Comparative Analysis of Laboratory-Scale Immunoglobulin G Purification Methods from Human Serum

Immunoglobulin G (IgG) purification is a critical process
for evaluating
its role in autoimmune diseases, which are defined by the occurrence
of autoantibodies. Affinity chromatography with protein G is widely
considered to be the optimal technique for laboratory-scale purification.
However, this technique has some limitations, including the exposure
of IgG to low pH, which can compromise the quality of the purified
IgG. Here, we show that alternative methods for IgG purification are
possible while maintaining the quality of IgG. Different techniques
for IgG purification from serum were evaluated and compared with protein
G-based approaches: Melon Gel, caprylic acid-ammonium sulfate (CAAS)
precipitation, anion-exchange chromatography with diethylamino ethyl
(DEAE) following ammonium sulfate (AS) precipitation, and AS precipitation
alone. The results demonstrated that the purification yield of these
techniques surpassed that of protein G. However, differences in the
purity of IgG were observed using GeLC-MS/MS. The avidity of purified
IgG against selected targets (SARS-CoV-2 and topoisomerase-I) was
similar between purified IgG obtained using all techniques and unpurified
sera. Our work provides valuable insights for future studies of IgG
function by recommending alternative purification methods that offer
advantages in terms of yield, time efficiency, cost-effectiveness,
and milder pH conditions than protein G.