The molecular basis for antibody stability in the bioprocess environment.
Doctoral thesis, UCL (University College London).
Of the four human IgG antibody subclasses IgG1-IgG4, IgG4 is unusual in that it does not activate complement and exhibits atypical self-association including the formation of bispecific antibodies. Given the therapeutic importance of human monoclonal antibodies their solution properties are critical to understanding clinical function and response to manufacture and storage. Thus IgG4 was studied under a range of relevant bioprocess, storage and accelerated degradation conditions and analysed by synchrotron X-ray scattering, analytical ultracentrifugation, circular dichroism and other relevant biophysical techniques. The first study was carried out at a range of protein concentrations at pH 7.4. This indicated a small concentration dependence of the IgG4 solution structure. The averaged conformation of the Fab regions appear able to hinder complement C1q binding to the Fc region and the self-association of IgG4 through the Fc region. These results provide a starting point to understand antibody structural stability during their manufacture. Low pH conditions were also studied as these are typically used for both viral inactivation and elution from protein A affinity resins during IgG manufacturing bioprocesses. Time and concentration dependent conformational changes and aggregation events were studied for the IgG4 at pH 3. It was observed that at all protein concentrations studied, the monomer size decreases over the first 100 minutes at pH 3. It was found that the molecular conformation changes along with an intramolecular increase in the beta-sheet content of the protein. At the higher protein concentrations, these events preceded aggregation suggesting that they may have a role in the propensity of the IgG4 to aggregate. The IgG4 was also studied over a range of temperatures at pH 7.4 using classical accelerated degradation experiments. However, no significant loss of protein was observed over the time and conditions studied.
|Title:||The molecular basis for antibody stability in the bioprocess environment|
|Additional information:||Permission for digitisation not received|
|UCL classification:||UCL > School of Life and Medical Sciences > Faculty of Life Sciences > Biosciences (Division of) > Structural and Molecular Biology
UCL > School of BEAMS > Faculty of Engineering Science > Biochemical Engineering
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