ves1αgenes expression is the major determinant ofBabesia bovis-infected erythrocytes cytoadhesion to endothelial cells

Abstract

Babesia boviscauses the most pathogenic form of babesiosis in cattle, resulting in high mortality in naive adults. This parasite invades red blood cells (RBCs) within the bovine hosts where they multiply and produce clinical disease.Babesia bovisexports numerous proteins into invaded RBCs changing its properties. Thus, the infected RBCs (iRBCs) are capable to cytoadhere in the microvasculature of internal organs and brain, leading to respiratory distress, neurologic signs, and mortality. Variant Erythrocyte Surface Antigen 1 (VESA1) is one of those exported proteins byB. boviswhich represents a major virulence factor due to its central role in immune evasion by antigenic variation and intravascular parasite sequestration. VESA1 is a heterodimer protein encoded byves1αandves1βmultigene family and localized on the ridges, the focal point for cytoadhesion. To gain further insights into the molecular mechanisms of cytoadhesion ofB. bovis, we panned the parasites with bovine brain microvasculature endothelial cells, which resulted in obtaining several clones with different cytoadherence abilities. The transcriptome analysis of 2 high and 2 low cytoadherent clones revealed thatves1αsequences were diversified, likely resulting from genomic recombination. On the other hand,ves1βsequences were almost identical among these 4 clones. Insertion and expression ofves1αof a clone with high binding intoef-1αlocus of a low binging clone increased cytoadherence confirming the role ofves1αsuggested by our transcriptome data. Whole genome sequencing of cytoadherent clones revealed active locus of ves1 on chromosome 2. These results suggest that VESA1a proteins encoded byves1αgenes determine the cytoadherence specificity and/or cytoadherence strength ofB. bovisand they are in the active site for recombination.