Molecular characterization of the Israeli B. bigemina vaccine strain and field isolates

- The RAP-1a of blood-derived Israeli Babesia bigemina field isolates.
- Shared 100% amino acid sequence identity.
- Comparison of RAP-1c from various Israeli B. bigemina field isolates revealed that the identity among the field isolates ranged from 98.2 to 100%.
- Based on sequence variations between the rap-1a of the vaccine strain and that of the field isolate, and between the rap-1c of the vaccine and that of the field isolates, nPCR-RFLP were developed that enable, differentiation between the vaccine strain and field isolates.

The present study demonstrated the genetic character of the Israeli Babesia bigemina vaccine strain and field isolates, based on rap-1a and rap-1c gene sequences. The RAP-1a of blood-derived Israeli B. bigemina field isolates shared 100% amino acid sequence identity. However, comparison of RAP-1c from various Israeli B. bigemina field isolates revealed that the total sequence identity among the field isolates ranged from 98.2 to 100%. High identity was observed when RAP-1a sequences from the Israeli vaccine strain and field isolates were compared with RAP-1a from Egypt, Syria, Mexico and South Africa, while, the Israeli RAP-1c sequences showed the highest identity to the Mexican isolate JG-29 and to the PR isolate from Puerto-Rico. Based on sequence variations between the rap-1a of the vaccine strain and that of the field isolate, and between the rap-1c of the vaccine strain and that of the field isolates, nPCR-RFLP procedures were developed that enable, for the first time differentiation between the Israeli B. bigemina vaccine strain and field-infection isolates. These assays could serve as fast and sensitive methods for detection and differentiation between Israeli B. bigemina vaccine strains and field isolates, as well as for epidemiological investigations.