Effect of Freund's adjuvants on guinea pigs infected with, or vaccinated against, Trichostrongylus colubriformis.

Soluble antigens that protected guinea pigs against experimental challenge with Trichostrongylus colubriformis were found to be less effective if injected as emulsions in Freund's adjuvants. This occurred despite the production of higher antibody titres in guinea pigs given emulsified antigen. Investigations of this phenomenon showed that an intraperitoneal injection of Freund's complete adjuvant (FCA) delayed rejection of primary infections and partially abrogated resistance to challenge infection. Administration of FCA/antigen emulsion to infected guinea pigs resulted in a prolonged blood eosinophilia which paralleled the increased longevity of the parasitosis. These findings suggest the need for caution in the selection of adjuvants for vaccination against gastrointestinal nematodes.