Common and isolate-restricted antigens of Anaplasma marginale detected with monoclonal antibodies.

Anaplasma marginale-infected erythrocytes were examined for the presence of maturation, isolate-restricted, and isolate-common antigens by indirect immunofluorescence with monoclonal antibodies. A panel of 18 monoclonal antibodies was used; none of the antibodies reacted with Anaplasma ovis, Babesia bigemina, babesia bovis, Trypanosoma brucei, Trypanosoma congolense, or uninfected bovine erythrocytes. Antigens common to all six A. marginale isolates were detected by nine antibodies. Single isolates from Florida, Southern Idaho, Northern Texas, and Virginia and two isolates from Washington state had four patterns of reactivity with a second panel of nine antibodies. Antigenically distinct stages were not detected, as sequential smears taken daily during acute infection had the same pattern of reactivity. The results demonstrate antigenic heterogeneity among isolates of A. marginale and the presence of common antigens. This information allows grouping of different isolates and, more importantly, provides a method for the identification and isolation of common antigens for diagnostic tests.