Isolation of protective antigens from the gut of Boophilus microplus using monoclonal antibodies

Monoclonal antibodies (mAb) were produced against midgut membrane (GM) antigens of Boophilus microplus. The isotypes of these mAb were established and their specificity characterized using double diffusion and Western blotting. GM antigens solubilized by Triton X-100 were precipitated by mAb QU13, and the precipitate was then injected into cattle to test for the presence of protective antigens. Vaccinated cattle challenged with 10-day-old larval ticks showed evidence of protection with a 62% reduction in eggs produced by ticks from vaccinated cattle compared to tick eggs from control cattle. In a second vaccine-challenge experiment, the dose of precipitate was increased and greater than 99% protection was provided to these vaccinated cattle following challenge (calculated from tick egg weights compared to the control group). The solubilized antigen(s) precipitated by QU13 were subjected to SDS-PAGE separation and the calculated sizes of these molecules were greater than 200,000, 80,000, 74,000, 62,000 57,000 and less than 30,000 MW.