Up-regulated expression of spherical body protein 2 truncated copy 11 is associated with reduced in vitro endothelial cell cytoadhesion by babesia bovis

Authors: GALLEGO-LOPEZ, GM - Washington State University; LAU, A.O.T - National Institutes Of Health (NIH); O'CONNOR, RM - Washington State University; Ueti, Massaro; COOKE, BM - Monash University; LAUGHERY, JM - Washington State University; GRACA, T - Washington State University; MADSEN-BOUTERSE, SA - Washington State University; OLDIGES, DP - Federal University Of Rio Grande Do Sul; Suarez, Carlos

Submitted to: International Journal for Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/2018
Publication Date: 5/31/2018
Citation: Gallego-Lopez, G., Lau, A., O'Connor, R., Ueti, M.W., Cooke, B., Laughery, J., Graca, T., Madsen-Bouterse, S., Oldiges, D., Suarez, C.E. 2018. Up-regulated expression of spherical body protein 2 truncated copy 11 is associated with reduced in vitro endothelial cell cytoadhesion by babesia bovis. International Journal for Parasitology. 49(2):127-137. https://doi.org/10.1016/j.ijpara.2018.05.015.
DOI: https://doi.org/10.1016/j.ijpara.2018.05.015

Interpretive Summary: Bovine babesiosis is currently controlled with drugs and live vaccines, but improved methods are needed. Improved control requires increasing our knowledge of the biology of the parasite and host-parasite interactions. This includes defining parasite molecules involved in modulating parasite virulence. Cytadhesion of Babesia bovis infected erythrocytes to epithelial cells in the microvasculature is a signature feature of infection and is associated with increased virulence by this parasite. In this study we demonstrate the association between up-regulation of sbp2t11 with significant reduction in cytoadhesion in Babesia bovis using a virulent line of transfected parasites over-expressing sbp2t11 and testing in an in vitro cytoadhesive assay. Future research will investigate whether SBP2t11, can act as regulatory/modulatory factors of cytoadhesion, which will help in the design of future improved vaccines.

Technical Abstract: The factors involved in virulence gain and /or loss in Babesia bovis remain unknown. Spherical body protein 2 truncated copies 11(sbp2t11) transcripts in B. bovis were recently reported to be a marker of attenuation for B. bovis strains. Increased cytoadhesion of B. bovis infected erythrocytes to capillary epithelial cells is a potential indicator of virulence in bovine babesiosis. In this study, we created a stable B. bovis transfected line over-expressing sbp2t11 to determine if sbp2t11 up-regulation is associated with changes in parasite cytoadhesion. B. bovis were cultured in vitro using micro-aerophilus stationary-phase (MASP) cultures. Transcript abundance analysis was analyzed by quantitative RT-PCR on total RNA. A transfected B. bovis line up-regulating sbp2t11 (sbp2t11up line) was generated using stable transfection, and five B. bovis clonal lines were derived from the sbp2t11up line by limiting dilution for characterization. We then compared the ability of infected erythrocytes derived from the sbp2t11up, clonal, virulent, attenuated, and negative control lines, to adhere to bovine brain endothelial cells using an in vitro static cytoadhesion assay followed by cytoadhesion selection, and quantified the level of sbp2t11 transcripts in each selected line. The results of these experiments demonstrated association between up-regulation of sbp2t11 with significant reduction in cytoadhesion. Confirmed up-regulation of sbp2t11 in B. bovis concomitant with reduction of iRBC cytoadherence to bovine brain endothelial cells is consistent with the previous finding that up-regulation of sbp2t11 is a marker of attenuation in B. bovis.