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Idiotypic modulation of the antibody response of mice to Echinococcus granulosus antigens.

In this work we analysed the modulation of the antibody response to Echinococcus granulosus antigens via anti-idiotype (Ab2) administration. In a first set of experiments, we determined the antibody response to hydatid cyst fluid antigen (HCFA) of mice immunized with Ab2. Results showed that Ab2 elicited anti-HCFA antibodies in mice that had never been exposed to HCFA before. Moreover, that response was characterized by booster effect, avidity maturation and an inverse correlation between avidity and Ab2 dose. We infected these mice and measured the titre and avidity of anti-HCFA antibodies during 250 days of infection. Lack of avidity maturation was the most important feature observed, suggesting that the parasite (either protoscolex or cyst) could modulate the antibody response of its host. In a second set of experiments, we investigated the presence of regulatory anti-idiotypes in the Ab2 preparation. In this context we treated neonates with different doses of Ab2, immunized them with HCFA 12 weeks later and determined their anti-HCFA titres. A specific and Ab2 dose-dependent suppression of the response to HCFA was observed, suggesting the existence of regulatory anti-idiotypes in the Ab2 preparation. Although this Ab2 could be involved in the regulation of the anti-HCFA response, other anti-idiotypes could also be involved. Our results show that it may be possible to improve the avidity of the anti-HCFA response via the administration of the anti-idiotype Ab. However, the live parasite could successfully revert this effect by mechanisms not yet characterized.