Antibody response against hydatid fluid, protoscolex and whole body of Echinococcus granulosus antigens in lambs

In this study, the immunogenicity of three types of antigens (hydatid fluid, protoscolices and whole body of E. granulosus) was investigated in lambs by ELISA. Sixteen 4-6-month-old lambs of mixed sexes were divided into 4 groups of 4 lambs (three immunized and one control group). Twelve lambs as immunized groups received 2 mg of hydatid fluid, protoscolices and whole body of E. granulosus antigens dissolved in I ml of PBS per immunization for each lamb, respectively. As an adjuvant, Freund's complete adjuvant (FCA) was mixed with antigens to form a water-in-oil emulsion which was inoculated subcutaneously on day I of the trial. Each control lamb was inoculated with a total of 2 ml of PBS emulsified in equal volumes of FCA. Lambs were boosted on day 28 with the same preparation as described above except that FCA was replaced by Freund's incomplete adjuvant (FIA). Three weeks after the second immunization, each lamb received a challenge infection with 2000 protoscolices intraperitoneally and also 10 gravid proglotid of E. granulosus orally. Sera were collected before and after immunization and serum antibodies were tested by ELISA. The results showed that the production of antibody had a significant difference between the test groups and the control (P<0.05). Lambs immunized with whole body of E. granulosus showed the highest antibody production. The level of antibody production between the lambs immunized with hydatid fluid and the protoscolices was not different significantly (P>0.05), whereas, the level of antibody production between the lambs immunized with hydatid fluid and whole body of E. granulosus was different significantly (P<0.05). The results of this study showed that the antigens of whole body of E. granulosus might be a good candidate for immunization and diagnosis of hydatid cyst in the intermediate hosts of E. granulosus.