Antibody-coated Beads Research Articles

Investigation and Demonstration for immunoassay technology based on impedance Amplifies of magnetic and dielectric microbeads

BackgroundBead-based immunoassays typically require researchers to perform the analysis in a laboratory setting, involving complex processing procedures, most of the time, constant potential or current instruments are used to measure the bio-impedance change. However, almost all biological materials are decorated on the electrode surface to obtain the maximum sensitivity, resulting in difficulty to clean, separate, and other applications of fixed bead-based immunoassay. ResultWe present an innovative unfixed bead-based immunoassay technology that utilizes electrical impedance characteristics, offering the advantages of being rapid, portable, miniaturized, and cost-effective. This technique which is known as Impedance-enhanced electrochemical immunoassay (IE-ECIA) employs antibody-coated Magnetic beads (MBs) and Dielectric beads (DBs) linked to antigens for quantitative with miniaturization electronic devices, which has been successfully applied in an immune impedance sensor for detecting the Dengue virus (DENV), which is an affordable test with a low-cost microfluidic impedance biosensor combined with immune magnetic and dielectric micro/nanobeads for antigen detection. HighlightThe proposed immunoassay technology introduces a novel microfluidic platform incorporating magnetic and dielectric beads alongside with an electrochemical impedance biosensor, therefore facilitating continuous-fluid quantitative analysis. This innovative and unconventional approach leverages free-motion multiplex beads housing magnetic and dielectric bead-bound antigens within a simple linear microchannel of microfluidic chip architecture, making the high-through measurements more efficient, enhanced Electrochemical immunoassay (ECIA) signals of Bio-on-magnetic-beads (BOMB). This advancement holds significant potential for enhancing diagnostic capabilities for emerging infectious diseases within clinical environments, thereby bolstering rapid detection capabilities and aiding in the advancement of novel pharmaceuticals, benefiting all the stakeholders.

Cascaded signal amplification strategy for ultra-specific, ultra-sensitive, and visual detection of Shigella flexneri.

Pathogen infections including Shigella flexneri have posed a significant threat to human health for numerous years. Although culturing and qPCR were the gold standards for pathogen detection, time-consuming and instrument-dependent restrict their application in rapid diagnosis and economically less-developed regions. Thus, it is urgently needed to develop rapid, simple, sensitive, accurate, and low-cost detection methods for pathogen detection. In this study, an immunomagnetic beads-recombinase polymerase amplification-CRISPR/Cas12a (IMB-RPA-CRISPR/Cas12a) method was built based on a cascaded signal amplification strategy for ultra-specific, ultra-sensitive, and visual detection of S. flexneri in the laboratory. Firstly, S. flexneri was specifically captured and enriched by IMB (Shigella antibody-coated magnetic beads), and the genomic DNA was released and used as the template in the RPA reaction. Then, the RPA products were mixed with the pre-loaded CRISPR/Cas12a for fluorescence visualization. The results were observed by naked eyes under LED blue light, with a sensitivity of 5CFU/mL in a time of 70min. With no specialized equipment or complicated technical requirements, the IMB-RPA-CRISPR/Cas12a diagnostic method can be used for visual, rapid, and simple detection of S. flexneri and can be easily adapted to monitoring other pathogens.

Studying Adipose Endothelial Cell/Adipocyte Cross-Talk in Human Subcutaneous Adipose Tissue.

Microvascular endothelial cells (MVECs) have many critical roles, including control of vascular tone, regulation of thrombosis, and angiogenesis. Significant heterogeneity in endothelial cell (EC) genotype and phenotype depends on their vascular bed and host disease state. The ability to isolate MVECs from tissue-specific vascular beds and individual patient groups offers the opportunity to directly compare MVEC function in different disease states. Here, using subcutaneous adipose tissue (SAT) taken at the time of insertion of cardiac implantable electronic devices (CIED), we describe a method for the isolation of a pure population of functional human subcutaneous adipose tissue MVEC (hSATMVEC) and an experimental model of hSATMVEC-adipocyte cross-talk. hSATMVEC were isolated following enzymatic digestion of SAT by incubation with anti-CD31 antibody-coated magnetic beads and passage through magnetic columns. hSATMVEC were grown and passaged on gelatin-coated plates. Experiments used cells at passages 2-4. Cells maintained classic features of EC morphology until at least passage 5. Flow cytometric assessment showed 99.5% purity of isolated hSATMVEC, defined as CD31+/CD144+/CD45-. Isolated hSATMVEC from controls had a population doubling time of approximately 57 h, and active proliferation was confirmed using a cell proliferation imaging kit. Isolated hSATMVEC function was assessed using their response to insulin stimulation and angiogenic tube-forming potential. We then established an hSATMVEC-subcutaneous adipocyte co-culture model to study cellular cross-talk and demonstrated a downstream effect of hSATMVEC on adipocyte function. hSATMVEC can be isolated from SAT taken at the time of CIED insertion and are of sufficient purity to both experimentally phenotype and study hSATMVEC-adipocyte cross-talk.

Toward the quantification of α-synuclein aggregates with digital seed amplification assays.

The quantification and characterization of aggregated α-synuclein in clinical samples offer immense potential toward diagnosing, treating, and better understanding neurodegenerative synucleinopathies. Here, we developed digital seed amplification assays to detect single α-synuclein aggregates by partitioning the reaction into microcompartments. Using pre-formed α-synuclein fibrils as reaction seeds, we measured aggregate concentrations as low as 4 pg/mL. To improve our sensitivity, we captured aggregates on antibody-coated magnetic beads before running the amplification reaction. By first characterizing the pre-formed fibrils with transmission electron microscopy and size exclusion chromatography, we determined the specific aggregates targeted by each assay platform. Using brain tissue and cerebrospinal fluid samples collected from patients with Parkinson's Disease and multiple system atrophy, we demonstrated that the assay can detect endogenous pathological α-synuclein aggregates. Furthermore, as another application for these assays, we studied the inhibition of α-synuclein aggregation in the presence of small-molecule inhibitors and used a custom image analysis pipeline to quantify changes in aggregate growth and filament morphology.

Isolation of yeast mitochondria by affinity purification using magnetic beads.

Isolated mitochondria have been widely utilized in various model organisms to investigate the diverse functions of the organelle. Techniques such as differential centrifugation, density gradient ultracentrifugation and antibody-coated magnetic beads are employed for isolation of the organelle from whole cells. However, mitochondria isolated using differential centrifugation are often contaminated with other organelles; isolation using density gradient ultracentrifugation can reduce contamination but is time-intensive and requires large amounts of starting materials; and mitochondria isolated using antibody-coated magnetic beads are irreversibly bound to the beads. Here, we provide a step-by-step protocol for the isolation of highly pure mitochondria from Saccharomyces cerevisiae using a magnetic bead affinity purification method that overcomes these limitations. This protocol describes how to isolate mitochondria, tagged by insertion of 6 histidines (6xHis) into the chromosomal copy of the TOM70 (Translocase of outer membrane 70) gene using Ni-NTA (nickel(II) nitrilotriacetic acid) paramagnetic beads, and the subsequent release of mitochondria from the beads using a buffer containing imidazole. We provide examples of expected results, highlighting the purity, integrity and import activity of isolated mitochondria. These affinity-purified mitochondria are intact and functional, containing less contamination with cytosol and other organelles compared to mitochondria isolated by other methods. Our method is adaptable and can be applied to other model organisms that can be genetically manipulated using CRISPR or other methods.

Abstract LB_C12: Alisertib and pembrolizumab in Rb-deficient head and neck squamous cell carcinomas (HNSCC)

Abstract Preclinical studies demonstrate that cancers with retinoblastoma (Rb) loss are dependent upon Aurora kinases for survival. Additionally, our lab demonstrated that human papilloma virus (HPV)+ cancer cells, in which the viral E7 leads to Rb degradation, undergo apoptosis and immunogenic cell death when treated with the Aurora kinase A inhibitor alisertib (Ali) supporting the clinical combination of pembrolizumab (P) and Ali. All patients received 200mg P every 21d in combination with Ali. Ten advanced solid tumor patients were treated in the phase I portion with the recommended phase II Ali dose of 40mg PO BID for 7d every 21d. There were no objective responses, but one phase I patient previously treated with P remains on therapy with stable disease (SD) for >2 years. The phase II study enrolled 14 patients with immunotherapy- and platinum- resistant HPV+ HNSCC. There were no objective responses, but 7 patients had SD: 3 of them for >10 months. PDL1 expression did not correlate with progression free survival (PFS, p=0.59). The median OS has not been reached. The median PFS was 1.4 months. Toxicities were as expected. Ali caused cytopenias that lead to dose reductions in 2 patients on the phase II trial at cycles 13 and 16. P had to be discontinued in one patient due to elevated liver function tests. Pharmacokinetic (PK) analysis for Ali was performed on cycle 1, d1 and d7 in 12 phase II patients. On d7, PK parameters increased with an accumulation index of 1.54. With limited sampling over the dosing interval, the mean values were: Cmax of 688 and 1300 ng/mL; ahalf-life 4.6 and 7.7 hours; estimated trough concentration at end of dosing period C12 of 278 and 512 ng/mL; and area under the concentration-time curve (AUC0-12) of 3754 and 9738 ng*h/mL on d1 and d7 respectively. These values were similar to prior findings with Ali indicating no drug interactions with P. Cell-free plasma was collected at baseline and every 2 cycles then subjected to a multiplex assay using antibody-coated beads and a fluorescent detection system for simultaneous quantification of 20 immune markers. Higher levels of IL-17 and pronounced increases in the levels of TH2 cytokines IL-10 and IL-4 along with the pro-inflammatory cytokine IL-1β in the in the pretreatment plasma correlated with poor outcome. Levels of cytokines representative of TH1 responses (e.g., IL-12, IFNγ) were not different between those 3 patients with prolonged SD vs. others. Analysis of the HPV ctDNA, ELISpot, and multi-color flow cytometry for phenotypic and functional characterization of lymphocyte/myeloid cells are underway and will be presented. Although there were no objective responses, the combination of Ali and P was well tolerated and led to prolonged SD in patients who had previously progressed on immunotherapy supporting our hypothesis that Aurora A inhibition can reverse immunotherapy resistance in Rb-deficient HNSCC. Additionally, an imbalance of cytokine response favoring TH2 and TH17 over TH1 immunity predicts poor outcome in HPV+ HNSCC patients treated with Ali and P. Citation Format: Faye M Johnson, Madison P O'Hara, J Jack Lee, Yun Qing, Hai Tran, Soma Ghosh, Lacin Yapindi, Peixin Jiang, Alexandre Reuben, George Blumenschein, Jagannadha Sastry. Alisertib and pembrolizumab in Rb-deficient head and neck squamous cell carcinomas (HNSCC) [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr LB_C12.

Comparison of four commercial immunomagnetic separation kits for the detection of Cryptosporidium.

Cryptosporidium spp. are protozoan parasites of significant health importance found in environmental waters globally. Four commercially available Cryptosporidium-specific immunomagnetic separation (IMS) kits used in various water sample matrices were analysed and compared. Beads were characterised by flow cytometry and tested for the recovery efficiencies for oocysts spiked into different matrices: river water sediment, clay sample, and filter backwash sample. Results showed that Dynabeads™ Cryptosporidium and Waterborne Crypto-Grab™ kits contained immunoglobulin IgM antibody-coated beads. In contrast, the BioPoint CryptoBead and the TCS Isolate kits contained immunoglobulin IgG antibody-coated beads. BioPoint CryptoBead was significantly coated with more antibodies and were able to capture oocysts more rapidly compared to the other beads. Recovery efficiencies of Dynabeads™, TCS Isolate® beads, and BioPoint CryptoBead ranged from 55 to 93% when tested against different sample matrices, with BioPoint CryptoBead resulting in the highest at 93% in reagent-grade water and Dynabeads™ at 55%, the lowest against clay samples. The Waterborne beads did not perform well on any samples, with recovery efficiencies ranging from 0 to 8%. Fluorescence microscopy analyses showed that both the IMS method and the sample matrix processed affect the quality of the membranes, with the cleanest samples for microscopy examination observed from BioPoint CryptoBead.

Negative Influence of Aging on Differentiation and Proliferation of CD8+ T-Cells in Dogs.

Immunosenescence is an age-related change in the immune system characterized by a reduction in naïve T-cells and an impaired proliferative capacity of CD8+ T-cells in older individuals. Recent research revealed the crucial impact of immunosenescence on the development and control of cancer, and aging is one of the causes that diminish the therapeutic efficacy of cancer immunotherapies targeting CD8+ T-cell activation. Despite dog cancer being defined as an age-related disease, there are few fundamental understandings regarding the relationship between aging and the canine immune system. Therefore, we aimed to elucidate the characteristics of immunosenescence in dogs and analyzed the effects of aging on the differentiation status and proliferation of canine CD8+ T cells using T-cell specific stimulation with anti-canine CD3/CD28 antibody-coated beads and interleukin-2. As a result, we found that older dogs have a lower proliferative capacity of CD8+ T-cells and a reduction in the naïve subset in their peripheral blood. Further analysis showed that older dogs had attenuated proliferation of the effector and central memory subsets. These results indicate the importance of maintaining less differentiated subsets to expand CD8+ T-cells in dogs and provide helpful insight into the development of dog immune therapies that require T-cell expansion ex vivo.

Elastic Microstructures: Combining Biochemical, Mechanical, and Topographical Cues for the Effective Activation and Proliferation of Cytotoxic T Cells.

The ex vivo activation and proliferation of cytotoxic T cells are critical steps in adoptive immunotherapy. Today, T cells are activated by stimulation with antibody-coated magnetic beads, traditionally used for cell separation. Yet, efficient and controlled activation and proliferation of T cells require new antibody-bearing materials, which, in particular, deliver mechanical and topographic cues sensed by T cells. Here, we demonstrate a new approach for the activation and proliferation of human cytotoxic T cells using an elastic microbrush coated with activating and costimulatory antibodies. We found that the microbrush topography affects the protrusion of the cell membrane and the elastic response to the forces applied by cells and can be optimized to yield the strongest activation of T cells. In particular, T cells stimulated by a microbrush showed a three-fold increase in degranulation and release of cytokines over T cells stimulated with state-of-the-art magnetic beads. Furthermore, the microbrush induced a T-cell proliferation of T cells that was more prolonged and yielded much higher cell doubling than that done by the state-of-the-art methods. Our study provides an essential insight into the physical mechanism of T-cell activation and proliferation and opens the floodgates for the design of novel stimulatory materials for T-cell-based immunotherapy.

Alternating Magnetic Field-Promoted Nanoparticle Mixing: The On-Chip Immunocapture of Serum Neuronal Exosomes for Parkinson's Disease Diagnostics.

The analysis of cargo proteins in exosome subpopulations has considerable value in diagnostics but a translatable impact has been limited by lengthy or complex exosome extraction protocols. We describe herein a scalable, fast, and low-cost exosome extraction using an alternating (AC) magnetic field to support the dynamic mixing of antibody-coated magnetic beads (MBs) with serum samples within 3D-printed microfluidic chips. Zwitterionic polymer-coated MBs are, specifically, magnetically agitated and support ultraclean exosome capture efficiencies >70% from <50 μL of neat serum in 30 min. Applied herein to the immunocapture of neuronal exosomes using anti-L1CAM antibodies, prior to the array-based assaying of α-synuclein (α-syn) content by a standard duplex electrochemical sandwich ELISA, sub pg/mL detection was possible with an excellent coefficient of variation and a sample-to-answer time of ∼75 min. The high performance and semiautomation of this approach hold promise in underpinning low-cost Parkinson's disease diagnostics and is of value in exosomal biomarker analyses more generally.

Immunomagnetic-bead enriched culturomics (IMBEC) for isolating pathobionts from feces of colorectal cancer patients.

Culturomics employs various cultivating conditions to obtain different types of bacteria and new species. However, current culturomics lacks a highly efficient method for isolating specific pathobionts. Immunomagnetic bead technology, which uses magnetic beads conjugated with antibodies for capturing the antigen to realize enrichment of the targets, has been employed as an alternative method. In this study, we developed a novel method, immunomagnetic bead-enriched culturomics (IMBEC), in which magnetic bead-conjugated antibodies purified from the fecal samples of patients with colorectal cancer (CRC) were used to enrich and isolate potential pathobionts. A protocol for enriching potential pathobionts via immunomagnetic capture was developed by optimizing the concentrations of coupling reagents, NaCl, and detergent. The efficacy of pathobiont enrichment was compared between antibody-coated magnetic beads (antibody group) and nonconjugated blank magnetic beads (blank group). To determine the proinflammatory potential of isolates from both groups, we investigated their ability to induce cytokine production in THP-1 macrophages. This protocol was employed for isolating bacteria from 10 fecal samples of patients with CRC, which were simultaneously compared with those isolated from the blank group. A total of 209 bacterial species were isolated from both groups, including 173 from the antibody group, 160 from the blank group, and 124 from both groups. Bacteria isolated from the antibody group produced more proinflammatory cytokines than those isolated from the blank group. IMBEC is a promising method for relatively specific isolation of potential pathobionts for a particular disease of interest.

Microsampling in Targeted Mass Spectrometry-Based Protein Analysis of Low-Abundance Proteins.

This paper presents a protocol with detailed descriptions for efficient sample cleanup of low-abundance proteins from dried samples. This is performed using bead-based proteolysis prior to proteotypic peptide affinity-capture and liquid chromatography tandem mass spectrometry (LC-MS/MS) determination. The procedure can be applied to both conventional dried samples using paper cards (e.g., dried blood spots [DBSs] and dried serum spots [DSSs]), as well as samples collected with newer sampling methods such as volumetric absorptive microsampling (VAMS). In addition to describing this procedure, the preparation of both trypsin beads and antibody-coated beads is presented in a step-by-step manner in this work. The advantages of the presented procedure are time-efficient proteolysis using beads and selective robust cleanup using peptide affinity-capture. The current procedure describes the determination of the low-abundance small-cell lung cancer (SCLC) biomarker, progastrin-releasing peptide (ProGRP), in dried serum (both DSSs and VAMS). Detailed procedures for bead preparation make it easier to implement the workflow in new applications or other laboratories. It is demonstrated that the results may be dependent on the sampling material; for the present project, higher signal intensities were seen for samples collected using VAMS compared to DSSs.

Purified complement C3b triggers phagocytosis and activation of human neutrophils via complement receptor 1

The complement system provides vital immune protection against infectious agents by labeling them with complement fragments that enhance phagocytosis by immune cells. Many details of complement-mediated phagocytosis remain elusive, partly because it is difficult to study the role of individual complement proteins on target surfaces. Here, we employ serum-free methods to couple purified complement C3b onto E. coli bacteria and beads and then expose human neutrophils to these C3b-coated targets. We examine the neutrophil response using a combination of flow cytometry, confocal microscopy, luminometry, single-live-cell/single-target manipulation, and dynamic analysis of neutrophil spreading on opsonin-coated surfaces. We show that purified C3b can potently trigger phagocytosis and killing of bacterial cells via Complement receptor 1. Comparison of neutrophil phagocytosis of C3b- versus antibody-coated beads with single-bead/single-target analysis exposes a similar cell morphology during engulfment. However, bulk phagocytosis assays of C3b-beads combined with DNA-based quenching reveal that these are poorly internalized compared to their IgG1 counterparts. Similarly, neutrophils spread slower on C3b-coated compared to IgG-coated surfaces. These observations support the requirement of multiple stimulations for efficient C3b-mediated uptake. Together, our results establish the existence of a direct pathway of phagocytic uptake of C3b-coated targets and present methodologies to study this process.

Isolation of the B Cell Immune Synapse for Proteomic Analysis.

Recent technical developments have fueled increasing utilization of proteomics to gain new insights into various aspects of cellular behavior. In this chapter, we describe a method to specifically isolate immune synapses from mouse primary B cells. The method utilizes antibody-coated magnetic beads to induce the formation of the immune synapses and describes a protocol for the extraction of the cell-bead adhesions for mass spectrometry analysis. Finally, this method enables unveiling the large-scale protein content of the immune synapse.

Microfluidic Magnetic Spatial Confinement Strategy for the Enrichment and Ultrasensitive Detection of MCF-7 and Escherichia coli O157:H7.

A microfluidic magnetic spatial confinement strategy was developed and employed to realize an ultrasensitive cell immunoassay. The straight confined channels in poly(dimethylsiloxane)-glass hybrid microchips were used as the enrichment and detection chambers for the proposed microfluidic magnetic cell immunoassays (μMCI). To accomplish the μMCI, prepared magnetic cell immunocomplexes were introduced into microchannels and preconcentrated in the detection zone under a permanent magnet. The magnetic cell immunocomplexes were constructed from aptamer-/antibody-coated magnetic beads and antibody-linked horseradish peroxidase-labeled target cells to guarantee the specificity and enhance the detection signal generated from the enzyme reaction. The sensitivity enhancement of μMCI was confirmed in a one-dimensional space confined microchamber, especially in the analysis of cells having more enzyme conjugating sites on their surface. This spatial confinement strategy based μMCI was then applied for model cell detection in the microchannel, the limits of detection (LODs) were 2 cells/mL for MCF-7 and 34 colony-forming unit/mL for Escherichia coli O157:H7 (E. coli O157:H7), which corresponded to up to 1202-fold LOD sensitivity improvement compared to the results of the similar immunoassays in microwell plates. The satisfactory selectivity and reproducibility of the strategy were also obtained. Moreover, it enabled rare MCF-7 detection in whole blood and E. coli O157:H7 detection in milk after time-shortened incubation. Constructing an appropriate confined space, this strategy can be extended to detect various cells with higher sensitivity, which provides a valuable approach for rare cell detection in practical applications.

ODP010 Relaxin Receptor RXFP1 Knockout in Adipose Tissue Progenitor Cells Results in Resistance to High Fat Diet-Induced Weigh Gain

Abstract Relaxin is a polypeptide hormone that signals through its cognate receptor RXFP1. Previous work demonstrated that global RXFP1-knockout mice developed age-related adipose tissue fibrosis and dysfunction. Our preliminary data suggested that adipose tissue progenitor cells (APC) express RXFP1 in the white adipose tissue in mice. To determine the role of APC in relaxin signaling, we crossed floxed RXFP1 mice (RXFP1-fl/fl) with mice expressing tamoxifen-inducible CRE recombinase under control of the platelet-derived growth factor receptor-β (PDGFRβ) promoter to produce conditional RXFP1 knockout in adipose tissue progenitor cells and fibroblasts (RXFP1-PKO). After tamoxifen treatment, both RXFP1-fl/fl and RXFP1-PKO mice were placed on a high fat diet (58% calories from fat) supplemented with sucrose and fructose in the drinking water, or chow diet for 16 weeks. At the end of the study, body mass composition was measured using an Echo-MRI instrument. Adipose tissue fibrosis was assessed histologically by Sirius red staining. In response to the HFD, the control (fl/fl) mice reached an average weight of 48.3 ± 0.6g, while the RXFP1-PKO mice were resistant to weight gain, reaching only 40.3 ±3g (p&amp;lt;. 05). The body mass composition changed in the RXFP1-fl/fl mice on HFD (34. 0% fat/55.2% lean) compared to chow (14.7% fat/68.9% lean). The RXFP1-PKO mice had a significantly lower gain in fat mass on HFD (29.7% fat/59.1% lean on HFD; 12.6% fat/71. 0% lean on chow) compared to the RXFP-fl/fl mice. Histological analysis of the inguinal white adipose tissue (iWAT) revealed that while RXFP1-fl/fl mice developed adipocyte hypertrophy in response to the HFD, the RXFP1-PKO mice had smaller adipocyte size. This was accompanied by increased pericellular and perivascular fibrosis in the iWAT as determined by Sirius red staining. To determine if differentiation of APC was altered by loss of RXFP1, the stromal-vascular fraction of iWAT was extracted by collagenase treatment, and the APC isolated using antibody-coated magnetic beads (Miltenyi Biotec). The purified cells were cultured to confluence, treated with or without tamoxifen to induce CRE expression, then treated with differentiation cocktail. The APC from the RXFP1-PKO mice had a marked impairment in the ability differentiate to mature adipocytes after treatment with tamoxifen compared to untreated cells. In summary, the loss of RXFP1 in PDGFRβ-expressing cells resulted in resistance to HFD-induced weight and adipose tissue mass gain. This was accompanied by increased fibrosis in the iWAT and decreased adipocyte size. The APC had decreased adipogenic potential after loss of RXFP1. Taken together, the findings support a role for RXFP1 in the differentiation of adipose tissue progenitor cells, and in adipose tissue expansion after exposure to an obesogenic diet. Presentation: No date and time listed

Bone marrow derived long-lived plasma cell phenotypes are heterogeneous and can change in culture

Bone marrow-derived long-lived plasma cells (LLPCs) are thought to be a major source of alloantibody in sensitized transplant patients. However, studies of LLPCs have been hampered not only by the fact that they are rare and difficult to isolate and culture but also due to the lack of consensus regarding a definitive cell-surface phenotype. The goal of the current study was to determine if LLPCs have a specific, stable cell-surface phenotype. PCs were isolated from high-volume (120cc) bone marrow aspirates that were enriched first by negative selection then positive selection using anti-CD38 antibody-coated beads and purified by cell sorting. A typical isolation resulted in >100,000 PCs that were sorted into 4 populations with variable numbers of PCs: CD19+/CD138+/CD38Hi (64.1% of the PCs), CD19-/CD138+/CD38Hi (20.9%), CD19+/CD138-/CD38Hi (10.7%), and CD19-/CD138-/CD38Hi (4.3%). The purity of each subset was 96–99%. Each subset contained PCs secreting IgG and IgA. Measles- and tetanus-specific PCs (i.e. putative IgG secreting, antigen-specific LLPCs). LLPCs were identified in both the CD19+/CD138+/CD38Hi and CD19-/CD138+/CD38Hi subsets and in the smaller CD138- subsets (when pooled). Thus, all CD38Hi subsets contained LLPCs. Cultured PCs maintained viability (>50%) and function and could be retrieved for analyses. During 7 days of culture, cell surface expression changed from baseline in many PCs. For example, approximately 20% of CD19 + CD138+/CD38Hi cells (the largest PC subset) became CD19-. CFSE assays showed no division and only a small percentage of LLPCs were Ki-67 positive suggesting that the cells did not divide in culture and that the antibody detected was not from plasmablasts. We conclude that human bone marrow LLPCs have a heterogeneous expression of CD19 and CD138, which can change during cell culture. The fact that LLPCs were found in all four subsets raises the possibility that a large percentage of PCs in the bone marrow may be LLPCs.

Cross-reactivity of antibodies to different rumen methanogens demonstrated using immunomagnetic capture technology.

Methane is produced in the rumen of ruminant livestock by methanogens, accounting for approximately 14.5% of anthropogenic greenhouse gas emissions in terms of global warming potential. The rumen contains a diversity of methanogens species, and only a few of these have been cultured. Immunomagnetic capture technology (ICT) is a simple and effective method to capture and concentrate target organisms in samples containing complex microflora. We hypothesized that antibody-coated magnetic beads could be used to demonstrate antibody specificity and cross-reactivity to methanogens in rumen samples. Sheep polyclonal antibodies raised against four isolates of rumen dwelling methanogens, Methanobrevibacter ruminantium strain M1, Methanobrevibacter sp. AbM4, Methanobrevibacter sp. D5, and Methanobrevibacter sp. SM9 or an equal mix of all four isolates, were used to coat paramagnetic beads. ICT was used together with flow cytometry and qPCR to optimize key parameters: the ratio of antibody to beads, coupling time between antibody and paramagnetic beads to produce immunomagnetic beads (IMBs), and optimal incubation time for the capture of methanogen cells by IMBs. Under optimized conditions, IMBs bound strongly to their respective isolates and showed a degree of cross-reactivity with isolates of other Methanobrevibacter spp. in buffer and in rumen fluid, and with resident methanogens in rumen content samples. The evidence provided here indicates that this method can be used to study the interaction of antibodies with antigens of rumen methanogens, to understand antigen cross-reactivity and antibody binding efficiency for the evaluation of antigens used for the development of a broad-spectrum anti-methanogen vaccine for the abatement of methane production.

Consequences of adjusting cell density and feed frequency on serum-free expansion of thymic regulatory T cells

BackgroundGiven the promising results from phase 1/2 clinical trials of therapy involving regulatory T cells (Tregs), it is critical to develop Treg manufacturing methods that use well-defined reagents. MethodsSeeking to maximize expansion of human thymic Tregs activated with anti-CD3/CD28 antibody-coated beads and cultured in serum-free medium, the authors investigated the effect of adjusting process parameters including cell density and cell concentration, and feeding strategy on Treg yield and quality. ResultsThe authors found that levels of expansion and viability varied with cell density on the day of restimulation. Tregs restimulated at low cell densities (1 × 105 cells/cm2) initially had high growth rates, viability and FOXP3 expression, but these parameters decreased with time and were less stable than those observed in cultures of Tregs restimulated at high cell densities (5 × 105 cells/cm2), which had slower growth rates. High-density expansion was associated with expression of inhibitory molecules and lower intracellular oxygen and extracellular nutrient concentrations as well as extracellular lactate accumulation. Experiments to test the effect of low oxygen revealed that transient exposure to low oxygen levels had little impact on expansion, viability or phenotype. Similarly, blockade of inhibitory molecules had little effect. By contrast, replenishing nutrients by increasing the feeding frequency between 2 days and 4 days after restimulation increased FOXP3, viability and expansion in high-density cultures. ConclusionThese data show the previously undescribed consequences of adjusting cell density on Treg expansion and establish a Good Manufacturing Practice-relevant protocol using non-cell-based activation reagents and serum-free media that supports sustained expansion without loss of viability or phenotype.

Development and Evaluation of Enzyme-Linked Viral Immune Capture Assay for Detection of SARS-CoV-2.

The pandemic of COVID-19 was caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 2019 and it has prompted unprecedented research activities for vaccines, therapeutics, and diagnostics. The real-time reverse transcriptase-polymerase chain reaction (RT-PCR) is the gold standard method of diagnosis; however, immune-based assays offer cost-effective, deployable, easy-to-read solutions for diagnosis and surveillance. Here, we present the development, optimization, and testing of an enzyme-linked viral immune capture assay (ELVICA). It utilizes the spike antigen as the detected target of the virus and antibody-coated beads to capture the virus and enrich the detection. This method can be readout by luminescent and colorimetric equipment. It can also be visualized by the imaging system, offering a variety of detection approaches. ELVICA showed specificity to SARS-CoV-2-pseudotyped viruses as compared to MERS-CoV-pseudotyped viruses. As compared to RT-PCR, ELVICA showed high compatibility in detecting the virus in patient respiratory samples, especially for samples that are below a Ct value of 32 in RT-PCR. This assay is readily adaptable for detecting other pathogens and serves as a quick and affordable diagnostic tool.