Antineoplastic effects of long-term Trichinella spiralis infection on B-16 melanoma.

Oral infection of mice with Trichinella spiralis has been shown to induce a potentiation of the delayed hypersensitive (DTH) response to BCG. The present investigation was initiated to determine whether nematode-induced potentiation of DTH influenced the induction and progression of a transplantable mouse tumor. B6D2F1/J mice were orally infected with 200 T. spiralis larvae 176 days preceding subcutaneous administration of 5 X 10(5) viable B-16 melanoma cells. The antineoplastic effects of long-term nematode infection were assessed by daily observation of the animals monitoring development and progression of neoplastic nodules. Control mice developed tumors by day 28 following tumor challenge, while none of the corresponding T. spiralis-infected animals demonstrated any signs of neoplasia. All control mice died within 60 days, while none of the nematode-infected animals developed detectable neoplasms. This phenomenon suggested that the presence of well-established larval cysts was capable of stimulating host antineoplastic activity.