A Flare Risk Index Informed by Select Immune Mediators in Systemic Lupus Erythematosus

OBJECTIVE

Systemic lupus erythematosus (SLE) is marked by immune dysregulation linked to varied clinical disease activity. Using a unique longitudinal cohort of SLE patients, this study sought to identify optimal immune mediators informing an empirically refined flare risk index (FRI) reflecting altered immunity prior to clinical disease flare.

METHODS

Thirty-seven SLE-associated plasma mediators were evaluated by microfluidic immunoassay in 46 samples obtained in SLE patients with an imminent clinical disease flare (preflare) and 53 samples obtained in SLE patients without a flare over a corresponding period (pre-nonflare). SLE patients were selected from a unique longitudinal cohort of 106 patients with classified SLE (meeting the American College of Rheumatology 1997 revised criteria for SLE or the Systemic Lupus International Collaborating Clinics 2012 revised criteria for SLE). Autoantibody specificities, hybrid SLE Disease Activity Index (hSLEDAI) scores, clinical features, and medication usage were also compared at preflare (mean ± SD 111 ± 47 days prior to flare) versus pre-nonflare (99 ± 21 days prior to nonflare) time points. Variable importance was determined by random forest analysis with logistic regression subsequently applied to determine the optimal number and type of analytes informing a refined FRI.

RESULTS

Preflare versus pre-nonflare differences were not associated with demographics, autoantibody specificities, hSLEDAI scores, clinical features, nor medication usage. Forward selection and backward elimination of mediators ranked by variable importance resulted in 17 plasma mediator candidates differentiating preflare from pre-nonflare visits. A final combination of 11 mediators best informed a newly refined FRI, which achieved a maximum sensitivity of 97% and maximum specificity of 98% after applying decision curve analysis to define low, medium, and high FRI scores.

CONCLUSION

We verified altered immune mediators associated with imminent disease flare, and a subset of these mediators improved the FRI to identify SLE patients at risk of imminent flare. This molecularly informed, proactive management approach could be critical in prospective clinical trials and the clinical management of lupus.

Neurofilament-light chain quantification by Simoa and Ella in plasma from patients with dementia: a comparative study

Neurofilament light chains (NfL) are neuron-specific cytoskeletal proteins whose plasmatic concentrations have been explored as a clinically useful marker in several types of dementia. Plasma concentrations of NfL are extremely low, and just two assays are commercially available for their study: one based on the SiMoA technology and one based on Ella. We thus studied plasma levels of NfL with both platforms to check the correlation between them and to assess their potential in the diagnosis of neurodegeneration. Plasma NfL levels were measured on 50 subjects: 18 healthy controls, 20 Alzheimer's disease, and 12 frontotemporal dementia patients. Ella returned plasmatic NfL levels significantly higher than SiMoA, however the results were strongly correlated (r = 0.94), and a proportional coefficient of 0.58 between the two assays was calculated. Both assays detected higher plasma NfL levels in patients with dementia than in the control group (p < 0.0001) and allowed their discrimination with excellent diagnostic performance (AUC > 0.95). No difference was found between Alzheimer's and Frontotemporal dementia either using SiMoA or Ella. In conclusion, both the analytical platforms resulted effective in analysing plasma levels of NfL. However, the correct interpretation of results requires the precise knowledge of the assay used.

State-of-the-art and emerging trends in analytical approaches to pharmaceutical-product commercialization

The biopharmaceutical landscape continues to evolve rapidly, and associated modality complexity and the need to improve molecular understanding require concomitant advances in analytical approaches used to characterize and release the product. The Product Quality Attribute Assessment (PQAA) and Quality Target Product Profile (QTPP) frameworks help catalog and translate molecular understanding to process and product-design targets, thereby enabling reliable manufacturing of high-quality product. The analytical target profile forms the basis of identifying best-fit analytical methods for attribute measurement and continues to be successfully used to develop robust analytical methods for detailed product characterization as well as release and stability testing. Despite maturity across multiple testing platforms, advances continue to be made, several with the potential to alter testing paradigms. There is an increasing role for mass spectrometry beyond product characterization and into routine release testing as seen by the progress in multi-attribute methods and technologies, applications to aggregate measurement, the development of capillary zone electrophoresis (CZE) coupled with mass spectrometry (MS) and capillary isoelectric focusing (CIEF) with MS for measurement of glycans and charged species, respectively, and increased application to host cell protein measurement. Multitarget engaging multispecific modalities will drive advances in bioassay platforms and recent advances both in 1- and 2-D NMR approaches could make it the method of choice for characterizing higher-order structures. Additionally, rigorous understanding of raw material and container attributes is necessary to complement product understanding, and these collectively can enable robust supply of high-quality product to patients.

Bioanalytical Challenges in Support of Complex Modalities of Antibody-Based Therapeutics

Antibody-based therapeutic classes are evolving from monoclonal antibodies to antibody derivatives with complex structures to achieve advanced therapeutic effect. These antibody derivatives may contain multiple functional domains and are often vulnerable to in vivo biotransformation. Understanding the pharmacokinetics of these antibody derivatives requires a sophisticated bioanalytical approach to carefully characterize the whole drug and each functional domain with respect to quantity, functionality enabled by biotransformation, and corresponding immune responses. Ligand binding assays and liquid chromatography-mass spectrometry assays are predominantly used in bioanalytical support of monoclonal antibodies and are continuously used for antibody derivatives such as antibody drug conjugate and bispecific antibodies. However, they become increasingly cumbersome in coping with increased complexity of drug modality and associated biotransformation. In this mini-review, we examined the current pharmacokinetic assays in the literature for antibody drug conjugate and bispecific antibodies, and presented our view of promising bioanalytical technologies to address the distinct bioanalytical needs of complex modalities.

Improving Chinese hamster ovary host cell protein ELISA using Ella®: an automated microfluidic platform

Chinese hamster ovary (CHO) cells are a mammalian cell line used in the production of therapeutic proteins. Host cell proteins (HCPs) are process-related impurities that are derived from the host cell expression system. During biopharmaceutical drug development, removal of HCPs is required. Enzyme-linked immunosorbent assay (ELISA) is a common technique to quantitate HCPs, but is a labor-intensive process that takes up to 7 h. Ella^® is an automated instrument that utilizes microfluidics and glass nanoreactors to quantitate HCPs in 75 min using similar ELISA reagents. The antibodies and antigens are captured on three distinct glass nanoreactors, resulting in sensitive reproducible data. Our results indicate that Ella quantitates CHO HCPs with precision, accuracy, sensitivity and trends comparable with our traditional CHO HCP ELISA.

Taking advantage of a high-throughput flow cytometer for the implementation of an ADCC assay for regulatory compliance

Technological advances allowed the development of high-throughput instruments such as IntelliCyt iQue Screener PLUS®. Here, we took advantage of this technology to transfer a previously validated cytotoxicity assay. The evaluated parameters were cell permeability, caspase activation and phosphatidyl serine exposure. The assay was accurate (r2 = 0.90), precise (%CV ≤ 18.90) and specific. These results showed that this technology is suitable to be used in control quality environments. In addition, the automation provided a faster acquisition and analysis of data with precise and accurate results. This application could be implemented to evaluate another in vitro mechanism of action of different biotherapeutics.

Customizable Multiplex Antibody Array Immunoassays with Attomolar Sensitivities

We have developed a customizable contact printed multiplex immunoassay capable of simultaneously measuring up to five analytes with attomolar sensitivities. This enzyme-linked immunosorbent assay (ELISA) was based on spotting different antibodies in a circular pattern at the bottom of a microtiter plate well. Unlike traditional antibody printing for ELISA that prints a capture antibody specific to a target of interest, in this ELISA we printed unique "anchor" antibodies at the well surface, each having a high affinity for a specific peptide target. By coupling each peptide to a unique assay capture antibody, this array of anchor antibodies enabled a customizable contact printed multiplex immunoassay workflow. As a proof of concept, we developed a 5-plex assay measuring interleukin 5 (IL-5), interleukin 6 (IL-6), interleukin 10 (IL-10), interleukin 22 (IL-22), and tumor necrosis factor alpha (TNF-α). Measurements of these five analytes in serum and plasma correlated well between the method utilizing the anchor antibodies and peptides and the traditional capture antibody printing approach, with r² values of 0.99, 0.93, 0.99, 0.96, and 0.75 for IL-5, IL-6, IL-10, IL-22, and TNFα, respectively. This approach makes customizable multiplex ultrasensitive ELISA available to laboratories without access to the precision printing instrumentation and will be useful for antibody screening, custom assay development, biomarker detection, and protein profiling for diagnostic applications.

Sensitivity and binding kinetics of an ultra-sensitive chemiluminescent enzyme-linked immunosorbent assay at arrays of antibodies

We have characterized the sensitivity and kinetics of a multiplex immunoassay system based on detection of chemiluminescence (CL) at arrays of antibodies. This enzyme-linked immunosorbent assay (ELISA) was based on the spotting of different antibodies in a circular pattern at the bottom of a well of a microtiter plate. Sandwich immunocomplexes within each spot were labeled with horse radish peroxidase, and CL was generated locally to each spot in the array from turnover of luminol substrate. CL from the arrays across the plate was collected in single images; long exposure times were used to maximize sensitivity, and short exposure times were used to extend the dynamic range at higher signals. Image analysis was used to determine the intensity of light from each spot in the array, and intensity was converted to concentration of protein via comparison to a calibration curve. To determine the intrinsic sensitivity of the CL ELISA array, streptavidin horseradish peroxidase (SA-HRP) was captured on an array spotted with biotinylated detection antibodies. The limit of detection (LOD) of SA-HRP was 105 aM, or 3200 enzymes per 50 μL. A single-plex assay for prostate specific antigen (PSA) was developed that had an LOD of 79 aM when the microtiter plate was shaken orbitally, comparable to the most sensitive immunoassays reported to date. Normalization of CL signals in the PSA assay to signal per molecule of SA-HRP showed that the efficiency of the shaken assay was ~40%. When the plates were not shaken, the efficiency was ~4.5%, i.e., ~9-fold lower than when shaken. To better understand the theoretical basis of the sensitivity of these assays, we developed COMSOL numerical models of the binding kinetics at the array for plates that were shaken orbitally and those not shaken. Experimental data from the orbitally shaken PSA assay were best modeled by inertial mixing in a three-layer system that included a 8-μm-thick concentration boundary layer. Experimental data from the unshaken PSA assay were well modeled by diffusion-limited kinetics. A single-plex assay for IL-10 was developed with an LOD of 69 aM or 1.5 fg/mL, and used to measure this cytokine in plasma and serum of 10 healthy individuals. A 5-plex assay for IL-5, IL-6, IL-10, IL-22, and TNF-α was developed with LODs of 56 aM, 237 aM, 69 aM, 88 aM, and 373 aM, respectively. The assay was used to measure these 5 cytokines in the plasma and serum of the same individuals. The correlation in concentration of IL-10 measured in single-plex and multiplex assays was good (r2 = 0.89; bias = 14.5%). The factors that result in the high sensitivity of CL ELISA arrays-mostly high signal to noise ratio of extended chemiluminescent imaging-are discussed. This multiplex CL ELISA could be used for sensitive profiling of multiple proteins for in vitro diagnostics and biomarker detection in the development of therapeutics.

Development and evaluation of an ultrasensitive free VEGF-A immunoassay for analysis of human aqueous humor

Aim: Novel bifunctional VEGF-A neutralizing therapies are being developed for the treatment of retinal vascular diseases such as age-related macular degeneration and diabetic retinopathy. In developing new therapeutic drugs, only small aqueous humor sample volumes are available for analyzing several parameters. Highly sensitive detection methods must be applied in analyzing VEGF-A levels in ocular fluids in order to demonstrate VEGF-A suppression following drug administration. Experimental: A highly sensitive immunoassay for VEGF-A was developed on the single molecule array (Simoa) platform, and validated before being used for the analysis of clinical aqueous humor samples from patients treated with anti-VEGF-A therapeutics. Results: This highly sensitive immunoassay allows the detection of baseline VEGF-A levels and suppression effects after drug administration, even in sample volumes as low as 12 μl. Conclusion: The Simoa VEGF-A assay is a valuable tool for the reliable monitoring of VEGF-A suppression after intravitreal administration of anti-VEGF-A drugs.

Use of Ella® to facilitate drug quantification and antidrug antibody detection in preclinical studies

Aim: To explore the usability of the Ella® platform for preclinical analysis of therapeutic antibodies and antidrug antibodies (ADA). Experimental: Two well-established ELISAs for the measurement of human IgG and ADA were transferred to the Ella platform. ELISA and the Ella platform were compared using assay qualification data and results of preclinical sample analysis. Results: The performance and results of both assays on the Ella platform were comparable to those of ELISA. The Ella platform had several advantages, including time efficiency, low sample consumption and a high degree of automation. ADA were assessed on Ella for the first time. Conclusion: The Ella platform is a promising tool for the analysis of preclinical samples.