Thermal aggregation of human immunoglobulin G in arginine solutions: Contrasting effects of stabilizers and destabilizers

[Display omitted] •Aggregation of immunoglobulin G (IgG) is a major obstacle in pharmaceutical applications.•Thermal aggregation pathway of IgG was mediated via soluble oligomers.•Arginine cannot prevent the formation of soluble oligomers but can inhibit the insoluble aggregation during heat treatment.•Protein stabilizer of sugars can suppress the formation of soluble oligomers after heat treatment.•The different behavior of aggregation results from the fast soluble oligomer formation and slow insoluble aggregation. Arginine is widely used as aggregation suppressor of proteins in biotechnology and pharmaceutics. However, why the effect of arginine depends on the types of proteins and stresses, including monoclonal antibodies, is still unclear. Here we investigated the precise processes of the thermal aggregation of human immunoglobulin G (IgG) in the presence of additives. As expected, arginine was the best additive to suppress the formation of insoluble aggregates during heat treatment, though it was unable to preserve the monomer content. A systematic analysis of the additives showed that sugars and kosmotropic ion inhibit the formation of soluble oligomers. These behaviors indicate that the thermal aggregation of IgG occurs by (i) the formation of soluble oligomers, which is triggered by the unfolding process that can be stabilized by typical osmolytes, and (ii) the formation of insoluble aggregates through weak cluster–cluster interactions, which can be suppressed by arginine. Understanding the detailed mechanism of arginine will provide useful information for the rational formulation design of antibodies.