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Purity is a critical quality attribute (CQA) that must be monitored during AAV manufacturing. Impurities in protein products can be dangerous and impact efficacy. For example, protein impurities in final drug products may lead to undesirable immune responses in patients, so detecting total protein is critical for revealing impurities in preparative protein production. Traditional methods for total protein detection rely on SDS-PAGE with dyes like Coomassie Blue, or more sensitive stains like SYPRO Ruby and silver stain. However, SDS-PAGE requires large sample volumes, a lot of hands-on time, and it is poorly reproducible. Also, the use of staining dyes often comes with a lot of waste and can require specialized imaging equipment to which not every researcher has access.
Here, we present a new workflow that enables total protein detection of AAVs on the Simple Western capillary electrophoresis-based immunoassay platform with a sensitivity that exceeds SYPRO Ruby. While SYPRO Ruby requires at least 1 ng of protein for reliable detection, Simple Western can reliably detect as little as 150 pg. These findings should enable researchers who are currently using SDS-PAGE to monitor purity to apply the automated platform and sensitivity improvements enabled by this workflow to assess AAV purity using smaller AAV sample sizes.
During adeno-associated virus (AAV) manufacture, critical quality attributes must be monitored including the presence, identity, and purity of viral vector proteins. Traditionally, the identity and purity of these proteins is monitored by Western blot using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). However, SDS-PAGE is notoriously challenging and labor-intensive. Additionally, AAVs are limited in sample size as they are difficult to manufacture, and demand outstrips supply. Here, we have developed a method to monitor the purification of AAV2 using automated capillary electrophoresis followed by immunoassay and total protein detection directly in the capillary, eliminating the need for SDS-PAGE. AAV2 was purified from HEK293 cell lysate using affinity chromatography, and the steps of the purification process (load, flow-through, wash and elution) were monitored by the capillary-based immunoassay. VP1, VP2 and VP3 capsid proteins were resolved and identified either individually or simultaneously, depending on the AAV antibody used for detection, and the total protein assay monitored the presence of impurities. The sensitivity of this assay reduced sample size down to 3 µL of sample, corresponding to approximately 400 pg or 1x108 genomic copies loaded per well. We anticipate that this in-capillary immunoassay and total protein detection can replace traditional SDS-PAGE methods in AAV manufacturing workflows.
Protein phosphorylation is a reversible reaction that is integral in numerous signaling cascades. Characterization of signaling cascades has been largely detected by immunoblotting with phospho-specific antibodies, which may or may not have enough specificity or affinity. Currently, a separate lysate without any phosphatase inhibitors or a separate blot is needed to determine an antibody’s specificity. Here we describe a simple assay that leverages automation and quantitation with capillary electrophoresis-based immunoassay (CEIA) to assess the specificity of these antibodies with a single lysate preparation. In this study, three lysate models are used: K562 ± TNFα treatment, 50 ng/mL phorbol myristate acetate (PMA) differentiated THP-1 ± 1 μg/mL lipopolysaccharide (LPS) treatment, and cytotoxic T lymphocytes (CTL) ± 10 ng/mL PMA and 500 ng/mL ionomycin treatment. K562 cell lysates are commercially purchased whereas THP-1 lysates are generated in-house. For CTL cells, whole blood cells from a single donor are isolated and expanded with commercially available kits. Expanded CTL cells are then stimulated with PMA and ionomycin for 15 minutes. Untreated and treated lysate samples are separated and captured to the inner lumen of the capillary wall with UV activated crosslink chemistry. Cross-linked proteins are treated with lambda phosphatase for 1 hour followed by the immunoassay to investigate the specificity of antibodies against phosphorylated protein targets respective to each activated pathway using either chemiluminescent or fluorescent detection. Preliminary data suggest phospho-specific signal decreased >90% with no significant changes to the non-specific noise. The method described here eliminates the need for multiple lysate preparations or an additional blot to assess an antibody’s specificity to a phosphorylated protein target.
The tumor microenvironment (TME) is a complex mixture of cancerous and non-cancerous cells, including immune cells like T-cells, macrophages, and neutrophils. The TME plays a key role in tumorigenesis and metastasis, and it has recently been recognized that it can dramatically shape a response to therapy. Thus, there is a pressing need to accurately identify and quantify the variety of cell types in any given TME. However, studying the TME presents major challenges. For example, the heterogeneity of the environment requires sensitive and high-resolution techniques to parse subpopulations of different cell types. This challenge is compounded by the severely limited sample size that can be obtained from donor tissues. To address these challenges, we use an in-capillary immunoassay with small sample sizes (3 µL) to identify immune cells commonly found in the TME. We also leverage single-cell Western to uncover trends in population heterogeneity. Human peripheral blood mononuclear cells (PBMCs) were differentiated into dendritic cells (DCs) and regulatory T cells (Tregs), and natural killer (NK) cells were expanded from isolated NK cells. These samples were then analyzed by in-capillary immunoassay and single-cell Western. These analyses revealed the identification and characterization of cell types, at both the single-cell and population level, based on the differential expression of protein biomarkers. Specifically, in-capillary immunoassay analysis identified mature populations by CD209 for DCs, a CD56+/CD3- phenotype for NK cells, and CD25 and Foxp3 expression for Tregs. Analysis of single cells provided further detail within these populations, for example, we observed FoxP3low and FoxP3high subpopulations in Tregs, and an unexpectedly large (81%) CD56-/CD3- subpopulation in undifferentiated PBMCs, suggesting the presence of other cell subtypes. We anticipate that the small sample size, automation, single-cell resolution, and multiplexing ability of these assays collectively will enable a more efficient and deeper characterization of the TME not possible with traditional immunoassays like Western blot and flow cytometry.
Multi-omic approaches can combine protein, DNA, and RNA analyses to elucidate diagnostic biomarkers and pathways, advancing our understanding of complex diseases. These assays, however, require different technologies and platforms to resolve the distinct physico-chemistries of protein and DNA/RNA. In contrast, single-platform quantification of proteins and nucleic acid markers offers many potential benefits, including reduced sample requirements, decreased inter-assay variability, streamlined and less error-prone workflows, and integrated results reporting. Here we demonstrate expanded capabilities of an established protein analysis system (Simple Western, ProteinSimple®) to characterize nucleic acids, and show that this system can quantify oncogenic tyrosine kinases, immune checkpoint proteins, RNA translocations, and other mRNA transcripts associated with targeted or immune-based therapies for non-small cell lung cancer (NSCLC).
Multiple myeloma has been comprehensively analyzed using high-throughput genomic technologies. Although a large number of biomarkers have been described, most of them were not subsequently validated at the protein level. In fact, the unresolved difficulties in studying the proteome have made the quantification of messenger RNA (mRNA) an indirect measure of protein expression. However, many studies have shown that levels of mRNA cannot be used as surrogates for protein levels. The amount of myeloma cells obtained after purification of patient samples is usually very limited, which precludes the possibility of quantify protein levels using standard Western Blot analysis.
Alzheimer disease (AD) affects mainly people over the age of 65 years, suffering from different clinical symptoms such as progressive decline in memory, thinking, language, and learning capacity. The toxic role of beta amyloid peptide (Ab) has now shifted from insoluble Ab fibrils to smaller, soluble oligomeric Ab aggregates (AβO). Many evidences suggest that the neurodegenerative process would be due to the interaction of AβO with binding targets, activation of stress kinases, hyperphosphorylation of tau protein, caspase activation, loss of synapse, neuronal death, loss of cholinergic function, generation of reactive intermediates of oxygen (oxidative stress), or glutamate excitotoxicity. Urgent need for efficient new therapies is high, but could only be successful with an extensively comprehension of AβO degeneration process. In the present work, based on an in vitro primary cell culture treated with AβO preparation, we have carefully studied the cytopathological effects of AβO on neuronal death and then we have investigated the effect of 17-beta Estradiol (β-estr) on the degeneration process induced by AβO. Briefly we used rat cortical neurons (from E15). The cells were seeded in 96-well plates and intoxicated with AβO solution after 11 days of culture for 24 hours. β-estr was used at 100 nM (final concentration) and was added as pretreatment (1h before injuries). A co-incubation with selective inhibitors was performed for the mechanistic study. In parallel, western blotting (WB) analysis was done to quantify protein levels and their activation. We showed that β-estr was able to significantly protect neurons as well as glial cells from degeneration decreasing the caspase 3 activation and the massive mitochondrial stress (induced by AβO). Preservation of neurite network and synapsis integrity was also observed. Moreover, the large hyperphosphorylation of tau protein induced by AβO was significantly reduced with β-Estr. A mechanistic study was also performed co-incubating inhibitors of main survival pathways to try to better understand the mode of action of β-estr and the pathway involved in the AβO toxicity. We showed that the effects of -Estr were fully abolished blocking the MEK pathway as well as the DNA repair pathway (PARP-g) or the mitochondrial anti-apoptotic pathway (Bcl2). Interestingly the effect was inexisting coincubating β-estr with TrK receptor or Ras/Raf inhibitors showing the predominant role of growth factors paythway in its neuroprotective effect. Finally, we showed a large inactivation of AKT protein in presence of AβO that was reversed even over activated in presence of β-Estr.