FIG 1.

Immunization with Pyfabb/f⁻ induces functional antibodies that inhibit hepatocyte invasion in vitro. (A and B) Optimization of the assay of antibody inhibition of liver-stage development. (A) Correlation between hepatocyte infection determined by bioluminescence (x axis) and by microscopy (y axis) for increasing amounts of sporozoites, as indicated. Pearson's correlation coefficient R = 0.983, P < 0.0001. (B) Inhibition of HepG2 cell invasion by P. yoelii PyGFP-luc sporozoites after incubation with increasing amounts of anti-CSP monoclonal antibody. The relative inhibition was calculated as a percentage of the average luminescence in the absence of antibody. Error bars correspond to standard deviations. (C) Inhibition of HepG2 cell invasion by PyGFP-luc sporozoites after incubation with a 1:10 dilution of serum obtained 9 days after the second dose of 50,000 Pyfabb/f⁻ sporozoites from BALB/c (white bar, n = 5) or C57BL/6 (black bar, n = 5) mice. The relative inhibition was calculated as a percentage of the average luminescence resulting from incubation with serum from mock-immunized mice of the same strain (n = 5). Error bars correspond to standard deviations. These data are representative of the results of three independent experiments.