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Sep 15, 2011 (Vol. 31, No. 16)

Recombinant Protein Expression Advances

Technology Evolves and Focus Shifts from Process to Dissecting Pathways of Interest

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    Analytical biosensors are used to screen strains as part of the high-throughput process of the Pfenex technology platform.

    Expressing recombinant proteins is one of the most challenging, but at the same time most important tasks in the life sciences. Irrespective of the specific protein and the downstream applications, some of the most significant questions involve identifying the best expression system, finding the ideal tag, and characterizing the optimal set of conditions to generate a functional protein. This process is often lengthy and costly, particularly when multiple combinations of expression systems and conditions need to be explored.

    A protein expression platform created by Pfenex that is based on the Pseudomonas fluorescens strain MB101 was designed to address some of these challenges. “It allows the biology to tell us what expression strain to use when producing a particular protein,” said Bertrand C. Liang, M.D., Ph.D., CEO.

    The Pfenex Expression Technology™ platform combines unique host strains and expression strategies, such as specific chaperones and protease deletions, to generate thousands of expression strains that can be analyzed in parallel at the preclinical stage of development. “It is particularly useful for difficult-to-express aglycosylated proteins,” Dr. Liang added.

    Initial protein characterization starts with small-scale expression that is followed by larger scale cultures grown under various conditions. The possibility to rapidly test specific strains for their ability to express a protein of interest makes it an attractive tool to generate new therapeutics particularly when there are time constraints, for example, when a new flu vaccine is required or for biodefense applications.

    Pfenex showed its ability to deliver on such projects when it was chosen to participate in the DARPA/DTRA-sponsored Accelerated Manufacturing of Pharmaceuticals, or AMP, program to develop technologies to deliver pandemically relevant clinical doses of a vaccine in a previously unrealized goal of less than 12 weeks.

    The AMP program culminated in a “live fire” test in which the agencies challenged Pfenex to express and produce the influenza H1N1 hemagglutinin protein, the active antigen in the pandemic flu vaccine. Pfenex scientists, through their parallel strain construction and processing technologies, successfully produced high-titer, high protein quality expression strains and along with collaborators purified the first clinical lots well within the 12-week challenge period.

    “Making proteins is hard. A platform that is high throughput and robotically enabled is the key, as it allows many different conditions to be explored at one time, to determine expeditiously the best approach to express high titers of quality protein in an active, soluble manner,” emphasized Dr. Liang.

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