Open AccessTransfected Babesia bovis Expressing a Tick GST as a Live Vector Vaccine
Author(s) -
Daiane P. Oldiges,
Jacob M. Laughery,
Nelson Júnior Tagliari,
Ronaldo Viana Leite Filho,
William C. Davis,
Itabajara da Silva Vaz,
Carlos Termigi,
Donald P. Knowles,
Carlos E. Suárez
Publication year - 2016
Publication title -
plos neglected tropical diseases
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.99
H-Index - 135
eISSN - 1935-2735
pISSN - 1935-2727
DOI - 10.1371/journal.pntd.0005152
Subject(s) - babesia bovis , biology , virology , rhipicephalus microplus , green fluorescent protein , vector (molecular biology) , microbiology and biotechnology , selectable marker , gene , plasmid , babesia , tick , genetics , recombinant dna
The Rhipicephalus microplus tick is a notorious blood-feeding ectoparasite of livestock, especially cattle, responsible for massive losses in animal production. It is the main vector for transmission of pathogenic bacteria and parasites, including Babesia bovis , an intraerythrocytic apicomplexan protozoan parasite responsible for bovine Babesiosis. This study describes the development and testing of a live B . bovis vaccine expressing the protective tick antigen glutathione-S-transferase from Haemaphysalis longicornis (HlGST). The B . bovis S74-T3B parasites were electroporated with a plasmid containing the bidirectional Ef-1α ( elongation factor 1 alpha ) promoter of B . bovis controlling expression of two independent genes, the selectable marker GFP-BSD ( green fluorescent protein–blasticidin deaminase ), and HlGST fused to the MSA-1 ( merozoite surface antigen 1 ) signal peptide from B . bovis . Electroporation followed by blasticidin selection resulted in the emergence of a mixed B . bovis transfected line (termed HlGST) in in vitro cultures, containing parasites with distinct patterns of insertion of both exogenous genes, either in or outside the Ef-1α locus. A B . bovis clonal line termed HlGST-Cln expressing intracellular GFP and HlGST in the surface of merozoites was then derived from the mixed parasite line HlGST using a fluorescent activated cell sorter. Two independent calf immunization trials were performed via intravenous inoculation of the HlGST-Cln and a previously described control consisting of an irrelevant transfected clonal line of B . bovis designated GFP-Cln. The control GFP-Cln line contains a copy of the GFP-BSD gene inserted into the Ef-1α locus of B . bovis in an identical fashion as the HIGST-Cln parasites. All animals inoculated with the HlGST-Cln and GFP-Cln transfected parasites developed mild babesiosis. Tick egg fertility and fully engorged female tick weight was reduced significantly in R . microplus feeding on HlGST-Cln-immunized calves. Collectively, these data show the efficacy of a transfected HlGST-Cln B . bovis parasite to induce detectable anti-glutathione-S-transferase antibodies and a reduction in tick size and fecundity of R . microplus feeding in experimentally inoculated animals.