Exposure to ambient air causes degradation and decreased in vitro potency of buparvaquone and parvaquone

Systematic review on buparvaquone resistance associated with non-synonymous mutation in drug binding genes site of Theileria annulate

Theileria annulata (T. annulata) is intra-erythrocytic protozoan parasite which is more prevalent in tropical and sub-tropical countries. It has a significant economic impact on the productivity of the dairy industry, and buparvaquone is used to treat infected animals in the prevalent regions of the world. Systematically, buparvaquone targets the cyto-b gene to break the electron transport chain (ETC) and Theileria annulata peptidyl-prolyl isomerase 1 (TaPIN1) gene to destabilize transcription factor JUN (c-JUN) to inhibit proliferation of infected cells, which ultimately leads to the death of T. annulata. The reported studies on drug resistance is due to inappropriate drug application, evolutionary characteristics of the cytochrome b (cyto-b) gene and oncogenic signaling pathways gene (TaPIN1) make the parasite resistant against buparvaquone. Hence, this systematic review was designed to find out non-synonymous mutation in genes (cyto-b and TaPIN1) responsible for drug resistance reported from Tunisia, Turkey, Egypt, Sudan, Iran, Pakistan, China and Germany with reference to the T. annulata Ankara strain of cyto-b (accession no. XM_949625.1) and TaPIN1 (accession no. TA18945) wild type genes. Non-synonymous point mutations were found in cyto-b (Q01 at 130-148 and Q02 at 253-262 regions) and TaPIN1 (A53P and A53T) genes. These point mutations are responsible for developing buparvaquone resistance against T. annulata infection. These genes can be used as biomarkers for the identification of drug resistance in any endemic area. To avoid the complication of drug resistance, development of genetically resistant cattle breeds, potent vaccines and anti-theilerial drugs (Trifloxystrobin and anti-cancerous) are currently required to control proliferating economically important T. annulata parasites.

Endochin-like quinolone-300 and ELQ-316 inhibit Babesia bovis, B. bigemina, B. caballi and Theileria equi

Background

The most common apicomplexan parasites causing bovine babesiosis are Babesia bovis and B. bigemina, while B. caballi and Theileria equi are responsible for equine piroplasmosis. Treatment and control of these diseases are usually achieved using potentially toxic chemotherapeutics, such as imidocarb diproprionate, but drug-resistant parasites are emerging, and alternative effective and safer drugs are needed. The endochin-like quinolones (ELQ)-300 and ELQ-316 have been proven to be safe and efficacious against related apicomplexans, such as Plasmodium spp., with ELQ-316 also being effective against Babesia microti, without showing toxicity in mammals.

Methods

The inhibitory effects of ELQ-300 and ELQ-316 were assessed on the growth of cultured B. bovis, B. bigemina, B. caballi and T. equi. The percentage of parasitized erythrocytes was measured by flow cytometry, and the effect of the ELQ compounds on the viability of horse and bovine peripheral blood mononuclear cells (PBMC) was assessed by monitoring cell metabolic activity using a colorimetric assay.

Results

We calculated the half maximal inhibitory concentration (IC₅₀) at 72 h, which ranged from 0.04 to 0.37 nM for ELQ-300, and from 0.002 to 0.1 nM for ELQ-316 among all cultured parasites tested at 72 h. None of the parasites tested were able to replicate in cultures in the presence of ELQ-300 and ELQ-316 at the maximal inhibitory concentration (IC₁₀₀), which ranged from 1.3 to 5.7 nM for ELQ-300 and from 1.0 to 6.0 nM for ELQ-316 at 72 h. Neither ELQ-300 nor ELQ-316 altered the viability of equine and bovine PBMC at their IC₁₀₀ in in vitro testing.

Conclusions

The compounds ELQ-300 and ELQ-316 showed significant inhibitory activity on the main parasites responsible for bovine babesiosis and equine piroplasmosis at doses that are tolerable to host cells. These ELQ drugs may be viable candidates for developing alternative protocols for the treatment of bovine babesiosis and equine piroplasmosis.