Schistosoma mansoni: Influence of infection on levels of translatable mRNA and on polypeptide synthesis in the ovotestis and albumen gland of Biomphalaria glabrata

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Larval trematode infection causes a disruption of normal reproductive activity in the molluscan intermediate host. Because relatively little is known about the dynamics of this host-parasite interaction, the effect of Schistosoma mansoni infection on translatable mRNA pools and on polypeptide synthesis was examined in the ovotestis (OT) and albumen gland (AG) of Biomphalaria glabrata. Total RNA was isolated from OTs and AGs from uninfected control snails and snails at 14, 21, and 28 days postinfection (pi) with 20 S. mansoni miracidia and subjected to a rabbit reticulocyte in vitro translation system. Quantitative densitometry of autofluorograms of one-dimensional SDS-PAGE slab gels revealed reductions in quantities of total proteins synthesized in vitro from RNA isolated from infected OTs at 21 and 28 days pi, but not at Day 14 pi. Similar reductions were seen in 10 individual polypeptides selected for a more detailed analysis. In contrast to the OT, Day 14 pi-infected AGs exhibited an initial increase in total protein synthesized in the in vitro translation system utilized, followed by significant reductions at 21 and 28 days pi. Selective modulation of labeled polypeptides was evident in 11 polypeptides chosen for a more detailed analysis. This general pattern of parasite inhibitory effects was also seen in parallel pulse-chase studies using [35S]methionine metabolic labeling of in vitro-cultured OTs and AGs. In these experiments, significant reductions in the amounts of labeled polypeptides found in culture supernatants at 14, 21, and 28 days pi were evident. Total polypeptide synthesis also was reduced in solubilized AGs from infected snails at 21 and 28 days pi. Results indicate that larval trematode infection induced a generalized disruption of polypeptide metabolism in OTs and AGs of B. glabrata. Such inhibition may occur at both the transcriptional and the translational levels and is initially manifested early in infection, during the time that daughter sporocysts begin to migrate and colonize the digestive gland and OT. © 1991.

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Experimental Parasitology

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