HYMENOLEPIS-DIMINUTA - METACESTODE-INDUCED REDUCTION IN THE SYNTHESISOF THE YOLK PROTEIN, VITELLOGENIN, IN THE FAT-BODY OF TENEBRIO-MOLITOR

Vitellogenin synthesis by the fat body has been monitored using in vit ro culture and immunoprecipitation. This system was found to be effici ent for measuring vitellogenin production in both non-infected Tenebri o molitor and those infected with Hymenolepis diminuta. In fat bodies from infected beetles, vitellogenin production was decreased by up to 75% (day 24 post-infection) and, at all times investigated, vitellogen in synthesis was significantly below control levels (days 3-30 post-in fection). Incubating fat bodies from control insects with isolated met acestodes indicated that this may be a direct effect by the parasite w hich is developmental stage-specific. Stage II, but not stage III-IV, nor heat-killed parasites could bring about this decrease in vitelloge nin. In addition, these effects may be density dependent within the ra nge of 2-20 parasites per fat body; only 2 metacestodes were necessary to cause a significant decrease. Since metacestodes do not take up vi tellogenin, nor limit the amount of [C-14]leucine available to the fat body for vitellogenin production, it is conceivable that the parasite produces a potent inhibitor of vitellogenin synthesis, or a molecule which induces cells within the fat body to do so.