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The dissertation is divided into five parts, namely studies on the parasite-host models in vivo, in vitro culture of Taenia taeniaeformis oncospheres, in vitro growth and maintenance of mature larvae of Taenia saginata and T. taeniaeformis, the antigens released by the latter in vitro and finally the immunogenic properties of these antigens. In Part I, four strains of T. taeniaeformis, from Belgium (B), Iraq (i), Malaysia (m) and Scotland (S), were compared as regards their infectivity for CF1 mice and Sprague-Dawley rats. Two strains, S and M, appeared to be almost exclusively adapted to mice and rats respectively. Mice were generally more susceptible than rats for strains B and I. Thin layer starch gel electrophoresis of extracts of T. taeniaeformis of these four strains showed different patterns for the isoenzymes of hexokinase. Part II is concerned with in vitro culture of T. taeniaeformis starting with oncospheres. Techniques for hatching and activating oncospheres based on peptic digestion followed by incubation in an artificial intestinal solution, gave unsatisfactory results. Better results were obtained by first disintegrating the embryophores with sodium hypochlorite, followed by stationary incubation in a culture medium containing trypsin, bile and serum. Attempts to cultivate these oncospheres in vitro were not as successful as those described by Heath (1973). Part III describes attempts to monitor the maintenance of T. taeniaeformis strobilocerci in vitro. The weight of the larvae, glucose uptake and lactic acid production were measured at regular intervals. None of these parameters proved to be suitable for comparing different media; the response was either too slow or too irregular to be reliable. Different types of culture for T. saginata metacestodes were tried. The best growth was obtained by using a diphasic medium with disrupted coagulated serum as the solid sub¬ strate. The most developed forms showed segmentation and early development of the sexual organs. Studies concerned with the nature of the metabolic antigens are described in Part IV. These were primarily concerned with establish¬ ing whether these antigens were materially different from somatic antigen or were merely the result of progressive disintegration of the worms in vitro. Immunoelectrophoresis, ELISA for detecting antibodies and ITAS-ELISA for detecting antigen each allowed the metabolic and somatic antigens to be distinguished. The former appeared to be similar to cyst fluid, in so far as precipitating antigens were concerned, whereas in the ELISA and ITAS-ELISA studies metabolic antigen seemed to give more specific results. Cyst fluid or somatic antigen gave less specificity with sera from mice infected with T. taeniaeformis or Taenia crassiceps. Furthermore, as the level of somatic antigen increased in culture fluids, so did the specificity decrease. This release of antigens into culture media was studied in relation to time for different culture media and also by comparing this for dead and living larvae maintained under the same in vitro conditions. The results suggested that the release rate for antigen as measured by ITAS-ELISA could provide a useful means of monitoring viii. such cultures, since the inverse relationship between this and the integrity of the cultured metacestodes was more consistent than any of the parameters studied in Part III or the release rate for metabolic antigen. Finally, a study of the efficacy of these metabolites as immunogens was undertaken in mice and rats and is described in Part V. The results of these experiments were inconsistent; some batches of culture antigen gave significant protection but no relationship between this and their protein content or the proportion of metabolic and somatic antigen could be demonstrated. |
