Normal oocyst production, normal sporozoite formation inside oocysts. Reduced number of hemolymph and salivary gland sporozoites despite the production of normal numbers of sporozoites within oocysts.

Normal numbers of salivary gland sporozoites are formed that show normal gliding motility. Mutant sporozoites show an in vitro invasion rate of HepG2 cells and development within the hepatocytes that is comparable to wild type parasites.When infected by mosquito bite, the mutant parasites were detected in blood 1 day later than wild type parasites. In contrast to a bite infection, there was no difference in the prepatent period of mutant and wild type parasites when the rats were infected by intravenous injection, indicating a 90% reduction in the infectivity of the sporozoites. By real time PCR a decrease of 90% in parasite load in the liver was detected in mice infected with the mutant parasites by mosquito bite compared to mice infected with wild type parasites.

Normal liver parasite load after injection of sporozoites. Normal development of liver stage parasites into maturing liver schizonts. PbPL-KO parasites produced approximately 60% fewer detached cells compared to WT parasites. A significant proportion of detached cells in the KO population showed an aberrant morphology; merozoites were not released into the hepatocyte cytoplasm but remained clustered together. At 54 hpi, before PVM rupture, no significant difference in the number of hepatocytes containing merozoites existed between WT, PbPL-KO and complemented parasites, indicating normal merozoite formation up to this time point. In contrast, at 65 hpi, a time point where the PVM is disrupted in normally developed WT parasites, a significantly higher number of attached hepatocytes containing merozoites was seen for PbPL-KO parasites compared to WT parasites, indicating impaired merozoite release. PbPL-KO parasites that developed to the merozoite stage either did not rupture the PVM at all or this process was significantly delayed.

Mutant sporozoites show an in vitro invasion rate of HepG2 cells and development within the hepatocytes that is comparable to wild type parasites.When infected by mosquito bite, the mutant parasites were detected in blood 1 day later than wild type parasites, indicating a 90% reduction in the infectivity of the sporozoites. In contrast to a bite infection, there was no difference in the prepatent period of mutant and wild type parasites when the rats were infected by intravenous injection. By real time PCR a decrease of 90% in parasite load in the liver was detected in mice infected with the mutant parasites by mosquito bite compared to mice infected with wild type parasites.