New antibody library speeds search for new detection tools

RICHLAND, Wash. ? Scientists at the Department of Energy’s Pacific Northwest National Laboratory have extracted part of the human immune system and reconstituted it in brewer’s yeast in a fashion that enables powerful machines to quickly identify new antibodies. The advance could have major repercussions for fundamental biological science as well as industries that use antibodies for sensors, biodetectors, diagnostic tools and therapeutic agents.

The technology could replace the need to produce antibodies within animals, such as mice, and opens up new possibilities for rapidly designing medical treatments more acceptable to the human immune system. Antibodies are proteins produced by white blood cells as part of the immune response.

“Our antibody library offers many advantages over traditional approaches. We expect it will be a more effective tool for scientists,” said Michael Feldhaus, PNNL scientist and lead author of a paper appearing in the February issue of Nature Biotechnology and posted online Jan. 21. “Regulated expression of these antibodies allows the library to be expanded while maintaining its diversity. Furthermore, our unique identification process means we can screen for antibodies in days rather than the months it may take using other approaches.”

Feldhaus and colleague Robert Siegel built a library of 1 billion human antibodies and expressed them on the surface of yeast cells using a platform designed by collaborator Dane Wittrup of the Massachusetts Institute of Technology. The combined technologies offer a more powerful, less expensive method for identifying antibodies.

Antibodies play an increasingly important role in industry because they are effective tools for recognizing specific molecules. When antibodies bind to a specific protein on bacteria, it signals other cells to either kill or remove the bacteria. In medical treatments, antibodies are being injected into the body to seek out specific proteins on cancerous cells, for example, and target treatment to those cells. Biowarfare detectors can use antibodies to locate proteins as a way of identifying harmful agents. Antibodies also are expected to play a major role in helping scientists to more fully understand various biological processes by identifying which proteins are present and if they interact with any other proteins in the cell.

Most importantly, by incorporating Wittrup’s yeast surface display method, PNNL scientists can readily modify how an antibody binds to proteins. Being able to increase how tightly a protein and antibody bind together, for example, could increase antibody effectiveness for detecting pathogens or disease.

The library developed at PNNL identifies antibodies more quickly, thus reducing labor costs. To accelerate the identification process, PNNL combined two types of cell sorters ? high-throughput parallel magnetic cell sorting and high-resolution linear flow cytometric cell sorting ? to isolate specific antibodies very quickly.

Wittrup originally developed the yeast surface display as a way to improve the binding of antibodies to chemicals while working at the University of Illinois in the late 1990s. Now, he uses PNNL’s antibody library with his display platform in a multitude of studies, many directed at development of novel cancer therapeutics.

Says Wittrup, “This yeast library provides a powerful and direct route to the in vitro isolation of useful antibodies, and is a complementary approach to analogous alternatives such as phage display and ribosome display. We expect the wide availability of this library will open a door into antibody engineering technology for life sciences researchers currently using classic mouse hybridoma methods to make affinity reagents. PNNL should significantly impact the research community through the broad distribution of this library.”