Detection and quantitation of hepatitis-B surface antigen immune complexes (HBsAg-ICs) by an antigen-specific method. I. Detection and quantitation of in vitro prepared HBsAg-ICs.

An antigen-specific method has been developed for direct detection and quantitation of HBsAg-ICs. The method involves (1) precipitation of HBsAg-ICs with 3.5% PEG; (2) dissociation of the PEG precipitated ICs by treatment with NaSCN, NaI, KBr, low or high pH buffers, trypsin or papain; and (3) detection and titration of HBsAg and/or anti-HBs liberated from ICs. Treatment with 2 M and 3 M NaSCN, papain or trypsin liberates HBsAg, while following treatment with 3 M and NaI free anti-HBs is detectable. Trypsin digestion (2 mg/ml, 30 min at 37 degrees C) proved to be most effective for disrupting HBsAg-ICs formed at equivalence as well as in excess of antigen or antibody. After trypsin digestion of the sample RPHA, RIA and ELISA may be used as a third step. Th