Abstract
BackgroundThe phylum Apicomplexa comprises a wide variety of parasites of significant medical and economic relevance. These parasites have extremely different host and tissue tropisms; for example Toxoplasma gondii can invade virtually any nucleated cell and infect almost all warm-blooded vertebrates, whereas Eimeria tenella infects only chickens and is restricted in its growth to epithelial cells of the caecum. Proteins released from the microneme secretory organelles (MICs) are critical for apicomplexan invasion of host cells and allow parasites to bind a diverse range of host cell oligosaccharide epitopes. MICs bear modular arrangements of sequences with adhesive proteins and interestingly the sialic-acid binding MAR (microneme adhesive repeat) domain containing proteins (MCPs) are suggested to make significant contributions to the different host and tissue tropisms of T. gondii and E. tenella.ResultsIn this study, we evaluated the binding capacity of Type I MAR domains from novel E. tenella MCPs. Variants of the previously described HxT motif were analysed showing that HxT and VxT variants bind, whereas HxS and YxE variants did not. One of these MCP containing a single MAR (EtMCP2) showed an apical localization when expressed as a fusion with the fluorescent reporter mCherry in transgenic populations and a similar pattern of transcripts per zoite during endogenous development in vitro as the well-characterised microneme protein EtMIC2.ConclusionsVariation in the binding properties of the MAR of different EtMCPs was confirmed and their ability to bind a wider range of sialic acids and terminal linkages should be studied. In addition, transgenesis technology has been used for first time in Eimeria parasites as a rapid tool for the study of endogenous protein localization by fusion with a fluorescent reporter.
Highlights
The phylum Apicomplexa comprises a wide variety of parasites of significant medical and economic relevance
Type I microneme adhesive repeat (MAR) from E. tenella MAR containing proteins (MCP) has low conservation in their binding domains MAR from EtMIC3 (Fig. 1a) and from the four identified EtMCP proteins (Fig. 1b) of E. tenella were aligned in order to predict their potential binding properties (Table 1)
We report the use of this technology as a convenient and rapid tool for the study of endogenous protein localization; being able to visualise the location of overexpressed proteins fused to a fluorescent reporter has allowed a previously uncharacterised MAR containing protein to be tentatively assigned to the microneme organelle
Summary
The phylum Apicomplexa comprises a wide variety of parasites of significant medical and economic relevance. These parasites have extremely different host and tissue tropisms; for example Toxoplasma gondii can invade virtually any nucleated cell and infect almost all warm-blooded vertebrates, whereas Eimeria tenella infects only chickens and is restricted in its growth to epithelial cells of the caecum. MICs bear modular arrangements of sequences with adhesive proteins and interestingly the sialic-acid binding MAR (microneme adhesive repeat) domain containing proteins (MCPs) are suggested to make significant contributions to the different host and tissue tropisms of T. gondii and E. tenella. Seven species of the genus Eimeria (Apicomplexa, Coccidia) cause chicken coccidiosis, a disease with a huge economic impact in the poultry industry. Because the parasites do not replicate outside of their host, vaccine production requires large numbers of chickens to amplify lines of vaccinal parasites; this places a practical limitation on production and means that vaccines are costly compared to anticoccidial drugs [2]
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