Usefulness of Babesia bigemina gp45 Gene as a Genetic Marker

THOMPSON, C.; BARAVALLE, M.E; TORIONI DE ECHAIDE, S; SHKAP, V; MANGOLD, A; FARBER, M; ECHAIDE, I.

Mérida (México)

Conferencia; 9th Biennial Conference of Society for Tropical Veterinary Medicine; 2007

Babesia bigemina bigemina, one of the Apicomplexa hemoparasites that causes bovine babesiosis, is enzootic in areas infested with Rhipicephalus spp ticks, its natural vector. The gp45 gene codifying a glycoprotein expressed in the surface of the B. bigemina merozoites was previously studied by Fisher et al. (2001, Infect. Immun. 69: 3782-3790) who demonstrated genetic and transcriptional polymorphism among five Latin American strains evaluated. The aim of this work was to analyze the polymorphism on the sequences of the gp45 gene to characterize B. bigemina (Bbi) strains from different regions with distinctive phenotypes and multiplied in vivo or in vitro. Primers previously designed to amplify a sequence of 1098 nucleotides (nt) of gp45 were used to study this gene in pathogenic (P) and attenuated strains (A) from Argentina and Israel. The gp45 sequences of BbiS1A, BbiS2P, BbiS4 (isolate) and BbiM1A, BbiM2P strains from the NW and the NE of Argentina respectively, and the gp45 sequences of attenuated Vaccine (BbiVac) and Moledet (BbiMol) from Israel were compared to the reference sequence from the Mexican JG29 strain  (Genbank accession no. AF298630). The BbiS1A, BbiS2P, BbiVac and BbiMol are routinely multiplied in vitro; while BbiM1A, BbiS4 and BbiM2P are stored as frozen stabilates. The gp45 sequence was amplified from six of the seven strains evaluated, and it was no possible to amplify the sequence from BbiS2P. The alignment of the obtained sequences revealed that BbiS1A and BbiM1A, despite having a different geographic origin, showed 100% of identity between them and 75% respect to JG-29 with eight nt missing and one insertion of six nt. BbiS4 and BbiM2P had 98% similarity, while the strains from Israel showed a 100% identity between them. When pathogenic and isolate Argentinean strain and the Israelis strains where compared with the JG-29 they showed a 98% and a 99% of identity respectively. New primers were designed to amplify the BbiS2P strain. The neighbor-joining analysis allowed grouping the Argentinean attenuated strains in one cluster and the three Argentinean pathogenic strains, the isolate strain plus both Israelis strains in a second cluster. There is no evidence that these differences can be attributed either to different origins or multiplication system. Ongoing investigations are carried out to validate the gp45 gene as a genetic marker for B. bigemina analyzing its stability during in vitro and in vivo multiplication and to study the distribution of this genotype in the babesiosis enzootic areas. This work was supported by the ANPCyT PICTO 12920 and TCP INTA EEA-Rafaela-Asoc. Coop. 426100.