Figure 4.

Moderate survival against blood-stage malaria infection following immunization with de-escalating doses of PSNPs compared to CFA/IFA adjuvanted vaccines. BALB/c mice were immunized intradermally at the base of tail (100 μl/immunization) and then a boost 3 weeks later with PBS alone (Naïve), MSP4/5 in CFA (80 μg per mouse, first immunization) or MSP4/5 in IFA (80 μg per mouse, boost immunization) or 3 different doses of PSNPs-MSP4/5 (2.1 × 10¹⁴, 3.7 × 10¹³, 1.7 × 10¹³ PSNPs/ml). Fourteen days after the last immunization, mice were challenged intraperitoneally with 5 × 10⁵ P. yoelii pRBCs and parasitemia levels were monitored starting at 3 days post-challenge. (A) Kaplan-Meier survival curve and percentage parasitemias of mice immunized with (B) Naïve -∙-, (C) MSP4/5 in CFA/IFA -■-, (D) 2.1 × 10¹⁴ PSNPs-MSP4/5 -▼-, (E) 3.7 × 10¹³ PSNPs-MSP4/5 -^*- and (F) 1.74 × 10¹³ PSNPs-MSP4/5 -▲-. ^**p < 0.01, ^***p < 0.001, with Mantel Cox Log Rank Test. Indicates mouse endpoint. Data shown are from 6 mice per experimental group.