Secreted protein with altered thrombospondin repeat (SPATR) is essential for asexual blood stages but not required for hepatocyte invasion by the malaria parasite Plasmodium berghei

Upon entering its mammalian host, the malaria parasite productively invades two distinct cell types, that is, hepatocytes and erythrocytes during which several adhesins/invasins are thought to be involved. Many surface-located proteins containing thrombospondin Type I repeat (TSR) which help establish host-parasite molecular crosstalk have been shown to be essential for mammalian infection. Previous reports indicated that antibodies produced against Plasmodium falciparum secreted protein with altered thrombospondin repeat (SPATR) block hepatocyte invasion by sporozoites but no genetic evidence of its contribution to invasion has been reported. After failing to generate Spatr knockout in Plasmodium berghei blood stages, a conditional mutagenesis system was employed. Here, we show that SPATR plays an essential role during parasite's blood stages. Mutant salivary gland sporozoites exhibit normal motility, hepatocyte invasion, liver stage development and rupture of the parasitophorous vacuole membrane resulting in merosome formation. But these mutant hepatic merozoites failed to establish a blood stage infection in vivo. We provide direct evidence that SPATR is not required for hepatocyte invasion but plays an essential role during the blood stages of P. berghei.