The Gel Microdrop (GMD) Secretion Assay involves encapsulating cells within a biotinylated agarose matrix, followed by capture and detection of cell-secreted molecules with fluorescent markers. This technology differs from other encapsulation methods in that the small size of the microdrop (<50 ?m diameter) creates a defined microenvironment around the cell without impeding the fusion of nutrients, antibodies, or nucleic acid probes into the GMDs, or the diffusion of secreted products out of the GMDs. Large numbers of GMDs can be readily analyzed using flow cytometry, and sub-populations of rare or high-secreting cells, as small as 0.1%, can be detected and recovered in one day. This assay format is a rapid alternative to limited dilution cloning (LDC)...
BioProcessing Journal Posts
The Sf-9 insect cell/baculovirus expression system is one of the most commonly used protein expression systems. It is the preferred system for generating large amounts of protein in a short period of time, and it has been successfully used to express several hundreds of different proteins. A representative list of the different proteins made in our laboratory over the past decade with the Sf-9 insect cell/BEVS system is given in Table 1. These proteins are often used in drug screening studies and structure function analysis. Proteins intended for therapeutic purposes are not normally produced using this technology, although a few examples do exist. There is also an unexplored potential for the cells to be used for the production of recombinant viral vectors. Recent reports demonstrating the ability of baculoviruses to express proteins in mammalian cells, with mammalian promoters, indicate that BEVS technology might soon have a major role to play in the field of gene delivery…
The baculovirus-insect cell system consists of a recombinant baculovirus vector and its host, which may be a lepidopteran insect larvae or an established lepidopteran insect cell line. Hundreds of different recombinant proteins have been produced using the baculovirus-insect cell system, facilitating biomedical research on protein structure, function, and the roles of various proteins in disease. In addition, many biotechnology companies are using this system to produce recombinant proteins for potential clinical use as vaccines, therapeutics, or diagnostic reagents…
It is well known that the characteristics of a cultured cell line do not always remain stable and may change upon continuous passage. Most continuous cell lines, even after cloning, possess several genotypes that are constantly changing. There are numerous selective and adaptive culture processes, in addition to genetic instability, that may promote phenotypic changes in cell growth, virus susceptibility, gene expression, et cetera. Similar detrimental effects of long term passaging of insect cells have also been reported for continuous cell lines. In this paper, we describe the isolation of cell clones from low passage BTI Tn5B1-4 cells (High FiveTM Cells), and report their growth characteristics and high level of recombinant protein production…
Cellular therapy is currently generating great interest in the treatment of a variety of diseases. In turn, this interest has stimulated the Center of Biologics Evaluation and Research of the Food and Drug Administration to examine its regulatory approach to the products used for these therapies. As a result, facilities preparing cell therapy products are now regarded as manufacturers, and are expected to comply with current Good Manufacturing Practices and/or the proposed current Good Tissue Practices. Compliance with these practices can be a culture shock to some academic centers whose background is firmly in research. The FDA has indicated that there is a sliding scale of compliance depending on the phase of the clinical study. The difficulty for centers is deciding where they fall on the compliance scale, as well as determining what changes must be made to come into compliance. This article reviews some of the factors that must be considered when making these decisions…
As product development proceeds in the field of cellular therapies, adequate product characterization remains a challenge for both IND Sponsors and FDA/CBER. Cellular therapy products are not considered to be well-defined products, and therefore the control and characterization of each stage of the production process helps to ensure product safety and consistency. Product characterization of cellular products includes demonstration of safety, plus determination of identity, purity, potency, and product stability. Development of appropriate specifications for each of these parameters is necessary for lot release, and also provides an important database of knowledge for addressing regulatory issues, such as lot-to-lot consistency and potential issues with product comparability, should the manufacturing process, or other aspects of product development, change over time…
The characterization of a batch cell culture process to produce a monoclonal antibody from a GS-NS0 mouse myeloma cell line is described. Productivity and cellular metabolism were monitored during scale-up to both characterize the process and aid in assessing cell culture stability. During fermentation scale-up studies, it was found that as culture generation number increased, productivity declined. In both flask and bioreactor cultures, declining production started abruptly at approximately generation 60. In this study, we assessed whether the decline in productivity was due to genetic instability of the cell line, which resulted in the generation of a non-producer sub-population, or a shift to a less productive state of cellular metabolism…