Figure 2.

Induction of antibody following immunization with PbPfs25DR3 ookinetes. The ability of each regime to generate Pfs25-specific antibody responses after administration was tested by ELISA against recombinant Pfs25 protein^12,17 and IFA against P. falciparum (NF54) ookinete/retort stages within the mosquito midgut 26 hours post-feed. (A) End -point anti-Pfs25 titers in serum. Bars show mean titers from 5 mice. Pre-immune/non-immunized serum did not recognize recombinant Pfs25. Error bars represent SEM. Bars show mean titers from 5 mice. Error bars represent SEM. (B) IFA against P. falciparum (NF54) ookinete/retort stages. Ability of generated serum to recognize native Pfs25 on the surface of sexual stages of P. falciparum post-fertilization was assessed by immunofluorescence on fixed, non-permeabilized parasites probed with anti-serum from each regime. To control for non Pfs25-specific signal, IFA was performed using serum from control regimes (7–12). Each panel shows an overlay of anti-Pfs25 signal (turquoise) and DNA labelled with DAPI (blue). Scalebar  =  5 µm. (C and D) The ability of induced titers to reduce both oocyst intensity (C) and infection prevalence (D) by DFA, and relationship with anti-Pfs25 titers. Small open circles denote estimates generated from mosquitoes fed on individual mice (Fig. 3) compared to the average from mosquitoes feeding on unimmunized mice) whilst the large filled dots show the average for the regimen as estimated using a generalized-linear mixed effect model. Vertical lines show 95% confidence interval on overall estimates. Point colours indicate the regimen tested, be it regime 1 (blue), 2 (green), 3 (purple), 4 (orange), 5 (red) or 6 (brown).