Abstract

BackgroundBovine babesiosis is a tick-borne disease caused by several species of Babesia which produce acute and fatal disease in cattle and affect livestock industry worldwide. Babesia ovata is a benign species widespread in east Asian countries and causes anemia, particularly in cattle which are co-infected with Theileria orientalis. The development of genetic manipulation methods is necessary to improve our understanding of the basic biology of protozoan pathogens toward a better control of disease. Such tools have not been developed for B. ovata, and are the aim of this study.MethodsIn this study we transfected constructs that were designed to evaluate the ability of several B. ovata promoter candidates to drive expression of a reporter luciferase. We found that the elongation factor-1 alpha intergenic region (ef-1α IG) and the actin 5’ non-coding region (NR) had highest promoter activities. To establish a stable transfection system, we generated a plasmid construct in which the ef-1α IG promoter drives gfp expression, and the actin 5’ NR mediates expression of the selectable marker hdhfr. The plasmid was designed for episomal transfection, as well as to integrate by double cross-over homologous recombination into the ef-1α locus. Circular or linearized plasmid was transfected by electroporation into in vitro cultured B. ovata and retention of the plasmid was facilitated by drug selection with 5 nM WR99210 initiated 48 h after transfection.ResultsAfter one-week cultivation with WR99210, GFP-expressing parasites were observed by fluorescence microscopy. Integration of the plasmid construct into the ef-1α locus was confirmed by PCR, Southern blot analysis, and sequencing of recombination sites. These results confirm successful development of a stable transfection system for B. ovata.ConclusionThe current study provides a fundamental molecular tool to aid in molecular and cellular studies of B. ovata.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1439-z) contains supplementary material, which is available to authorized users.

Highlights

  • Bovine babesiosis is a tick-borne disease caused by several species of Babesia which produce acute and fatal disease in cattle and affect livestock industry worldwide

  • Evaluation of the B. ovata promoter activities In order to evaluate promoter activity and to select promoters to be used for stable transfections, candidate promoters were chosen which were previously used for B. bovis or Plasmodium

  • Similar to the B. bovis ef-1α gene locus [17], two ef-1α gene copies are oriented head to head in the B. ovata genome, and the Intergenic region (IG) region was expected to have a bidirectional promoter activity

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Summary

Introduction

Bovine babesiosis is a tick-borne disease caused by several species of Babesia which produce acute and fatal disease in cattle and affect livestock industry worldwide. Babesia ovata is a benign species widespread in east Asian countries and causes anemia, in cattle which are co-infected with Theileria orientalis. The development of genetic manipulation methods is necessary to improve our understanding of the basic biology of protozoan pathogens toward a better control of disease. Such tools have not been developed for B. ovata, and are the aim of this study. Better understanding of the basic biology of Babesia spp. is crucial to design and develop new strategies for controlling the disease. Regarding Babesia spp., only two reports describe stable transfection systems, for B. bovis [7, 8]; one used blasticidin-S/blasticidin deaminase and the other employed WR99210/human dihydrofolate reductase (hdhfr) as selective markers

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