Comparisons of the topographic characteristics and electrical charge distributions among Babesia-infected erythrocytes and extraerythrocytic merozoites using AFM

Authors: SCUDIERO, L - Washington State University; MERCADO-ROJANO, DEJ - Washington State University; RUDOLPH, A - Washington State University; WANG, J - Washington State University; LAUGHERY, JACOB - Washington State University; Suarez, Carlos

Submitted to: Journal of Microscopy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2018
Publication Date: 4/2/2018
Citation: Scudiero, L., Mercado-Rojano, D.W., Rudolph, A., Wang, J., Laughery, J.M., Suarez, C.E. 2018. Comparisons of the topographic characteristics and electrical charge distributions among Babesia-infected erythrocytes and extraerythrocytic merozoites using AFM. Journal of Microscopy. 271(1):84-97. https://doi.org/10.1111/jmi.12697.
DOI: https://doi.org/10.1111/jmi.12697

Interpretive Summary: Improved control of Babesiosis parasites is urgently needed. Numerous gaps in knowledge of the parasite-host relationships impede the development of efficient tools for control. Atomic force microscopy (AFM) and Kelvin probe potential microscopy (FM-KPFM) techniques were used to obtain detailed microscopic information on size, texture, roughness and surface potential of normal and infected Babesia bovis, B. bigemina and B. caballi erythrocytes. In addition, AFM and FM-KPFM allowed a detailed view of free merozoites revealing shape and topography of the surface of paired and single parasites and its surface potential for the first time. A significant increase in diameter of the infected Babesia cells was measured compared to normal erythrocytes. B. bigemina and B. caballi infected erythrocytes, don’t display the surface ridges typical in B. bovis parasites. Extraerythrocytic B. bovis, B. bigemina and B. caballi merozoites also revealed differences in size and shape. FM-KPFM images reveal an unequal electric charge distribution, with higher positive surface potential above the erythrocyte regions harboring B. bovis parasites whereas surface potential of paired extraerythrocytic B. bovis Mo7 merozoites revealed an asymmetric potential. These observations may help explaining the unique cyto-adhesive properties of B. bovis infected erythrocytes, and mechanisms involved in erythrocyte invasion.

Technical Abstract: Tick-borne Babesia parasites are responsible for costly diseases worldwide. Improved control and prevention tools are urgently needed, but development of such tools is limited by numerous gaps in knowledge of the parasite-host relationships. We hereby used atomic force microscopy (AFM) and Kelvin probe potential microscopy (FM-KPFM) techniques to compare size, texture, roughness and surface potential of normal and infected Babesia bovis, B. bigemina and B. caballi erythrocytes. In addition, AFM and FM-KPFM allowed a detailed view of extraerythrocytic merozoites revealing shape and topography of the surface of paired and single parasites and its surface potential. B. bovis infected erythrocytes display distinct surface texture and overall roughness compared to non-infected erythrocytes, B. bigemina and B. caballi infected erythrocytes, which don’t display the surface ridges typical in B. bovis parasites. Observations of extraerythrocytic B. bovis, B. bigemina and B. caballi merozoites using AFM also revealed differences in size and shape between these three parasites. Finally, similar to what was previously observed for Plasmodium infected erythrocytes, FM-KPFM images reveal an unequal electric charge distribution, with higher positive surface potential above the erythrocyte regions that are likely associated with B. bovis parasites than over its remainder regions. In addition, the surface potential of paired extraerythrocytic B. bovis Mo7 merozoites also revealed an asymmetric potential distribution. These observations may be important to better understand the unique cyto-adhesive properties of B. bovis-infected erythrocytes, and to speculate on the role of differences in the distribution of surface charges in the biology of the parasites.