FIG. 3.

Correlation between ELISA units and growth inhibition activity in vitro. From the individual monkey serum on 17 days after the final immunization (just before parasite challenge), IgG was purified using protein G columns. The antibody titers of the purified IgGs were determined by ELISA, and the GI activities were determined by a standardized GI assay with P. falciparum FVO parasites in vitro. The antibody units in the GI assay wells as determined by ELISA units against MSP1₄₂ FVO antigen were plotted on the abscissa and the percent inhibition in the GI assay on the ordinate. There is a significant positive correlation between the ELISA units and the percent inhibition by GI assay (Spearman rank correlation, 0.864; P = 0.0003). The line is the best fit for the hyperbolic function.