Detection, purification by immunoaffinity chromatography and properties of β-1,3-glucan-specific lectins from the sera of several insect species

A lectin specific for beta-1,3-glucans has previously been purified from the cockroach, Blaberus discoidalis. Using polyclonal antiserum against the lectin, similar molecules with agglutinating activity were detected in the sera of several cockroach species, namely, B. craniifer, Leucophaea maderae, Gromphadorhina portentosa, and Periplaneta americana, by various methods including immunodiffusion, immunoelectrophoresis and Western blotting. Immunoaffinity chromatography using purified antibody against the B. discoidalis beta-1,3-glucan-specific lectin immobilized on CNBr-activated Sepharose 4B matrix was successfully employed to purify the equivalent molecules from sera of these cockroaches. The purified lectins have molecular masses of ca. 520 kDa by gel filtration and subunit mass estimates of 80-82 kDa by SDS-PAGE. Moreover, they have a similar overall structure to B. discoidalis lectin when examined by electron microscopy. The purified lectin enhanced the activation of prophenoloxidase by laminarin. Localization of the beta-1,3-glucan-specific lectin using antibody against the B. discoidalis lectin showed that the molecule was associated with the haemocyte surface as well as in the cytoplasm of these cells of B, craniifer, L. maderae and P. americana. (C) 1998 Elsevier Science Ltd. All rights reserved.