Immunization of cats with tissue cysts, bradyzoites, and tachyzoites of the T-263 strain of Toxoplasma gondii.

Previous studies have demonstrated that oral administration to cats of tissue cysts of the oocyst-negative mutant strain of Toxoplasma gondii, T-263, induces immunity to oocyst shedding following challenge. Experiments were designed to compare the levels of protection induced by T. gondii T-263 when tissue cysts, bradyzoites released from tissue cysts, and tachyzoites were administered to cats. In 1 experiment, groups of cats received 2 oral doses of intact tissue cysts or released bradyzoites of T. gondii T-263 and were challenged 47 days later with the oocyst-producing strain of T. gondii T-265. All cats seroconverted following immunization and none of them shed oocysts following challenge. In a second experiment, groups of cats received tachyzoites of T. gondii T-263 as a single oral dose and either 1 or 2 intraduodenal doses; they were challenged 60 days after the last vaccination. All cats seroconverted following immunization. Following challenge, all cats shed oocysts except for 2 of 7 cats that received 2 intraduodenal doses of tachyzoites. Thus, orally administered bradyzoites of T. gondii T-263, either contained in intact tissue cysts or liberated from cysts, induced immunity to oocyst shedding. In contrast, tachyzoites did not completely protect against oocyst shedding, even when delivered directly to the duodenum and despite the development of high antibody titers.

Putative polypeptide transfer from male to female Schistosoma mansoni.

Mature males and females, and unisexual females of Schistosoma mansoni were incubated in medium containing [14C]leucine. By use of polyacrylamide gel electrophoresis and fluorography no differences were detected in their ability to synthesize polypeptides. Male worms thus labelled were paired for various periods with unlabelled mature or unisexual females both in vitro and by surgical implantation into hamsters. Female worms paired in vitro had two controls: an accompanying female that did not pair and an additional female placed in the conditioned medium after removal of the other worms. After separation and washing, only small amounts of label were found in females by liquid scintillation counting despite the release by males of substantial amounts of label into the medium. No label was detected in fluorograms of polyacrylamide electrophoresis gels of re-paired females after 7 days' exposure to X-ray film, but a faint pattern of normal polypeptides above 50 kDa did develop after 6 weeks. In light microscope autoradiographs a low grain count was found over sections of unlabelled females paired with labelled males but this was no greater than that over females incubated in medium that had formerly held males. We have been unable to detect any polypeptide reported to be synthesized exclusively by male worms and transferred in large amounts to females. Although female worms did take up small amounts of male-derived metabolic products, the transfer of a specific polypeptide of 66 kDa in significant quantities did not take place under the conditions investigated.

Schistosoma mansoni: the effect of thiosinamine in vivo and in vitro.

It has been found that treatment of mice infected with Schistosoma mansoni with thiosinamine for five days had a significant effect on the formation of normal egg-shells within the ootype of female worms. The protein material, not organized into complete egg-shells, was nevertheless tanned and the surface of these amorphous masses was formed into microspines. Normal egg-shell formation was restored following drug withdrawal. The process of egg-shell formation consists of the integration of the physical moulding of egg-shell precursors derived from the vitelline cells, associated with the chemical process of protein tanning. It is suggested that thiosinamine treatment in vivo results in disruption of egg-shell formation by causing a breakdown in the moulding process and not by the inhibition of protein tanning involving the enzyme polyphenoloxidase. Treatment of worms with the drug under in vitro conditions resulted in a more enhanced effect of egg-shell formation.