Normal numbers of salivary gland sporozoites are formed. Infection of mice by mosquito bite or by inoculation of salivary gland sporozoites did not result in a blood stage infection. Sporozoites show normal hepatocyte traversal and invasion in vitro.

Normal numbers of salivary gland sporozoites are formed. Sporozoites lack sap1 transcripts. Infection of mice by mosquito bite or by inoculation of salivary gland sporozoites did not result in a blood stage infection. Sporozoites show normal gliding, hepatocyte traversal and invasion in vitro.

Normal numbers of motile sporozoites are formed. Sporozoites show normal traversal and invasion of hepatocytes in vitro. Development of liver stages is completely aborted soon after invasion of sporozoites. Intravenous injection of up to 500.000 Pbslarp sporozoites never led to full development of parasites in the liver as assayed by in vivo imaging of parasite liver loads or analysis of blood stage infection.

To analyse in more details the fate of slarp sporozoites, time-lapse fluorescence microscopy was used to image control p230p-GFP (RMgm-1026) and slarp-GFP parasites in HepG2 cultures from 7 to 24 hours postinfection. Transformation of elongated sporozoites into round forms was observed with both p230p-GFP and slarp-GFP. However, whilst p230p-GFP persisted in the culture and started growing over the observation period, slarp-GFP failed to develop and died, as evidence by disappearance of the GFP signal from infected cells. No detectable sign of death of infected host cells was observed by microscopy, suggesting that elimination of the slarp mutant parasites, unlike other liver stage-arresting mutants19, does not result from host cell apoptosis.

intravital imaging of bioluminescent parasites was used to analyse the fate of slarp P. berghei sporozoites in vivo after intravenous inoculation into C57BL/6 mice. Control p230p-GFP-LUC parasites were readily detectable in the liver of infected mice 24 h after injection of sporozoites, and the signal further increased at 48 h. All mice developed a patent parasitemia, as shown by positive Giemsa-stained blood smears and diffusion of the luminescence signal in the entire mouse body at day 4 post-infection. In sharp contrast, mice injected with slarp-GFP-LUC showed no luminescence signal above background at any of the time points examined, and none of the animals became patent, in total agreement with published data showing that slarp P. berghei sporozoites fail to convert into blood stages.

Infection of rats and mice by mosquito bite or by inoculation of salivary gland sporozoites did not result in a blood stage infection. Sporozoites show normal hepatocyte traversal and invasion in vitro.The number of infected hepatocytes decreased over time in vitro. Mutant liver stages remained very small throughout the culture time, around 34 m, which roughly corresponds to the size of 1218h wild type parasites. Most mutant parasites were blocked at the one nucleus stage, even at late time points of infection.

Infection of mice by mosquito bite or by inoculation of salivary gland sporozoites did not result in a blood stage infection. Sporozoites show normal gliding, hepatocyte traversal and invasion in vitro. In vitro in HepG2-CD81 cells the number of developing liver stages gradually decrease between 6 and 12h after infection and sharply decrease between 18 and 24h after infection. In addition, the liver stages failed to growth and develop.