Downregulation of the secreted protein with an altered thrombospondin repeat (SPATR) impacts the infectivity of malaria sporozoites

Abstract

The identification of surface proteins of the sporozoite stage of malaria parasites important for sporozoite infectivity could aid in the improvement of the efficacy of vaccines targeting pre-erythrocytic stages. Thus, we set out to disclose the role of the secreted protein with an altered thrombospondin repeat (SPATR), which is highly expressed in sporozoites. Previous studies showed an essential function in blood stages, while no role was detected in sporozoites despite high expression. To achieve downregulation of expression in sporozoites while maintaining blood stage expression, a promoter swap approach was used to generate a mutant where the Plasmodium berghei spatr gene was placed under transcriptional control of the hado gene promoter. Downregulation of expression in oocysts and sporozoites resulted in formation of sporozoites with impaired motility, strongly reduced capacity to invade salivary glands, and decreased infectivity to mice. In conclusion, we revealed a new role for SPATR in sporozoite infectivity, highlighting the importance to use complementary methods in studies on sporozoite biology.

The claudin-like apicomplexan microneme protein is required for gliding motility and infectivity of Plasmodium sporozoites

“…Like CLAMP, SPATR is conserved in Apicomplexa and is essential in asexual blood stages of the parasite life cycle. Interestingly, a recent study based on conditional knockdown in P. berghei showed that sporozoites lacking SPATR have impaired motility, strongly reduced capacity to invade salivary glands and decreased infectivity to mice (Costa et al, 2022), a phenotype that is similar to the one we observed with CLAMP-deficient parasites. Costa et al excluded a role of SPATR in TRAP secretion, based on the detection of TRAP at the surface of mutant sporozoites by immunofluorescence (Costa et al, 2022).…”

“…Interestingly, a recent study based on conditional knockdown in P. berghei showed that sporozoites lacking SPATR have impaired motility, strongly reduced capacity to invade salivary glands and decreased infectivity to mice (Costa et al, 2022), a phenotype that is similar to the one we observed with CLAMP-deficient parasites. Costa et al excluded a role of SPATR in TRAP secretion, based on the detection of TRAP at the surface of mutant sporozoites by immunofluorescence (Costa et al, 2022). In our hands, surface staining of TRAP did not show any overt difference between untreated and rapamycin-treated parasites, irrespective of stimulation of microneme secretion (S3 Fig) . It is possible however that surface immunostaining may not capture the entire dynamics of TRAP secretion and shedding.…”

“…In addition to TRAP, various proteins have been identified as involved in sporozoite gliding motility, such as the TRAP-related protein (TREP) (Combe et al, 2009; Steinbuechel and Matuschewski, 2009), LIMP (Santos et al, 2017) or the Secreted Protein with Altered Thrombospondin Repeat (SPATR) (Costa et al, 2022). Like CLAMP, SPATR is conserved in Apicomplexa and is essential in asexual blood stages of the parasite life cycle.…”

“…Costa et al . excluded a role of SPATR in TRAP secretion, based on the detection of TRAP at the surface of mutant sporozoites by immunofluorescence (Costa et al, 2022). In our hands, surface staining of TRAP did not show any overt difference between untreated and rapamycin-treated parasites, irrespective of stimulation of microneme secretion ( S3 Fig ).…”

A conserved complex of microneme proteins mediates rhoptry discharge inToxoplasma

“…The latter corroborates prior work, which found that inhibitory antibodies can block P. falciparum invasion of blood cells (Chattopadhyay et al , 2003). In P. berghei, Pb SPATR is required for blood stages and is likely required in sporozoites, suggesting the CLAMP complex is important for host cell invasion in multiple stages of the parasitic life cycle (Gupta et al , 2020; Costa et al , 2022). Though we were unable to make a conditional knockdown strain for Pf CLIP, the PlasmoGEM project finds that the CLIP homolog in P. berghei is also essential during blood stages (Bushell et al , 2017).…”