UNIFORMITY OF PROTECTIVE ANTIGENS AMONG ISOLATES OF THE CATTLE TICK, BOOPHILUS-MICROPLUS

Gut membrane antigens were extracted from ten isolates of the cattle t ick Boophilus microplus; the antigen extracts were probed with bovine antisera and three murine monoclonal antibodies (mAbs) in Western blot s and dot-ELISA. The antisera had been obtained from cattle which were vaccinated with larval and gut extracts of B. microplus, and which we re subsequently protected (84% and 94% respectively) against challenge with B.microplus. One of the mAbs (QU13) has been demonstrated to pre cipitate protective antigens from the midgut of B.microplus. Gut antig ens from all ten isolates displayed similar reactivity profiles agains t bovine antisera and also against mAbs in Western blots. The end-poin t titres of antigens in dot-ELISA showed four-fold variation between i solates against bovine antisera, and also against mAb QU13. Larval mem brane antigen extracted from N-strain B.microplus reacted with QU13 in dot-ELISA, indicating that protective antigens are common to, both la rval and adult stages of B.microplus. It was concluded that protective antigens recognized by QU13 and antigens recognized by sera from prot ected cattle were conserved between the ten isolates examined, and bet ween life-cycle stages.