One Cell Systems Awarded NSF Phase II SBIR Grant to Develop High Throughput Method For Screening Single Cells Based on Amount of Protein Production

 Cambridge, MA…May 29, 1998….The National Science Foundation recently awarded One Cell Systems, Inc. a $400,000 Phase II Small Business Innovation Research grant (SBIR) to develop a high throughput method for screening transfected cells based on level of protein secretion. The technology relies on the combination of micro-encapsulation using gel microdrops (GMDs), a novel secreted protein capture format and fluorescence activated cell sorting (FACS). Live, intact high secretor or rare cells are recovered for subsequent cloning in a highly streamlined process that takes only one day.

Secreted proteins are a cornerstone of the biotechnology industry. $9.6 billion of the more than $10 billion in annual biopharmaceutical revenues resulted from sales of secreted proteins. Although by some estimates, only a small fraction of all proteins are secreted by cells, these are the most likely to exhibit therapeutic potential.

"Development of a high throughput method for screening and recovering single cells based on the level of protein secretion is a major innovation", Patricia McGrath, President and CEO said. "Limiting dilution cloning is labor intensive and highly variable. Use of this novel secretion assay format will give biopharmaceutical companies a competitive advantage in rapidly moving products to commercialization", she continued.

Using the CellSys 100™ Microdrop Maker, cells are encapsulated in CelBioGel™, a biotinylated matrix, and incubated with streptavidin and biotinylated capture antibody against the secreted protein. Captured protein is detected by binding of a fluoresceinated reporter antibody. Using FACS, the fluorescence intensity of each GMD can be quantified and single cells recovered based on level of protein secretion. Viable cells which outgrow the matrix can be cloned resulting in profound cell line enrichment or isolation of rare cells. Studies have shown that the secretion phenotype is heritable.

Conceptually similar to an ELISA sandwich format, each 25 µm GMD functions as a miniaturized microtiter well. The ability to capture and quantify protein secretion at the individual cell level is not possible using other assay formats and is a compelling feature of GMD secretion technology. As soon as fluorescence signal from reporter antibody exceeds background within the agarose matrix, GMDs can be flow sorted to recover high secretor or rare producer cells. For many cells, this period is as short as 15 minutes. At least 5 million cells of interest can be screened in one hour using conventional sorters.

In comparison, limiting dilution cloning involves several cell growth cycles and intermittent analysis of thousands of microtiter plate wells over a period of months. Other inherent advantages of flow cytometry include the ability to screen large numbers of cells in a relatively short time and the ability to identify sub-populations.

Although FACS is now used to identify producers on the basis of intracellular antibody binding, cells are rendered non viable, making subsequent cloning impossible. Furthermore, since secreted molecules rapidly dissociate from the originating cell, isolation of single cells based on amount of protein production is not currently possible. Micro-encapsulation essentially fools the flow cytometer into analyzing GMDs as if they were cells, making analysis of captured secreted proteins possible. Development of a rapid method for producing highly specific monoclonal antibodies and other proteins will speed up commercialization of novel therapeutic, diagnostic and imaging reagents.

 One Cell Systems, Inc. is marketing the secretion assay under an annual lease program. In addition, the Company is providing screening services at its facility in Cambridge, MA.

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