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

The role of heat shock protein 90 in the proliferation of Babesia gibsoni in vitro

The present study investigated the role of heat shock protein 90 (HSP90) in the proliferation and survival of Babesia gibsoni in vitro. To detect the effect on the entry of B. gibsoni into host erythrocytes, the parasite was incubated with an antibody against B. gibsoni HSP90 (BgHSP90) for 24 hr. The results of this experiment demonstrated that both the incorporation of [³H]hypoxanthine into the nucleic acids of B. gibsoni and the number of parasites were not altered, indicating that an anti-BgHSP90 antibody did not directly inhibit the entry of the parasite into erythrocytes. Moreover, two HSP90 inhibitors, geldanamycin (GA) and tanespimycin (17-AAG), were used to evaluate the function of BgHSP90. GA and 17-AAG decreased both the incorporation of [³H]hypoxanthine and the number of infected erythrocytes, suggesting that BgHSP90 plays important roles in DNA synthesis and the proliferation of B. gibsoni. The effect of 17-AAG on the parasites was weaker than that of GA. Additionally, the effect of GA on the survival and superoxide generation of canine neutrophils was assessed. The survival of canine neutrophils was not affected. The superoxide generation was strongly suppressed by GA. This result indicated that GA inhibited the function of canine neutrophils. Additional studies are necessary to elucidate the role of BgHSP90 in the proliferation of the parasite.

Characterisation of the Theileria orientalis Piroplasm Proteome across Three Common Genotypes

Theileria orientalis is an emerging apicomplexan pathogen of cattle occurring in areas populated by the principal vector tick, Haemaphysalis longicornis. Unlike transforming Theileria spp. that induce cancer-like proliferation of lymphocytes via their schizont stage, T. orientalis destroys host erythrocytes during its piroplasm phase resulting in anaemia. The underlying pathogenic processes of T. orientalis infection are poorly understood; consequently, there are no vaccines for prevention of T. orientalis infection and chemotherapeutic options are limited. To identify antigens expressed during the piroplasm phase of T. orientalis, including those which may be useful targets for future therapeutic development, we examined the proteome across three common genotypes of the parasite (Ikeda, Chitose and Buffeli) using preparations of piroplasms purified from bovine blood. A combination of Triton X-114 extraction, one-dimensional electrophoresis and LC-MS/MS identified a total of 1113 proteins across all genotypes, with less than 3% of these representing host-derived proteins. Just over three quarters of T. orientalis proteins (78%) identified were from the aqueous phase of the TX-114 extraction representing cytosolic proteins, with the remaining 22% from the detergent phase, representing membrane-associated proteins. All enzymes involved in glycolysis were expressed, suggesting that this is the major metabolic pathway used during the T. orientalis piroplasm phase. Proteins involved in binding and breakdown of haemoglobin were also identified, suggesting that T. orientalis uses haemoglobin as a source of amino acids. A number of proteins involved in host cell interaction were also identified which may be suitable targets for the development of chemotherapeutics or vaccines.