The immunization of cattle against Babesia divergens with fractions of parasitized erythrocytes.

A lysate of erythrocytes infected with Babesia divergens was subjected to isoelectric focusing within a pH range of 3.5-9.5. The focused proteins were split into 2 fractions depending on pH (1) those from 3.5-6.5 and (2) those from 6.5-9.5. The acidic fraction was used as an immunogen for groups of 5 adult cows using 2 different adjuvants, saponin and a mixture of muramyldipeptide (MDP) and incomplete Freund's adjuvant (IFA). Two other groups of 5 cows were simultaneously treated with the alkaline fraction and a sample of the complete lysate with the MDP/IFA adjuvant. The treated cows plus a control group were infected with 2.5 X 10(8) erythrocytes infected with a homologous strain of B. divergens. When compared with the controls all pre-treated groups were protected to some degree. There were significant differences between the treated groups with the group which received MDP/IFA combined with the acidic fraction showing most resistance to the infection. The experiment also showed that the MDP/IFA adjuvant produced more protection than the saponin.