A New ELISA to Overcome the Pitfalls in Quantification of Recombinant Human Monoclonal Anti-HBs, GC1102, by Commercial Immunoassays

Several methods for the quantification of human anti-HBs, an antibody to hepatitis B surface antigen (HBsAg), have been developed based on enzyme reaction, chemiluminescence, fluorescence, and radioactivity for application to human serum or plasma. Commercial anti-HBs immunoassay kits use a sandwich method in which a bridge is formed by the anti-HBs between a HBsAg immobilized solid matrix and the labeled HBsAg. However, this direct sandwich enzyme-linked immunosorbent assay (ELISA) is insufficient to accurately evaluate the activity of the human monoclonal anti-HBs, GC1102. As an alternative, we developed an indirect anti-HBs ELISA (anti-HBs qELISA-v.1) that improved detection of anti-HBs. In this current study, we further optimized this indirect method to minimize nonspecific binding of human serum, by employing incubation buffers containing animal serum, Tween 20, skim milk, and a low pH washing buffer. This new and improved method, termed anti-HBs qELISA-v.2, showed accurate quantification of plasma-derived hepatitis B immune globulin (HBIG) and was comparable to results obtained with commercial ELISA (r = 0.93) and RIA (r = 0.85) kits. Further, the GC1102 in human serum could be precisely measured using the anti-HBs qELISA-v.2 without limitations of nonspecific binding.