Effect of buparvaquone on the expression of interleukin 2 receptors in Theileria annulata-infected cells.

Theileria annulata-infected cells were cultured in the presence or absence of human recombinant interleukin 2 (hrIL-2). This growth factor proved to be capable of enhancing the growth of the infected cells: its effect was marked, particularly when the cells were seeded at low densities, and it varied from cell line to cell line. The infected cells produced a factor that possessed the biological activities of IL-2, since their supernatants could enhance the proliferation of concanvalin A-stimulated (Con A) blasts. The reactivity of the parasitized cells to hrIL-2 was abolished following their treatment with the antitheilerial drug buparvaquone. In addition, the drug inhibited the binding of 125I-IL-2 to T. annulata-infected cells but failed to suppress its binding to Con A blasts. Northern blot analysis revealed that the drug had no effect on the expression of the alpha chain of the IL-2 receptor (IL-2R). Therefore, it is possible that buparvaquone interferes with the expression of the beta chain of the IL-2R. The role of IL-2 and the IL2R in the permanent proliferation of T. annulata-infected cells is discussed.

Effect of cyclosporin A on the proliferation of bovine lymphocytes to concanavalin A and on the growth of Theileria annulata-infected bovine cells.

After being inoculated by Hyalomma ticks, the sporozoites of Theileria annulata invade bovine lymphocytes, where they subsequently differentiate to schizonts. The infected cells are induced to a continuous proliferation which can be enhanced by human recombinant interleukin 2 (hrIL-2). In the present study, we examined the influence of cyclosporin A (CsA) on the growth of schizont-containing cells and compared with its effect on bovine peripheral blood lymphocytes (PBL) responding to Concanavalin A (ConA). In both cell types, the proliferation was inhibited in a dose dependent manner, which was not restorable in T. annulata-infected cells even after addition of hrIL-2. In contrast, ConA-blasts were able to undergo a proliferative response provided they were treated with high doses of CsA. Both, T. annulata-infected cells and bovine ConA-blasts express IL-2 receptors (IL-2R). The binding of radiolabelled hrIL-2 to ConA-blasts and T. annulata-infected cells was only partially inhibited after treatment with CsA. CsA was not toxic for the parasites, since the treated cells still contained schizonts which did not show any morphological abnormality.

Buparvaquone but not cyclosporin A prevents Theileria annulata-infected bovine lymphoblastoid cells from stimulating uninfected lymphocytes.

The influence of Buparvaquone on the morphology, proliferation, and stimulation with T and B cell mitogens of Theileria annulata-infected cells was studied. In addition, the stimulatory capacity of the infected cells before and after treatment with Buparvaquone or cyclosporin A (CsA) was also examined and compared to that of ConA-stimulated bovine peripheral blood cells (PBL). After incubation of the cells for 4 days with Buparvaquone only few schizonts were detectable in the cells. Prolongation of the incubation time to 8, 12, or 14 days eliminated completely the parasites. Despite the elimination of the parasites, the cells were still unable to undergo a proliferative response to Con A or PWM. However, the drug did not interfere with the response of normal PBL to these mitogens. Furthermore, Buparvaquone but not CsA inhibits the generation of mixed lymphocyte reaction (MLR). None of the drugs could prevent ConA-blasts from stimulating autologous PBL. These results suggest that the antigen expressed by the infected cells and recognised by the responder PBL was induced by the schizonts.