Immunocapture Enzyme-Linked Immunosorbent Assay for Assessment of In Vitro Potency of Recombinant Hepatitis B Vaccines

Quantification of hepatitis B surface antigen (HBsAg) or relative in vitro potency in the final vaccines is a prerequisite for hepatitis B vaccine batch release. The commercial kit for automated analysis (AxSYM) is expensive, and an alternative is required for the estimation of HBsAg in hepatitis B vaccines. Mouse monoclonal antibodies (MAbs) specific for HBsAg were developed and characterized. One of the monoclonal antibodies (HBs06) was used in development of an immunocapture ELISA (IC-ELISA) as an unlabeled capture antibody and biotin-labeled detection antibody. The IC-ELISA was standardized and validated using experimental hepatitis B vaccine batches with various HBsAg concentrations per dose and commercial vaccines. The vaccine was treated with an alkaline solubilizer to desorb the HBsAg from Algel-adjuvanted vaccines before testing, and the sensitivity of the test was 5 ng/ml. A good correlation could be observed between the HBsAg estimates derived by both formats, except for the higher HBsAg concentration range, where the IC-ELISA format could estimate closer to the actual values than AxSYM. There was a significant correlation between the estimated relative potencies of the two methods. There was lack of correlation between the in vivo potency and the relative in vitro potency. However, the estimates of IC-ELISA were comparable to the in vivo values when compared with the estimates of AxSYM. The IC-ELISA can therefore be considered to be a reliable test for deriving in vitro relative potency and antigen concentration in vaccine batches for batch control and release.