Babesia bovis: culture of laboratory-adapted parasite lines and clinical isolates in a chemically defined medium

Babesiosis caused by Babesia spp. is a disease of both veterinary and human importance. Here, we describe a method to continuously culture laboratory lines and field isolates of Babesia bovis in vitro in a chemically defined medium using (ALBU)MAX II as an alternative to bovine serum. Further, we have successfully cultured parasite isolates directly from cattle that failed to grow in traditional serum-containing medium. Variation of atmospheric gas composition and culture volumes to determine optimal growth conditions revealed that a 600-microl culture in an atmosphere comprising 5% O(2), 5% CO(2), and 90% N(2) achieved a significantly higher percentage of parasitized red blood cells than any other combination tested. The process could be scaled up to reliably produce large volumes of parasites. Supplementation of the culture medium with hypoxanthine further improved parasite growth. B. bovis cultured in this way could be the basis of an alternative, safer vaccine and a reliable source of parasites and exoantigens for parasitological research.