficiency for discovering potential antibody candidates that can induce or inhibit recruitment of immune cells to the tumor microenvironment.

A high-throughput inhibition assay to study MERS-CoV antibody interactions using image cytometry

The emergence of new pathogens, such as Middle East respiratory syndrome coronavirus (MERS-CoV), poses serious challenges to global public health and highlights the urgent need for methods to rapidly identify and characterize potential therapeutic or prevention options, such as neutralizing antibodies. Spike (S) proteins are present on the surface of MERS-CoV virions and mediate viral entry. S is the primary target for MERS-CoV vaccine and antibody development, and it has become increasingly important to understand MERS-CoV antibody binding specificity and function. Commonly used serological methods like ELISA, biolayer interferometry, and flow cytometry are informative, but limited. Here, we demonstrate a high-throughput protein binding inhibition assay using image cytometry. The image cytometry-based high-throughput screening method was developed by selecting a cell type with high DPP4 expression and defining optimal seeding density and protein binding conditions. The ability of monoclonal antibodies to inhibit MERS-CoV S binding was then tested. Binding inhibition results were comparable with those described in previous literature for MERS-CoV spike monomer and showed similar patterns as neutralization results. The coefficient of variation (CV) of our cell-based assay was <10%. The proposed image cytometry method provides an efficient approach for characterizing potential therapeutic antibodies for combating MERS-CoV that compares favorably with current methods. The ability to rapidly determine direct antibody binding to host cells in a high-throughput manner can be applied to study other pathogen-antibody interactions and thus can impact future research on viral pathogens.

High-throughput screening of hybridoma supernatants using multiplexed fluorescent cell barcoding on live cells

With current available assay formats using either immobilized protein (ELISA, enzyme-linked immunosorbent assay) or immunostaining of fixed cells for primary monoclonal antibody (mAb) screening, researchers often fail to identify and characterize antibodies that recognize the native conformation of cell-surface antigens. Therefore, screening using live cells has become an integral and important step contributing to the successful identification of therapeutic antibody candidates. Thus the need for developing high-throughput screening (HTS) technologies using live cells has become a major priority for therapeutic mAb discovery and development. We have developed a novel technique called Multiplexed Fluorescent Cell Barcoding (MFCB), a flow cytometry-based method based upon the Fluorescent Cell Barcoding (FCB) technique and the Luminex fluorescent bead array system, but is applicable to high-through mAb screens on live cells. Using this technique in our system, we can simultaneously identify or characterize the antibody-antigen binding of up to nine unique fluorescent labeled cell populations in the time that it would normally take to process a single population. This has significantly reduced the amount of time needed for the identification of potential lead candidates. This new technology enables investigators to conduct large-scale primary hybridoma screens using flow cytometry. This in turn has allowed us to screen antibodies more efficiently than before and streamline identification and characterization of lead molecules.