Complete Plasmodium falciparum liver-stage development in liver-chimeric mice
Ashley M. Vaughan, … , Alexander Ploss, Stefan H.I. Kappe
Ashley M. Vaughan, … , Alexander Ploss, Stefan H.I. Kappe
Published September 10, 2012
Citation Information: J Clin Invest. 2012;122(10):3618-3628. https://doi.org/10.1172/JCI62684.
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Technical Advance Infectious disease

Complete Plasmodium falciparum liver-stage development in liver-chimeric mice

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.

Authors

Ashley M. Vaughan, Sebastian A. Mikolajczak, Elizabeth M. Wilson, Markus Grompe, Alexis Kaushansky, Nelly Camargo, John Bial, Alexander Ploss, Stefan H.I. Kappe

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Figure 4

Correlation of LS burden with liver humanization in FRG huHep mice and comparison of LS density in P. falciparum–infected FRG huHep mice, FRG NOD huHep mice, and P. yoelii–infected BALB/cJ mice.

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Correlation of LS burden with liver humanization in FRG huHep mice and c...
(A) Liver tissue fragments (each point on the graph represents a single sample) taken from a 7-day LS infection of 2 FRG huHep mice (female littermates who received the same human donor hepatocytes) were analyzed by qRT-PCR for P. falciparum 18S rRNA burden (Pf18S, arbitrary units) as well as the level of humanization based on the ratio of hapoAI transcripts relative to mGAPDH transcripts (arbitrary units). The results show a statistically significant, linear relationship (coefficient of determination, R2 = 0.87–0.89) between LS burden and liver humanization in the 2 mice. (B) The level of P. falciparum LS burden in the FRG huHep mouse was compared with that of the FRG NOD huHep mouse and P. yoelii rodent malaria LS burden in BALB/cJ mice. LS burden is shown as LS/cm2 50-μm liver section/106 sporozoites injected. Average LS counts per liver section were determined by analyzing at least 6 nonserial 50-μm liver sections from 3 individual mice. Humanized mice had huHep repopulation levels above 80%. The results show that the FRG huHep and FRG NOD huHep mice support robust P. falciparum LS infections. Data for B represent mean ± SD.