Chicken anti-protein G for the detection of small amounts of protein G.
Streptococcal protein G, similar to staphylococcal protein A, is the Fc-binding proteins that seems best suited for affinity-purification of mouse, rat or human monoclonal antibodies. We have developed a sandwich-ELISA for monitoring of protein G leakage from such columns. It utilizes microtitre plates coated with chicken anti-protein G to capture protein G, and biotinylated chicken anti-protein G to detect bound protein G. Chicken IgG is one of a very few IgG that does not show any Fc reactivity with protein G. It is thus possible to make an antigen-specific assay for protein G. This assay can be used to detect protein G in IgG containing solutions, such as monoclonal antibody preparations. The method can be used to detect 1 x 10(-7) g protein G/1 in the presence of human serum or human IgG.