Protein Modifications during Antiviral Heat Bioprocessing and Subsequent Storage

Antiviral heat treatment is routinely used in the bioprocessing of therapeutic proteins as a means of reducing viral load. However, in protein formulations containing sucrose this form of bioprocessing can lead to protein modifications. Using a model protein, hen egg white lysozyme, we investigated the effects of antiviral heat treatments in the presence of sucrose on protein integrity during subsequent long-term protein storage. Although heat treatment alone resulted in protein modification, subsequent medium- to long-term storage of both lyophilized and liquid samples at room temperature or above led to further protein modifications. The majority of these modifications were due to the formation of glycation and advanced glycation end products via the reaction of reducing sugars and their autoxidation products (derived from hydrolyzed sucrose) with function groups on the protein surface. These findings have implications for the improvement of therapeutic protein bioprocessing to ensure protein product quality.