Assessment of the diagnostic value of 99mTc-radiolabelled specific antibodies in experimental hydatidosis.

We assessed the potential of 99mTc labelled specific polyclonal antibodies (99mTc-PoAb) for the diagnosis of hydatid disease by immunoscintigraphy. Experimentally infected mice and rabbits were used for this purpose. A specific rabbit antibody recognizing total somatic antigen from hydatid membranes (HCMA) was obtained. PoAb biological activity before labelling was checked according to Barbieri et al. 99mTc-PoAb labelling was performed according to Thakur et al.; the radiochemical purity was higher than 90%. The following studies of 99mTc-PoAb were made: post-labelling biological activity; in vitro stability; blood and renal kinetics in normal mice up to 24 hours after intravenous (i.v.) and intraperitoneal (i.p.) administration; biodistribution in normal and infected mice after i.p. or i.v. injection, and in rabbits after i.v. administration. Biodistribution studies in normal mice, after both administration routes, showed considerable hepatic uptake of activity. An important uptake in cysts after i.p. administration in mice, indicating successful targeting, was also confirmed by autoradiography images. Intravenously administered 99mTc PoAb was not significantly targeted to peritoneal cysts in either animal species, due to inherent limitations to these animal models. Results obtained with i.p. administration suggest that specific hydatid imaging may be possible. Both the mice and rabbit models revealed hepatic uptake which, combined with the short isotope half-life, prevent the drawing of any final conclusions regarding the usefulness of 99mTc-labelling in hydatid disease.