Determination by enzyme-linked immunosorbent assay of the optimal dose of staphylococcal leukocidin for systemic immunization of dairy cows.

A dose-response study was conducted to determine the optimal dose of staphylococcal leukocidin toxin to use for systemic vaccination of lactating dairy cows. Each of 5 groups of cows (8 cows/group) were given 2 injections of crude leukocidin (dose range, 9 to 2,700 mg). Antileukocidin antibody concentration in milk samples collected before vaccination and at 4 and 10 weeks after vaccination was determined by use of an ELISA. The highest antibody concentration at postvaccination sample collection dates was observed in cows of the group immunized with 900 mg of leukocidin. This appeared to be the optimal vaccination dose for production of antileukocidin antibodies in the mammary gland of lactating cows.