Individual heterogeneity in erythrocyte susceptibility to Babesia divergens is a critical factor for the outcome of experimental spleen-intact sheep infectionsLaurence Malandrin1, Maggy Jouglin1, Emmanuelle Moreau2 and Alain Chauvin2
1 INRA, UMR 1300 BioEpAR, ENVN, Atlanpôle – La Chantrerie, BP 40706, F-44307 Nantes Cedex 03, France
2 École Nationale Veterinaire, UMR 1300 BioEpAR, ENVN, Atlanpôle – La Chantrerie, BP 40706, F-44307 Nantes Cedex 03, France
Received 20 August 2008; accepted 25 February 2009; published online 27 February 2009
Abstract - Susceptibility of sheep erythrocytes to Babesia divergens was investigated in vitro and a high inter-individual variability in their ability to support parasite population development was demonstrated, with some individuals having refractory red blood cells (RBC). As neither changes in growth conditions nor the use of different B. divergens strains influenced the level of susceptibility, the main factor postulated for this variability is the erythrocyte itself. Sheep therefore represent an excellent in vitro model to study the parasite-erythrocyte interaction. In addition, the existence of refractory RBC should help in the identification of the erythrocyte components required for B. divergens development. Experimental infections were carried out on spleen-intact sheep characterized by refractory or fully susceptible erythrocyte types. These differences translated into the successful infection of only those animals with susceptible erythrocytes: infected animals showed no clinical signs, but maintained an asymptomatic persistent infection, as usually observed in the natural bovine host. Sheep therefore represent model organisms that can allow us to study interactions between B. divergens and its vertebrate host at different levels of biological organisation, from the target cell to the intact animal, and represent an experimental infection model of concomitant immunity. Only a low percentage (13%) of the sheep population tested possessed susceptible erythrocytes and the potential role of sheep as a natural host or reservoir of B. divergens is discussed.
Key words: Babesia divergens / sheep / erythrocyte / red blood cell / experimental animal model
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© INRA, EDP Sciences 2009