Fig. 6.

Bioluminescence imaging of P. berghei liver stage egress. a Luminescence values obtained from in vivo imaging of C57BL/6 mice infected with 5000 sporozoites of PbFLuc. Dotted line shows the peak of luminescence after which the first obvious decrease in signal from the mouse liver in vivo after around 48 h occurs. b Egress measured by first appearance of parasites in the periphery. 2 μl of blood were obtained via tail vein puncture and lysed in 20 μl of 1 × PLB for bioluminescence measurement. Luminescence values of peripheral blood from C57BL/6 and Balb/c mice infected with 5000 PbNLuc sporozoites obtained at the indicated time points post-sporozoite injection until 70 h, showing the kinetics of egress as measured by PbNLuc. c Representative luminescence-based assay of egress at the indicated time points in 4 separate C57BL/6 and Balb/c mice. 2 μl of blood were obtained via tail vein puncture and lysed in 20 μl of 1 × PLB for bioluminescence measurement. While egress of PbNLuc is detected earliest at 36 h post-infection, egress of PbFLuc is detected for the first time at 60 h post-infection. d Success of passages of liver-egressed parasites from 36 h onwards into naïve mice. Six C57BL/6 mice were infected with 5000 sporozoites each, and at 36, 40, 42 44, 52, 56 and 60 h post-sporozoite injection, 20 μl of blood removed, diluted in 200 μl of 1 × PBS and the 220 μl intravenously injected into 3 naïve mice. It was later (at 70–90 h post-infection) assessed whether the inoculum had produced an infection in these recipient mice. e Comparative kinetics of egress as measured by luminescence in the blood, in mice infected by intravenous injection of 5000 sporozoites, or by mosquito feeds (5 mosquitoes) [luminescence measured in photons per second (p/s); ***p < 0.001; error bars in all graphs represent standard deviations (SD)]