TRSP is dispensable for the Plasmodium pre-erythrocytic phase

Abstract

Plasmodium sporozoites deposited in the skin following a mosquito bite must migrate and invade blood vessels to complete their development in the liver. Once in the bloodstream, sporozoites arrest in the liver sinusoids, but the molecular determinants that mediate this specific homing are not yet genetically defined. Here we investigate the involvement of the thrombospondin-related sporozoite protein (TRSP) in this process using knockout Plasmodium berghei parasites and in vivo bioluminescence imaging in mice. Resorting to a homing assay, trsp knockout sporozoites were found to arrest in the liver similar to control parasites. Moreover, we found no defects in the establishment of infection in mice following inoculation of trsp knockout sporozoites via intravenous and cutaneous injection or mosquito bite. Accordingly, mutant sporozoites were also able to successfully invade hepatocytes in vitro. Altogether, these results suggest TRSP may have a redundant role in the completion of the pre-erythrocytic phase of the malaria parasite. Nonetheless, identifying molecules with paramount roles in this phase could aid in the search for new antigens needed for the design of a protective vaccine against malaria.

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

“…Finally, the wells were washed and the slides mounted with antifade solution. Image acquisition and analysis was performed as previously described (26). Briefly, 25 images per (which was not certified by peer review) is the author/funder.…”

“…Finally, the wells were washed and the slides mounted with antifade solution. Image acquisition and analysis was performed as previously described (26). Briefly, 25 images per well, corresponding to a total area of 0.57 mm 2 , were taken using IN Cell Analyzer 2000 (GE Healthcare).…”

“…Female Anopheles stephensi SDA-500 mosquitoes reared in the Center for the Production and Infection of Anopheles at the Pasteur Institute in Paris, France, were fed on infected SWISS, CD1 or NMRI mice 3-5 days after emergence and kept at 21 ± 0.5 ºC and 70% humidity. A feeding using naïve mice was performed 6-7 days after the infectious feeding (26).…”

Secretory Organelle Function in the Plasmodium Sporozoite

“…TRSP (thrombospondin-related sporozoite protein) is a sporozoite-specific protein containing a TSR domain localized to the rhoptries in oocyst and salivary gland-derived sporozoites [75]. Although a recent study deemed TRSP dispensable in Pb pre-erythrocytic stages [76], earlier work using a different Pb strain suggested that it is involved in hepatocyte invasion, particularly at the entry point, since a marked reduction of knockout intracellular sporozoites and a rise in the frequency of partially invaded parasites was observed, suggesting a role in completing cell entry [77]. The roles of RON2 and RON11 in substrate attachment and motility consequently impact the invasion of hepatocytes [22,26].…”

Physical Interactions With Bacteria and Protozoan Parasites Establish the Scavenger Receptor SSC4D as a Broad-Spectrum Pattern Recognition Receptor

“…Parasites were prepared as previously described: Neospora caninum tachyzoites (Nc-1, ATCC 50843) (36), Plasmodium berghei ANKA strain blood merozoites (clone 676cl1) (37), Trypanosoma brucei brucei Lister 427 bloodstream forms (38), Leishmania major strain LV39, and Leishmania tarentolae strain Parrot-TarII promastigotes (39). A green fluorescent protein (GFP)-expressing T. brucei brucei Lister 427 line was engineered by cloning an enhanced gfp into a modified pHD1034 vector where the puromycin resistance cassette was replaced by the hygromycin resistance from the pHD1145 vector.…”