Antibody titers or units as measured by ELISA or similar assays represent only a semi-quantitative measurement of the antibody concentration. In the present study, a truly quantitative assay for evaluating antibody concentrations was developed. In the new assay, IgG and IgA antibody concentrations are expressed in absolute gravimetric units (weight/ml) rather than by more ambiguous terms such as titers or units. The procedure is based on the comparison of known concentrations of IgG or IgA bound to anti-F(ab)'(2) with the binding of an unknown concentration of antibodies to a specific antigen. We applied the new assay to the measurement of HIV1-gp160 specific IgG and IgA concentrations in cervicovaginal secretions (CVS), saliva, and sera of infected women. Measurement of antibody activity was obtained by comparing the amount of specific antibodies to the amount of total immunoglobulins found in the same compartment. Because of its quantitative and comparative nature, the assay was named comparative antibody gravimetric evaluation assay (CAGE).
Copyright 2000 Wiley-Liss, Inc.