A PROTECTIVE CONCEALED ANTIGEN FROM BOOPHILUS-MICROPLUS - PURIFICATION, LOCALIZATION, AND POSSIBLE FUNCTION

A membrane protein that can be used successfully to vaccinate cattle a gainst the tick Boophilus microplus has been purified and characterize d. The mature protein, which is referred to as Bm91, has an apparent m .w. of 86,000, an isoelectric point of 4.8 to 5.2, and is glycosylated , with an affinity for lentil lectin. Bm91 is of relatively low abunda nce, with approximately 300 to 400 mu g being recovered from 1 kg of s emiengorged adult female ticks. The protein is located largely in the salivary gland and gut of these ticks. Partial amino acid sequence dat a for the protein show striking similarities to that of mammalian angi otensin-converting enzyme, suggesting that the Ag may have an enzymati c function. The protein seems not to be recognized by sera from cattle with extensive exposure to ticks under natural conditions. The immuni ty induced by vaccination, therefore, represents another example of va ccination against a hematophagous parasite with ''concealed'' Ags.