Host sphingolipids support liver stage development.

During the asymptomatic liver stage resides within a parasitophorous vacuole (PV) that protects the parasite from immune clearance while also restricting nutrient exchange with its host cell. Although it is known that must scavenge resources from its environment, the specific nutrients sequestered and the mechanisms for transporting them to the PV are poorly understood, particularly during the liver stage. In this study, we investigated the role of host lipids and discovered that sphingolipids are critical for both liver stage development and invasion. Specifically, exogenous C16-ceramide enhanced parasite development and nuclear replication, while sphingomyelin in the host cell membrane was essential for parasite invasion. Live microscopy studies using NBD labeled sphingolipids further found that exogenous lipids are actively transported into the PV with sphingolipid scavenging occurring at all tested time points throughout the liver stage. This was, in part, supported by the host ceramide transporter, CERT1. CERT1 was enriched at the PV and genetic disruption significantly reduced both load and ceramide trafficking into the PV. Finally, we identified proteins of the host salvage pathway as critical for the liver stage using chemical and genetic approaches. In particular, depletion of and affected PV size and infection rate, but not invasion. Our findings enhance our understanding of host-parasite lipid interactions and may offer novel therapeutic targets to reduce disease burden.IMPORTANCE, the causative agent of malaria, remains a significant global health challenge, placing approximately half the world's population at risk of infection. Despite the existence of antimalarial treatments, the emergence of drug-resistant parasites highlights the urgent need to identify novel therapeutic targets. The liver stage represents a promising avenue for drug discovery as inhibiting parasite development would prevent both symptomatic disease and transmission to the mosquito vector. In this study, we examined the role of host sphingolipids and found that members perform distinct functions, supporting parasite invasion and/or development. We also identified several host proteins that influence liver stage viability and contribute to sphingolipid acquisition. In addition to their role in the liver stage, sphingolipids are known to be critical for the asexual and sexual blood stages, suggesting that targeting host sphingolipid metabolism could offer a novel multistage therapeutic strategy against malaria.