Normal numbers of salivary gland sporozoites produced.

Normal numbers of sporozoites are formed that are infective to cultured hepatocytes. Parasites arrest during development in hepatocytes after a period of growth. In most parasites no merozoites are formed as shown by the low level of MSP1 expression. After intravenous injection of sporozoites, 6 out of 46 mice developed a blood stage infection.

In vitro invasion of hepatocytes by the sporozoites is not affected. Liver stage development is strongly impaired. Sporozoites initiate the transformation of the banana-shaped, elongated sporozoite to a spherical liver trophozoite. However, they show a severe defect in their ability to complete transformation into liver trophozoites. They lack the capacity to develop into mature liver schizonts. Infection of highly susceptible, young Sprague-Dawley rats by intravenous inoculation of high numbers of sporozoites (100.000) did not result in blood stage infection.

Immunofluorescence and Western blot analyses performed 24 h after GAS/MAGEA3 sporozoite invasion into HepG2 cells showed that MAGEA3 was expressed in GAS/MAGE-A3-infected cells.

(Strongly) reduced development of liver stages

In vitro invasion of hepatocytes by the sporozoites is not affected. Liver stage development is strongly impaired. In vivo (BALB/c mice), the number of liver stages at 2 hours after intravenous injection of sporozoites is reduced by 75%. The number of liver stages at 24h were reduced by >95%. liver stages could not be detected at 40h after infection. Liver stages were morphologically similar to wt liver stages at 6 and 12h after infection, a time when the intrahepatocytic transformation from elongate sporozoite to spherical trophozoites commences. Antibody staining for UIS4, a resident parasitophorous vacuole membrane (PVM)protein, showed a typical circumferential pattern, which indicates that the PVM is present. Liver stages did not develop into schizonts but appeared to be arrested at the trophozoite stage. Arrested liver stages did not persist in the liver after 40h. Infection of BALB/c mice by intravenous inoculation of high numbers of sporozoites (50.000) did not result in blood stage infection.