Humoral immune response and delayed-type hypersensitivity in rabbits infected with Trypanosoma equiperdum.

Trypanosoma equiperdum is the causative agent of dourine, a parasitic venereal disease of equids. In this work, rabbits were infected with T. equiperdum strain OVI; serological tests (complement fixation test, ELISA and immunoblotting), used for the diagnosis of dourine in horses, were applied to study rabbit humoral immune response and to characterise T. equiperdum antigen pattern recognised by antibodies from infected rabbits. Moreover a protein extract of T. equiperdum strain OVI was produced and tested in skin tests on infected rabbits to detect the cell-mediated response induced by T. equiperdum, in order to evaluate its use in the field diagnosis of dourine. Sera of infected rabbits recognized in immunoblotting Trypanosoma protein bands with molecular weight below 37 kDa, providing a serological response comparable with that already observed in dourine infected horses. Moreover the trypanosome protein extract was capable to produce in vivo delayed-type hypersensitivity (DHT Type IV) in rabbits and proved itself to be non-toxic and non-sensitizing.