Therapeutic antibodies have greatly improved the treatment of many diseases; however, their safety and efficacy are often altered by their immunogenicity as many patients frequently develop anti-drug antibodies. There is growing evidence that protein aggregation can result in enhanced immunogenicity. We aim to better understand the role of antibody aggregates in the initiation of a specific T-cell response to therapeutic antibodies. We developed a model of nanosized oligomeric infliximab (IFX) aggregates, by exposing the native antibody to ultraviolet light. IFX aggregates were characterized using size exclusion chromatography and dynamic light scattering methods. Then, using an autologous co-culture model with monocyte-derived dendritic cells (moDC) and CD4 T cells purified from the blood of healthy donors, we identified a higher frequency of CD4 T cells recognizing IFX aggregates, compared to the native antibody. However, IFX aggregates did not induce moDC maturation, evaluated by phenotypic markers expression analysis, as well as inflammatory cytokines and chemokines production, suggesting that these aggregates can increase T-cell responses without being recognized as a danger signal by moDCs. Moreover, we studied by flow cytometry the internalization mechanisms of fluorescent native or aggregated IFX by moDCs and found that IFX aggregates tend to be more internalized compared to native IFX. Moreover, the main internalization pathway seems to be endocytosis. The receptors and signaling pathways implicated are currently under investigation. 
In conclusion, our results indicate that oligomeric aggregates have a significant role in immune system activation. As the tendency of therapeutic antibodies to aggregate is a key challenge in the product manufacturing and formulation, these data emphasize the importance of assessing the cellular mechanisms that drive the immune response to aggregated proteins to anticipate and prevent immunogenicity of therapeutic antibodies.