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Infection and Immunity, August 1999, p. 3921-3928, Vol. 67, No. 8
Department of Pathobiology, College of
Veterinary Medicine, University of Florida, Gainesville, Florida
Received 27 January 1999/Returned for modification 12 March
1999/Accepted 19 May 1999
Babesia bovis, an intraerythrocytic parasite of cattle,
is sequestered in the host microvasculature, a behavior associated with
cerebral and vascular complications of this disease. Despite the
importance of this behavior to disease etiology, the underlying mechanisms have not yet been investigated. To study the components involved in sequestration, B. bovis parasites that induce
adhesion of the infected erythrocytes (IRBCs) to bovine brain capillary endothelial cells (BBEC) in vitro were isolated. Two clonal lines, CD7A+I+ and CE11A+I
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Cytoadherence of Babesia bovis-Infected
Erythrocytes to Bovine Brain Capillary Endothelial Cells Provides
an In Vitro Model for Sequestration
, were derived from a
cytoadherent, monoclonal antibody 4D9.1G1-reactive parasite population.
This antibody recognizes a variant, surface-exposed epitope of the
variant erythrocyte surface antigen 1 (VESA1) of B. bovis
IRBCs. Both clonal lines were cytoadhesive to BBEC and two other bovine
endothelial cell lines but not to COS7 cells, FBK-4 cells, C32 melanoma
cells, or bovine brain pericytes. By transmission electron microscopy,
IRBCs were observed to bind to BBEC via the knobby protrusions on the
IRBC surface, indicating involvement of components associated with
these structures. Inhibition of protein export in intact, trypsinized
IRBCs ablated both erythrocyte surface reexpression of parasite protein
and cytoadhesion. IRBCs allowed to recover surface antigen
expression regained the ability to bind endothelial cells,
demonstrating that parasite protein export is required for
cytoadhesion. We propose the use of this assay as an in vitro model to
study the components involved in B. bovis cytoadherence and sequestration.
*
Corresponding author. Mailing address: Department of
Pathobiology, Box 110880, University of Florida, Gainesville, FL
32611-0880. Phone: (352) 392-4700 ext. 5826. Fax: (352) 392-9704. E-mail: allredd{at}mail.vetmed.ufl.edu.
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