Complete Plasmodium falciparum liver stage development in liver-chimeric mice

The Journal of clinical investigation (Impact Factor: 13.77). 09/2012; 122(10):3618-28. DOI: 10.1172/JCI62684
Source: PubMed

ABSTRACT Plasmodium falciparum, which causes the most lethal form of human malaria, replicates in the host liver during the initial stage of infection. However, in vivo malaria liver-stage (LS) studies in humans are virtually impossible, and in vitro models of LS development do not reconstitute relevant parasite growth conditions. To overcome these obstacles, we have adopted a robust mouse model for the study of P. falciparum LS in vivo: the immunocompromised and fumarylacetoacetate hydrolase-deficient mouse (Fah-/-, Rag2-/-, Il2rg-/-, termed the FRG mouse) engrafted with human hepatocytes (FRG huHep). FRG huHep mice supported vigorous, quantifiable P. falciparum LS development that culminated in complete maturation of LS at approximately 7 days after infection, providing a relevant model for LS development in humans. The infections allowed observations of previously unknown expression of proteins in LS, including P. falciparum translocon of exported proteins 150 (PTEX150) and exported protein-2 (EXP-2), components of a known parasite protein export machinery. LS schizonts exhibited exoerythrocytic merozoite formation and merosome release. Furthermore, FRG mice backcrossed to the NOD background and repopulated with huHeps and human red blood cells supported reproducible transition from LS infection to blood-stage infection. Thus, these mice constitute reliable models to study human LS directly in vivo and demonstrate utility for studies of LS-to-blood-stage transition of a human malaria parasite.

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Available from: Ashley M Vaughan, Dec 18, 2013
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    • "Salivary gland dissections were performed at days 14–19. Production of P. falciparum sporozoites and the infection of FRG KO huHep mice with P. falciparum were performed as previously described (Vaughan et al., 2012). "
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    ABSTRACT: Plasmodium vivax malaria is characterized by periodic relapses of symptomatic blood stage parasite infections likely initiated by activation of dormant liver stage parasites-hypnozoites. The lack of tractable P. vivax animal models constitutes an obstacle in examining P. vivax liver stage infection and drug efficacy. To overcome this obstacle, we have used human liver-chimeric (huHep) FRG KO mice as a model for P. vivax infection. FRG KO huHep mice support P. vivax sporozoite infection, liver stage development, and hypnozoite formation. We show complete P. vivax liver stage development, including maturation into infectious exo-erythrocytic merozoites as well as the formation and persistence of hypnozoites. Prophylaxis or treatment with the antimalarial primaquine can prevent and eliminate liver stage infection, respectively. Thus, P. vivax-infected FRG KO huHep mice are a model to investigate liver stage development and dormancy and may facilitate the discovery of drugs targeting relapsing malaria. Copyright © 2015 Elsevier Inc. All rights reserved.
    Cell host & microbe 03/2015; DOI:10.1016/j.chom.2015.02.011 · 12.19 Impact Factor
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    • "Detection of PTEX components in gametocytes, sporozoites, and late liver stages (Vaughan et al., 2012; Matthews et al., 2013) indicates that the putative translocation machinery is available during these stages of infection. For instance, two core PTEX components, PTEX150, and EXP2 (de Koning-Ward et al., 2009), localize to the parasite/host interface in mature P. falciparum liver-stage parasites in human hepatocytes from infected liver-chimeric mice (Vaughan et al., 2012). PTEX150, EXP2 and the third core PTEX protein HSP101 are present in P. berghei salivary gland sporozoites and liver-stage merozoites in cultured hepatoma cells (Matthews et al., 2013). "
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    ABSTRACT: Obligate intracellular pathogens actively remodel their host cells to boost propagation, survival, and persistence. Plasmodium falciparum, the causative agent of the most severe form of malaria, assembles a complex secretory system in erythrocytes. Export of parasite factors to the erythrocyte membrane is essential for parasite sequestration from the blood circulation and a major factor for clinical complications in falciparum malaria. Historic and recent molecular reports show that host cell remodeling is not exclusive to P. falciparum and that parasite-induced intra-erythrocytic membrane structures and protein export occur in several Plasmodia. Comparative analyses of P. falciparum asexual and sexual blood stages and imaging of liver stages from transgenic murine Plasmodium species show that protein export occurs in all intracellular phases from liver infection to sexual differentiation, indicating that mammalian Plasmodium species evolved efficient strategies to renovate erythrocytes and hepatocytes according to the specific needs of each life cycle phase. While the repertoire of identified exported proteins is remarkably expanded in asexual P. falciparum blood stages, the putative export machinery and known targeting signatures are shared across life cycle stages. A better understanding of the molecular mechanisms underlying Plasmodium protein export could assist in designing novel strategies to interrupt transmission between Anopheles mosquitoes and humans.
    Cellular Microbiology 12/2013; 16(3). DOI:10.1111/cmi.12251 · 4.82 Impact Factor
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    • "At day 5 postinfection, cryopreserved sporozoites express both PfEBA-175 and PfMSP-1 (Figure 3C). The parasites we observed were similar in size to what has been reported in other in vitro settings ($10–15 mm at day 5) (Mazier et al., 1985; van Schaijk et al., 2008) but smaller than those reported in vivo (Shortt et al., 1951; Shortt and Garnham, 1948; Vaughan et al., 2012) (Figures 2L and 3B). Importantly, we demonstrated that the rate at which parasites progressed to the schizont stage between day 3 and day 6 postinfection was higher in infected MPCCs (33%) relative to the commonly used hepatoma line HC04 (14%) (Figure 2K). "
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    ABSTRACT: The Plasmodium liver stage is an attractive target for the development of antimalarial drugs and vaccines, as it provides an opportunity to interrupt the life cycle of the parasite at a critical early stage. However, targeting the liver stage has been difficult. Undoubtedly, a major barrier has been the lack of robust, reliable, and reproducible in vitro liver-stage cultures. Here, we establish the liver stages for both Plasmodium falciparum and Plasmodium vivax in a microscale human liver platform composed of cryopreserved, micropatterned human primary hepatocytes surrounded by supportive stromal cells. Using this system, we have successfully recapitulated the full liver stage of P. falciparum, including the release of infected merozoites and infection of overlaid erythrocytes, as well as the establishment of small forms in late liver stages of P. vivax. Finally, we validate the potential of this platform as a tool for medium-throughput antimalarial drug screening and vaccine development.
    Cell host & microbe 07/2013; 14(1):104-15. DOI:10.1016/j.chom.2013.06.005 · 12.19 Impact Factor
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