An in vitro model of intestinal infection reveals a developmentally regulated transcriptome of Toxoplasma sporozoites and a NF-κB-like signature in infected host cells.

Pascale S Guiton,John C Boothroyd,Heather M Fritz,Janelle M Sagawa,Silvia N Moreno

doi:10.1371/journal.pone.0173018

Pascale S Guiton, John C Boothroyd + Show 3 more

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https://doi.org/10.1371/journal.pone.0173018

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Journal: PloS one	Publication Date: Mar 31, 2017
Citations: 17	License type: CC BY 4.0

Affiliation: Stanford University, Washington State University

Abstract

Toxoplasmosis is a zoonotic infection affecting approximately 30% of the world’s human population. After sexual reproduction in the definitive feline host, Toxoplasma oocysts, each containing 8 sporozoites, are shed into the environment where they can go on to infect humans and other warm-blooded intermediate hosts. Here, we use an in vitro model to assess host transcriptomic changes that occur in the earliest stages of such infections. We show that infection of rat intestinal epithelial cells with mature sporozoites primarily results in higher expression of genes associated with Tumor Necrosis Factor alpha (TNFα) signaling via NF-κB. Furthermore, we find that, consistent with their biology, these mature, invaded sporozoites display a transcriptome intermediate between the previously reported day 10 oocysts and that of their tachyzoite counterparts. Thus, this study uncovers novel host and pathogen factors that may be critical for the establishment of a successful intracellular niche following sporozoite-initiated infection.

Highlights

Toxoplasma gondii is one of the most successful eukaryotic pathogens of medical and veterinary importance, as it can infect humans and a very large number of warm-blooded animals worldwide [1]
There are three developmental forms in the T. gondii complex life cycle that are key to infection in an intermediate host: sporozoites within sporulated oocysts that are ingested from the environment, rapidly growing tachyzoites that disseminate the infection within a host, and the slowly dividing bradyzoites in tissue cysts that produce the chronic infection [4]
All kitten and mouse experiments were conducted conforming to the guidelines of the American Association for Accreditation of Laboratory Animal Care (AAALAC) protocol and the Transcriptomic analysis of Toxoplasma sporozoites during infection of intestinal epithelial cells institutional guidelines set by the Office of Campus Veterinarian at Washington State University (Animal Welfare Assurance A04592)

Summary

Introduction

Toxoplasma gondii is one of the most successful eukaryotic pathogens of medical and veterinary importance, as it can infect humans and a very large number of warm-blooded animals worldwide [1]. The non-replicating sporozoites convert to tachyzoites that swiftly replicate and disseminate to other organs and tissues [12] Despite their critical role in transmission and initiation of new T. gondii infection, the technical challenges associated with the study of oocysts and sporozoites, from their production to handling them in a laboratory setting, have hindered our understanding of the molecular interactions of this developmental form with its host. Notwithstanding these difficulties, comparative transcriptomic and proteomic analyses of T. gondii oocysts, examined 0, 4 and 10 days after shedding from the cat, have been performed and the results compared to similar data for tachyzoites and bradyzoites [13,14]. These findings broaden our understanding of the very first interactions of Toxoplasma sporozoites with its host and reveal genes that may mediate fundamental processes of this initial encounter

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