Download Role of Protein Aggregates in the Immunogenicity of Protein Therapeutics

CHEMICAL ENGINEERING - Role of Protein Aggregates in the Immunogenicity of Protein Therapeutics
Immunogenicity of protein therapeutics presents a major challenge to the development of protein-based
therapeutic products. For virtually every therapeutic protein product, some of the patients mount an immune
response to the therapeutic, creating antibodies that bind to the drug. Frequently, this immune response results
in reduced efficacy of the drug; occasionally, more serious side effects (e.g., anaphylaxis, death) result. The
cause of immune response to protein therapeutics is not clear. In principle, most protein therapeutics are
chemically identical to endogenously produced molecules, yet they stimulate responses as if they were foreign
bodies. A leading hypothesis is that protein aggregates, which are ubiquitous in protein therapeutics, may be
responsible for the breaking of natural immune tolerance. In preliminary experiments conducted in murine
models, we have observed a positive correlation between aggregate levels and anti-drug antibody titers.
Furthermore, these studies have suggested that aggregate particle size distribution, structure and chemical
composition may play important roles in determining immunogenicity, and that aggregates with varying
characteristics may stimulate immune response through different cellular pathways (e.g., direct B-cell
stimulation, or via T-cell modulated B-cell response), creating antibodies of a variety of isotypes (e.g., IgG1,
IgG2a, IgG2b, IgG3).
In this project, we examine more closely the immune response in mice to various types of aggregates of murine
growth hormone. Emphasis is placed on isolating, fractionating and characterizing aggregates produced as a
result of stresses that proteins typically experience during processing and administration to patients (e.g.,
freeze-thawing, exposure to air-water or silicone oil-water interfaces), and testing the immune responses
resulting from their administration in animal models. B- and T-cell responses are characterized by fluorescenceactivated cell sorting and antibody isotype analysis.