A nonsubjective assay for antigenic modifications of the Babesia bovis-parasitized erythrocyte surface.

Intracellular protozoan parasites induce numerous alterations in the invaded host cell, including antigenic modifications of the host cell plasma membrane. We have developed a quantifiable, non-subjective assay for the detection of novel antigenic reactivities on the host cell surface using as a model system bovine erythrocytes infected with Babesia bovis. Infected erythrocytes, metabolically labeled with L-[35S]methionine, were sensitized by incubation with bovine immune serum, then were captured in microtiter plates coated with rabbit anti-bovine IgG antibody. This technique enabled specific capture of B. bovis-infected cells with immune infection sera raised against B. bovis but not with similar sera raised against Babesia bigemina. This assay should be easily applicable to the study of other parasitic diseases.