Aggregation and innate immune response modulating impurities

Abstract

Abstract Therapeutic proteins can induce immune responses that affect the safety and efficacy even if derived from human sequences. The factors that contribute to the immunogenicity of this therapeutics are poorly understood, but protein aggregation is thought to facilitate it. Previously, our lab showed that trace levels of product or process derived innate immune response modulating impurities (IIRMIs) can also increase product immunogenicity. In this study we hypothesized that protein aggregates and IIRMIs may synergize to facilitate product immunogenicity and explored it using clinical grade Human Serum Albumin (HSA) and Intravenous Immunoglobulin (IVIG) proteins as model. Protein aggregations formed by mechanical stress (shaking and stirring) were characterized by SDS-PAGE, turbidity, MFI and FlowCAM. Cellular responses to aggregated proteins with trace levels of IIRMs were tested in human PBMC. We show that stirring and shaking resulted in the formation of stable aggregates with size ranges of 2 – 50 μm for stirred HSA; and 2–100 μm for IVIG. Despite the similarity in size, the functional assays showed that aggregates of IVIG result in increased mRNA expression of IL-8, IL-6, IL-1β and CCL-2 whereas HSA aggregates did not. Further, we analyzed how the aggregated product changed the transcriptome using Nanostring and showed that aggregated IVIG (shaken or stirred) significantly increased the mRNA of CCL2, CCL7, CCL3, CCL24, CSF1, CXCL2, IRAK1, EGR2, CEBPβ, PPARg, TNFSF15 and whereas HSA aggregates did not. Similarly MAPKs (pp38, pERK and pJNK) and pAKT were activated when PBMC were stimulated with IVIG aggregates but not HSA aggregates. Lastly, we examined whether the effect was mediated by Toll like receptors.