Fig. 8. Rabbit antibodies induced by CSP/230/CPQ and passively transferred to mice confer protection to transgenic sporozoite challenge.

Rabbits were thrice immunized with CSP (20 µg) and 230 (10 µg), admixed with CPQ or Alum. 10 mg purified IgG was then intravenously injected into mice 18 h prior to sporozoite challenge with PbPfCSP, transgenic P. berghei parasites expressing P. falciparum CSP. Prior to challenge, antigen-specific rabbit antibodies in mouse sera were detected against (a) CSP and (b) 230, as determined by ELISA. Control mice did not receive any IgG. c Parasite liver burden (assessed with qPCR) in mice challenged with intravenous inoculation of 2000 PbPfCSP sporozoites. A human anti-CSP mAb (mAb317, 300 µg) was used as a positive control. The percent inhibition in parasite liver burden was determined by using qPCR to assess parasite 18S rRNA relative to mouse GAPDH mRNA, relative to mice that did not receive IgG. For (a) and (b), the lines represent geometric mean, and two-sided Student T-test using log-transformed data was used to analyze differences, ^****p < 0.0001. For c, the lines represent median and a Mann-Whitney U-test was used to analyze differences, ^****p < 0.001. Red symbols indicate bivalent, liposome-displayed CSP/230.