The in vitro inhibition of proteases from Cryptobia salmositica Katz by a monoclonal antibody (MAb-001) against a glycoprotein on the pathogenic haemoflagellate

The monoclonal antibody (MAb-001), which was produced against a surface membrane glycoprotein on C. salmositica , significantly inhibited the activities of the intracellular proteases of the parasite. The total activity in the partially purified metallo-protease, and about 80% of activity in the partially purified cysteine protease, were inhibited by the antibody (at 10 μg protein ml^–1). The inhibitory effects of the antibody on the proteases were also demonstrated using haemoglobin (substrate)-SDS-PAGE. The activities of the metallo-protease band (200 kDa) and the three cysteine protease bands (66, 70 and 97 kDa) were inhibited by MAb-001, but the activity of the fourth cysteine protease band (49 kDa) was not affected. Similar inhibitory effects of the antibody were also found in the crude protease extract (parasite lysate), except that more antibody was required to obtain the same level of inhibition. The metallo-protease band was more sensitive than the cysteine protease bands to the antibody.