Progress towards understanding the interactions between Babesia and its tick vector

Babesia bovis is a tick-borne hemoprotozoan parasite that is the etiologic agent of bovine babesiosis, also known as cattle tick fever. This protozoan parasite has a complex life cycle within vertebrate and invertebrate hosts. Within the mammalian host Babesia parasites infect bovine erythrocytes and undergo asexual reproduction while in the tick vector, the parasites reproduce sexually in the lumen of the midgut.  To identify genes and proteins critical for the Babesia life cycle, we isolated parasites from infected bovines, tick hemolymph, and induced in vitro sexual stages.  We used these B. bovis parasite stages to compare gene and protein expression between life-stages during infection of cattle and the tick vector. Transcriptome and proteomic analyses revealed a set of genes and proteins that was upregulated during tick vector infection. Several proteins expressed by B. bovis sexual stages during development in the midgut and kinetes isolated from tick hemolymph were identified, including HAP2, 6CYS, KSP, and GCC2/GCC3. These proteins were identified as surface exposed by a live immunofluorescence assay and are, therefore, suitable targets for bovine antibodies interfering with parasite development within the tick vector. These datasets may help to develop transmission-blocking vaccines targeting B. bovis parasites in tick midgut and/or hemolymph.