Preparation of a Hydatid Cyst Antigen and its Use in the Serodiagnosis of Hydatid Disease in Livestock.
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A method for precipitating beta-lipoproteins from serum was used for the isolation and partial purification of antigens from hydatid cyst fluid (HCF. In addition to two main antigens of hydatid cyst origin, beta-lipoproteins of host origin were also precipitated. The host contaminants were removed by absorptions using insoluble immunoadsorbents. One of the HCF antigens was selected for further studies because of its limited cross-reactions with other parasites. An antiserum (goat No. 880) was prepared by repeated injections of precipitin bands cut out from immunodiffusion gels. After appropriate absorptions, the antiserum was found to be specific for the selected antigen. The antigen referred to as "aptigen 880" was purified by elution from a monospecific immunoadsorbent prepared from the gammaglobulin fraction of the goat No. 880 antiserum. The puri'fied antigen was shown to be present in the following parasites: T. saginata , C. tenuicollis , Moniezia expanSa, Oesophagostomum c radiatum, and Avitellina centripunctata. The antigen was not found in crude saline extracts of the following 4 parasites: Ostertagia ostertagi, Haemonchus~contortus,Trichuris vulpis Ascaridia galli, Ascaris suum, Fasciola gigantica, Stilesia hepatica and Paramphistomum microbothrium. The antigen was detected in saline extracts of protoscolices of hydatid cysts, but not in crude extracts of the germinal and laminar layers of hydatid cysts. The purified antigen was used in the indirect hemagglutihation (IRA) test and the enzyme-linked immunosorbent assay (ELISA). Serum samples from 225 sheep and goats free from hydatid disease and 68 sera from animals with hydatid cysts were examined by the IHA test. When a titre of 1:128 or above was considered significant, 63 out of 68 sera from infected animals showed positive reactions, giving a sensitivity of 92.7%. Two out of 225 normal sera (0.9%) also had significant titres. When a titre of 1:256 or above was considered positive, absolute specificity was achieved, but only'44 out of 68 sera (64.7%) from infected animals showed positive reactions, indicating a 28% reduction in sensitivity. Bovine sera from 34 animals without hydatid cysts, of which 10 were infected with C. bovis, and 8 with Fasciola spp. and 34 sera from animals with hydatid disease were examined by the ELISA method. Absolute specificity was achieved when a titre of 1:6,400 or above was considered -significant. Thirty-one out of 34 sera from infected animals gave positive reactions, giving a sensitivity of 91.2%. It is concluded that antigen "880" is one of the more specific antigens of hydatid cysts. This study indicates that antigen 88011 might be successfully used in serodiagnostjc tests for hydatidosis in animals .