120 Vaccination against Taenia Taeniaeformis

Species of tapeworms belonging to the family Taenidae are among the most important helminth parasites of man and domestic animals. Taeniasis and cysticercosis are serious problems of public health and economy in developing countries. The ultimate control of these diseases depends on the development of effective prophylactic vaccines. Although vaccines against bacterial and viral infections are commonplace, no effective vaccine is yet available against many helminth infections. Among the cestodes, studies on antigen purification and characterization have largely been limited to use for immunodiagnosis (1-11). One of the problems is the difficulty in obtaining suitable experimental models for vaccination trials. Taenia taeniaeformis, which has a life cycle involving only two hosts, viz. cats and rodents, is an ideal experimental model. The role of metabolites secreted by tissue cestodes in stimulating a host immune response has been suggested by Smyth (12), and Gemmel and MacNamara (13). The effectiveness of these excretory and secretory antigens (ESAg) 1 has been demonstrated previously in other helminths (14-16). In cestodes, several workers have studied artificial immunization against T. ovis (17), Mesocestoides corti (18), and T. p is i formis (19) using ES-Ag collected from in vitro culture media, and T. taeniaeformis using the in vivo method of implanting living larvae enclosed within diffusion chambers into the host (20). In the present study, the humoral and cell-mediated immunities induced by ES-Ag and somatic antigen (Som-Ag), obtained from whole larval homogenate, were studied in detail. Es-Ag and Som-Ag were found to be highly effective in protecting the rat against challenge infection. Furthermore, an antigen fraction purified from both the Es-Ag and Som-Ag was also highly effective, when injected in small quantities together with complete Freund's adjuvant (CFA), in protecting rats against challenge infections of T. taeniaeformis.