IDENTIFICATION AND CHARACTERIZATION OF ANTIGENIC COMPONENTS OF SHEEP HYDATID FLUID BY IMMUNOELECTROPHORESIS.

Sheep hydatid fluid was analyzed by immunoelectrophoretic methods. Nineteen antigenic components were detected. Tests with homologous and heterologous antisera showed that ten of the bands were of parasite origin. The characteristic features and staining reactions of each band were determined. In a group of diagnostic sera, eight of the ten parasite bands were identified. The host components which produce cross-reactions in diagnostic sera and with antinormal human serum were identified. The role of host components as a cause of nonspecific reactions and the importance of using antigenic fractions free of host components are discussed. The contents of human or animal hydatid cysts have served as antigen since the introduction of serological tests for hydatidosis. Cyst materials have been obtained from naturally infected man, sheep, pig, cow, and horse. Grafia (1946) and Norman et al. (1957) obtained reproducible results with cysts from one animal source for a particular test, but Bensted and Atkinson (1953) and Garabedian et al. (1957) did not find consistent differences attributable to the source of the antigen. In the Parasitology Unit of the Communicable Disease Center, studies of echinococcus antigens and their sensitivity in immunodiagnostic tests have been under investigation for several years (Kagan and Norman, 1963a, b; Kagan, 1963). In recent research an analysis of sheep hydatid fluid (SHF) was reported with emphasis on characterization of host and parasite antigens by double diffusion methods (Norman et al., 1964). The usefulness of immunoelectrophoresis for the analysis of the antigenic mosaic of parasites has been reported by various workers (Biguet et al., 1962a, b; Received for publication 30 April 1964. * Present address: Department of Microbiology, University of Navarra School of Medicine, Pamplona, Spain. This study was made during the tenure of a fellowship from the Juan March Foundation, Madrid, Spain. Chordi et al., 1964; Norman et al., 1964). In this paper studies of SHF analyzed by immunoelectrophoretic methods are reported. The number of antigen-antibody systems in SHF visualized by this method was determined and antigenic components of parasite and host origin were identified. Attempts were also made to determine which antigenic components were active in detecting antibody in the sera of humans infected with hydatid disease. To isolate parasite from host components, hydatid fluid was absorbed with host serum. The immunoelectrophoretic bands which were missing on subsequent immunoelectrophoresis were listed as host components. The electrophoretic mobility of the hydatid fluid components was determined and the specific stainng characteristics of some antigenic bands were investigated. Such information is of value for the preparation of more specific antigenic fractions for use in diagnostic serology. MATERIAL AND METHODS One liter of pooled sheep hydatid fluid (SHF) was dialyzed 24 hr in running tap water and concentrated approximately tenfold by pervaporation. The cyst fluid contained 0.333 mg N/ml after concentration. The same lot of material was used for all experiments. The antigen was stored at -20 C with merthiolate added as a preservative (1: 10,000). A normal sheep serum (NSS) and a normal human serum (NHS) were collected and preserved with 1: 10,000 merthiolate.