Experimental Infection of Calves with Transfected Attenuated Expressing the Bm86 Antigen and eGFP Marker: Preliminary Studies towards a Dual Anti-Tick/Babesia Vaccine

Bovine babesiosis, caused by and , is a major tick-borne disease of cattle with global economic impact. The disease can be prevented using integrated control measures including attenuated vaccines, babesicidal drugs, and tick control approaches. Vaccination of cattle with the Bm86-based recombinant vaccine reduces the fitness of and , but several booster inoculations are required to maintain protection. Herein, we generated a stable transfected strain of expressing an enhanced GFP (eGFP) and a chimeric version of Bm86 (/Bm86/eGFP). The eGFP was expressed in the parasite cytoplasm, whereas Bm86 was displayed on the surface of merozoites. Three splenectomized calves experimentally infected with /Bm86/eGFP showed mild signs of acute disease and developed long-lasting antibody responses to and native Bm86. No evidence of sequestration of parasites in the cerebral capillaries was found upon postmortem analysis, confirming attenuation of the strain. This is the first report of transfected expressing the tick antigen Bm86 on the merozoite surface that elicits an antibody response to native Bm86. These results represent a proof of concept for a novel live, attenuated, tagged dual-vaccine approach to attempt simultaneous control of babesiosis and tick infestation.