Anti-piroplasmic activity of novobiocin as heat shock protein 90 inhibitor against in vitro cultured Theileria equi and Babesia caballi parasites

• Published in: Ticks and tick-borne diseases 2021-07, Vol.12 (4), p.101696-101696, Article 101696
• Main Authors: Suthar, A., Maji, C., Gopalkrishnan, A., Raval, S.H., Kumar, R., Kumar, S.
• Format: Article
• Language: English
• Subjects: Babesia caballi; Cell cytotoxicity; Haemolytic activity; In vivo organ toxicity; Novobiocin; Theileria equi
• ISSN: 1877-959X; 1877-9603
• DOI: 10.1016/j.ttbdis.2021.101696

[Display omitted] •In vitro Theileria equi and Babesia caballi growth inhibitory efficacy of the Hsp-90 inhibitor drug novobiocin was investigated.•Novobiocin significantly arrested the in vitro growth of T. equi and B. caballi parasites with respective 50 % inhibitory concentration values of 165 μM and 84.85 μM.•The drug was found safe on horse peripheral blood mononuclear cells and red blood cells with very high specific selective index.•Organ toxicity of novobiocin was assessed in a mouse model and no adverse effects of the drug was observed at a dose rate of 50 mg/kg body weight. Theileria equi and Babesia caballi are the causative agents of equine piroplasmosis (EP). Currently, imidocarb dipropionate (ID) is the only available drug for treating the clinical form of EP. Serious side effects and incomplete clearance of infection is a major drawback of ID. Heat-shock proteins (Hsp) play a vital role in the life cycle of these haemoprotozoans by preventing alteration in protein conformation. These Hsp are activated during transmission of EP sporozoites from the tick vector (poikilotherm) to the natural host (homeotherm) and facilitate parasite survival. In the present study, we targeted the heat shock protein 90 (Hsp-90) pathway of T. equi and B. caballi by using its inhibitor drug - novobiocin. Dose-dependent efficacy of novobiocin on the growth of T. equi and B. caballi was observed in in vitro culture. Additionally, we examined dose-dependent cell cytotoxicity on host peripheral mononuclear cells (PBMCs) and haemolytic activity on equine red blood cells (RBC). In vivo organ toxicity of novobiocin was also assessed in a mouse model. The IC50 (50 % inhibitory concentration) value of novobiocin against T. equi and B. caballi was 165 μM and 84.85 μM, respectively. Novobiocin significantly arrested the in vitro growth of T. equi and B. caballi parasites at 100 μM and 200 μM drug concentration, respectively. In vitro treated parasites had distorted nuclear material and showed no further viability. Based on the equine PBMCs and RBC, the drug was found to be safe even at 1000 μM concentration and the CC50 (50 % cytotoxicity concentration) values were 11.63 mM and 261.97 mM. Very high specific selective index (SSI) values (70.47 and 1587) were observed for equine PBMCs and RBC, respectively. Organ-specific biochemical markers and histopathological examination indicated no adverse effect of the drug at a dose rate of 50 mg kg body weight in the mouse model. The