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Gamma-Immunoglobulin Response Characterization, in COVID-19 Convalescent Patients, Against the Spike Protein S2 Subunit with Eight Linear Peptides for Monoclonal Antibody Generation

By Airela Llamo, Daily Hernández, Cristina García, Marcos González, Williams Ferro, Hilda Garay, David Diago, Abel Fajardo, Luis Espinosa, Sigifredo Padilla, Leonardo Gómez, Glay Chinea, and Rodolfo Valdés
Volume 22, Open Access (March 2023)

The SARS-CoV-2 spike protein S2 subunit plays an essential role in the virus-host cell membrane fusion process. Therefore, the subject of this study was to characterize the gamma-immunoglobulin (IgG) response, in a group of COVID-19 convalescent patients, against the S2 subunit with eight linear peptides to generate a monoclonal antibody (mAb) against the immunodominant linear peptide to be used for therapeutic and diagnostic purposes. Results of antibody percentages against assessed linear peptides were 100% for A21P73, A21P74, A21P75, A21P76, M20P51, M20P65, M20P83, and 66.7% for M20P85. Plasma samples were also used for purifying IgG to corroborate specificity against the same linear peptides, where results reproduced those applying plasmas directly to ELISA-plates. Within these peptides, A21P75 was chosen as immunodominant (100% of recognition with higher absorbance). The A21P75 linear peptide showed poor immunogenicity in mice (1:4000–8000 after four doses), allowing the generation of a CB.HS2A21P75 hybridoma for mAb production that recognized the A21P75 linear peptide with middle-to-high affinity constant (Kaff) (0.8×108 M-1).

This study concludes that the A21P75 linear peptide is the assessed immunodominant linear peptide for this COVID-19 convalescent patient group. This peptide is located in the HR1 region that plays an important role in SARS-CoV-2 host cell membrane fusion process and is highly conserved between SARS-CoV-2 and SARS-CoV. Thus, due to CB.S2A21P75 mAb specificity and Kaff, it might be the proper reagent to study inhibition of virus-host cell membrane fusion, and as a diagnostic reagent for coronavirus. Finally, the combination of A21P75 linear peptide with other peptides (e.g., receptor binding domain [RBD]) could be suitable reagents for the development of vaccines and therapeutic antibodies with virus infection-blocking capacity.

Llamo A, Hernández D, García C, González M, Ferro W, Garay H, Diago D, Fajardo A, Espinosa L, Padilla S, Gómez L, Chinea G, Valdés R. Gamma-immunoglobulin response characterization, in COVID-19 convalescent patients, against the spike protein S2 subunit with eight linear peptides for monoclonal antibody generation. BioProcess J, 2023; 22.

Posted online March 6, 2023.





Human IgG Fc Production Through Methanol-Free Pichia pastoris Fermentation

By Ying Yang, Knut Madden, and Ma Sha
Volume 21, Open Access (November 2022)

Nowadays, therapeutic monoclonal antibodies (mAbs) are predominantly produced with mammalian cell culture systems such as those using Chinese hamster ovary (CHO) cells. Efforts are underway to reduce the costs of this process to meet the increasing global demand in biopharmaceuticals; meanwhile, cheaper and faster expression systems are being investigated as alternatives. The yeast, Pichia pastoris, has become a substantial workhorse for recombinant protein production. However, the N-linked glycosylation in P. pastoris, namely high mannose glycosylation, is significantly different from that in CHO or other mammalian cells, including human cells. In this study, a SuperMan5 strain of P. pastoris was constructed using Pichia GlycoSwitch® technology to successfully produce a more mammalian-like immunoglobulin G (IgG) fragment crystallizable (Fc), which showcases the potential of P. pastoris as a next-generation mAb production platform. Importantly, in this study, a strong methanol-independent promoter, PUPP, was applied, which only requires glycerol feeding for protein production. Most P. pastoris promoters used for protein expression are derived from genes in the methanol metabolism pathway, creating safety concerns due to the flammable nature of methanol, especially at large scale. Here, a fed-batch SuperMan5 P. pastoris fermentation was carried out in which methanol induction, as well as its affiliated safety risks, were eliminated. Overall, this study provides insights into the development of safe and cost-effective industrial mAb production approaches independent of mammalian cell culture.

Yang Y, Madden K, Sha M. Human IgG Fc production through methanol-free Pichia pastoris fermentation. BioProcess J, 2022; 21.

Posted online November 21, 2022.


Demonstrating “Abdala” Subunit Vaccine Thermostability Study

By Mabel Izquierdo, Yassel Ramos, Lourdes Costa, Rodolfo Valdés, Yamila Martínez, Mónica Bequet-Romero, Vladimir Besada, Gerardo García, Galina Moya, Glay Chinea, Jennifer Rojas, José Marcelo, Ivan Andujar, Joaquín González, Mareysis Ruiz, Yurisleydis Aldama, Marta Ayala, Jorge Valdés, and Miladys Limonta
Volume 21, Open Access (September 2022)

From a regulatory standpoint, vaccine stability must be demonstrated, along with the prediction of stability during temperature excursions, before a vaccine can be approved for use in humans.

In this work, Abdala subunit vaccine thermostability was studied under thermal stress conditions (2–8°C [control], 25°C, 37°C, 45°C, and 60°C) for 15 days. Molecular integrity of the vaccine active pharmaceutical ingredient was monitored by SDS-PAGE, immunoblotting, RP-HPLC, mass spectrometry, and circular dichroism spectroscopy analysis. While functionality was monitored by immunogenicity assay, inhibition of binding between receptor-binding domain (RBD) and receptor, angiotensin converting enzyme 2 (ACE2), and RBD/ACE2 binding assay.

Results showed that no degradation, loss of disulfide bridges, nor modifications of secondary structure of the RBD molecule were detected at 25°C and 37°C. Moreover, high titers (1:48,853-1:427,849) of anti-RBD-specific mouse antibodies were detected with the ability to inhibit, to different degrees, the binding between RBD/ACE2.

In conclusion, the Abdala subunit vaccine is stable under thermal stress and storage conditions, which has an advantage over non-subunit vaccines previously approved or currently in development against COVID-19. The demonstrated high stability of this vaccine is a key factor in ensuring vaccine effectiveness, extending immunization coverage with fewer production runs, simplifying immunization logistics, and reducing cold chain-associated costs.

Izquierdo M, Ramos Y, Costa L, Valdés R, Martínez Y, Bequet-Romero M, Besada V, García G, Moya G, Chinea G, Rojas J, Marcelo J, Andujar I, González J, Ruiz M, Aldama Y, Ayala M, Valdés J, Limonta M. BioProcess J, 2022; 21.

Posted online September 15, 2022.




Study of a Single-Use Stirred Tank Bioreactor for Manufacturing a Therapeutic Protein in a High Cell Density Microbial Fermentation

By Angus Thompson and Shaunah Rutter
Volume 20, Open Access (Nov 2021)

Stirred tank single-use bioreactors (SUBs) have been widely adopted for production of biopharmaceuticals such as monoclonal antibodies in mammalian cell culture. However, they are seldom used for commercial production of biologics with microbial fermentation. SUBs offer time-saving advantages because they do not require significant downtime for cleaning and sterilization, so finding a SUB that can perform well with high cell density microbial fermentation processes has the potential to increase the number of production runs. Therefore, for this study, a His-tagged protease inhibitor was chosen as a model protein to demonstrate that the Sartorius Biostat STR® MO, a SUB recently developed for microbial fermentation, is suited for recombinant protein production by high cell density Escherichia coli fermentation processes.

At 50 L scale, the SUB achieved good process control and allowed an oxygen uptake rate (OUR) of up to 240 mmoles/L/h. The fermentation runs produced up to 5.8 g/L of the soluble recombinant protein and a dry cell weight of >60 g/L at the end of fermentation. Additionally, the SUB showed a similar fermentation profile when compared with data from parallel runs in 15 L sterilise-in-place (SIP) vessels using identical media and process parameters. This study indicates that with a minimum investment of capital resources, stirred tank SUBs could be used in pilot-scale manufacturing with high cell density microbial fermentations to potentially shorten the timelines and costs of advancing therapeutic proteins to clinic.

Thompson A, Rutter S. Study of a single-use stirred tank bioreactor for manufacturing a therapeutic protein in a high cell density microbial fermentation. BioProcess J, 2021; 20.

Posted online November 5, 2021.


Robust and Scalable GMP Manufacturing of Chondrocyte Cell Therapy for Cartilage Regeneration

By Vinayak Virupaksh Kedage, Rajesh Pratap Singh, Parvathi Chandran, Vidya Jadhav, Sujata Shinde, and Satyen Sanghavi
Volume 20, Open Access (Nov 2021)

Cell therapy has emerged as a promising technology that involves implanting live cells to replace/repair and restore normal function of damaged tissue. Autologous chondrocyte implantation (ACI) has been proven effective for the regeneration of articular cartilage in defective cartilage tissue. The process starts with the collection of healthy tissue from an eligible patient, then isolation and expansion of desired cells in vitro under good manufacturing practice (GMP) conditions, qualification before release of the final cell product, and finally, implantation into the patient. The promise to deliver autologous cell therapies has its own challenges in robust and reproducible manufacturing. To commercialize a cell therapy, it is imperative that a robust and scalable manufacturing process is set up that is consistent, in terms of quality and quantity, in order to deliver the intended therapeutic effect.

We analysed the manufacturing parameters of over 100 cartilage samples that were used to deliver our proprietary, commercialized autologous cell therapy. The paper addresses the most cited challenges in the manufacturing of autologous cell therapies and describes a robust process of in vitro human chondrocyte cell culture. Also included are key factors in manufacturing for attaining a high-quantity and quality product for articular cartilage regeneration.

Kedage VV, Singh RP, Chandran P, Jadhav V, Shinde S, Sanghavi S. Robust and scalable GMP manufacturing of chondrocyte cell therapy for cartilage regeneration. BioProcess J, 2021; 20.

Posted online November 1, 2021.


Optimization of a Conventional Glycosylation Analytical Method Using Machine Learning and Experimental Design

By Eliza Yeung and Philip Ramsey
Volume 20, Open Access (Oct 2021)

Glycosylation is one of the most common post-translational modifications in mammalian-expressed biologics, and is considered to be a critical quality attribute of therapeutic glycoproteins. Due to its biological relevance, physiochemical assessment on the glycosylation profile is always important to the success of a drug development initiative. This article describes the combination of experimental design and machine learning techniques applied to characterize and optimize a conventional, non-derivatized glycoprofiling method on glycans derived from a human immunoglobulin using high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Two independent experimental designs, a 16-run definitive screening design (DSD) and a 28-run central composite design (CCD), were incorporated with a machine learning technique known as “self-validating ensemble modeling (SVEM)” and used to build predictive models for four chromatographic responses. We show that the predictive models created using SVEM on the DSD data reliably predicted the behavior of the chosen responses when applied to CCD validation data. This demonstrates that the DSD is an efficient alternative to the larger, traditional CCD in which the combination of experimental design and machine learning can effectively characterize and optimize analytical methods.

Yeung E, Ramsey P. Optimization of a conventional glycosylation analytical method using machine learning and experimental design. BioProcess J, 2021; 20.

Posted online October 15, 2021.


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