Bead-based Assay Research Articles

Identification of Antibodies to DQβ:DRα Interisotypic Heterodimers in Human Sera.

HLA class II antigens, DR, DQ, and DP, comprised an α and β chains, which typically combine, within the same isotype, to form the major histocompatibility complex:peptide complex. Interisotypic pairing is not commonly observed. Although reports of DQβ:DRα heterodimers exist, the pairing was reported to be unstable and, therefore, not studied to any extent. DQβ:DRα single antigens were produced through transfectant cell lines and used to identify and characterize positive reactive human sera by a multiplex bead-based assay. Stable DQβ:DRα transfectants were constructed. Cell surface staining with class II-specific monoclonal antibodies revealed that some DQB1 alleles appear to be more efficient in expressing DQβ:DRα heterodimers. Interestingly, alleles within the same serological group varied in their efficiency of forming dimers on the cell surface. For example, DQβ0601:DRα had the highest transfection and cell membrane expression efficiency among 16 common DQB1 alleles tested. In contrast, DQβ0603:DRα-positive transfectants demonstrated minimal surface expression. Assembly of DQβ0601:DRα was not affected by the presence of a DQα chain. DQβ0601:DRα and DQβ0603:DRα single-antigen beads were used to screen human sera. Positive sera were identified that reacted to the unique epitopes of DQβ0601:DRα protein on the cell surface of the transfectants. Our studies have demonstrated that unique DQβ:DRα heterodimers can be formed and are stably expressed on the cell surface. Such antigenic combinations, presented on single-antigen beads, demonstrated that patient sera can react with such heterodimers. Investigations on the potential clinical roles of antibodies against such interisotypic heterodimers are now possible.

Potential of a Bead-Based Multiplex Assay for SARS-CoV-2 Antibody Detection.

Serological assays for SARS-CoV-2 play a pivotal role in the definition of whether patients are infected, the understanding of viral epidemiology, the screening of convalescent sera for therapeutic and prophylactic purposes, and in obtaining a better understanding of the immune response towards the virus. The aim of this study was to investigate the performance of a bead-based multiplex assay. This assay allowed for the simultaneous testing of IgG antibodies against SARS-CoV-2 spike, S1, S2, RBD, and nucleocapsid moieties and S1 of seasonal coronaviruses hCoV-22E, hCoV-HKU1, hCoV-NL63, and hCoV-OC43, as well as MERS and SARS-CoV. We compared the bead-based multiplex assay with commercial ELISA tests. We tested the sera of 27 SARS-CoV-2 PCR-positive individuals who were previously tested with different ELISA assays. Additionally, we investigated the reproducibility of the results by means of multiple testing of the same sera. Finally, the results were correlated with neutralising assays. In summary, the concordance of the qualitative results ranged between 78% and 96% depending on the ELISA assay and the specific antigen. Repeated freezing-thawing cycles resulted in reduced mean fluorescence intensity, while the storage period had no influence in this respect. In our test cohort, we detected up to 36% of sera positive for the development of neutralising antibodies, which is in concordance with the bead-based multiplex and IgG ELISA.

Long-term Elevation of Complement Factors in Cerebrospinal Fluid of Patients With Borna Disease Virus 1 Encephalitis.

Borna disease virus 1 (BoDV-1) causes rare but severe zoonotic infections in humans, presenting as encephalitis. The case-fatality risk is very high and no effective countermeasures have been established so far. An immunopathology is presumed, while data on immune responses in humans are limited. Evidence of a role of the complement system in various neurological disorders and in viral infections of the central nervous system is increasing and specific inhibitors are available as therapeutic options. In this study, we investigated factors of the complement system in the cerebrospinal fluid (CSF) of patients with BoDV-1 infections (n = 17) in comparison to noninflammatory control CSF samples (n = 11), using a bead-based multiplex assay. In addition, immunohistochemistry was performed using postmortem brain tissue samples. We found an intrathecal elevation of complement factors of all complement pathways and an active cascade during human BoDV-1 infections. The increase of certain complement factors such as C1q was persistent, and C3 complement deposits were detected in postmortem brain sections. Intrathecal complement levels were negatively correlated with survival. Further investigations are warranted to clarify whether targeting the complement cascade by specific inhibitors might be beneficial for patients suffering from severe BoDV-1 encephalitis.

Development and Validation of Multiplex Assays for Mouse and Human IgG and IgA to Neisseria gonorrhoeae Antigens.

There is an urgent need for vaccines against Neisseria gonorrhoeae, the causative agent of gonorrhea. Vaccination with an outer membrane vesicle-based Neisseria meningitidis vaccine provides some protection from N. gonorrhoeae; however, the mechanisms underlying this cross-protection are unknown. To address this need, we developed multiplexed bead-based assays for the relative quantification of human and mouse IgG and IgA against N gonorrhoeae antigens. The assays were evaluated for analyte independence, dilutional linearity, specificity, sensitivity, intra- and interassay variability, and robustness to sample storage conditions. The assay was then used to test samples from mice and humans immunized with an N meningitidis outer membrane vesicle vaccine.

Abstract 3773: Bladder cancer risk stratification with the Oncuria 10 plex bead-based urinalysis assay using three different Luminex xMAP instrumentation platforms

Abstract Introduction and Objectives: Oncuria® is a bead-based multiplex fluorescence immunoassay that coordinately measures 10 protein biomarkers in urine samples. The current study compared assay performance and output when urine samples were evaluated with the Oncuria assay using three different fluorescence-analyzing instruments commonly used in diagnostic laboratories worldwide. Methods: We compared the performance of the clinically validated Oncuria bladder cancer (BC) multiplex immunoassay when data output was generated on three different analyzer systems. Voided urine samples from 36 subjects (18 with BC and 18 Controls) were reacted with Oncuria test reagents in three 96 well microtiter plates, and consecutively evaluated on the LED/image based MagPix, and laser/flow based Luminex 200 and FlexMap 3D (all xMAP instruments from Luminex Corp., Austin, TX). The BC assay uses magnetic bead based fluorescence technology (xMAP, Multi-analyte profiling; Luminex) to simultaneously quantify 10 protein analytes in urine specimens [i.e., angiogenin (ANG), apolipoprotein E (ApoE), carbonic anhydrase IX (CA9), CXCL8/interleukin-8 (IL-8), matrix metalloproteinase-9 (MMP-9), matrix metalloproteinase-10 (MMP-10), serpin A1/alpha-1 anti-trypsin (A1AT), serpin E1/plasminogen activator inhibitor-1 (PAI-1), CD138/syndecan-1 (SDC1), and vascular endothelial growth factor-A (VEGF-A)]. Results: All three platforms categorized all 10 analytes in identical samples at nearly identical concentrations, with variance across systems typically <5%. While the most contemporary instrument, the FlexMap 3D, output higher raw fluorescence values than the two comparator systems, standard curve slopes and analyte concentrations determined in urine samples were concordant across all three units. Forty-four percent of BC samples registered ≥1 analyte above the highest standard concentration, i.e., A1AT (n=7/18), IL-8 (n=5), and/or ANG (n=2). In Controls, A1AT was higher in one sample. Conclusions: In conclusion, the Oncuria BC assay performed similarly well across three different flow analysis platforms for all 10 analytes simultaneously evaluated in urine samples. This agreement across instruments indicates that the test is amenable to standardized performance in laboratories using existing xMAP, without requiring costly outlays for new equipment. Citation Format: Sunao Tanaka, Toru Sakatani, Kaoru Murakami, Richard T. Waldron, Walter Morales, Wayne Hogrefe, Charles J. Rosser, Hideki Furuya. Bladder cancer risk stratification with the Oncuria 10 plex bead-based urinalysis assay using three different Luminex xMAP instrumentation platforms [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3773.

Abstract 3642: Phenotypic biomarkers of aqueous humor extracellular vesicles from retinoblastoma eyes

Abstract Purpose: Retinoblastoma (RB) is the most common pediatric intraocular cancer, yet tumor biopsies are contraindicated. This challenge emphasizes the need for investigation of non-tissue biomarkers. Extracellular vesicles (EVs), which are secretory vesicles containing bioactive molecules, have emerged as promising biomarker candidates due to their ability to be phenotyped using known tetraspanin markers. Aqueous humor (AH) provides an exciting liquid biopsy source for intraocular tumor information, with EVs having recently been identified in AH. Our laboratory has previously proposed that CD63/81+EVs are associated with retinoblastoma, but specific tumor-derived markers have not been linked to AH EVs using traditional tetraspanin assays. In this study, we employed MACSPlex, a high-dimensional magnetic bead-based immunoassay, to further explore RB-EV. Methods: 7 AH samples consisting of two congenital glaucoma (GLC) samples and five RB samples taken at the time of primary enucleation were analyzed. We utilized Macsplex, a multiplex bead-based flow cytometry assay, to analyze the expression profiles of surface markers found on EVs. With 39 capture beads coated with monoclonal antibodies for 37 different EV surface antigens and two negative controls, the mean fluorescence intensity (MFI) of APC conjugated antibody cocktail from three tetrapanins (CD9, CD63 and CD81) on EVs captured by each surface antigen could be measured by flow cytometry. Enrichment ratios were then calculated by normalizing the fluorescence of each signal to the mean fluorescence of CD9, CD63, and C81. Results: Macsplex analysis of the 2 GLC AH samples demonstrated a strong CD63 dominance compared with RB AH. The mean CD63 enrichment ratio for GLC samples was 2.6 (S.D. = 0.34), and 1.3 (S.D. = 0.27) in RB samples, with a p-value of 0.069. In comparison to the GLC patients, the analysis of EVs in the AH of the 5 RB samples exhibited a greater co-dominance of CD63/CD81 positivity consistent with past research on RB EVs. The mean CD81 enrichment ratio for the 5 RB samples was 1.5 (S.D. = 0.26), in contrast to 0.3 (S.D. = 0.24) in GLC AH, with a p-value of 0.03. Interestingly, 4 out of the 5 RB AH samples demonstrated very strong CD133 signals, which is a known cancer marker. Deeper investigation into one RB AH sample utilizing single tetraspanin detection revealed higher coexpression of CD63 and CD81 with CD133 than seen with CD9. The CD133 enrichment ratio for the CD81, CD63, and CD9 single channel experiments were 6.6, 3.4, and 1.5 respectively. Conclusions: Comparison between this study and previous work done by our group demonstrate a high concordance between results utilizing Macsplex and Exoview. However, this is the first study identifying the expression of CD133, a cancer stem cell marker, on retinoblastoma-derived EVs in AH. Macsplex technology illustrates an incredible clinical potential of AH EVs for characterizing retinoblastoma phenotype in vivo. Citation Format: Anne Amacker, Chen-Ching Peng, Bibiana J. Reiser, Jesse L. Berry, Liya Xu. Phenotypic biomarkers of aqueous humor extracellular vesicles from retinoblastoma eyes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3642.

Abstract 5294: Conditionally active CD28xVISTA bispecific antibodies induce myeloid-driven tumor-specific T-cell co-stimulation for improved cancer immunotherapy

Abstract Introduction: Tumor-specific recruitment of co-stimulatory bispecific antibodies (bsAbs) has emerged as a promising therapeutic strategy. Here, we investigated pH-selective CD28xVISTA bsAbs to act selectively within the acidic tumor microenvironment (TME). Our CD28xVISTA bsAbs are designed for tripartite “trans-activation” of CD28 in the TME, aiming for enhanced T-cell-mediated cancer cell killing while minimizing systemic T-cell activation and Cytokine Release Syndrome (CRS) risk. Experimental Procedures: We evaluated various CD28xVISTA bsAbs, focusing on a prototype 1+2 format with monovalent CD28 binding, bivalent VISTA binding and Fc receptor interaction null mutations (BS2). BS2 was tested for T-cell trans-activation using Jurkat-IL-2-luciferase reporter cells in the presence of HEK293 cells expressing membrane bound OKT3-scFv and CHO cells expressing human VISTA. BS2’s potency was further evaluated in an xCelligence-based human T-cell killing assay that dynamically monitors growth of LNCaP prostate cancer cells co-cultured with VISTA+ Kasumi-3 cells, alone or in combination with a CD3xPSMA bispecific T-cell engager. T-cell activation and proliferation were also measured using flow cytometry with CD3, CD4, CD8 and CD25 markers. Additionally, we modified BS2 to introduce pH-selective VISTA binding, limiting its activity to the TME, and tested this version in a syngeneic mouse model in combination with anti-murine PD-1 (anti-mPD-1). Finally, cytokine release from human PBMCs, co-cultured with human umbilical vein endothelial cells (HUVECs) and treated with the pH-selective BS2 (or TGN1412 as a positive control), was measured using a bead-based multiplex immune assay. Results: Our data show that the combination of anti-mPD-1 and our prototype CD28xVISTA bsAb (BS2) with pH-selective VISTA binding significantly inhibited tumor growth in vivo. In vitro, CD28xVISTA co-stimulation in trans by BS2 potentiated the activity of a CD3xPSMA bispecific T-cell engager in our human T-cell killing assay. Cytokine release assessments demonstrated negligible induction of inflammatory cytokines, indicating a favorable safety profile for this antibody. Conclusion: Our study demonstrates the feasibility of cis and trans CD28 co-stimulation using a CD28xVISTA bsAb (BS2). This approach, which bypasses the need for tumor-associated antigens (TAAs) required by other CD28xTAA bispecifics in development, suggests a potentially safer alternative for T-cell engagement and stimulation. Moreover, our novel myeloid-directed TME-selective co-stimulation strategy with a CD28xVISTA bsAb may broaden the potential for T-cell engagement approaches in solid tumors by enabling rational combinations with existing CD3xTAA T-cell engagers without competing for the same target. Citation Format: Thomas Thisted, Zhi-Gang Jiang, Zuzana Biesova, Adejumoke Onumajuru, Yuliya Kleschenko, Kanam Malhotra, Vikas Saxena, Arnab Mukherjee, F. Donelson Smith, Edward H. van der Horst. Conditionally active CD28xVISTA bispecific antibodies induce myeloid-driven tumor-specific T-cell co-stimulation for improved cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5294.

Abstract 3438: Associations between estimated endotoxin exposure and circulating immunological markers among male farmers

Abstract Occupational exposure to endotoxin has been associated with reduced lung cancer risk. Farmers who perform certain tasks (e.g., raising hogs) can be highly exposed to endotoxin. The mechanisms through which endotoxin could confer a lower risk of lung cancer, while likely to be immune mediated, are not clear. To address this gap, we evaluated associations between estimated endotoxin exposure and circulating immunologic markers among male farmers in the Biomarkers of Exposure and Effect in Agriculture (BEEA) study. Our investigation included 122 non-smoking farmers from Iowa, oversampling those raising hogs (n=61). We evaluated 58 serologic markers, including some linked to lung cancer, that were measured using multiplex bead-based assays. Based on an algorithm linking personal air measurements in BEEA and published data to reported farming tasks, we estimated cumulative endotoxin exposure in the last 30 days and 12 months before sample collection. We used multivariable linear regression to estimate geometric mean ratios of immune markers across exposure quartiles, overall and by season of sample collection. Higher endotoxin exposure in the last 30 days was associated with increased levels of FGF-2, MIP-3A/CCL20, and sIL-4R (Ptrend ≤ 0.02), and with decreased levels of MDC/CCL22 (Ptrend = 0.02). In analyses stratified by season, the positive associations with FGF-2 and MIP-3A/CCL20 were most apparent in the winter (Ptrend = 0.002 and 0.03, respectively); we also observed an inverse association with sCD27 levels in the summer (Ptrend = 0.03). Similar patterns were observed for endotoxin exposure in the last 12 months. This study is the first to use novel algorithm-based endotoxin exposure estimates to evaluate associations with intermediate lung cancer-related markers. Several markers were associated with endotoxin levels in an exposure-response manner. Our findings suggest possible biological mechanisms through which endotoxin may reduce risk of lung cancer. Table 1. Associations between estimated endotoxin exposure in the last 30 days and selected serum im Citation Format: Somayina C. Ezennia, Laura E. Beane-Freeman, Vicky C. Chang, Shuai Xie, Gabriella Andreotti, Melissa C. Friesen, Jonathan N. Hofmann. Associations between estimated endotoxin exposure and circulating immunological markers among male farmers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3438.

T-Cell Subtypes and Immune Signatures in Cutaneous Immune-Related Adverse Events in Melanoma Patients under Immune Checkpoint Inhibitor Therapy.

Immune checkpoint inhibition (ICI) improves outcomes in melanoma patients, but associated T-cell activation frequently leads to immune-related cutaneous adverse events (cutAEs). To dynamically identify T-cell subtypes and immune signatures associated with cutAEs, a pilot study was performed in stage III-IV melanoma patients using blood samples for flow cytometry and cytokine analysis. Blood samples were taken from patients before initiation of ICI (naive), at the onset of a cutAE, and after 6 months of ICI treatment. Overall, 30 patients were treated either with anti-PD1 monotherapy or with anti-PD-1/anti-CTLA-4 combination therapy. Flow cytometry analysis of PBMCs showed that ICI induced an overall shift from a Th2 towards a Th1 profile. Twelve patients (40%) developed cutAEs, which were associated with increased Th22 cells and Th17 cells, supported by a tendency to have elevated Th17/Th22-associated cytokines such as IL-17A, IL-22 and IL-23 levels in the plasma. Cytokine signatures specific for urticaria and T-cell-mediated cutAEs were identified in the plasma of patients by a bead-based assay. IL-10 was elevated in non-responders and, interestingly, during cutAEs. In conclusion, we identified distinct immune signatures based on the Th17/Th22 pathway in cutAEs, both in PBMCs and plasma. In addition, our finding of upregulated IL-10 during cutAEs supports the notion of treating these patients early and adequately to avoid implications for the overall outcome.

Salivary α-amylase activity is associated with cardiometabolic and inflammatory biomarkers in overweight/obese, non-diabetic Qatari women.

Obesity, prevalent in approximately 80% of Qatar's adult population, increases the risk of complications like type 2 diabetes and cardiovascular diseases. Predictive biomarkers are crucial for preventive strategies. Salivary α-amylase activity (sAAa) inversely correlates with obesity and insulin resistance in adults and children. However, the connection between sAAa and cardiometabolic risk factors or chronic low-grade inflammation markers remains unclear. This study explores the association between serum sAAa and adiposity markers related to cardiovascular diseases, as well as markers indicative of chronic low-grade inflammation. Serum samples and clinical data of 1500 adult, non-diabetic, Overweight/Obese participants were obtained from Qatar Biobank (QBB). We quantified sAAa and C reactive protein (CRP) levels with an autoanalyzer. Cytokines, adipokines, and adiponectin of a subset of 228 samples were quantified using a bead-based multiplex assay. The associations between the sAAa and the adiposity indices and low-grade inflammatory protein CRP and multiple cytokines were assessed using Pearson's correlation and adjusted linear regression. The mean age of the participants was 36 ± 10 years for both sexes of which 76.6% are women. Our analysis revealed a significant linear association between sAAa and adiposity-associated biomarkers, including body mass index β -0.032 [95% CI -0.049 to -0.05], waist circumference β -0.05 [95% CI -0.09 to -0.02], hip circumference β -0.052 [95% CI -0.087 to -0.017], and HDL β 0.002 [95% CI 0.001 to 0.004], albeit only in women. Additionally, sAAa demonstrated a significant positive association with adiponectin β 0.007 [95% CI 0.001 to 0.01]while concurrently displaying significant negative associations with CRP β -0.02 [95% CI -0.044 to -0.0001], TNF-α β -0.105 [95% CI -0.207 to -0.004], IL-6 β [95% CI -0.39 -0.75 to -0.04], and ghrelin β -5.95 [95% CI -11.71 to -0.20], specifically within the female population. Our findings delineate significant associations between sAAa and markers indicative of cardiovascular disease risk and inflammation among overweight/obese adult Qatari females. Subsequent investigations are warranted to elucidate the nuances of these gender-specific associations comprehensively.

Antiproliferative and immunomodulative potential of Citrullus colocynthis and its bioactive compounds in human lymphocytes and lung cells

Ethnopharmacological relevanceCitrullus colocynthis (L.) Schrad is a member of the Cucurbitaceae plant family which has been used in traditional medicine for the treatment of lung diseases such as asthma and bronchitis. Aim of the studyThe study was conducted to investigate antiproliferative and immunomodulating effects of C. colocynthis and isolated cucurbitacins on human T lymphocytes and lung epithelial cells in order to evaluate their potential in the treatment of airway diseases. Materials and methodsDifferent concentrations of an ethanolic extract of C. colocynthis fruits and cucurbitacins B (CuB), E (CuE) and E-glucopyranoside (CuE-Glu) were analysed for their cytotoxicity and immunomodulatory potential on Peripheral Blood Mononuclear Cells (PBMCs) of healthy donors and on the epithelial lung cancer cell line A549. Viability and proliferation were tested using WST1 and CFSE assays. Flow cytometric analysis of AnnexinV/PI staining was used to investigate cell death through apoptosis/necrosis. Effects on regulatory mechanisms of T lymphocytes, such as CD69 and CD25 marker activation, cytokine production of the cytokines interleukin 2 (IL2), tumor necrosis factor α (TNFα) and interferon γ (IFNy) were also analysed via flow cytometry. Influences on the activator protein 1 (AP1), nuclear factor of activated T-cells (NFAT) or nuclear factor ‘kappa-light-chain-enhancer’ of activated B-cells (NFκB) pathways were analysed in the Jurkat reporter cell line. Cytokine secretion in A549 cells stimulated with virus-like particles was analysed using the bead-based Legendplex™ assay. ResultsNon-toxic concentrations of C. colocynthis and CuE-Glu showed dose-dependent effects on viability and proliferation in both T lymphocytes and A549 cells. The extracts inhibited lymphocyte activation and suppressed T cell effector functions, which was also shown by lower production of cytokines IL2, TNFα and IFNy. A dose dependent inhibition of the pathways NFκB, NFAT and AP1 in Jurkat cells could be observed. In A549 cells, especially CuE and CuE-Glu showed inhibitory effects on cytokine production following a simulated viral infection. Unglycosylated cucurbitacins were more effective in suppressing the immune function in lymphocytes than glycosylated cucurbitacins, however this activity is limited to cytotoxic concentrations. ConclusionIn our study we could confirm the immunmodulating effect of C. colocynthis and cucurbitacins B, E and E-glucopyranoside in vitro by suppression of different pathways of inflammation and T cell proliferation. Activity in a lung cell model using a virus-like stimulation shows promise for further research regarding cucurbitacins in airway diseases.

Combining Bioorthogonal Chemistry with Fluorescent Silica Nanoparticles for the Ultrasensitive Detection of the HIV-1 p24 Antigen.

Early detection and viral concentration monitoring of human immunodeficiency virus in resource-poor settings are important to control disease spread and reduce mortality. Nucleic acid amplification tests are expensive for low-resource settings. Lateral flow antibody tests are not sensitive if testing is performed within 7-10 days, and these tests are not quantitative. We describe a signal enhancement technique based on fluorescent silica nanoparticles and bioorthogonal chemistries for the femtomolar detection of the HIV-1 p24 antigen. We developed a magnetic bead-based assay, wherein we used fluorescent-dye-encapsulated silica nanoparticles as reporters. The number of reporters was increased by using bioorthogonal chemistry to provide signal enhancement. The limit and range of detection of the sandwich immunoassay using alternating multiple layers for p24 in human serum were found to be 46 fg/mL (1.84 fM) and 46 fg/mL to 10 ng/mL, respectively. This simple assay was 217-fold higher in sensitivity compared to that of commercial enzyme-linked immunoassays (limit of detection of 10 pg/mL).

MIB Guides: Measuring the Immunoreactivity of Radioimmunoconjugates

Immunoglobulins, both full-length antibodies and smaller antibody fragments, have long been regarded as effective platforms for diagnostic and therapeutic radiopharmaceuticals. The construction of radiolabeled immunoglobulins (i.e., radioimmunoconjugates) requires the manipulation of the biomolecule through the attachment of a radiohalogen or the bioconjugation of a chelator that is subsequently used to coordinate a radiometal. Both synthetic approaches have historically relied upon the stochastic modification of amino acids within the immunoglobulin, a process which poses a risk to the structural and functional integrity of the biomolecule itself. Not surprisingly, radioimmunoconjugates with impaired antigen binding capacity will inevitably exhibit suboptimal in vivo performance. As a result, the biological characterization of any newly synthesized radioimmunoconjugate must include an assessment of whether it has retained its ability to bind its antigen. Herein, we provide straightforward and concise protocols for three assays that can be used to determine the immunoreactivity of a radioimmunoconjugate: (1) a cell-based linear extrapolation assay; (2) a cell-based antigen saturation assay; and (3) a resin- or bead-based assay. In addition, we will provide a critical analysis of the relative merits of each assay, an examination of the inherent limitations of immunoreactivity assays in general, and a discussion of other approaches that may be used to interrogate the biological behavior of radioimmunoconjugates.

Comprehensive domain-specific analysis and immunoglobulin G profiling of anti–factor VIII antibodies using a bead-based multiplex immunoassay

BackgroundAntibodies against factor (F)VIII are a major complication in the treatment of patients with severe hemophilia A. The Nijmegen-Bethesda assay (NBA) is the gold standard for detection of neutralizing antibodies (inhibitors), whereas both inhibitors and nonneutralizing antibodies can be detected by immunoassays such as enzyme-linked immunosorbent assay (ELISA) and multiplex bead-based assays. ObjectivesEvaluation of an in-house Luminex bead-based assay (LumiTope) compared with a commercially available ELISA and NBA. MethodsThe LumiTope method comprised full-length and B-domain–deleted FVIII as well as 9 purified FVIII single or multidomains. The respective proteins were coupled to magnetic beads to detect domain-specific immunoglobulin (IgG; IgG1-4) anti-FVIII antibodies in a large cohort of patients with hemophilia A with and without inhibitors. ResultsOverall, LumiTope assay had a high sensitivity (94.9%) and specificity (91.2%), particularly in patients with low-titer inhibitors compared with ELISA (sensitivity of 72.2% vs 27.7%). IgG4 was the most abundant IgG subclass in NBA-positive patients. NBA-positive and -negative patients showed different domain profiles. Patients with genetic variants in the heavy chain predominantly exhibited antibodies specific to this chain, while those with a light-chain variant showed a more diverse distribution of antibody specificities. Patients with an intron 22 inversion resembled those with a light-chain defect, with a majority of antibodies targeting the light chain. ConclusionLumiTope assay provides a sensitive and specific method for not only detection but also domain specification of anti-FVIII-antibodies. Implementation of bead-based assays could improve antibody detection, profiling, and comparability of results and complement NBA.

The effect of plasma cytokines on the expression of adiponectin and its receptors in the synovial membrane of joints and the infrapatellar fat pad in patients with rheumatoid arthritis and osteoarthritis

BackgroundRheumatoid arthritis (RA) is an autoimmune inflammatory disease that leads to joint destruction. Numerous pro-inflammatory mediators, including adipokines, play an important role in the pathogenesis of RA. ObjectiveThe aim of the study was to investigate the relationships between selected plasma cytokines and expression of adiponectin and its receptors in the synovium and the infrapatellar fat pad in patients with RA and osteoarthritis (OA). MethodsBlood, synovium and fat pad samples from 18 patients with RA and 18 with OA were collected during joint replacement surgery. Spearman rank correlations between plasma concentrations of selected cytokines (IL-1β, IL-2, IL-4, IL-6, IL-7, IL-8, IL-10, IL-12 p40, IL-13, IL-17, G-CSF and GM-CSF) and the expression of adiponectin and its receptors were determined. Plasma levels of cytokines were determined using a magnetic bead-based multiplex assay, mRNA expression of adiponectin and its receptors were determined by real-time PCR. ResultsIn OA patients, there were significant positive correlations between adiponectin expression in the synovial membrane and plasma levels of IL-1β, IL-4, G-CSF and GM-CSF, as well as a significant positive correlation between adiponectin expression in the fat pad and plasma levels of GM-CSF. In addition, OA patients showed significant negative correlations between AdipoR1 and AdipoR2 expression in the synovial membrane and plasma IL-6 levels, as well as between AdipoR2 expression in the synovial membrane and plasma MCP-1 and TNF-α levels. In patients with RA, there were no significant correlations between adiponectin expression in the synovial membrane and infrapatellar fat pad and plasma levels of the cytokines studied. In addition, RA patients showed a statistically significant negative correlation between AdipoR1 expression in the synovial membrane and plasma levels of TNF-α, IL-7, IL-12 and IL-13, and a significant negative correlation between AdipoR1 expression in the infrapatellar fat pad and plasma levels of IL-1β. ConclusionsAdiponectin and its receptors showed the correlations with several plasma cytokines, however, a thorough understanding of the role of adiponectin in RA and OA requires further investigation.

Association Between Cervical Inflammatory Mediators and Prevalent Cervical Human Papillomavirus Infection.

Inflammatory mediators are important regulators of immune response and can modulate the inflammation caused by viral infections, including human papillomavirus (HPV). In this study, we evaluated the association between cervical immune mediators, including chemokines, cytokines, and growth factors with HPV infections. We used a nonmagnetic bead-based multiplex assay to determine 27 immune mediators in cervical secretions collected from 275 women in a prospective longitudinal cohort design. All the study participants were age 18 years or older, had a history of vaginal sexual intercourse, were not currently pregnant, and had no history of cervical disease or hysterectomy. The mean (±standard deviation) age of the participants was 41 (±8) years, and about half (51% [141/275]) were HPV-positive, of whom 7% (10/141) had low-risk HPV (lrHPV), 61% (86/141) had high-risk HPV (hrHPV), and 32% (45/141) had both lrHPV and hrHPV infections. Higher concentrations of some immune mediators were associated with HPV infections, including eotaxin, interferon-gamma, interleukin (IL)-1β, IL-2, IL-4, IL-7, IL-8, IL-9, IL-10, IL-12p70, IL-13, IL-15, macrophage inflammatory protein (MIP)-1α, MIP-1β, regulated upon activation normal T-cell expressed and secreted (RANTES), and tumor necrosis factor (TNF)-α and any HPV; IL-2, IL-4, IL-5, IL-7, IL-10, IL-12p70, and IL-13 and lrHPV; and eotaxin, interferon, IL-1B, IL-4, IL-7, IL-8, IL-9, IL-10, IL-13, IL-15, MIP-1α, MIP-1β, RANTES, TNF-α concentrations, and hrHPV infections. Higher concentrations of granulocyte macrophage colony-stimulating factor, IL-1 receptor antagonist (IL-1Ra), and monocyte chemotactic protein-1 (MCP-1) were associated with reduced odds of any HPV, while IL-1Ra and MCP-1 were associated with reduced odds of hrHPV infections. Several chemokines, cytokines, and growth factors are associated with group-specific HPV infections in this population of women. These important findings contribute to the understanding of the immune response to HPV, cytokine profiles and their potential implications for cervical pathogenesis, and can guide future research in this field.

Exploration of bromodomain ligand-linker conjugation sites for efficient CBP/p300 heterobifunctional degrader activity

Synthesis of proteolysis targeting chimeras (PROTACs) involves conjugation of an E3 ligase binding ligand to a ligand targeting a protein of interest via a rigid or flexible chemical linker. The choice of linker conjugation site on these ligands can be informed by structural analysis of ligand-target binding modes, the feasibility of synthetic procedures to access specific sites, and computational modeling of predicted ternary complex formations. Small molecules that target bromodomains - epigenetic readers of lysine acetylation - typically offer several potential options for linker conjugation sites. Here we describe how varying the linker attachment site (exit vector) on a CBP/p300 bromodomain ligand along with linker length affects PROTAC degradation activity and ternary complex formation. Using kinetic live cell assays of endogenous CBP and p300 protein abundance and bead-based proximity assays for ternary complexes, we describe the structure-activity relationships of a diverse library of CBP/p300 degraders (dCBPs).

Advancing Toxoplasma gondii multiplex serology.

Toxoplasma gondii is a pathogen of significant public health concern due to its widespread prevalence and zoonotic potential. However, our understanding of key aspects, such as risk factors for infection and disease, potential outcomes, and their trends, remains limited. Seroepidemiological studies in large cohorts are invaluable for addressing these questions but remain scarce. Our revised multiplex serology assay equips researchers with a powerful tool capable of delivering T. gondii serum antibody measurements with high sensitivity and specificity under diverse assay conditions. This advancement paves the way for the integration of T. gondii antibody measurements into multi-pathogen multiplex serology panels, promising valuable insights into public health and pathogen interactions.

A196 CSF2 AUTOANTIBODIES AS A SEROLOGICAL MARKER FOR CROHN'S DISEASE

Abstract Background Crohn’s disease (CD) is a chronic inflammatory disorder of the gastrointestinal tract that severely affects quality of life. Despite technological advances, CD diagnoses remain difficult and invasive, with delayed diagnoses correlated with worse prognosis and complications. CD is multifactorial, involving complex interactions between genetic and environmental risk factors, which leads to difficulty in identifying a cause and cure. However, research alludes to an underlying dysregulation of immune activity that leads to chronic intestinal inflammation. Mononuclear phagocytes (MNP) are essential immune cells that promote intestinal homeostasis through supporting immune tolerance, antimicrobial activity, and barrier integrity. A crucial cytokine that promotes the survival and function of intestinal MNP is Colony Stimulating Factor 2 (CSF2). Intriguingly, previous work in our lab demonstrated that CSF2 autoantibodies (CSF2-Ab) can be detected in the serum of every third CD patient and antedate the onset of CD by up to 6 years. In contrast, these titers are not seen in healthy donors or ulcerative colitis. Moreover, CSF2-Ab were predictive of disease location and severity, and are able to neutralize CSF2 by binding to glycosylations, impacting downstream signaling in MNP. These data suggest a role for CSF2-Ab in promoting intestinal immune dysregulation in CD. Aims Our work aims to characterize CSF2-Ab and their role in CD. Methods We developed a bead-based flow cytometric assay to screen CD patient serum for CSF2-Ab in several cohorts that contain samples at time points prior to, at, and after diagnosis. Results Our preliminary data demonstrate that our assay is rapid and specific for detecting CSF2-Ab of various isotypes in human serum and can be validated using ELISA. Furthermore, we show that this assay can be used to determine the epitope specificity of CSF2-Ab in CD patients in just one single sample. Conclusions We have developed a rapid and accessible assay to predict CD development years before diagnosis using minimal serum samples. Moreover, this screen will enable subclassification of patients based on their autoantibody reactivity to glycovariants of CSF2. Glycovariants that escape recognition by CD-specific CSF2-Ab could potentially be used as a therapeutic to ameliorate disease. Beyond treatment, understanding how CSF2-Ab epitope specificity and isotypes may change over the course of disease development will serve as a roadmap for elucidating the role of CSF2-Ab in CD. Funding Agencies CAG, CIHR

Cross-Platform Comparison of Highly Sensitive Immunoassays for Inflammatory Markers in a COVID-19 Cohort.

A variety of commercial platforms are available for the simultaneous detection of multiple cytokines and associated proteins, often employing Ab pairs to capture and detect target proteins. In this study, we comprehensively evaluated the performance of three distinct platforms: the fluorescent bead-based Luminex assay, the proximity extension-based Olink assay, and a novel proximity ligation assay platform known as Alamar NULISAseq. These assessments were conducted on human serum samples from the National Institutes of Health IMPACC study, with a focus on three essential performance metrics: detectability, correlation, and differential expression. Our results reveal several key findings. First, the Alamar platform demonstrated the highest overall detectability, followed by Olink and then Luminex. Second, the correlation of protein measurements between the Alamar and Olink platforms tended to be stronger than the correlation of either of these platforms with Luminex. Third, we observed that detectability differences across the platforms often translated to differences in differential expression findings, although high detectability did not guarantee the ability to identify meaningful biological differences. Our study provides valuable insights into the comparative performance of these assays, enhancing our understanding of their strengths and limitations when assessing complex biological samples, as exemplified by the sera from this COVID-19 cohort.