Characterization of immune responses of cattle to erythrocyte stroma, Anaplasma antigen, and dodecanoic acid-conjugated Anaplasma antigen: cell-mediated immunity.

Sonically disrupted normal erythrocyte stroma (SES) and two anaplasma antigens (sonically disrupted anaplasma antigen; SAA, and French pressure cell disrupted anaplasma antigen; FAA) were prepared from normal and Anaplasma marginale-infected blood. The SAA and FAA antigens were chemically modified by conjugation with dodecanoic acid (SAADA and FAADA). Significant (P less than or equal to 0.05) anti-anaplasma lymphocyte-transformation responses were obtained from all cattle given SAA, SAADA, or FAADA vaccines. Only cows given SAA developed anti-anaplasma antibody. Mild antierythrocyte lymphocyte-transformation responses were obtained from most vaccinated animals. Delayed hypersensitivity to erythrocyte antigen was not detected. The SAA-vaccinated cows had the highest degree of protection in that they developed a smaller percentage of parasitemia and had less severe anemia than did other cattle in the study. The SAADA- and FAADA-vaccinated cattle developed a good cell-mediated immune response, but poor humoral immune response and had lower parasitemias than did challenge-exposed controls; but they developed severe anemia. It is suggested that cellular and humoral mechanisms are essential for protection in anaplasmosis. Evidence of protection from clinical anaplasmosis was not observed in SES-vaccinated cows.