IMMUNOLOGICAL RESPONSES OF MAMMALIAN HOST AGAINST TAPEWORM INFECTIONS .X. IMMUNIZATION OF SHEEP AGAINST TAENIA HYDATIGENA AND T OVIS WITH CHEMICALLY OR PHYSICALLY TREATED EMBRYOS

Following activation, the embryos of Taenia hydatigena and T. ovis were formalized or frozen before being injected parenterally into sheep. These treatments were performed in an attempt to prevent embryos developing into cysts at the site of injection as occurs when normally activated embryos are injected. The protection induced by these treated embryos has been compared with that induced by activated embryos injected without further treatment as well as that induced by embryos disrupted by sonic oscillation. Cysts did not develop from the treated embryos in more than one-third of the animals injected. In contrast, cysts developed in all the animals injected with normal embryos. The percentage protection induced to the homologous challenge infection in the sheep immunized with the treated or the normally activated intact embryos was of the order of ≥90% total protection (i.e. prevention of the establishment of embryos and the destruction of cysts). This percentage was not dependent on whether cysts did or did not develop from the injected embryos. Negligible immunity was induced to the homologous challenge infection in the animals immunized with disrupted embryos. Embryos survival but not necessarily cyst development seemed to be required for the stimulation of protection. © 1969.