AbstractA glycoprotein (BM86) from the gut cells of the cattle tickBoophilus microplus, when used to vaccinate cattle, has been shown to protect cattle from tick infestation. A recombinant BM86 protein is the principal component of a novel tick vaccine currently under development. The nature of the anchorage of BM86 to tick gut epithelial cells has been investigated using BM86 fromB. microplusand recombinant BM86 proteins expressed in insect cells using the baculovirus expression system. BM86 fromB. microplusand a full length recombinant BM86 are shown to be anchored to the extracellular surface of tick gut epithelial cells and baculovirus‐infected insect cells, respectively by a glycosyl‐phosphatidyl inositol membrane anchor. A recombinant BM86 truncated by the removal of a hydrophobic region coding for thirty amino acids at the carboxy‐terminal end was secreted from baculovirus‐infected Sf9 cells. This secreted form of recombinant BM86 showed strong protective activity against ticks in cattle vaccinated with this