Avoiding Proteolysis During Protein Purification

Storage Stability of Plant-Based Drinks Related to Proteolysis and Generation of Free Amino Acids

The market for plant-based drinks (PBDs) is experiencing a surge in consumer demand, especially in Western societies. PBDs are a highly processed food product, and little is known about this relatively new food product category when compared to bovine milk. In the present study, the storage stability, proteolysis and generation of free amino acids were investigated in commercially available PBDs over the course of a one-year storage period. Generally, pH, color and protein solubility were found to be stable in the PBDs during storage, except for the pea-based product, which showed less protein solubility after storage. The pea-based drinks also had higher initial levels of free N-terminals prior to storage compared with levels for the other plant-based drinks, as well as significantly increasing levels of total free, and especially bitter free, amino acids. The development of free amino acids in the oat-based drink indicated that the released amino acids could be involved in various reactions such as the Maillard reaction during the storage period.

Quantitative analysis of residual aurintricarboxylic acid in biotherapeutic process streams using liquid chromatography triple quadrupole mass spectrometry

Aurintricarboxylic acid (ATA) is an excipient that can be added to the therapeutic protein manufacturing process as a component of the Chinese hamster ovary (CHO) cell culture media. ATA inhibits cell apoptosis and promotes cell growth in both serum-free and protein-free media. The addition of ATA is beneficial to the manufacturing process at the cell growth stage, however, residual ATA not consumed by cells can have toxicological effects on patients and its removal is required during downstream processing. To ensure manufacturing control and patient safety, the determination of residual ATA during downstream processing of biotherapeutics is required. The aim of this study was to develop and validate a liquid chromatography triple quadrupole mass spectrometry method for monitoring process clearance of ATA during downstream processing. Chromatographic separation of ATA was achieved using a 50 × 3 mm, 3 µm Imtakt Cadenza HS-C18 column and a triple quadrupole mass spectrometer operated in selected reaction monitoring mode was used for sensitive and specific detection. Linearity was assessed over a range of 62.5 ng/mL to 2000 ng/mL. Accuracy and precision were within 20% of the theoretical spike levels across the three concentration levels evaluated utilising two different antibodies, an IgG1 and an IgG4. Analyte specificity and selectivity were deemed acceptable based on no extraneous peaks detected. The method was successfully applied to monitoring process clearance of ATA in a tangential flow filtration (TFF) unit operation for downstream processing of monoclonal antibodies.

Impact of the Amyotrophic Lateral Sclerosis Disease on the Biomechanical Properties and Oxidative Stress Metabolism of the Lung Tissue Correlated With the Human Mutant SOD1G93A Protein Accumulation

Amyotrophic lateral sclerosis (ALS) is the most common motor neuron disease, and ALS incidence is increasing worldwide. Patients with ALS have respiratory failure at the disease’s end stages, leading to death; thus, the lung is one of the most affected organs during disease progression. Tissue stiffness increases in various lung diseases because of impaired extracellular matrix (ECM) homeostasis leading to tissue damage and dysfunction at the end. According to the literature, oxidative stress is the major contributor to ECM dysregulation, and mutant protein accumulation in ALS have been reported as causative to tissue damage and oxidative stress. In this study, we used SOD1^G93A and SOD1^WT rats and measured lung stiffness of rats by using a custom-built stretcher, where H&E staining is used to evaluate histopathological changes in the lung tissue. Oxidative stress status of lung tissues was assessed by measuring glucose 6-phosphate dehydrogenase (G6PD), 6-phosphogluconate dehydrogenase (6-PGD), glutathione reductase (GR), glutathione s-transferase (GST), catalase (CAT), and superoxide dismutase 1 (SOD1) levels. Western blot experiments were performed to evaluate the accumulation of the SOD1^G93A mutated protein. As a result, increased lung stiffness, decreased antioxidant status, elevated levels of oxidative stress, impaired mineral and trace element homeostasis, and mutated SOD1^G93A protein accumulation have been found in the mutated rats even at the earlier stages, which can be possible causative of increased lung stiffness and tissue damage in ALS. Since lung damage has altered at the very early stages, possible therapeutic approaches can be used to treat ALS or improve the life quality of patients with ALS.

Quantification of residual AEBSF-related impurities by reversed-phase liquid chromatography

During research of a broadly neutralizing antibody (bNAb) for HIV-1 infection, site-specific clipping was observed during cell culture incubation. Protease inhibitor, 4-(2-aminoethyl) benzenesulfonyl fluoride (AEBSF), was supplemented to the cell culture feeding to mitigate clipping as one of the control strategies. It led to the need and development of a new assay to monitor the free AEBSF-related impurities during the purification process. In this work, a reversed-phase liquid chromatography (RPLC-UV) method was developed to measure the total concentration of AEBSF and its major degradant product, 4-(aminoethyl) benzenesulfonic acid (AEBS-OH). This quantitative approach involved hydrolysis pre-treatment to drive all AEBSF to AEBS-OH, a filtration step to remove large molecules, followed by RPLC-UV analysis. The method was qualified and shown to be capable of measuring AEBS-OH down to 0.5 μM with good accuracy and precision, which was then applied for process clearance studies. The results demonstrated that a Protein A purification step in conjunction with a mock ultrafiltration/diafiltration (UF/DF) step could remove AEBSF-related impurities below the detection level. Overall, this study is the first to provide a unique approach for monitoring the clearance of free AEBSF and its related degradant, AEBS-OH, in support of the bNAb research.