THE EFFECT OF VARIOUS ADJUVANTS ON THE HUMORAL IMMUNE-RESPONSE OF SHEEP AND CATTLE TO SOLUBLE AND MEMBRANE MIDGUT ANTIGENS OF BOOPHILUS-MICROPLUS

Sheep and cattle were immunized with soluble and membrane midgut antig ens of the cattle tick, Boophilus microplus in association with variou s adjuvants, and antibody levels to soluble and membrane midgut extrac ts were measured by enzyme-linked immunosorbent assay (ELISA). The adj uvants used were Quil A, Freund's incomplete adjuvant (FIA) and alumin ium hydroxide (Al(OH)(3)). Significant antibody levels to midgut membr ane antigen (GM) were not detected in the sera of sheep immunized with GM plus Al(OH)(3). However, membrane and soluble midgut antigens comb ined with Quil A generated significantly higher levels of antibodies i n sheep than these antigens emulsified in FIA (P<0.05). In cattle, alt hough soluble midgut antigen (GS) plus Quil A induced significantly hi gher levels of antibodies compared with GS in FIA (P<0.05), neither pr eparation provided significant protective immunity against challenge w ith B. microplus (46% and 22%, respectively). A soluble form of membra ne midgut antigen extracted by low ionic strength buffer (LI-GM) when combined with Quil A provided 83% and 87% protection against challenge with B. microplus in two separate experiments. Quil A was clearly sup erior to FIA and Al(OH)(3) as an adjuvant for these tick antigens.