Immunomodulation of lambs following treatment with a proteasome preparation from infective larvae of Trichostrongylus colubriformis

Proteinases are known to be capable of prolonging the survival of endoparas ites in a host. We were therefore interested in knowing whether immunizatio n of lambs against a proteasome (multisubunit proteinases) preparation obta ined from Trichostrongylus colubriformis infective third-stage larvae (L3) would have any effect on the immune response to a single challenge infectio n with the same organism. A total of 21 penned lambs aged 8 months were div ided into 3 equal groups. Group 1 was immunized on three occasions with inc reasing amounts of a proteasome-enriched fraction obtained from infective L 3. Group 2 was given a similar amount of protein from the initial supernata nt of homogenized larvae. Group 3 (controls) received adjuvant plus saline solution only. All groups were challenged with 60,000 infective T. colubuif ormis larvae at 28 days after the last immunization. Significant protection was obtained only when the initial supernatant extract was used to immuniz e lambs. The proteasome preparation seemed to have immunosuppressive effect s through the stimulation of nonspecific IgE production. Significantly lowe r levels of specific IgE were observed in lambs immunized with the proteaso me-enriched fraction, and levels of specific IgG antibodies were increased. We suggest that proteasome fractions of T. colubriformis may serve as usef ul, preparations for the study of mechanisms of IgE production in parasitiz ed sheep.