Continuous propagation of Babesia duncani in vitro in human erythrocytes and the availability of a mouse model of B. duncani lethal infection make this parasite an ideal model to study Babesia biology and pathogenesis. Two culture media, HL-1 and Claycomb, with proprietary formulations are the only culture media known to support the parasite growth in human erythrocytes; however, the HL-1 medium has been discontinued and the Claycomb medium is often unavailable leading to major interruptions in the study of this pathogen. To identify alternative media conditions, we evaluated the growth of B. duncani in various culture media with well-defined compositions. We report that the DMEM-F12 culture medium supports the continuous growth of the parasite in human erythrocytes to levels equal to those achieved in the HL-1 and Claycomb media. We generated new clones of B. duncani from the parental WA-1 clinical isolate after three consecutive subcloning events in this medium. All clones showed a multiplication rate in vitro similar to that of the WA-1 parental isolate and cause fatal infection in C3H/HeJ mice. The culture medium, which can be readily reconstituted from its individual components, and the tools and resources developed here will facilitate the study of B. duncani.
Keywords: Babesia duncani; DMEM-F12; babesiosis; erythrocytes; in vitro culture; parasite; virulence.