Inhibition of the in vitro growth of babesia bigemina, babesia caballi and theileria equi parasites by trifluralin analogues

Authors: SILVA, MARTA - Washington State University; Knowles Jr, Donald; DOMINGOS, A - New University Of Lisbon; ESTEVES, A - University Of Portugal; ANTUNES, S - New University Of Lisbon; Suarez, Carlos

Submitted to: Ticks and Tick Borne Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2017
Publication Date: 4/10/2017
Citation: Silva, M.G., Knowles, D.P., Domingos, A., Esteves, A.M., Antunes, S., Suarez, C.E. 2017. Inhibition of the in vitro growth of babesia bigemina, babesia caballi and theileria equi parasites by trifluralin analogues. Ticks and Tick Borne Diseases. 8(4):593-597.

Interpretive Summary: Bovine and equine babesiosis caused by Babesia bovis, B. bigemina and B. caballi, and equine theileriosis caused by Theileria equi are global tick borne hemoprotozoan diseases characterized by fever, anemia, weight losses and abortions. A common feature of these diseases are transition from acute to chronic phases, in which parasites may persist in the hosts for life. Antiprotozoal drugs are important for managing infection and disease. Previous research demonstrated that trifluralin analogues, designated (TFLAs) 1-15, have the ability to inhibit the in vitro growth of B. bovis. All TFLAs tested in the study showed inhibitory effects against the three parasites. TFLA 2, TFLA 11, TFLA 13 and TFLA 14 were the most effective inhibitors for the three species tested, with estimated. Importantly, TFLA 2, 13 and 14 did not caused statistically significant hemolytic activity on bovine and equine erythrocytes, and TFLA 2, 11 and 13 had no detectable toxic effects on bovine and equine erythrocytes under the conditions tested, suggesting that these drugs do not compromise erythrocyte viability. We concluded that the demonstrated ability of the trifuralin analogues to inhibit in vitro growth of Babesia sp. and Theileria equi, and their lack of toxic effects on erythrocytes supports further in vivo testing and eventually, their development as novel alternatives for the treatment of babesiosis and theileriosis.

Technical Abstract: Background: Bovine and equine babesiosis caused by Babesia bovis, B. bigemina and B. caballi, and equine theileriosis caused by Theileria equi are global tick borne hemoprotozoan diseases characterized by fever, anemia, weight losses and abortions. A common feature of these diseases are transition from acute to chronic phases, in which parasites may persist in the hosts for life. Antiprotozoal drugs are important for managing infection and disease. Previous research demonstrated that trifluralin analogues, designated (TFLAs) 1-15, which specifically bind to regions of alpha-tubulin protein in plants and protozoan parasites, have the ability to inhibit the in vitro growth of B. bovis. Methods: The inhibitory activity of TFLAs 1-15 minus TFLA 5 was tested in vitro against cultured B. bigemina, B. caballi and T. equi. The four TFLAs with greatest inhibitory activity were then analyzed for hemolytic activity and toxicity against erythrocytes. Results: All TFLAs tested in the study showed inhibitory effects against the three parasites. TFLA 2, TFLA 11, TFLA 13 and TFLA 14 were the most effective inhibitors for the three species tested, with estimated IC50 between 5.1 and 10.1 µM at 72h. The drug’s solvent (DMSO/ethanol) did not statistically affect the growth of the parasites nor cause hemolysis. Also, TFLA 2, 13 and 14 did not caused statistically significant hemolytic activity on bovine and equine erythrocytes at 15 µM, and TFLA 2, 11 and 13 had no detectable toxic effects on bovine and equine erythrocytes at 15 µM, suggesting that these drugs do not compromise erythrocyte viability. Conclusion: The demonstrated ability of the trifuralin analogues to inhibit in vitro growth of Babesia sp. and Theileria equi, and their lack of toxic effects on erythrocytes supports further in vivo testing and eventually, their development as novel alternatives for the treatment of babesiosis and theileriosis.