Identification and localization of glutathione S-transferase as a potential target enzyme in Brugia species

Brugia filarial nematodes are pathogenic lymphatic-dwelling parasites that, like other helminths, may modify the host's defense mechanisms by a major detoxification process involving glutathione-binding proteins such as gluta thione S-transferases (GSTs). In the present study, soluble extracts of thi rd-stage larvae, adult male and female worms, microfilariae of either B. pa hangi or B. malayi or the adult worm excretory-secretory products of B. mal ayi were used to determine GST activity. These extracts and affinity-purifi ed fractions of B. pahangi adult worms had a specific enzymatic activity wh en 1-chloro-2,4-dinitrobenzene was used as a substrate. The observance of t his enzyme in all life cycle stages of Brugia spp. demonstrates its ubiquit ous nature. Lavage of intraperitoneally infected jirds, but not that of uni nfected jirds, also showed increased enzymatic activity, suggesting that GS T is secreted in vivo. Soluble proteins of both Brugia spp. were strongly r ecognized by antibodies in sera from rabbits immunized with affinity-purifi ed native GST of Onchocerca volvulus. Immunohistochemical studies localized these proteins in adult worms, demonstrating cross-reactivity between the GST of these two filarial nematodes. The effect of this enzyme on the motil ity and viability of adult worms, microfilariae, and larvae was tested in v itro using a battery of known GST inhibitors. Of all those tested, ethacryn ic acid, N-ethylmalemide, 4-nitropyridine-oxide, or 1-chloro-2,4-dinitroben zene at micromolar concentrations reduced the viability and motility of mic rofilariae, third-stage larvae, and adult worms. These results suggest that Brugia GSTs are major metabolic enzymes and may play an important role in the parasite's survival.