Rapid Droplet-Based Systems for Antibody Drug Discovery

Technology

This method utilizes a single-cell platform wherein the cells of interest are physically separated from the other cells in a reaction vessel, such as a multi-well plate, microchip, microfluidic chip, or Nanopen. These cells present a cell surface protein and are genetically engineered to be encoded with a foreign test protein, such as an antibody, antigen, or reporter molecule. Depending on the purpose of the screening conducted, cells will secrete the foreign test protein and express the reporter molecule if the test protein activates the cell surface protein. Another screening method consists of contacting a single isolated cell with a test-reagent comprised of the reporter molecule. If the reporter molecule successfully gains entry to the cell by binding to the cell surface protein, cells will secrete the foreign test protein and express the reporter molecule. Through genetic modification, the presence and level of expression of the reporter molecule indicates the molecular state of the cell. In this way, an antibody’s ability to neutralize, prevent, or reduce viral infection can be rapidly analyzed in a single cell format. This approach has numerous applications in medicine including immune protection mechanisms, precision therapeutics, and vaccine development.

Problem Addressed

This method provides a more efficient way to selectively screen for active antibodies and proteins within large-volume cell libraries in a high-throughput manner. Drug discovery assays of this kind examine how various proteins interact with cells. However, former strategies required long and technical processes of expressing and purifying proteins. Moreover, existing methods such as cell-based assays are infrequently readily compatible with the direct selection of functional protein variants that are crucial to many important drug classes, such as antibodies. In addition, alternative approaches for functional protein analysis often require multi-cell droplet compartmentalization along with the sorting of a sensor cell and protein-secreting cell. These dual cell approaches within a single droplet generally have a much lower throughput and present higher technical complexity. In contrast, this novel approach allows for the recovery of the protein-secreting cell via a genetically engineered selection marker associated with the active antibody, enabling the selection of cells that show the desired activity.  

Advantages

• The methods allow for the functional screening of high-volume soluble protein libraries in a rapid and cost-effective manner.  

• By sorting single cells rather than droplets, these methods are compatible with a broader range of cellular equipment. 

• The methods enable the recovery of the polypeptide secreting cell linked with a selection marker associated with the activity of the antibody, thereby allowing for easy selection of cells that show desired activity. 

• By engineering the same cell to secret the test protein and express the surface membrane, this method eradicates the need to express and purify proteins in a non-native solubilized format for screening.  

Publications

Fahad, A.S., Chung, C.Y., López Acevedo, S.N. et al. Cell activation-based screening of natively paired human T cell receptor repertoires. Sci Rep 13, 8011 (2023). https://doi.org/10.1038/s41598-023-31858-4