The Selection of a Hepatocyte Cell Line Susceptible to Plasmodium falciparum Sporozoite Invasion That Is Associated With Expression of Glypican-3

Abstract

<i>In vitro</i> studies of liver stage (LS) development of the human malaria parasite <i>Plasmodium falciparum</i> are technically challenging; therefore, fundamental questions about hepatocyte receptors for invasion that can be targeted to prevent infection remain unanswered. To identify novel receptors and to further understand human hepatocyte susceptibility to <i>P. falciparum</i> sporozoite invasion, we created an optimized <i>in vitro</i> system by mimicking <i>in vivo</i> liver conditions and using the subcloned HC-04.J7 cell line that supports mean infection rates of 3-5% and early development of <i>P. falciparum</i> exoerythrocytic forms-a 3- to 5-fold improvement on current <i>in vitro</i> hepatocarcinoma models for <i>P. falciparum</i> invasion. We juxtaposed this invasion-susceptible cell line with an invasion-resistant cell line (HepG2) and performed comparative proteomics and RNA-seq analyses to identify host cell surface molecules and pathways important for sporozoite invasion of host cells. We identified and investigated a hepatocyte cell surface heparan sulfate proteoglycan, glypican-3, as a putative mediator of sporozoite invasion. We also noted the involvement of pathways that implicate the importance of the metabolic state of the hepatocyte in supporting LS development. Our study highlights important features of hepatocyte biology, and specifically the potential role of glypican-3, in mediating <i>P. falciparum</i> sporozoite invasion. Additionally, it establishes a simple <i>in vitro</i> system to study the LS with improved invasion efficiency. This work paves the way for the greater malaria and liver biology communities to explore fundamental questions of hepatocyte-pathogen interactions and extend the system to other human malaria parasite species, like <i>P. vivax</i>.