Translational Proteomics for Transfusion Medicine: Resolution of the IVIG Proteomes of Different Geographically Sourced and Prepared IVIG Immunotherapies

Abstract

AbstractIntravenous Immunoglobulin’s (IVIG’s) are prepared from thousands of donor plasmas and as a result comprise an extreme broad mix and depth of Antibody (Ab) specificities. IVIG formulations available in Australia are from both local and overseas donor sources and extracted using a variety of purification methods and immunoglobulin purities, with the Australia-derived and prepared IVIG listed at >98% and the overseas-derived preparations at ≥ 95%. Because of these differences it was predicted that the formulations might individually vary in composition and that together with obvious genetic and geographic antigenic (Ag) environment differences may result in notable variability between formulations. Hence a focussed comparative proteomic profiling of IVIG formulations was undertaken to identify notable similarities and differences across products. Comparisons between formulations did reveal marked qualitative differences in 2D-gel Antibody profiling that included parameters of isoelectric charge (pI), as well as immunoglobulin (Ig) monomer to dimer ratio variability between products, including high molecular weight (MW) immunoglobulin multimers for some. These notable differences were in part quite likely a product of the respective purification methods used, and capacity to select (or de-select) for antibodies of such different properties. Furthermore, for identification of non-Ig proteins carried over from plasma through purifications Mass spectrometry was performed. This identified a few such ancillary proteins, and their identities, in general, differed between formulations. Proteins detected included the most abundant protein of plasma, albumin, as well as other mostly large and abundant proteins; RAG1 - V(D)J recombination activating protein1, gelsolin, complement Factor-B, serotransferrin, tetranectin, NADH ubiquinone oxidoreductase, caspase 3 and VEGFR1. An alternate strategy used commercial Multiplex xMAP assay to detect cytokines, which are small and present in plasma at trace but highly active quantities. This revealed various different cytokine profiles across the formulations studied. The identification of additional proteins, and especially cytokines in IVIGs, is particularly notable, and the positive, negative or null biological relevance for clinical use, needs resolution. Collectively these findings reveal marked differences between Australian and overseas-derived (non-Australian) IVIGs in immunoglobulin composition and biochemical characteristics, and presence of additional carry-over proteins from plasma. These findings prompt the need for further evaluation of the micro-compositions of individual formulations. Perhaps detailed mining and improved comparative understanding of each IVIG formulation, may enable highly tailored and strategic clinical use of certain formulations that are personalised best-fit treatments for particular conditions. Such as in treatment of a neuropathy, as compared to another formulation, more suited for treating a particular infectious disease. The most salient and overarching study conclusion is need for caution in attributing equivalence across IVIGs.