A new set of molecular markers for the genotyping of Babesia bovis isolates

Abstract

Babesia bovis is a tick-borne apicomplexan pathogen that remains an important constraint for the development of cattle industries worldwide. The existence of different strains and subpopulations has long been described in this hemoparasite. However, few molecular markers have been reported for strain genotyping and characterization. Minisatellite sequences show high levels of variation and therefore provide excellent tools for both the genotyping and population genetic analysis. In this work we report a set of five molecular markers containing minisatellites that showed a variable degree of polymorphism in several American strains. We have used a bioinformatics approach to search for marker sequences contained in open reading frames. Five genes were chosen and primers were designed in conserved regions flanking the repeat region. Two of the genes were the previously described Bv80/Bb-1 and TRAP. The other three genes were named p200, Antigen 3 and Desmoyokin. Amplification by PCR, sequencing and comparative analysis of 11 strains from Argentina, Brazil, Uruguay, Mexico and USA determined that the tandem repeats varied in number and sequence among the isolates. Genome analysis of the five markers revealed that they were single copy and distributed across the four B. bovis chromosomes. When the new markers were analyzed in an experimental infection, absolute sequence conservation was found, indicating the stability of these markers during the course of infection. These markers were also stable during three syringe passages through calves. The application of this panel of molecular markers could provide new molecular tools for the genotyping of B. bovis isolates and analysis of changes in parasite populations following vaccination.