Immune responses of cows to a chemically modified anaplasma antigen

Cows were vaccinated at 0 and 28 days with either a standard or a chemically modified anaplasma antigen. The humoral antibody response was measured by the anaplasma complement-fixation and card agglutination tests. The antibody response to bovine erythrocyte antigens was also evaluated. Peripheral blood leukocytes were collected for an in vitro lymphocyte-transformation test. Both groups of vaccinated cows developed a significant cell-mediated response as measured by lymphocyte-transformation test. However, only the cows given the standard anaplasma antigen developed anaplasma antibody and significant titer of bovine erythrocyte antibodies. Vaccinated and control cows were challenge exposed 1 month after the 2nd antigen injection. The vaccinated cows developed lower levels of parasitemia than did the control nonvaccinated cows.