Inhibitory effect of allicin on the growth of Babesia and Theileria equi parasites.

Allicin is an active ingredient of garlic that has antibacterial, antifungal, antiviral, and antiprotozoal activity. However, the inhibitory effects of allicin on Babesia parasites have not yet been examined. In the present study, allicin was tested as a potent inhibitor against the in vitro growth of bovine and equine Babesia parasites and the in vivo growth of Babesia microti in a mouse model. The in vitro growth of Babesia bovis, Babesia bigemina, Babesia caballi, or Theileria equi was inhibited by allicin in a dose-dependent manner and had IC50 values of 818, 675, 470, and 742 µM, respectively. Moreover, allicin significantly inhibited (P < 0.001) invasion of B. bovis, B. bigemina, B. caballi, and T. equi into the host erythrocyte. Furthermore, mice treated with 30 mg/kg of allicin for 5 days significantly (P < 0.05) reduced the parasitemia of B. microti over the period of the study. To further examine the potential synergism of allicin with diminazene aceturate, growth inhibitory assays were performed in vitro and in vivo. Interestingly, combinations of diminazene aceturate with allicin synergistically potentiated its inhibitory effects in vitro and in vivo. These results indicate that allicin might be beneficial for the treatment of babesiosis, particularly when used in combination with diminazene aceturate.

Specific antibody to a conserved region of Babesia apical membrane antigen-1 inhibited the invasion of B. bovis into the erythrocyte.

Apical membrane antigen-1 (AMA-1) is a microneme protein that exists in all apicomplexan parasites and plays an indispensable role in the invasion into host cell. Central region of ectodomains I and II of Babesia bovis apical membrane antigen-1 (BbAMA-1P) is highly conserved with these of Babesia species and may be beneficial for vaccine development against babesiosis. In the present study, recombinant protein encoding the central region of B. bovis AMA-1 (rBbAMA-1P) was produced in Escherichia coli and its antiserum was prepared in mice for further molecular characterization. Anti-rBbAMA-1P serum specifically reacted with corresponding authentic protein of B. bovis as determined by Western blotting and IFAT. Cultured B. bovis treated with anti-rBbAMA-1P serum showed significant reduction in the in vitro growth of the parasites. Moreover, preincubated free merozoites with 1mg/ml anti-rBbAMA-1P serum inhibited their efficiency in the invasion into erythrocytes (RBCs) by 61% and 70% at 3h and 6h, respectively. Our data suggest that the central region of domains I and II of BbAMA-1 may serve as a vaccine candidate against babesiosis.

Evaluation of in vitro and in vivo inhibitory effects of fusidic acid on Babesia and Theileria parasites.

Fusidic acid known to has antibacterial, antifungal, and antimalarial activities. Fusidic acid blocks translation elongation factor G gene in Plasmodium falciparum. In the present study, the inhibitory effects of fusidic acid on the in vitro growth of bovine and equine Babesia parasites were evaluated. The inhibitory effect of fusidic acid on the in vivo growth of Babesia microti was also assessed. The in vitro growth of four Babesia species that were tested was significantly inhibited (P<0.05) by micromolar concentrations of fusidic acid (IC(50) values=144.8, 17.3, 33.3, and 56.25 µM for Babesia bovis, Babesia bigemina, Babesia caballi, and Theileria equi, respectively). Combinations of fusidic acid with diminazene aceturate synergistically potentiated its inhibitory effects in vitro on B. bovis and B. caballi. In B. microti-infected mice, fusidic acid caused significant (P<0.05) inhibition of the growth of B. microti at the dose of 500 mg/kg BW relative to control group. These results indicate that fusidic acid might be incorporated in treatment of babesiosis.