Bioluminescence images were acquired with a 7-cm FOV, medium binning factor and exposure time of 10–30 s. Quantitative analysis was performed by measuring the luminescence signal intensity per well using the ROI settings of the living image 3.0 software. ROI measurements are expressed Acalabrutinib cost in total flux of photons. Per cent inhibition was calculated by the following formula; 1 – (average bioluminescence in immune plasma sample/average bioluminescence in naive plasma sample)* 100%. In all experiments and assays, comparisons between two groups were performed by a Mann–Whitney U-test

using prism software version 5.0 (Graphpad, San Diego, CA, USA). P < 0.05 is considered statistically significant. Overall comparisons over three groups or more was performed by Kruskal–Wallis test. Calculations of sample sizes were performed (power 0.85; α = 0.05) by estimation of differences between IV and ID groups. To compare protective efficacy conferred by ID or IV immunization, mice immunized by either RAS or CPS protocols were challenged by infectious mosquito bites. Irrespective of the immunization protocol, ID immunization induced lower protection in BALB/cByJ (50%) and C57BL/6J (7–13%) mice as compared to 90–100% protection after IV immunization

(Table 1). Development of blood-stage parasites in unprotected ID immunized mice showed no significant delay compared to control mice. To evaluate whether infection by IV or ID routes resulted in different magnitude of Exoribonuclease liver infection, we measured in vivo parasite liver Fostamatinib concentration loads in C57BL/6 mice by real-time imaging after IV or ID injection of identical doses of fresh PbGFP-Luccon sporozoites. Mice that received IV injection showed a clear bioluminescent signal originating from the site of the liver as from 30 h post-infection

onwards. This signal subsequently further increased covering the whole liver area at 44 h post-infection (Figure 1a). In contrast, ID injection did not result in a bioluminescent signal distinct from background at 30 and 35 h post–infection, while a weak signal was visible at 44 h. After ID injection, mice showed approximately a 30-fold lower parasite liver load (P < 0.0001) compared to IV injected mice (Figure 1b). These data show a strong association [P < 0.001 (χ2 = 49.08, (d.f. = 1)] between the number of parasites reaching the liver in this experiment and the level of protection conferred by different routes of sporozoite administration as shown in preceding immunization experiments. We next assessed cellular immune responses after IV or ID immunization of C57BL/6j mice. Following RAS or CPS IV immunization, proportions of CD8+ T cells with effector memory phenotype (Tem) were significantly increased in both liver (P = 0.008) and spleen (P = 0.008). With the exception of one CPS mouse, this expansion of CD8+ Tem cells was not observed in any of the ID immunized mice, remaining at baseline levels similar to naïve mice (Figure 2a).