Figure 5
Immunogenicity and protective efficacy of ultra-low dose R21/AS01 and RTS,S/AS01. BALB/c mice (n = 10 per group) received 3 immunizations, 2 weeks apart of either R21/AS01 or RTS,S/AS01 at range of doses (0.05 µg, 0.16 µg or 0.5 µg). (A) Two weeks after the final immunization NANP-specific IgG was measured by ELISA. Lines indicate the medians and groups compared by Kruskal-Wallis test with Dunn’s multiple comparison post-test comparing all pairs of groups. At this time all immunized mice and 9 naïve mice were challenged with 1000 transgenic P. berghei parasites expressing P. falciparum CSP. Blood-stage parasitemia was monitored from day 5 after challenge by thin-film blood smear, and time to 1% parasitemia calculated using linear regression. The results are presented in Kaplan–Meier survival graphs and survival curves compared by Log-rank (Mantel–Cox) Test. (B) Comparison of protective efficacy between all mice vaccinated with either RTS,S/AS01 (n = 30) or R21/AS01 (n = 30). (C) Protective efficacy compared between RTS,S/AS01 and R21/AS01 at the different doses. Four months after the first challenge the surviving mice were re-challenged as before along with 8 naïve mice. (0.5 µg RTS,S/AS01: n = 10, 0.16 µg RTS,S/AS01: n = 8, 0.05 µg RTS,S/AS01: n = 7, 0.5 µg R21/AS01: n = 8, 0.16 µg R21/AS01: n = 10, 0.05 µg R21/AS01: n = 10). (D) Comparison of protective efficacy after re-challenge between all mice vaccinated with either RTS,S/AS01 (n = 25) or R21/AS01 (n = 28). (E) Protective efficacy after re-challenge compared between RTS,S/AS01 and R21/AS01 at the different doses. (F) Four months after the second challenge the surviving mice were re-challenged a second time as before along with 6 naïve mice RTS,S/AS01: n = 18 or R21/AS01: n = 21.
