FASCIOLA-HEPATICA - IRRADIATION-INDUCED ALTERATIONS IN CARBOHYDRATE AND CATHEPSIN-B PROTEASE EXPRESSION IN NEWLY EXCYSTED JUVENILE LIVER FLUKE

Irradiation hits been successful in the attenuation of infective stage parasites for use as vaccines against a number of parasites including Fasciola spp. The mechanisms of action of irradiation-attenuated vacc ines, however, are nor clearly understood. in this study, we examined the effect of 3, 10, and 40 krad of gamma-irradiation on the expressio n of carbohydrates and cathepsin-B by newly excysted juvenile Fasciola hepatica (NEJ). Following irradiation of metacereariae, the expressio n of concanavalin A (ConA)-specific sugars was decreased on the surfac e of NEJ and the expression of wheat germ agglutinin (WGA)-specific su gars was increased in the gut and reduced on the surface of NEJ. Cathe psin proteases are a major component of liver fluke excretory/secretor y material (ES) and can cleave host immunoglobulin (IE) Cathepsin-B pr otease was localized in nonirradiated NEJ to the gut lumen and to secr etory granules within the gut epithelia. Irradiation of fluke with 3, 10, and 40 krad of gamma-rays significantly reduced the tissue express ion of cathepsin-B at 8 hr postirradiation in an appal early dose-depe ndent manner. After a further 24 hr culture tissue expression of cathe psin-B was significantly reduced in 10- anti 40-krad-irradiated NEJ. P rotease activity of ES samples collected over a 24-hr period from irra diated and nonirradiated NEJ cultured in vitro were tested using a rab bit Ig cleavage assay. The proteolytic activity of ES from 10- and 40- krad-irradiated NEJ was reduced during tile initial 6 hr in culture an d between 12 and 24 hr when compared to ES from nonirradiated controls . Biosynthetic labeling experiments using [S-35]methionine and [S-35]c ysteine indicated that ES material was actively synthesised during 48 hr in vitro culture, Therefore, from this study, we conclude that gamm a-irradiation of NEJ alters expression of cathepsin-B protease and WGA - and ConA-specific sugars which may be detrimental to parasite invasi on and contribute ro the protective immune responses generated in the host by irradiation-attenuated metacercariae of Fasciola spp. (C) 1996 Academic Press, Inc.