Extensive Chemical Modifications in the Primary Protein Structure of IgG1 Subvisible Particles Are Necessary for Breaking Immune Tolerance.

A current concern with the use of therapeutic proteins is the likely presence of aggregates and submicrometer, subvisible, and visible particles. It has been proposed that aggregates and particles may lead to unwanted increases in the immune response with a possible impact on safety or efficacy. The aim of this study was thus to evaluate the ability of subvisible particles of a therapeutic antibody to break immune tolerance in an IgG1 transgenic mouse model and to understand the particle attributes that might play a role in this process.

Determination of the Density of Protein Particles Using a Suspended Microchannel Resonator.

One of the analytical tools for characterization of subvisible particles, which gained popularity over the last years because of its unique capabilities, is the resonance mass measurement technique. However, a challenge that this technique presents is the need to know the exact density of the measured particles in order to obtain accurate size calculations. The density of proteinaceous subvisible particles has not been measured experimentally yet and to date researchers have been using estimated density values.

Comparative Evaluation of Two Methods for Preparative Fractionation of Proteinaceous Subvisible Particles--Differential Centrifugation and FACS.

Purpose: The goal of this study was to compare and evaluate two preparative techniques for fractionation of proteinaceous subvisible particles. This work enables future studies to address the potential biological consequences of proteinaceous subvisible particles in protein therapeutic products.

Methods: Particles were generated by heat stress and separated by size using differential centrifugation and FACS (Fluorescence-activated cell sorter).

Selective Oxidation of Methionine and Tryptophan Residues in a Therapeutic IgG1 Molecule.

Oxidation of methionine and tryptophan are common degradation pathways for monoclonal antibodies and present major analytical challenges in biotechnology. Generally, protein oxidation is detectable in stability and/or stressed samples (e.g.