Implementation of Plate Imaging for Demonstration of Monoclonality in Biologics Manufacturing Development

Coupling picodroplet microfluidics with plate imaging for the rapid creation of biomanufacturing suitable cell lines with high probability and improved multi-step assurance of monoclonality

BACKGROUND

There is an expectation from regulatory agencies that cell lines used in the commercial production of biopharmaceuticals are derived from a single cell progenitor. Traditional methods of single cell cloning include the use of the limiting dilution cloning method which often requires multiple rounds of low cell density cell plating and either microscopic evaluation that wells contain single cells and/or the calculation of a statistically derived probability of monoclonality.

METHODS AND RESULTS

We have combined the single cell screening, deposition and picodroplet imaging ability of Sphere Fluidics' Cyto-Mine technology with the plate imaging capability of the Solentim Cell Metric to create a novel workflow for the generation of high producing clonal cell lines with both high probability and assurance of monoclonality. The efficiency of three key stages of the process (single cell picodroplet encapsulation, single picodroplet dispensation and single cell settling in the focal plane of the plate imager) was determined and a probability calculation was derived using the Wilson Score Interval method. The combined probability that a single cell is encapsulated into a picodroplet, is deposited into the correct well of a 96-well plate and that a cell settles into the focal plane of the plate imager yields a combined > 99% probability of monoclonality. Furthermore, visual verification of a single cell progenitor is obtained at multiple steps throughout the cloning workflow.

CONCLUSION

This novel methodology for the rapid creation of high quality clonal cell lines for biomanufacturing purposes has many advantages over more traditional approaches including improved assurance of single cell derivation, integrated imaging capability, assay flexibility, equipment utilization time and in-process cell line segregation.

High-throughput and automation advances for accelerating single-cell cloning, monoclonality and early phase clone screening steps in mammalian cell line development for biologics production

Mammalian cell line development is a multistep process wherein timelines for developing clonal cells to be used as manufacturing cell lines for biologics production can commonly extend to 9 months when no automation or modern molecular technologies are involved in the workflow. Steps in the cell line development workflow involving single-cell cloning, monoclonality assurance, productivity and stability screening are labor, time and resource intensive when performed manually. Introduction of automation and miniaturization in these steps has reduced the required manual labor, shortened timelines from months to weeks, and decreased the resources needed to develop manufacturing cell lines. This review summarizes the advances, benefits, comparisons and shortcomings of different automation platforms available in the market for rapid isolation of desired clonal cell lines for biologics production.

Retrospective assessment of clonal origin of cell lines

Cell lines used for the manufacture of recombinant proteins are expected to arise from a single cell as a control strategy to limit variability and ensure consistent protein production. Health authorities require a minimum of two rounds of limiting dilution cloning or its equivalent to meet the requirement of single cell origin. However, many legacy cell lines may not have been generated with process meeting this criteria potentially impeding the path to commercialization. A general monoclonality assessment strategy was developed based on using the site of plasmid integration for a cell's identity. By comparing the identities of subclones from a master cell bank (MCB) to each other and that of the MCB, a probability of monoclonality was established. Two technologies were used for cell identity, Southern blot and a PCR assay based on plasmid-genome junction sequences identified by splinkerette PCR. Southern blot analysis revealed that subclones may have banding patterns that differ from each other and yet indicate monoclonal origin. Splinkerette PCR identifies cellular sequence flanking the point(s) of plasmid integration. The two assays together provide complimentary data for cell identity that enables proper monoclonality assessment and establishes that the three legacy cell lines investigated are all of clonal origin.

Developing therapeutic monoclonal antibodies at pandemic pace

The time from discovery to proof-of-concept trials could be reduced to 5–6 months from a traditional timeline of 10–12 months.