Electrochemiluminescence Assay Research Articles

Identifying immune biomarkers associated with human trauma as potential therapeutic targets

Abstract Severe trauma can induce systemic immunosuppression, which makes understanding the biomarker profiles of trauma patients critical for therapeutic development and for predicting potential immune responses to treatments such as biomedical implants. Our goal was to establish a data set containing levels of a large array of biomarkers measured in blood from human trauma patients. Multiplex electrochemiluminescence assays were conducted to measure the levels of 59 biomarkers in 1000 blood samples collected from patients at the time of admission to trauma centers. Injury types were categorized as motor vehicle crashes (n=448), falls (n=221), gun wounds (n=78), stabbings (n=117), or other traumatic injuries. Patients ranged in age from 18 to 101, with a mean age of 42.7 for male patients (n= 725) and 49.8 for female patients (n= 272). There were no significant differences in biomarker expression levels between the different injury types. Differences in age distributions of male and female patients for each injury type were not found to be statistically significant, except in the case of falls, which had a higher average age for female patients compared to male patients. MIF, MIP-5, and YKL-40 had the highest expression, with concentrations of 554148 ± 62938 pg/mL, 17409 ± 919 pg/mL, and 98793 ± 10015 pg/mL (mean ± 95 % CI) respectively, at 1:100 dilution. Further experiments are currently being conducted to establish biomarker profiles for control uninjured human samples, and data comparing the profiles of trauma patients and uninjured controls will be presented. Overall, this work provides a resource for understanding immune responses to injury and potentially developing new therapeutics with these biomarker profiles in mind. This work was supported by the National Institute of Biomedical Imaging and Bioengineering

Ublituximab, a Novel, Glycoengineered Anti-CD20 Monoclonal Antibody (mAb), Demonstrates Enhanced Antibody-Dependent Cellular Cytotoxicity (ADCC) Relative to Other Anti-CD20 mAbs (P7-3.011)

Ublituximab, a Novel, Glycoengineered Anti-CD20 Monoclonal Antibody (mAb), Demonstrates Enhanced Antibody-Dependent Cellular Cytotoxicity (ADCC) Relative to Other Anti-CD20 mAbs (P7-3.011)

Abstract 4351: Multiplex detection of G12/G13 KRAS mutations with an electrochemiluminescent hybridization assay

Abstract Purpose: Oncogenic Kirsten rat sarcoma virus (KRAS) mutations are the most prevalent cancer mutations in all human tumors. Also, genotyping the KRAS gene has become increasingly important with the emergence of new evidence highlighting differences in downstream signaling pathways, tumor microenvironment composition, treatment responses and prognoses linked to specific single nucleotide polymorphisms (SNPs) in the G12 or G13 codons. FDA approval of G12C-specific anti-KRAS drugs highlights the importance of the development of reliable SNP assays to interrogate the mutation status in a tumor sample. Currently available genotyping assays are based on NGS, PCR, or ddPCR. These methods can be time-consuming, costly, suffer from amplification bias, or require follow-up testing or bioinformatics skills to analyze. Building on Meso Scale Discovery’s (MSD) existing technology, we aimed to develop a method for the identification of eight KRAS SNPs located on the G12-G13 codons in a single reaction. Methods: Ten-spot, 96-well N-PLEX plates were used for the study. SNP-specific upstream probes carrying unique 5′ leader sequences complementary to spot-specific captures on the N-PLEX plates were designed for eight KRAS genotypes (WT, G12R, G12C, G12S, G12A, G12D, G12V, G13D). Locus-specific downstream probes were 5’ phosphorylated for ligation and 3’ biotinylated for detection. Synthetic DNA targets were used as assay calibrators, and commercially available FFPE reference samples were tested for validation. DNA (10 ng) was PCR amplified with primers flanking the KRAS mutation sites. A multiplexed mixture of upstream and downstream probes was hybridized to the amplicons, and 30 cycles of ligation was performed using DNA ligase in a thermal cycler. Samples were subsequently hybridized to spot-specific capture oligonucleotides on the surface of the assay plates and detected with SULFO-TAG labeled streptavidin. Electrochemiluminescence readout was collected on an MSD imager. Results: Optimization of probe concentrations and ligation temperature was performed to maximize signal-to-background ratios and assay specificity. Spike recovery experiments using artificial target DNA showed successful identification of KRAS mutant genotypes at spike levels as low as 0.1% over wild-type background. Validation experiments with gDNA extracted from FFPE reference samples confirmed that the multiplex SNP assay can accurately differentiate eight KRAS genotypes in samples with >0.4% tumor burden. Conclusion: These data highlight a novel approach to simultaneously identify eight KRAS genotypes from 10 ng of DNA input in a single reaction within 4-5 hours. The assay is capable of identifying double mutants and can provide a semiquantitative assessment of tumor burden without the need for follow-up testing. Citation Format: Annamaria Szabolcs, Timothy J. Break, Isaac H. Shin, Seth B. Harkins, Jacob N. Wohlstadter. Multiplex detection of G12/G13 KRAS mutations with an electrochemiluminescent hybridization assay. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4351.

Preventing rheumatoid arthritis: Lessons from that of type 1 diabetes

Preventing rheumatoid arthritis: Lessons from that of type 1 diabetes

Enhanced electrochemiluminescence immunoassay: 2. Enabling signal detection at an early stage of incubation for rapid point-of-care testing

Signal detection in a label-based immunoassay is performed normally when the antigen/antibody binding reaction reaches the equilibrium state during the incubation period of an assay process. Shortening the incubation period in an assay helps reduce the turnaround time and is particularly valuable for point-of-care testing, but the cost is the reduction of signal level and, possibly, measurement precision as well. This work demonstrates that the signal loss could be offset by the stronger emission of an electronically neutral ruthenium(II) complex label, Ru(2, 2′-bipyridine) (bathophenanthroline disulfonate)[4-(2, 2′-bipyridin-4-yl)butanoic acid], used in the electrochemiluminescence (ECL) immunoassay. Combined with the uniquely well-established flow-through washing process in the automated ECL analyzers and the precise control over liquid handling, the assays performed with a 5-minute incubation period showed the same signal level and measurement precision as those of conventional ECL assays. Additionally, the absence of biotin and streptavidin components in the reagent formulation avoids the biotin-streptavidin interaction during assay incubation and fundamentally eliminates the interference of biotin, especially when used in some high-dose therapies. The results obtained from the procalcitonin prototype kit and the supporting evidence from other preliminary reagents (for SARS-CoV-2 N protein and troponin T) are general. The nonequilibrium detection, along with the downsized instrument design, makes the enhanced ECL (EECL) technology a fast high-performance POCT platform that provides the same high-quality data as those generated from the widely deployed [Ru(bpy)3]2+based laboratorial ECL systems.The anticipated regulatory approval and follow-up clinical implementation will beasignificant stride in the decade-long pursuit of novel ECL labels.

Assessing the Impact of Immunogenicity and Improving Prediction of Trough Concentrations: Population Pharmacokinetic Modeling of Adalimumab in Patients with Crohn's Disease and Ulcerative Colitis.

Predicting adalimumab pharmacokinetics (PK) for patients impacted by anti-drug antibodies (ADA) has been challenging. The present study assessed the performance of the adalimumab immunogenicity assays in predicting which patients with Crohn's disease (CD) and ulcerative colitis (UC) have low adalimumab trough concentrations; and aimed to improve predictive performance of adalimumab population PK (popPK) model in CD and UC patients whose PK was impacted by ADA. Adalimumab PK and immunogenicity data obtained from 1459 patients in SERENE CD (NCT02065570) and SERENE UC (NCT02065622) were analyzed. Adalimumab immunogenicity was assessed using electrochemiluminescence (ECL) and enzyme-linked immunosorbent (ELISA) assays. From these assays, three analytical approaches (ELISA concentrations, titer, and signal-to-noise [S/N] measurements) were tested as predictors for classifying patients with/without low concentrations potentially affected by immunogenicity. The performance of different thresholds for these analytical procedures was assessed using receiver operating characteristic curves and precision-recall curves. Based on the results from the most sensitive immunogenicity analytical procedure, patients were classified into PK-not-ADA-impacted and PK-ADA-impacted subpopulations. Stepwise popPK modeling was implemented to fit the PK data to an empirical adalimumab two-compartment model with linear elimination and ADA delay compartments to account for the time delay to generate ADA. Model performance was assessed by visual predictive checks and goodness-of-fit plots. The classical ELISA-based classification (with 20ng/mL ADA as lower threshold) showed a good balance of precision and recall, to determine which patients had at least 30% adalimumab concentrations below 1µg/mL. Titer-based classification with the lower limit of quantitation (LLOQ) as threshold showed higher sensitivity to classify these patients compared to the ELISA-based approach. Therefore, patients were classified as PK-ADA-impacted or PK-not-ADA impacted using the LLOQ titer threshold. In the stepwise modeling approach ADA-independent parameters were first fit using PK data from titer-PK-not-ADA-impacted population. The identified ADA-independent covariates included the effect of indication, weight, baseline fecal calprotectin, baseline C-reactive protein, baseline albumin on clearance; and sex and weight on volume of distribution of the central compartment. Pharmacokinetic-ADA-driven dynamics were characterized using PK data for the PK-ADA-impacted population. The categorical covariate based on the ELISA classification was the best at describing the additional effect of immunogenicity analytical approaches on ADA synthesis rate. The model was able to adequately describe the central tendency and variability for PK-ADA-impacted CD/UC patients. The ELISA assay was found to be optimal for capturing impact of ADA on PK. The developed adalimumab popPK model is robust in predicting PK profiles for CD and UC patients whose PK was impacted by ADA.

The dual-crosslinked prospective values of RAI14 for the diagnosis and chemosurveillance in triple negative breast cancer

Objective The exploration of non-invasive biomarkers for assessing tumor response is critical to optimize treatment decisions. In this study, we aimed at determining the potential role of RAI14 in the early diagnosis and evaluation of chemotherapy efficacy in triple-negative breast cancer (TNBC). Methods We recruited 116 patients newly diagnosed with breast cancer, 30 patients with benign breast disease and 30 healthy controls. In addition, 57 TNBC patients were collected in serum at different time points (C0, C2 and C4) for chemotherapy monitoring. The expression of serum RAI14 and CA15-3 were quantified by Elisa and electrochemiluminescence assay, respectively. Then we compared the performances of markers with the chemotherapy efficacy assessed by imaging. Results RAI14 is significantly overexpressed in TNBC and is linked to adverse clinicopathological features such as tumor burden, CA15-3 levels and the ER, PR, and HER2 status of the patients. ROC curve analysis showed that RAI14 improves the diagnostic performance for CA15-3(AUCRAI14 = 0.934 vs. AUCCA15-3 = 0.836), especially embodied in early-stage breast cancer diagnosis and patients with CA15-3 negativity. Furthermore, RAI14 behaves well in reproducing treatment response which was consistent with clinical Imaging assessment. Conclusions Recent studies showed that RAI14 has a complementary effect to CA15-3 and a test combining the two parameters can improve the detection rate of early triple-negative breast cancer. At the same time, RAI14 plays a more important role in chemotherapy monitoring than CA15-3 as the change in its concentration is in line with the tumor volume variation. Taken together, RAI14 is a reliable novel marker in the early diagnosis and chemotherapy monitoring of triple-negative breast cancer.

Seroconversion in COVID-19 Infection and Comparison of Antibody Responses in Symptomatic Versus Asymptomatic Individuals

Coronavirus disease (COVID-19) is an infectious disease caused by a newly discovered coronavirus. Following infection, antibodies are formed against the spike (S) and nucleocapsid (N) proteins, which are the primary viral antigens of SARS-CoV-2. This study aims to determine the antibody response three weeks post-infection and its persistence. To study antibody responses in COVID-19-positive individuals and to compare the degree of antibody response in symptomatic and asymptomatic individuals. The persistence of the antibody response was also assessed. Adult patients (> 15 years of age) who were diagnosed as COVID-19-positive by RT-PCR, three weeks after swab positivity were tested for total antibody levels against COVID-19 antigens by electrochemiluminescence assay. Out of 226 individuals, 129 were symptomatic and 97 were asymptomatic. Among the 129 symptomatic individuals, 74 exhibited an antibody response, whereas in the asymptomatic individuals, only 10 exhibited an antibody response. The antibody response was found to be significant in symptomatic individuals compared to that in asymptomatic individuals (p < 0.05). All follow-up individuals were seropositive at the end of both 6 and 8 months. Antibodies against SARS-CoV-2 persist for 8 months following infection. Despite the waning of antibodies against the nucleocapsid antigen, there was no complete disappearance of antibodies.

P649 Does serum triiodothyronine-to-thyroxine (T3/T4) ratio predict therapeutic outcome to anti-TNF therapies in biologic-naïve patients with active luminal Crohn’s disease?

Abstract Background Lower serum free triiodothyronine-to-thyroxine (fT3/fT4) ratio has been linked to non-response to treatment in a range of diseases, including in biologic-treated patients with IBD. We sought to assess whether baseline serum fT3/fT4 ratio predicted primary non-response (PNR) and non-remission to infliximab and adalimumab in patients with Crohn’s disease. Methods We included 997 adult participants from the Personalised Anti-TNF Therapy in Crohn’s Disease study (PANTS). Thyroid function tests, using the Roche Elecsys TSH immunoassay and T3 and T4 electrochemiluminescence assays, were measured on stored baseline samples (prior to biologic treatment). PNR, assessed at week 14, was defined as treatment failure (including IBD-related surgery), ongoing corticosteroid use, or both CRP failing to fall to ≤3 mg/L, or by 50% from baseline, and HBI failing to fall to ≤4, or by 3 points. Non-remission, assessed at week 54, was defined as either CRP of > 3mg/L or HBI of >4 points, ongoing corticosteroid therapy, or exit for treatment failure. Results Serum fT3, fT4 and TSH concentrations were similar in infliximab (n=549) and adalimumab treated (n=448) patients. Baseline median [IQR] fT3/fT4 ratios were lower in women than men (0.30 [0.27 - 0.34] vs 0.32 [0.28 - 0.36], p<0.001), in patients with more severe inflammatory disease, and in patients receiving corticosteroids (0.28 [0.25 - 0.33] vs 0.32 [0.29 - 0.36], p<0.001). Multivariable logistic regression analysis demonstrated that fT3/fT4 ratio was independently associated with PNR at week 14 (OR 0.51, 95% CI 0.31 – 0.85, p = 0.009), however when stratified by drug and adjusted for variables known to be associated with PNR, low fT3/fT4 ratio remained associated with PNR for adalimumab, but not infliximab. After excluding patients treated with corticosteroids at baseline, there was no difference in fT3/fT4 ratio in those who experienced PNR compared to those who did not (PNR: [128/630] 0.31 [0.28 – 0.35] vs no PNR: [502/630] 0.32 [0.29 – 0.36], p = 0.095). The optimal threshold to determine PNR was 0.31 (AUC 0.57 [95% CI 0.54 - 0.61] sensitivity 0.62 [95% CI 0.41 - 0.74], specificity 0.53 [95% CI 0.42 - 0.73]). No association was seen for baseline fT3/fT4 ratio and non-remission or changes in faecal calprotectin concentrations at week 54. Conclusion Lower baseline serum fT3/fT4 ratio was independently associated with female sex, higher inflammatory burden at baseline, and baseline corticosteroid use, and predicted PNR to anti-TNF therapy at week 14, but not non-remission or change in faecal calprotectin concentrations at week 54. Overall, however, the diagnostic accuracy of baseline fT3/fT4 ratio to predict PNR to anti-TNF treatment was modest, limiting its clinical utility.

Electrochemiluminescence Amplification in Bead-Based Assays Induced by a Freely Diffusing Iridium(III) Complex.

Heterogeneous electrochemiluminescence (ECL) assays employing tri-n-propylamine as a co-reactant and a tris(2,2'-bipyridine)ruthenium(II) ([Ru(bpy)3]2+) derivative as an emissive label are integral to the majority of academic and commercial applications of ECL sensing. This model system is an active research area and constitutes the basis of successfully commercialized bead-based ECL immunoassays. Herein, we propose a novel approach to the enhancement of such conventional ECL assays via the incorporation of a second metal coordination complex, [Ir(sppy)3]3- (where sppy = 5'-sulfo-2-phenylpyridinato-C2,N), to the experimental system. By employing ECL microscopy, we are able to map the spatial distribution of ECL emission at the surface of the bead, from [Ru(bpy)3]2+ labels, and solution-phase emission, from [Ir(sppy)3]3-. The developed [Ir(sppy)3]3--mediated enhancement approach elicited a significant improvement (70.9-fold at 0.9 V and 2.9-fold at 1.2 V vs Ag/AgCl) of the ECL signal from [Ru(bpy)3]2+ labels immobilized on the surface of a polystyrene bead. This dramatic enhancement in ECL signal, particularly at low oxidation potentials, has important implications for the improvement of existing heterogeneous ECL assays and ECL-based microscopy, by amplifying the signal, opening new bioanalytical detection schemes, and reducing both electrode surface passivation and deleterious side reactions.

Study of thyroid dysfunction in people living with HIV in Nepalese population undergoing antiretroviral therapy: a cross-sectional study.

Thyroid dysfunction is one of the most common endocrine disorders in people living with HIV (PLHIV). The abnormality in thyroid function has been linked with the adverse effects of prolonged antiretroviral therapy (ART) in PLHIV, but its prevalence remains obscure. The present study aimed to determine the prevalence of impaired thyroid function and its relationship to ART duration in Nepalese people living with HIV. This cross-sectional clinical laboratory based study was conducted at SRL Diagnostics Nepal, Pvt. Ltd. from October 2021 to May 2022. Two hundred and three HIV-seropositive patients enrolled at Tribhuvan University Teaching Hospital (TUTH) in Kathmandu, Nepal were examined for their thyroid function test (TFT) by analyzing the serum T3, T4, and TSH concentrations using a fully automated COBAS e411 analyzer (Roche Diagnostics, USA) based on the electrochemiluminescence assay (ECLIA). Out of 203 PLHIV, 22 (10.83%) had a thyroid disorder, with subclinical hypothyroidism (n = 16, 72.73%) being the most common, followed by subclinical hyperthyroidism (n = 3, 13.63%). Thyroid dysfunction had no significant correlation with HIV/ART duration (p = 0.304) and sex (p = 0.419), whereas, the risk of thyroid dysfunction was induced with the rise in the age of the PLHIV (p = 0.002, ϕ = 0.274). There were no significant differences in the mean serum T3, T4 and TSH values among different sexes and the HIV/ART duration, however a significant difference in the mean values of TSH (F (3, 199) = 3.231, p = 0.023) and T3 (F (3, 199) = 4.587, p = 0.004) among the different age-groups were shown. The mean T3 values also indicated a gradual decrease with increasing age. The study revealed subclinical hypothyroidism as the prevailing thyroid disorder associated with PLHIV. The risk of thyroid dysfunction in PLHIV was neither gender specific nor being attributed by the ART duration in Nepalese population; however, elderly PLHIV were highly susceptible to the risk of thyroid disorder.

Comparison of the prevalence of SARS-CoV-2 nucleoprotein antibodies in healthcare workers and an unselected adult and paediatric all-comer patient population: insights from a longitudinal study of healthcare workers and concurrent serial cross-sectional studies of patients at an academic medical centre in Austria

ObjectivesThis study aimed to estimate and compare the prevalence of the virus-specific antibodies against the SARS-CoV-2 nucleoprotein antigen (anti-SARS-CoV-2 N) in healthcare workers and an all-comer paediatric and adult patient...

A method for detection of anti-drug antibodies to a biotherapeutic (CSL112) with endogenous counterpart (apolipoprotein A-I) using a novel sample pre-treatment electrochemiluminescence assay

BackgroundThere are numerous challenges encountered during clinical testing for an immunogenic response to a plasma-derived therapeutic. Distinguishing between antibodies that recognize endogenous versus therapeutic protein can be particularly difficult. This study focused on CSL112 (human plasma-derived apolipoprotein A-I; apoA-I), which is in clinical development for reducing the risk of recurrent major adverse cardiovascular events following acute myocardial infarction. AimTo develop and validate a high-throughput, highly sensitive and specific assay to detect antibodies to CSL112 that can be used for immunogenicity assessment in large clinical studies. ResultsWe developed a clinical anti-drug antibody (ADA) assay utilizing an immunoglobulin purification step that improved specificity and drug tolerance, demonstrating that measurement of pre-existing or treatment emergent ADAs was highly dependent on assay format. The Sample Pre-treatment Electrochemiluminescence (ECL; SPECL) assay incorporates a protein A extraction of serum samples before a bridging assay is performed on an ECL platform. The assay is qualitative, sensitive (lower limit of quantification <39 ng/mL) and has a drug tolerance of 0.5 mg/mL in line with U.S. Food and Drug Administration requirements for clinical immunogenicity assays for therapeutic proteins. Importantly, the SPECL assay demonstrated the absence of antibodies to both apoA-I and CSL112 both prior to drug exposure and after repeated dosing across multiple trials (n = 970 subjects). ConclusionThe SPECL method has been validated and applied to support the CSL112 preclinical and clinical development program and has broader application to similar protein therapeutics. Attributes of the methodology include high drug tolerance, high sensitivity, selectivity, and precision. This format is amenable to automation providing the high throughput and reduced variability required to support large scale clinical studies that span extended time periods.

Performance Enhancement of Electrochemiluminescence with the Immunosensor Controlled Using Magnetized Masks for the Determination of Epithelial Cancer Biomarker EpCAM.

The performance of an electrochemiluminescence (ECL) immunosensor was improved with a particle gradient. SiO2-coated magnetic beads were adopted as nanocarriers for gradient manipulation and immobilized with the primary antibody. Cadmium telluride quantum dots were coated with a layer of protein G for conjugation and orientation of the secondary antibody as signal labels. ECL immunosensor gradients on the electrode were formed by magnetolithography (ML) with magnetized nickel masks of column and stripe arrays. The immunosensor generally aggregated as an island on the substrate, leading to a decrease of efficiency in the characteristic signals. Stripe arrays of magnetized nickel were designed to generate cylindrical magnetic flux on the substrate to improve the particle manipulation with the gradient. Various gradients of the sandwich-structured immunosensor substantially affected the electrochemical performance. Compared to the gradient-free immunosensor, the gradient of the immunosensor generated by ML using a 3 μm stripe array mask enhanced the ECL intensity ∼2.2 times. The results of quantification of epithelial cell adhesion molecules (EpCAM) with the gradient immunosensor showed a broad linear range (15-420 pg mL-1), a low limit of detection (5.5 pg mL-1), and high reliability for EpCAM-spiked serum samples, indicating that the immunosensor gradient substantially enhances the performance of the ECL assay.

1959. Lower B-Cell Responses Rather Than Circulating Antibody Titres Are Associated With SARS-CoV-2 Infection Post Third Dose COVID-19 Vaccination

Abstract Background Which components of the immune response to SARS-CoV-2 vaccination best protect against subsequent infection remains unclear. We explored SARS-CoV-2 specific antibody and B-cell responses post 3rd dose vaccine and their relationship to subsequent SARS-CoV-2 infection. Methods In a multicentre prospective cohort, adult subjects provided samples before and 14 days (d14) post 3rd dose vaccine with Pfizer-BioNTech 162b2. At 18-22 weeks post vaccine, subjects self-reported SARS-CoV-2 infection (confirmed by PCR or antigen test). We used electrochemiluminescence assays to quantify antibodies to SARS-CoV-2 spike subunit 1 (S1), subunit 2 (S2) and receptor-binding domain (RBD) in plasma (reported in WHO IU/mL). In a subset of subjects, we assessed SARS-CoV-2 specific differentiated B-cell (plasma cell) and memory B-cell responses from peripheral blood mononuclear cells. Unstimulated plasma cells, and memory B cells stimulated with R848 and IL2, were seeded on plates coated with RBD or full Spike antigen and antigen-specific responses measured by ELISpot (Mabtech ELISpot, Sweden). We compared between group differences by Wilcoxon signed rank or Mann–Whitney tests. Data are median [IQR] unless specified. Results Of 133 subjects (age 43 [32-50], 81.2% female (table 1), 77 subjects in the B-cell subgroup (table 2)), 47 (35.3%) reported SARS-CoV-2 infection post 3rd vaccine. Antibody titres, plasma cell and memory B-cell responses all increased significantly at d14 post 3rd vaccine (Table 1 &amp; 2, all P&amp;lt; 0.001). Although d14 antibody titres did not differ in those with and without subsequent infection (table 1), those reporting subsequent infection had significantly lower d14 RBD-specific plasma cells and a lower proportion of RBD-specific memory B-cells (Figure 1a-b, both P&amp;lt; 0.05). Similar results were observed with full-spike-specific memory B-cell responses (Figure 1d). The differences persisted when the non-infected group was restricted only to those reporting a confirmed close contact (n=26). Conclusion Infection following 3rd dose vaccine is associated with lower d14 circulating and memory B cell responses, but not antibody titres, suggesting B-cell responses better predict protection against subsequent SARS-CoV-2 infection. Disclosures All Authors: No reported disclosures.

Plasma Interleukin-6 Predicts Clinical Decline After Completion of Dexamethasone Therapy in Severe COVID-19.

Prospective observational cohort. ICUs in three University of Washington affiliated hospitals between July 2020 and April 2021. Patients admitted to an ICU with COVID-19 who completed a course of dexamethasone. We identified 65 adult patients with severe COVID-19 who completed a 10-day course of dexamethasone, of whom 60 had plasma samples collected within 3 days of dexamethasone completion. We measured IL-6 with a clinical-grade electrochemiluminescent assay and a larger panel of inflammatory biomarkers (IL-8, Monocyte Chemoattractant Protein-1, Monocyte Inflammatory Protein-1 alpha, interferon gamma, C-X-C Motif Chemokine Ligand 10, WBC, bicarbonate) with a research immunoassay. We defined clinical decline by the occurrence of incident severe kidney injury, incident or escalating shock or fever, worsening hypoxemia, or death within 5 days of completion of dexamethasone. We estimated risk for clinical decline by standardized log2 transformed biomarker concentration using multivariable logistic regression. Clinical decline post-dexamethasone was common, occurring in 49% of patients (n = 32). Among all biomarkers, IL-6 levels were most strongly associated with clinical decline. After adjustment for age, sex, and study site, the odds of post-dexamethasone clinical decline were 7.33 times higher per one sd increase in log2 transformed IL-6 concentrations (adjusted odds ratio, 7.33; CI, 2.62-20.47; p < 0.001). The discriminatory power of IL-6 for clinical decline was high (cross-validated mean area under the receiver operating characteristic curve, 0.90; 95% CI, 0.79-0.95). Clinical decline after completion of dexamethasone for severe COVID-19 is common. IL-6 concentrations obtained prior to completion of dexamethasone may have utility in identifying those at highest risk for subsequent worsening. If validated, future work might test whether plasma IL-6 could be used as a tool for a personalized approach to duration of dexamethasone treatment in severe COVID-19.

An electrochemiluminescence assay for quantification of Denileukin Diftitox and its anti-drug antibodies in rat serum

Denileukin Diftitox (DD), comprising fragments of diphtheria toxin (DT) and interleukin-2 (IL2), was developed for the treatment of lymphoma and has been approved for marketing in Japan. Toxicological evaluation including pharmacokinetics and immunogenicity in preclinical animals is important for drug development and thus the assays of DD and anti-drug antibody (ADA) were developed by electrochemiluminescence (ECL) detection. For the DD assay, ruthenium-labeled anti-DT Ab and biotinylated anti-IL2 Ab were mixed with serum samples and the mixture was captured by streptavidin-coated wells for ECL detection. For the ADA assay, signals of immuno-complex of biotinylated DD, ruthenium-labeled DD, and ADA, bound to streptavidin plate were determined. DD was quantifiable from 10 ng/mL. Accuracy and precision of quality control samples were within ±20% and 20%, respectively, and stability of DD in rat serum was successfully assessed. Precision of positive control samples of ADA was within the acceptance criteria and cut point values for ADA detection in the screening and confirmatory assay were determined by statistical analysis. Drug-induced ADA was detected by screening assay followed by confirmatory assay. The developed method was successfully applied to assess pharmacokinetics and immunogenicity to support toxicity studies in rats.

Association of biomarkers and risk scores with subclinical left ventricular dysfunction in patients with type 2 diabetes mellitus.

Subclinical LV dysfunction (LVD) identifies heart failure (HF) risk in type 2 diabetes mellitus (T2DM). We sought the extent to which clinical scores (ARIC-HF, WATCH-DM), natriuretic peptides (NTpBNP) and troponin (hs-TnT) were associated with subclinical LV dysfunction (LVD). These associations could inform the ability of these tests to identify which patients should undergo echocardiography. Participants with T2DM were prospectively recruited from three community-based populations. ARIC-HF risk at 4years and WATCH-DM scores were calculated from clinical data. NTpBNP and hs-TnT were measured using an electro-chemiluminescence assay. All underwent a comprehensive echocardiogram. We calculated the sensitivity and specificity of clinical scores and biomarkers to identify abnormal global longitudinal strain (GLS ≥ -16%)), diastolic function (E/e' ≥ 14 or e' < 8cm/s), left atrial volume index (LAV > 34ml/m2) and LV hypertrophy (LV mass index > 88g/m2 (F) > 102g/m2(M)). Of 804 participants (median age 69years [inter-quartile range (IQR) 65-73], 36% female), clinical scores suggested significant HF risk (median ARIC-HF 8% [IQR 4-12]; WATCH-DM 10 points [IQR 8-12]), and the median NTpBNP was 50pg/mL [IQR 25-101] and hs-TnT 9.6pg/mL [IQR 6.8-13.6]. Abnormal GLS was present in 126 (17%), elevated E/e' in 114 (15%), impaired e' in 629 (78%), increased LAV in 351 (44%) and LV hypertrophy in 113 (14%). After adjustments for age, body-mass index, and renal function, each standard deviation increase in NTpBNP was associated with a GLS increase of 0.32 (p < 0.001) and hs-TnT increase by 0.26 (p < 0.001). Similar trends were observed with ARIC-HF (standardised β = 0.22, p < 0.001) and WATCH-DM (standardised β = 0.22, p < 0.001) in univariable analyses. However, none of the risk assessment tools provided satisfactory discrimination for abnormal GLS (AUC 63%), diastolic indices (e' AUC 54-61%) or LV mass (AUC 59-67%). At a sensitivity of 90%, there was an unacceptably low (< 50%) specificity. Although risk assessment based on clinical scores or biomarkers would be desirable to stratify HF risk in people with T2DM, they show a weak relationship with subclinical LVD.

Combined Detection of Islet Autoantibodies for Clinical Diagnosis of Type 1 Diabetes in the Low-Prevalence Population.

Single positive islet autoantibodies (IAbs), sometimes detected in healthy individuals and patients with low-risk of developing type 1 diabetes (T1D), are considered to be irrelevant to the development of diabetes, making it difficult to diagnose and classify adult-onset diabetes. To determine the significance and clinical value of IAbs in T1D diagnosis in the low-prevalence population, and to explore whether an electrochemiluminescence IAb detection assay can improve the clinical utility of IAbs in the immunodiagnosis of T1D in the low-prevalence population. A total of 633 newly diagnosed patients with adult-onset diabetes (≥18 years old) were divided into 2 groups according to their clinical phenotypes: 575 patients with age at diagnosis ≥35 years and body mass index (BMI) ≥ 24 kg/m2 were considered a low-prevalence population (population with a low prevalence of T1D) and the other 58 patients were considered a high-prevalence population. All the samples from 633 participants were tested with IAbs using standard radiobinding assays (RBAs) and electrochemiluminescence (ECL) assays in parallel. Compared with the high-prevalence population, fewer positive IAbs (94/575, 16.3% vs 28/58, 48.3%) were detected in the low-prevalence population, and more of whom (69/94, 73.4% vs 9/28, 32.2%) were positive for a single IAb, with glutamate decarboxylase antibodies being the most prevalent single IAb. Single-IAb detection in the low-prevalence population did not always suggest the T1D phenotype. Combined detection of IAbs by RBA and ECL assay had a significant clinical utility to distinguish autoimmune diabetes in the low-prevalence population with low BMI, poor β-cell function at the diagnosis, and an accelerated decline in β-cell function during the follow-up. Combined autoantibody detection by RBA and ECL assays improved differentiating autoimmune from nonautoimmune diabetes in the low-prevalence population.

Brain insulin signaling and neurodegeneration: IRS‐1 isolated from neuronal enriched extracellular vesicles associates with frontal lobe gray matter volume in cognitively unimpaired adults

AbstractBackgroundBrain insulin signaling, as measured by insulin signaling proteins in neuronal enriched extracellular vesicles (nEVs), has previously been associated with gray matter (GM) volume in the temporal lobe of nondemented older adults and in multiple brain regions in those with Alzheimer’s clinical syndrome (Walker et al, 2021; Mullins et al, 2017). We sought to extend these findings by performing a voxel‐wise analysis to test the relationship between whole‐brain GM volume and nEV tyrosine phosphorylated IRS‐1 (pY‐IRS‐1) in a cognitively unimpaired sample enriched for AD risk.MethodCognitively‐unimpaired adults (n=47) from the Wisconsin Registry for Alzheimer’s Prevention underwent MRI and blood collection (Table 1). nEVs were isolated from plasma samples by immunoprecipitation targeting neuronal marker L1CAM. pY‐IRS‐1 was measured in nEVs using an electrochemiluminescence assay (Meso Scale Discovery, Rockville, Maryland) (Mustapic et al, 2017). T1‐weighted images were analyzed using the FMRIB Software Library (FSL), where images were first normalized to MNI space and segmented into WM, GM, and CSF using FSL’s FLIRT, FNIRT, and FAST tools and resulting GM maps were smoothed with a Gaussian kernel (sigma = 3.5mm). General linear models and non‐parametric testing (FSL randomise) were used to assess voxelwise associations between nEV pY‐IRS‐1 concentration and GM volume, while controlling for sex and age effects. Significant associations between GM volume and nEV pY‐IRS‐1 were defined as p &lt; 0.01, uncorrected.ResultWe observed lateralized positive associations between nEV pY‐IRS‐1 and GM volume in the right frontal lobe (Figures 1 and 2). After correcting for multiple comparisons, we observed no significant relationships between nEV pY‐IRS‐1 concentration and GM volume.ConclusionPrevious studies indicate that lower nEV pY‐IRS‐1 is associated with lower GM volume in regions such as the temporal and parietal lobes. Here, we determined that lower nEV pIRS‐1 concentrations were associated with lower GM volume laterally in the right frontal lobe of healthy middle‐aged and older adults. Future studies are needed to determine the mechanism by which disrupted insulin signaling in the brain may cause GM loss in these regions.