LECTIN-BINDING TO EXTRACELLULARLY MELANIZED MICROFILARIAE OF BRUGIA-MALAYI FROM THE HEMOCOEL OF ANOPHELES-QUADRIMACULATUS

Binding patterns of fluorescein isothiocyanate (FITC)- and gold-conjug ated lectins to extracellularly melanized sheathed and exsheathed micr ofilariae of subperiodic Brugia malayi, isolated from and in situ in t he abdominal hemocoel of Anopheles quadrimaculatus 72-hr postinfection , were examined. Five FITC-conjugated lectins [Helix pomatia agglutini n (HPA), Arachis hypogaea (peanut agglutinin-PNA), Triticum vulgaris ( wheat germ agglutinin-WGA), Lens culinaris (lentil-LCH), and Concanava lin A (Con A)] with specificities for different carbohydrate moieties were tested for binding to isolated melanized microfilariae and observ ed with transmitted light and fluorescence microscopy. All five FITC-l ectins bound strongly to the acellular material accompanying the melan in deposits on the surface of isolated melanized microfilariae. Signif icant inhibition of FITC-lectin binding occurred when lectins were pre incubated with their complementary carbohydrates before testing. H. po matia agglutinin binding was totally inhibited by N-acetyl-D-glucosami ne and N-acetyl-D-galactosamine. Other lectins were partially inhibite d, such as PNA by galactose and lactose; WGA by N-acetylneuraminic aci d; LCH by N-acetyl-D-glucosamine, mannose, glucose, and methyl alpha-D -mannopyranoside; and Con A by mannose and methyl alpha-D-mannopyranos ide. Three gold-conjugated lectins (HPA, PNA, and Con A), examined by using transmission electron microscopy, bound to the outer surface of the acellular material associated with the melanin deposits on isolate d melanized microfilarial sheaths and melanized microfilariae and to t he remnants of lysed hemocytes found in the proximity of the melanized deposits. Con A in the presence of gold-labeled horseradish peroxidas e, examined by using transmission electron microscopy, showed random b inding within the melanized capsule formed around the microfilarial sh eath in situ. These results indicate that the acellular material accom panying melanin deposits on melanized microfilarial sheaths and sheath ed and exsheathed microfilariae contain several glycoconjugates with e xposed carbohydrate moieties and are possibly glycoproteins. These gly coproteins could be the by-products of the activation of the prophenol oxidase by the microfilariae. (C) 1995 Academic Press, Inc.