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Dec 1, 2009 (Vol. 29, No. 21)

Assessment of Cell-Line Performance

Crucial Step in Process Development Can Be Aided with Smaller-Scale Technologies

  • Baculovirus Experiments

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    MedImmune has evaluated a number of small-scale systems and shaking-well plates in its quest to find a better model for manufacturing.

    Jared Cartwright, Ph.D., head of protein production at the technology facility at York University, discussed the integration of the Micro 24 and the Appliflex single-use bioreactor in baculovirus experiments. At York, this system is used for parallel expression screening so that 10–50 mg samples can be obtained for customers’ structural biology needs in protein target and biocatalysis work.

    Insect-cell production involves infecting the cells with the Autographa californica multiple polyhedral virus. The York team has been using the flashBAC system to improve its transfer vectors and can now produce recombinant baculovirus—but it still wants to screen and optimize protein expression.

    One issue in this work is how adherent and suspension cell culture compare. The team has found found the best results when it optimizes in suspension, rather than adherent, culture, using the Micro 24 system. “This gives us near direct scale-up conditions we can work with,” Dr. Cartwright said. He added that multiplicity of infection (MOI) is very important.

    Tiffany Rau, Ph.D., principal scientist, microbial and cell culture development at GlaxoSmithKline (GSK), described validation of scale up and the incorporation of the Micro 24 screening reactor in process development, which was, traditionally, all done in shake flasks.

    “We were finding issues, and we needed a better way of screening cell lines.” For instance, an apparently low titer clone in shake flasks can become a winner in the bioreactor, so good cell lines may be thrown away. The reverse may happen, with those cell lines that are great in shake flasks not being good in process optimization.

    Now GSK process development scientists screen in a controlled environment and then identify those clones that respond to feed earlier. Investigation of design space, pH, temperature, and oxygen in the system is a big part of tech transfer. “We are redefining how we do cell-line selection using microreactors, to carry out rank ordering of clones.” 

    The Micro 24 can also be used for troubleshooting—for instance with clones that have growth issues in shake flasks. The microreactor is used to see if oxygen and pH control helped, which cannot easily be done in a shake-flask system. pH issues are therefore more easily identified using the microreactor. According to Dr. Rau, more process factors can be investigated with the microreactor and, in the future, GSK will be implementing them in cell-line selection.

    Andreas Schneider, Ph.D., director, global sales at Innovatis, now part of Roche, described how to keep up with sample analysis from high-throughput screening systems. In 2005, Innovatis began looking into online monitoring of many parameters, like optical density and pH, but in some cases it could not readily measure cell count or metabolites. Then, working with Bayer, it developed the BaychroMAT®, which is a steam-sterilized sample port for auto sampling.

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