The production and purification of immunoglobulins of the gamma isotype, particularly human IgG1, for diagnostic or therapeutic applications is now fairly routine. In the past decade IgE-based therapeutics have also gained momentum. IgE is important for host defense against parasites and for protective inflammation. Yet, IgE-mediated signaling through its receptors is also a focal point of inflammatory allergic disease. The constant region of IgE, is a homodimer containing duplicate pairs of three unique Ig-fold domains (Cε2, Cε3, and Cε4), and is responsible for binding its two receptors, FcεRI and CD23, also known as FcεRII.
This application note focuses on the utility of differential scanning calorimetry (DSC) to inform multiple aspects of the biotherapeutic development processes of IgG and IgE. DSC enables the study of protein unfolding rapidly and with out the use of labelling or artificial probes. The technique determines the heat absorbed by the sample as the protein unfolds, giving a measure of its thermostability and an indication of long-term stability.
In particular in the work described here, it is shown that DSC provides insights for handling, purifying, and formulating IgG and IgE drug products. The ability of circular dichroism (CD) to contribute to these findings is contrasted to what can be discerned using DSC. DSC enables the investigation of protein stability at the level of individual domains within multi-domain proteins, an aspect that is less transparent in data obtained by CD.
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