Babesia bovis: Dextran sulphate as an adjuvant for and precipitant of protective immunogens

Abstract Dextran sulphate, a chemical with some specificity for lipoproteins, was used to precipitate a fraction from a soluble extract of Babesia bovis -infected erythrocytes. The precipitate, in combination with dextran sulphate as an adjuvant, was used to vaccinate naive calves. The vaccinates and a group of control calves were challenged with virulent homologous B. bovis . The vaccinates showed delayed and decreased parasitaemias comparative to the controls. The antibody response to vaccination was primarily against the infected erythrocyte being of both IgG 1 and IgG 2 classes. We believe this is the first report of B. bovis antibody being detected in the IgG 2 class. Lipase inhibition and chemical analysis suggested babesial lipid or lipoprotein was sufficiently immunogenic to produce serologically detectable antibody and presumably to elicit immunity.