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Endothelial cells are a replicative niche for entry of Toxoplasma gondii to the central nervous system

Abstract

An important function of the blood–brain barrier is to exclude pathogens from the central nervous system, but some microorganisms benefit from the ability to enter this site. It has been proposed that Toxoplasma gondii can cross biological barriers as a motile extracellular form that uses transcellular or paracellular migration, or by infecting a host cell that then crosses the blood–brain barrier. Unexpectedly, analysis of acutely infected mice revealed significant numbers of free parasites in the blood and the presence of infected endothelial cells in the brain vasculature. The use of diverse transgenic parasites combined with reporter mice and intravital imaging demonstrated that replication in and lysis of endothelial cells precedes invasion of the central nervous system, and highlight a novel mechanism for parasite entry to the central nervous system.

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Figure 1: T. gondii infection of the vascular compartment.
Figure 2: Detection of free T. gondii tachyzoites in the vascular compartment.
Figure 3: T. gondii tachyzoites invade ECs in vivo and in vitro.
Figure 4: T. gondii egress from ECs in vivo.
Figure 5: Replication of T. gondii in ECs is required for parasites to cross the BBB.

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Acknowledgements

C.K. was supported by research grant KO 4609-1/1 from the German Research Foundation (DFG). This work was supported by grants from the National Institutes of Health (NIH AI 41158 to C.A.H., NIH NS065116 to A.A.K., NIH AI041930 to D.J.B.), the American Heart Association (14BGIA20380675 to M.B.L. and 15POST25550021 to N.U.) and the University of Arizona and the BIO5 Institute (A.A.K.). Imaging experiments were performed in the PennVet Imaging Core Facility on instrumentation supported by NIH S10RR027128, the School of Veterinary Medicine, the University of Pennsylvania, and the Commonwealth of Pennsylvania. sIgM-ko mice were provided by G. Debes (University of Pennsylvania). C.A.H is the Mindy Halikman Heyer President's Distinguished Chair.

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Authors

Contributions

C.K. performed the majority of the experiments. N.U. and M.B.L. performed and analysed the microfluidic chamber experiments. J.D. and G.H.P. helped with sample collection. D.J.B. provided the CPS parasites. A.A.K. provided Cre-secreting parasites. D.A.C., J.H. and D.B.M were involved in study design. C.K. and C.A.H. wrote the paper. All authors discussed the results and commented on the manuscript.

Corresponding author

Correspondence to Christopher A. Hunter.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Figures 1-6 (PDF 4603 kb)

Supplementary Video 1

Intravital imaging of circulation kinetics of T. gondii after i.v. infection. (MOV 2595 kb)

Supplementary Video 2

Intravital imaging of the lysis of an infected Tie2-GFP+ endothelial cell in a large blood vessel in the brain. (MOV 3398 kb)

Supplementary Video 3

Intravital imaging of the lysis of an infected Tie2-GFP+ endothelial cell in a capillary in the brain and parasite entry into the parenchyma. (MOV 4775 kb)

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Konradt, C., Ueno, N., Christian, D. et al. Endothelial cells are a replicative niche for entry of Toxoplasma gondii to the central nervous system. Nat Microbiol 1, 16001 (2016). https://doi.org/10.1038/nmicrobiol.2016.1

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