FIG 5.

Assessing the duration of vaccine-induced protection after homologous challenge. (A to C) Parasitemia levels in BALB/c mice that received three doses of 10⁶ chemically treated nRBCs (control) or P. yoelii 17X pRBCs (vaccinated) prior to challenge with 10⁵ P. yoelii 17X pRBCs at 1 month (A), 3 months (B), or 9 months (C) after the final dose. Disease severity was evaluated in control and vaccinated mice according to hemoglobin levels (D to F), clinical scores (G to I), and survival (J to L) after homologous challenge at 1 month (left panels), 3 months (middle panels), or 9 months (right panels) after the final dose. The groups challenged at 1 month contained nine mice; all other groups contained ten mice. Error bars show the SEM for each group. +, mice that succumbed to infection. Peak parasitemia was significantly lower in vaccinated mice than in control mice at each time point (***, P = 0.0001; ****, P < 0.0001). Data were analyzed using an unpaired, two-tailed t test.