The in vitro effects of serum on the adults, metacercariae, and eggs of Opisthorchis viverrini.

Adult and juvenile Opisthorchis viverrini liver-flukes incubated in hamster chronic infection serum (CIS) developed tegumental precipitates which enclosed the entire parasite. Adult worms appeared dead by 48 hours in CIS and juvenile worms by 18 hours. No such reactions were observed in normal hamster serum (NHS). Heat inactivation of CIS at 56 degrees C abolished the precipitin reactivity against both adult and juvenile parasites though reactivity was regained upon addition of NHS or guinea-pig serum. Reactivity was also abolished by heat inactivating CIS at 60 degrees C but reactivity was not regained upon addition of NHS or guinea-pig serum. Coarse granular precipitates and blebs were observed around eggs in CIS and this activity was abolished by heat inactivating serum at 60 degrees C but not 56 degrees C. Aging of adult parasites in vitro for nine or 27 days before testing against CIS did not affect the development of tegumental precipitates although freeze-thaw killing of adult parasites before testing against CIS resulted in a marked reduction in the extent of the tegumental precipitate reaction. These results show that serum from O. viverrini-infected hamsters contains a component(s), possibly a specific immunoglobulin(s) capable of reacting with adult, juvenile and egg state parasitic antigens. These findings are discussed in relation to immunopathological processes that might be operating in the liver of the infected host.