Over the past decade, recombinant human antibodies have become established as an important class of therapeutic proteins. Engineered mammalian cell lines that express high levels of these antibodies are therefore of considerable value, yet require up to a year in development time. To accelerate this process, an Australian team has recently reported an improved FACS method involving 2-colour sorting that facilitates the selection of high-expressing cells.

The utility of FACS is well-established for selecting cell clones producing high levels of recombinant proteins. Nevertheless, most widely-used FACS protocols for this purpose involve complex strategies such as microdrop techniques or surface affinity matrix methodologies, all of which are labour-intensive and involve multiple preparative steps of appreciable technical complexity.

Investigators at Acyte Biotech in Sydney , Australia , have now developed a more facile approach for the FACS-based selection of high-producing clones for antibody expression. The Acyte team used heavy and light chain-specific expression of intracellular fluorescent reporters to identify cells without complex preparative procedures or the need for labour-intensive workflows . To achieve this result, the group constructed antibody expression vectors that simply attached an IRES-linked eGFP or eYFP sequence to the respective heavy or light chain cassette. This approach takes advantage of the fact that sufficient intracellular levels of light chain are an important prerequisite to achieve high rates of antibody secretion.

The Acyte approach has the advantage of being rapid and co-factor independent, using only standard selection and amplification strategies and requiring only a single 488-nm wavelength excitation source that is common to most cytometers. The project was led by Noelle-Ann Sunstrom and was recently reported in an advanced online publication in Biotechnology and Bioengineering .

Article by Sunstrom and colleagues on FACS of high mAb-expressing clones, Biotechnology & Bioengineering , August 2007

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